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Vector Signals
Maddy Chang McDonough
24 episodes
1 month ago
A private, AI-curated podcast delivering 15-20 minute deep dives into the latest Nature articles on mosquito-borne viruses and AI-driven therapeutic breakthroughs. Designed for the researchers of the Saleh Lab at Institut Pasteur, each episode distills cutting-edge science into accessible insights—so you can stay current, even during your busiest bench days.
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Life Sciences
Science
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All content for Vector Signals is the property of Maddy Chang McDonough and is served directly from their servers with no modification, redirects, or rehosting. The podcast is not affiliated with or endorsed by Podjoint in any way.
A private, AI-curated podcast delivering 15-20 minute deep dives into the latest Nature articles on mosquito-borne viruses and AI-driven therapeutic breakthroughs. Designed for the researchers of the Saleh Lab at Institut Pasteur, each episode distills cutting-edge science into accessible insights—so you can stay current, even during your busiest bench days.
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Life Sciences
Science
Episodes (20/24)
Vector Signals
Medfly Gut Microbiota and Insecticide Resistance (September 2025)

Gut Microbiota and Insecticide Resistance in the Mediterranean Fruit Fly (Ceratitis capitata)

Source: Charaabi, K., Hamdene, H., Djobbi, W. et al. Assessing gut microbiota diversity and functional potential in resistant and susceptible strains of the mediterranean fruit fly. Sci Rep 15, 33456 (2025). https://doi.org/10.1038/s41598-025-01534-w
Dates: Received - 06 November 2024 | Accepted - 06 May 2025 | Published - 29 September 2025


Executive Summary

This briefing document synthesizes findings from a study investigating the link between gut microbiota and insecticide resistance in the Mediterranean fruit fly (Ceratitis capitata), a destructive agricultural pest. The research reveals a strong correlation between resistance to common insecticides (malathion, dimethoate, and spinosad) and significant alterations in the composition and functional potential of the fly's gut bacterial community.

Resistant strains of the medfly, developed over 36 generations of insecticide exposure, exhibit significantly lower microbial diversity compared to their susceptible counterparts. This reduction in diversity is accompanied by a profound shift in the gut's bacterial landscape. Specifically, the phylum Bacillota and the genera Enterococcus and Klebsiella are substantially enriched in resistant flies. Conversely, the dominant phylum Pseudomonadota and the genera Serratia and Buttiauxella are sharply reduced.

Functional analysis predicts that the gut microbiota of resistant flies possess enhanced metabolic capabilities for xenobiotic biodegradation. These enriched pathways are associated with the breakdown of various toxic environmental chemicals, suggesting a direct or indirect role in insecticide detoxification. The findings indicate that symbiont-mediated resistance is likely a key mechanism in the medfly, driven by the synergistic effect of multiple bacterial species rather than a single microbe. This research opens new avenues for pest management strategies that could target the gut microbiome to mitigate insecticide resistance.

Background and Research Objectives

The Mediterranean fruit fly (Ceratitis capitata), or medfly, is a highly polyphagous pest that infests over 300 plant species, causing billions of dollars in annual economic losses worldwide. These losses stem from reduced agricultural production, costly control measures, and restricted market access. While methods like the Sterile Insect Technique (SIT) are used, the predominant control practice remains the application of chemical insecticides.

The widespread and excessive use of insecticides has led to the development of significant resistance in medfly populations, undermining control efforts. While resistance is often linked to genetic traits in the insect, such as increased enzyme activity, recent evidence from other species suggests that symbiotic gut microorganisms can play a crucial role. These bacteria may contribute to resistance by directly metabolizing toxic substances or by modulating the host's detoxification gene expression.

Despite extensive research on the medfly's gut microbiota in relation to its fitness and SIT applications, the connection to insecticide resistance has remained largely unexplored. This study aimed to address this gap by investigating the potential association between the medfly gut microbiota and insecticide resistance. The primary objectives were to:

  1. Characterize and compare the gut microbiota community structure between insecticide-susceptible (IS) and insecticide-resistant (IR) strains of the medfly.
  2. Identify specific bacterial taxa that correlate with resistance phenotypes.
  3. Predict the functional differences between the microbiomes of susceptible and resistant strains.

Experimental Design and Methodology

To achieve its objectives, the study employed a controlled laboratory selection process and advanced sequencing techniques.

  • Strain Development: Three insecticide-resistant (IR) strains were developed from a susceptible parent strain (IS) originally from Egypt (Egypt II). For 36 successive generations, populations were exposed to increasing concentrations of one of three insecticides: malathion (ML-SEL strain), dimethoate (Dm-SEL strain), or spinosad (Sp-SEL strain). The selection pressure was calibrated to achieve 50-70% mortality in each generation.
  • Resistance Confirmation: Toxicological bioassays were conducted on the 36th generation of each IR strain and the IS strain. The lethal concentration required to kill 50% of the population (LC50) was calculated to quantify the level of resistance. The results confirmed a significant increase in tolerance in the selected strains.


 | Strain | Insecticide | LC50 (ppm) | Resistance Ratio (RR) vs. IS Strain
 | IS | Malathion | 18.8 | -
| ML-SEL (G36) | Malathion | 1872.2 | 99.23-fold
| IS | Dimethoate | 0.85 | -
| Dm-SEL (G36) | Dimethoate | 215.79 | 252.68-fold
| IS | Spinosad | 0.55 | -
| Sp-SEL (G36) | Spinosad | 133.79 | 241.49-fold

  • Microbiota Analysis: Gut tissues were dissected from adult flies of all four strains. Genomic DNA was extracted, and the V3-V4 region of the 16S rRNA gene was amplified and sequenced. Bioinformatic analyses, including Principal Coordinate Analysis (PCoA), Non-metric Multidimensional Scaling (NMDS), and Linear discriminant analysis Effect Size (LEfSe), were used to analyze microbial diversity, structure, and to identify potential biomarkers. Functional potential was predicted using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database.

Key Findings: Shifts in Gut Microbiota Composition

The study revealed dramatic and statistically significant differences between the gut microbiomes of insecticide-susceptible and resistant medflies.

Reduced Microbial Diversity in Resistant Strains

A primary finding was that all three IR strains exhibited significantly lower bacterial richness and diversity compared to the IS parent strain (p < 0.05). This suggests that insecticide exposure acts as a strong selective pressure, favoring the growth of a specialized subset of bacteria that can tolerate or metabolize the toxic compounds. This "selection-cumulation effect" leads to an enrichment of resistance-associated bacteria at the expense of overall diversity.

Altered Bacterial Abundance at Phylum and Genus Levels

The composition of the gut microbiota was fundamentally altered in the resistant strains.

  • Phylum-Level Shifts: While the phylum Pseudomonadota was dominant in all strains, its relative abundance decreased significantly in the IR strains (from 91.03% in IS to 70.85-75.27% in IR). Conversely, the abundance of the phylum Bacillota increased dramatically (from 8.94% in IS to 24.70-28.90% in IR).
  • Genus-Level Shifts: The most pronounced changes occurred at the genus level, pointing to specific bacteria potentially involved in resistance.


 | Bacterial Genus | Relative Abundance in IS Strain | Change in IR Strains | Specific Details
 | ...

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1 month ago
13 minutes

Vector Signals
Mosquito Diversity and Vector Distribution in Kerala, India (Aug 2025)

Mosquito Diversity and Public Health Risk in Kerala, India: A Synthesis of a Multi-District Survey

Source: Mathiarasan, L., Natarajan, R., Aswin, A. et al. Diversity and spatiotemporal distribution of mosquitoes (Diptera: Culicidae) with emphasis on disease vectors across agroecological areas of Kerala, India. Sci Rep 15, 30603 (2025). https://doi.org/10.1038/s41598-025-16357-y
Date: 
Received - 29 May 2025 | Accepted - 14 August 2025 | Published - 20 August 2025


Executive Summary

This document synthesizes the findings of an extensive entomological survey conducted across five agroecological districts of Kerala, India. The research reveals a remarkably diverse mosquito fauna, identifying 108 species, including 14 known disease vectors, which underscores the region's complex public health challenges. The study highlights the overwhelming predominance of Stegomyia albopicta (54.82% of all collected specimens), a highly adaptable vector for dengue and chikungunya, posing a significant and ongoing threat.

Key findings indicate that artificial, human-made habitats—such as discarded tires, plastic containers, and latex collection cups—are the primary breeding grounds, supporting greater species diversity than natural habitats and pointing to critical deficiencies in solid waste management. The Wayanad district was identified as a major biodiversity hotspot for mosquitoes, attributed to its unique ecological niches. The investigation also yielded significant scientific discoveries, including the description of a new species, Heizmannia rajagopalani, and the first regional records of several other species. The co-existence of multiple vectors for arboviruses, malaria, and filariasis creates a complex risk profile that necessitates comprehensive surveillance and targeted, ecologically-informed control strategies.

1. Overview of the Entomological Survey

The study was designed to conduct a comprehensive assessment of mosquito biodiversity, spatiotemporal distribution, and habitat preferences across diverse ecological settings in Kerala, India, a state known for its unique agro-geographical features and history of mosquito-borne disease (MBD) outbreaks.

  • Objective: To evaluate mosquito species composition, spatial and temporal distribution, and ecological and habitat preferences to inform public health risk assessment and vector control strategies.
  • Scope and Duration: The survey was conducted from February 2016 to September 2017 in five districts selected for their varied ecotypes:
     
    • Wayanad (forested, high altitude)
  •  
    • Ernakulam (coastal, plantation)
  •  
    • Pathanamthitta (Western Ghats, plantation)
  •  
    • Idukki (mountainous, tea cultivation)
  •  
    • Thiruvananthapuram (capital, urban/rural/coastal)
  •  
  • Methodology: The research employed a dual sampling approach, collecting both immature (larvae, pupae) and adult mosquitoes. Immature specimens were collected from 777 habitats, while 4,021 adult mosquitoes were collected from 422 sites. Species were identified using standard morphological and taxonomic keys.
  • Total Collection: A total of 12,535 mosquito specimens were collected and identified.

2. Species Composition and Abundance

The survey revealed a rich and diverse mosquito fauna, highlighting a complex ecosystem of both nuisance species and medically important vectors.

Overall Diversity

A total of 108 mosquito species belonging to 28 genera were identified. The genus Culex exhibited the highest species richness (25.0%), followed by Anopheles (12.9%) and Stegomyia (10.2%).

Dominant Species

The vast majority of collected specimens were dominated by a few highly prevalent species:


 | Species | Percentage of Total Collection | Known Significance
 | Stegomyia albopicta | 54.82% | Primary vector for dengue, chikungunya, Zika
| Culex quinquefasciatus | 6.92% | Vector for lymphatic filariasis
| Hulecoeteomyia chrysolineata | 6.33% | Noted for diverse breeding patterns
| Armigeres subalbatus | 5.03% | Nuisance mosquito, prefers polluted water

Identified Disease Vectors

The study identified 14 known disease vector species, creating a multifaceted public health risk. The co-existence of primary and secondary vectors for various diseases complicates transmission dynamics.

  • Arboviruses (Dengue, Chikungunya, Zika, Japanese Encephalitis): St. albopicta, St. aegypti, Fredwardsius vittatus, Cx. tritaeniorhynchus, Cx. bitaeniorhynchus, Cx. gelidus, Cx. vishnui, Cx. pseudovishnui.
  • Malaria: Anopheles stephensi, An. culicifacies (primary vectors), and An. varuna (secondary vector).
  • Filariasis: Cx. quinquefasciatus, Mansonia uniformis, An. barbirostris.

While St. albopicta was abundant, other primary vectors were found in extremely low numbers, such as St. aegypti(1.43%), An. stephensi (0.06%), and An. culicifacies (0.01%). However, the study emphasizes that even low-density vector populations can sustain pathogen transmission cycles and cause outbreaks under favorable conditions.

3. Spatiotemporal Distribution and Biodiversity Hotspots

The distribution of mosquito species varied significantly across the five surveyed districts, revealing distinct biodiversity patterns influenced by local ecology.

District-Level Diversity

  • Wayanad District: Identified as a definitive hotspot for mosquito diversity, with the highest species richness (64 species, including 14 unique to the district). This is attributed to its diverse ecological niches, extensive forest cover, coffee plantations, and comparatively low human interference.
  • Thiruvananthapuram and Pathanamthitta Districts: Also exhibited high levels of diversity, with 60 and 59 species identified, respectively.
  • Ernakulam District: Showed a moderate level of diversity with 54 recorded species.
  • Idukki District: Displayed significantly lower species richness (34 species), a finding linked to the predominance of tea plantations, which do not provide suitable water-accumulating habitats for mosquito breeding.

A core group of 19 species was found across all five districts, indicating shared environmental determinants that support widespread mosquito populations.

Prevalence Patterns

Stegomyia albopicta was the predominant species in all five districts. In the Thiruvananthapuram district, it accounted for an exceptionally high 77.29% of collected mosquitoes. The second-most dominant species varied by district, suggesting that "one-size-fits-all" vector control methods would be ineffective and require tailored, localized strategies.

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2 months ago
14 minutes

Vector Signals
AI and Electric Fields for Automated Insect Monitoring (Aug 2025)

Briefing: Automated Insect Monitoring via AI and Electrical Field Sensors

Source: Odgaard, F.B., Kjærbo, P.V., Poorjam, A.H. et al. Automated insect detection and biomass monitoring via AI and electrical field sensor technology. Sci Rep 15, 29858 (2025). https://doi.org/10.1038/s41598-025-15613-5
Date: Received - 11 April 2025 | Accepted - 08 August 2025 | Published - 14 August 2025


Executive Summary

This document outlines a novel, automated insect monitoring system that uses electrical field sensors and artificial intelligence to provide a non-invasive, continuous alternative to traditional methods. The system addresses the critical need for improved insect monitoring in the face of global declines, aiming to overcome the labor-intensive, lethal, and temporally limited nature of conventional techniques like Malaise traps.

The core technology detects atmospheric electrical field modulations caused by flying insects. A differential sensor design suppresses environmental noise, while a cloud-based AI pipeline processes the signals. This pipeline employs a Convolutional Neural Network (CNN) for insect detection, a probabilistic algorithm for Wing-Beat Frequency (WBF) analysis, and a lookup-based algorithm for biomass estimation.


A field validation study conducted in a Danish nature reserve compared the system against standard Townes Malaise traps. The results demonstrated a moderate to strong positive correlation between sensor and trap data for insect counts (Spearman’s ρ up to 0.725). However, the correlation for biomass was weaker and not consistently significant. A major discrepancy in magnitude was observed, with sensors recording approximately three times more insect counts and 26 times more biomass than the traps. This is attributed to fundamental methodological differences (passive sensing vs. single capture) and significant uncertainty within the system's current biomass estimation algorithm.


Notably, the sensor system exhibited higher measurement consistency between its own units (sensor-sensor correlation for biomass ρ = 0.867) than paired Malaise traps (Malaise-Malaise correlation for biomass ρ = 0.641), although this difference was not statistically significant (P = 0.057). The study concludes that while the technology shows significant promise for scalable, non-lethal insect monitoring, the biomass algorithm requires substantial refinement and calibration before it can be used for absolute estimation.


1. The Challenge in Conventional Insect Monitoring

Insects, comprising over half of all described species, are vital for ecosystem stability through functions like pollination, nutrient cycling, and pest control. Alarming reports of declines in insect abundance, biomass, and species richness underscore the urgent need for effective monitoring to support conservation and safeguard ecosystem services.


However, conventional monitoring techniques present significant challenges:

• Labor-Intensive: Methods such as pan, pit, light, and Malaise traps require substantial manual effort for insect collection, sorting, counting, and weighing.

• Invasive and Lethal: These trap-based approaches remove insects from the local population, posing a potential threat to fragile species and raising ethical concerns. The validation study for this new system highlighted this impact, with 55,443 insects killed in just two Malaise traps during the sampling period.

• Limited Granularity: Traditional methods typically provide data at coarse temporal intervals (e.g., daily or weekly), limiting insights into finer-scale activity patterns.

Automation and non-invasive technologies are critical for overcoming these limitations, enabling continuous data collection across large areas without disrupting local ecosystems.


2. A Novel Automated Monitoring System

The presented system offers a comprehensive, automated solution for non-invasive insect monitoring, from data acquisition in the field to data analysis in the cloud.

2.1. Operating Principle and Sensor Design

The system's core innovation is its ability to passively detect flying insects by exploiting natural electrical effects.

• Detection Mechanism: As insects fly, they acquire a positive electrical charge through air friction (triboelectric effect) and disrupt the ambient atmospheric electric field. These combined effects create unique electrical signatures that the sensor detects.

• Differential Probe Design: To function in noisy outdoor environments, the sensor employs two identical electrostatic probes spaced 28 cm apart. This differential measurement approach effectively mitigates distant, common-mode noise sources like atmospheric disturbances and radio signals.

• Detection Volume: The design creates a detection volume sensitive to nearby insects. However, it also creates a "blind plane" of zero sensitivity on the symmetry plane directly between the two probes. The sensor's sensitivity is size-dependent, meaning larger insects are detectable at greater distances than smaller insects.


2.2. System Architecture and Data Pipeline

The system is composed of three integrated components:

1. Field Sensor Units: The core sensor, housed in a weatherproof unit, uses an ESP32 microcontroller to acquire signals, perform real-time preprocessing, and transmit data via cellular communication. The sensors are solar-powered for continuous daylight operation.

2. Cloud Processing Infrastructure: Data is sent to a cloud-based pipeline that performs a series of processing steps:

    ◦ Removes power line interference (50/60 Hz) using a specialized comb filter.

    ◦ Detects the presence of flying insects using an AI model.

    ◦ Calculates the Wing-Beat Frequency (WBF) of detected insects.

    ◦ Estimates the body mass of the insects.

3. User Interface: Processed data on insect activity (counts) and biomass is aggregated and made available through a user interface for analysis and export.


2.3. AI-Powered Data Processing

The analytical power of the system resides in its sophisticated data processing algorithms.

• Insect Detection (CNN): A Convolutional Neural Network (CNN) is used to classify 1-second signal segments. Each segment is converted into a spectrogram (a visual representation of frequency over time), which serves as the input to the CNN. The model was trained on a large, manually annotated dataset and demonstrated high classification performance on a held-out test set:

    ◦ AUC (Area Under Curve): 0.96

    ◦ F1-Score: 0.79

    ◦ Precision: 0.77

    ◦ Recall: 0.81

• WBF Calculation: For segments classified as containing an insect, the probabilistic YIN (pYIN) algorithm estimates the fundamental frequency, or WBF. A post-processing step filters out unreliable signals (e.g., those with a WBF below 20 Hz or with drastic frequency changes) to reduce false positives. Adjacent 1-second segments with similar WBFs are aggregated to represent a single, continuous insect event.

• Biomas...

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2 months ago
19 minutes

Vector Signals
Successive Feeding Impacts Wolbachia's Dengue Virus Inhibition in Aedes aegypti (July 2025)

Impact of Mosquito Feeding Behavior on Wolbachia-Based Dengue Control

Date: Received - 17 February 2025 | Accepted - 18 July 2025 | Published - 29 July 2025

Source: Johnson, R.M., Breban, M.I., Nolan, B.L. et al. Implications of successive blood feeding on Wolbachia-mediated dengue virus inhibition in Aedes aegypti mosquitoes. Nat Commun 16, 6971 (2025). https://doi.org/10.1038/s41467-025-62352-2

Executive Summary

This document synthesizes findings from a study on the interplay between mosquito feeding behavior and the effectiveness of Wolbachia bacteria in inhibiting the dengue virus (DENV-2). The central conclusion is that successive blood feeding by Aedes aegypti mosquitoes, a natural behavior often overlooked in laboratory settings, enhances the relative efficacy of the wAlbB Wolbachia strain. While frequent feeding accelerates virus dissemination in both Wolbachia-infected and uninfected (wildtype, WT) mosquitoes, the effect is significantly more pronounced in the WT population.

This leads to a critical insight: traditional single-feed laboratory experiments likely underestimate the real-world impact of Wolbachia-based control strategies. The modeling of epidemiologically relevant factors shows that the protective advantage of wAlbB over WT is magnified under conditions that mimic natural feeding patterns. These findings provide robust support for the ongoing deployment of Wolbachia-transinfected mosquitoes for dengue transmission control, suggesting their functional inhibition of DENV-2 may be even stronger than previously demonstrated.

--------------------------------------------------------------------------------

Introduction and Study Context

The release of Aedes aegypti mosquitoes transinfected with the Wolbachia pipientis bacterium is a promising novel strategy to combat the significant public health threat of dengue virus (DENV). Wolbachia inhibits virus transmission, but the mechanisms are not fully understood, and the effectiveness can be incomplete.

A critical factor often unaccounted for in laboratory assessments is the natural feeding behavior of Ae. aegypti, which frequently take multiple blood meals. Previous work has shown that this "successive feeding" can accelerate virus dissemination from the mosquito's midgut, thereby shortening the extrinsic incubation period (EIP)—the time required for a mosquito to become infectious.

This study investigated the hypothesis that successive blood feeding decreases the effectiveness of Wolbachia by facilitating more efficient DENV-2 dissemination in mosquitoes carrying the wMelM and wAlbB strains.


Key Findings

I. Successive Feeding Accelerates DENV-2 Dissemination

The study compared mosquitoes given a single infectious blood meal (single-fed, SF) to those given an additional non-infectious blood meal four days later (double-fed, DF).

• Increased Dissemination: At 7 days post-infection, a second blood meal significantly increased the rate of DENV-2 dissemination in both wildtype (WT) and wAlbB-infected mosquitoes.

• Higher Viral Titers: Correspondingly, double-fed WT and wAlbBmosquitoes exhibited higher DENV-2 genome equivalents (viral load) in their bodies compared to their single-fed counterparts.

• Temporal Shift: Time course experiments confirmed that successive feeding leads to earlier dissemination, effectively shortening the EIP in both WT and wAlbB mosquitoes. For example, at day 5 post-infection, dissemination in the double-fed WT group was significantly higher than in the single-fed group. A similar, though less pronounced, acceleration was observed in wAlbB mosquitoes at days 6 and 7.

II. Wolbachia Strain Performance and Density

The study reaffirmed the virus-inhibiting properties of Wolbachia and explored the role of bacterial density.

• Strong Virus Inhibition: Consistent with previous research, both Wolbachiastrains strongly inhibited DENV-2. Mosquitoes with wMelM showed stronger inhibition (fewer infections and disseminations) than those with wAlbB. Due to the extremely low infection rates in wMelM mosquitoes, many subsequent analyses focused on the wAlbB strain.

• Wolbachia Density: While a second blood meal slightly increased wAlbBdensity, there was no significant correlation between Wolbachia levels and DENV-2 levels in individual mosquitoes. Instead, higher DENV-2 titers were strongly associated with whether the infection had disseminated, suggesting that midgut escape allows for increased viral replication in other tissues.

III. Modeling the Extrinsic Incubation Period (EIP)

By modeling the time course data, the study quantified the impact of successive feeding on the EIP, defined as the time until 50% of mosquitoes develop a disseminated infection (EIP50).

• EIP50 Reduction in wAlbB Mosquitoes: Successive feeding significantly shortened the time to 50% dissemination in wAlbB mosquitoes.

wAlbB Mosquito Group | Estimated EIP50 (Days Post-Infection) | 95% Credible Interval
Single-Fed (SF) | 8.38 days | 7.72–9.01 days
Double-Fed (DF) | 6.86 days | 6.03–7.62 days

• High Dissemination in WT Mosquitoes: In WT mosquitoes, dissemination rates exceeded 50% at all examined time points for both single- and double-fed groups. This prevented the calculation of a precise EIP50 but highlighted their high susceptibility compared to Wolbachia-infected mosquitoes.

Core Conclusion: Enhanced Relative Efficacy of Wolbachia

The study's most significant contribution comes from modeling the epidemiological consequences of a shortened EIP. Researchers calculated the probability of a mosquito surviving beyond its EIP—a key factor for transmission potential.

• Survival Past EIP:

    ◦ Double-fed mosquitoes (both WT and wAlbB) were consistently more likely to survive beyond the EIP than single-fed mosquitoes.

    ◦ WT mosquitoes were always more likely to survive beyond the EIP than their wAlbB counterparts, regardless of feeding status or assumed lifespan (4, 7, or 10 days).

• The Critical Insight (Odds Ratio Analysis): The study calculated the odds ratio of a mosquito surviving past the EIP for wAlbB relative to WT. This comparison revealed that while successive feeding helps the virus in both groups, it helps the virus more in the WT group.

    ◦ The odds ratios for double-fed mosquitoes were much smaller than for single-fed mosquitoes. This indicates that the protective effect of wAlbB is magnified under successive feeding conditions.

    ◦ In the study's words: "although successive feeding did reduce EIP for wAlbB mosquitoes, successive feeding has a larger impact on EIP in WT mosquitoes. This suggests that wAlbB remains effective in inhibiting DENV-2 when considering successive feeding."


Implications and Study Limi...

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3 months ago
14 minutes

Vector Signals
AI for Culex Mosquito Identification using Wing Patterns (July 2025)

Detailed Briefing Document: Application of Wing Interference Patterns (WIPs) and Deep Learning (DL) for Culex spp. Classification

Application of wings interferential patterns (WIPs) and deep learning (DL) to classify some Culex. spp (Culicidae) of medical or veterinary importance
Arnaud Cannet, Camille Simon Chane, Aymeric Histace, Mohammad Akhoundi, Olivier Romain, Pierre Jacob, Darian Sereno, Marc Souchaud, Philippe Bousses & Denis Sereno
Scientific Reports volume 15, Article number: 21548 (2025)
Source: https://doi.org/10.1038/s41598-025-08667-y
Received - 28 November 2024 | Accepted - 23 June 2025 | Published - 01 July 2025


This briefing document reviews a study that successfully demonstrates the utility of combining Wing Interference Patterns (WIPs) with deep learning (DL) models for the accurate identification of Culex mosquito species. Culex mosquitoes are significant vectors for numerous arboviruses and parasites of medical and veterinary importance, including West Nile virus, Japanese encephalitis, Saint Louis encephalitis, and lymphatic filariasis. Traditional morphological identification methods are labor-intensive, prone to errors due to cryptic species or damaged samples, and often yield variable accuracy (e.g., ~64% average species-level accuracy in external assessments).

The research team developed a method leveraging the unique, stable interference patterns visible on transparent insect wing membranes (WIPs) as species-specific morphological markers. By integrating these WIPs with Convolutional Neural Networks (CNNs), the study achieved over 95% genus-level accuracy for Culex and up to 100% species-level accuracy for certain species. While challenges remain with underrepresented species in the dataset, this approach presents a scalable, cost-effective, and robust alternative or complement to traditional identification methods, with significant potential for enhancing vector surveillance and global health initiatives.


Key Themes and Important Ideas/Facts

1. The Challenge of Mosquito Identification and its Importance

  • Global Health Threat: Arthropod-transmitted pathogens, including viruses, bacteria, and parasites, are "among the most destructive infectious agents globally."
  • Vector Role of Culex: The Culex genus, comprising over 783 recognized species and 55 subspecies, "are recognized vectors of significant diseases, such as West Nile virus fever, Japanese encephalitis, Saint Louis encephalitis, or lymphatic filariasis."
  • Difficulty of Traditional Methods: "Traditional morphological identification is labor-intensive and relies on diagnostic features and determination keys." This method is "often challenged by cryptic species, overlapping morphological traits, and damaged specimens."
  • Need for Innovation: These limitations "emphasize the need for innovative identification methods to enhance entomological surveys."

2. Wing Interference Patterns (WIPs) as Species-Specific Markers

  • Nature of WIPs: WIPs are "visible color patterns caused by thin-film interference" on the thin, transparent wing membranes of insects, particularly smaller species. They become visible when wings are "illuminated in a dark, light-absorbing setting."
  • Species-Specific Consistency: "These Wing Interference Patterns (WIPs) show substantial variation between different species, while remaining relatively consistent within a species or between sexes."
  • Stability of WIPs: Unlike conventional iridescence, the "microstructure of insect wings functions as a dioptric system that stabilizes the interference pattern, making WIPs largely insensitive to viewing angle."
  • Potential as Morphological Markers: Due to their "species-specific consistency and interspecific variability, WIPs hold strong potential as morphological markers for insect classification, offering a promising alternative or complement to traditional taxonomic traits."

3. Integration of WIPs with Deep Learning (DL) for Classification

  • Previous Successes: WIPs and DL have previously "successfully demonstrated their utility in identifying Anopheles, Aedes, sandflies, and tsetse flies." This study extends the approach to Culex.
  • Methodology: The study applied "WIPs, generated by thin-film interference on wing membranes, in combination with convolutional neural networks (CNNs) for species classification."
  • CNN Advantages: Deep Convolutional Neural Networks (CNNs) are "most effective for image classification" and "automatically selects the optimal features during the learning process, making it particularly suitable for WIP classification tasks."
  • Dataset: The study used a refined dataset of "553 images representing WIPs from 7 species" for training, with a larger database including "572 images of 12 species across 5 subgenera" for general classification and 4,944 images of non-Culex Diptera as negative controls.

4. Classification Performance and Results

  • High Genus-Level Accuracy: The CNN achieved "genus-level classification accuracy exceeding 95.00%."
  • Variable Species-Level Accuracy: "At the species level, performance varied, with perfect accuracy (100.00%) for Cx. neavei and high accuracy (75.00% to 94.00%) for Cx. insignis, Cx. quinquefasciatus, and Cx. tritaeniorhynchus."
  • Comparison to Traditional Methods: The CNN-based method's species-level accuracy "ranging from 40 to 100%" can "surpass the performance of morphological identification reported in that assessment," where trained entomologists achieved "an average species-level accuracy of 64%."
  • Challenges with Underrepresented Species: "Misclassification occurred for Cx. thalassius and (accuracy 0.00%), while low 40.00% or moderate accuracy (50.00%) were recorded for Cx. univittatus and Cx. nebulosus respectively." This variation is attributed to "dataset limitations, particularly for poorly represented species."

5. Future Directions and Implications

  • Enhancing Robustness: "Expanding the dataset to include more specimens and diverse conditions–such as age, preservation state, and environmental origin–could improve accuracy."
  • Complementary Techniques: "Integrating complementary techniques like molecular barcoding or protein profiling can enhance dataset robustness and address cryptic species identification."
  • Standardization: "Standardizing imaging protocols is essential to minimize variability and ensure consistent image quality."
  • Evaluation Criteria: "Establishment of standardized criteria for evaluating the accuracy of AI/ML-based mosquito identification systems" is crucial for reliable benchmarking.
  • Scalability and Cost-Effectiveness: The "scalable and cost-effective nature of WIP imaging makes it suitable for large-scale biodiversity monitoring and entomological surveys."
  • Transformative Potential: The method "has the potential to become a transformative tool for vector surveillance and biodiversity research, advancing global health and ecological conservation efforts."
  • Broader Applicability: This approach aims to be "generalized to survey a broader range of Dipteran insects of major relevance to human health," supporting "more efficient species identification at broader scales."

Conclusion

The study successfully demonstrates that the fusion of Wing Interference Patterns (WIPs) and deep learning provides a promising and accurate tool for identifying Culex mosquitoes, a critical step in controlling vector-borne diseases. Despite current lim...

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4 months ago
16 minutes

Vector Signals
Battle of the Mosquitoes: Genetic War on Malaria (June 2025)

Detailed Briefing Document: The Battle of the Mosquitoes - A New Approach to Malaria Control

Source: Adepoju, P. Battle of the mosquitoes. Nat Med 31, 1722–1726 (2025). https://doi.org/10.1038/s41591-025-03753-0
Dates: Published - 11 June 2025 | Issue Date - June 2025


I. Executive Summary

This briefing document summarizes the key themes and facts from the provided source, "Battle of the Mosquitoes," detailing the innovative approach of using genetically modified mosquitoes to combat malaria, particularly in urban environments. The core of this strategy, pioneered by Oxitec, involves releasing male Anopheles stephensi mosquitoes engineered with a self-limiting gene, leading to a decline in malaria-carrying female mosquito populations. Djibouti is at the forefront of this experiment, driven by a dramatic resurgence of malaria cases linked to the invasive A. stephensi species, which thrives in cities and evades traditional control methods. The document highlights the painstaking scientific process, the urgent need for new solutions in the face of evolving malaria threats, the critical importance of community engagement to address skepticism about genetic modification, and the challenges of scaling up this technology across Africa amidst funding and regulatory hurdles.

II. Main Themes and Key Ideas

A. The Emergence of Anopheles stephensi as a "Game Changer" in Malaria Transmission

  • Shift in Malaria Epidemiology: For decades, malaria in Africa was predominantly a rural disease, but the arrival and rapid spread of Anopheles stephensi have fundamentally altered this landscape.
  • Urban Adaptation: Unlike A. gambiae, the traditional African malaria vector, A. stephensi "loves city life" and "thrives in urban environments, breeding in water storage tanks, wells and even discarded containers."
  • Ineffectiveness of Traditional Tools: "Traditional malaria control tools — such as bed nets and insecticides — have proven largely ineffective" against A. stephensi because it "bites outdoors and during the day" and exhibits "resistance to multiple insecticides."
  • Geographic Spread: Since its detection in Djibouti in 2012, A. stephensi has been reported in numerous other African and Middle Eastern countries, including Eritrea, Ethiopia, Ghana, Kenya, Nigeria, Somalia, Sudan, and Yemen (Fig. 2).
  • Urgent Threat: The "2024 World Malaria Report warns that without urgent intervention, A. stephensi could derail malaria elimination efforts, particularly in Africa."

B. Djibouti's Pioneering Role and the Severity of its Malaria Crisis

  • Dramatic Resurgence: Djibouti experienced a catastrophic increase in malaria cases, from "27 in 2012 to over 73,000 in 2020," directly linked to the arrival of A. stephensi.
  • Personal Impact on Leadership: Colonel Abdoulilah Ahmed Abdi, the health advisor to the president of Djibouti, himself contracted malaria, emphasizing the severity: "I had been working for years to protect people from malaria, and yet I found myself in a hospital bed, fighting it... It was one of the worst experiences of my life."
  • Urgency for Innovation: Abdi stresses, "Anopheles stephensi is a game changer. If we don’t act fast, it won’t just be Djibouti — it will be cities across Africa, battling a version of malaria we never thought possible." He notes, "We need something complementary to the existing tools — something sustainable and innovative."
  • High Stakes: The resurgence has "threatened both lives and economic growth, with the government citing lost tourism and investment as direct consequences."

C. Oxitec's Genetically Modified Mosquito Technology

  • Mechanism of Action: Oxitec's modified Anopheles stephensi mosquitoes are "bred with a self-limiting gene that ensures that only male offspring survive when they mate with wild females."
  • Targeted Approach: "The modified males don’t bite and don’t spread malaria, but when released into the wild, they seek out female mosquitoes — the ones responsible for disease transmission. Their female offspring don’t survive, causing a gradual decline in the malaria-carrying population."
  • Self-Limiting Nature: A key feature is that the mosquitoes are "self-limiting — meaning that once releases stop, they disappear. 'The moment you stop releasing our friendly males, they vanish from the environment,' Morrison said." This is intended to address regulatory and community concerns about unintended long-term consequences.
  • Painstaking Production Process: Creating these mosquitoes is a "painstaking, manual process."
  • Microinjection: Scientists "use microscopic glass needles to inject a tiny genetic construct into individual mosquito eggs — one by one." This requires extreme precision, with technicians stating, "If you’re too rough, the eggs explode," and "You have about a 30-minute window before they mature too much to inject." The best injectors manage about "1,000 eggs a day."
  • Quality Control: Each mosquito is "carefully examined," looking for a "tiny fluorescent marker inside the mosquitoes’ bodies — a glowing signature that confirms the genetic modification was successful."

D. Critical Role of Community Engagement and Addressing Skepticism

  • Historical Context of GMO Concerns: "Genetic modification remains a sensitive issue in Africa because it resonates with painful histories of external control and uneven benefit." Past issues with biological resource extraction and patented GM seeds have fostered "deep-rooted concerns over who controls the technology and who truly profits from it."
  • Djibouti's Education-First Approach: To counter skepticism and "conspiracy theories," the Djibouti project team adopted a deliberate, "education-first approach" with a focus on "building local expertise."
  • Local Ownership: Investment in training Djiboutian entomologists to master's and PhD levels and equipping a new African lab ensures "it’s our own people on the ground," who can speak authoritatively.
  • Transparency: Project leaders "hold regular public forums and Q&A sessions and conduct door-to-door outreach." "Every claim — how long the genetically modified males survive, that they don’t persist in the environment or cross-breed with other species — is shared openly, in simple language."
  • Direct Engagement: On-the-ground demonstrations (e.g., showing live GM males in secure cages) are used "to counter misinformation."
  • Collaborative Research: Joint surveys of breeding sites and mosquito lifecycles with local teams help "demystify the science and build a sense of collective ownership over the data."
  • Importance of Buy-in: William Moss of Johns Hopkins Malaria Research Institute emphasizes, "We can have all the technologies we want, but if they're not accepted by the community, they're not going to work."

E. Challenges to Scaling Up and Widespread Adoption

  • Regulatory Hurdles: The approval process in Africa is "rigorous" and "stepwise." Many African nations "must develop or adapt biosafety regulations, establish expert review committees and create public consultation processes from scratch, adding time and complexity to each country’s review pathway."
  • Funding Stagnation: "Global malaria funding has stagnated, and a recent freeze in US donor funding has threatened the future of current projects." This raises "concerns about long-term sustainability."
  • WHO's Cautious Stance: "Despite its potential, genetically modified mosquito technology is not yet a core component of the WHO’s malaria strategy." WHO "recognizes genetically modified mosquitoes ...
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4 months ago
16 minutes

Vector Signals
Greenland Mosquito Virome: Arctic Aedes Uniqueness (May 2025)

Briefing Document: Unique Virome of Arctic Mosquitoes in Greenland

Source: https://doi.org/10.1038/s41598-025-01086-z: "Metagenomic analysis of mosquitoes from Kangerlussuaq, Greenland reveals a unique virome" by Schilling, Jagdev, Thomas, & Johnson (2025). 

Date: Received - 17 January 2025 | Accepted - 02 May 2025 | Published - 17 May 2025


Subject: Metagenomic analysis of mosquito viromes in Kangerlussuaq, Greenland and implications in the context of climate change.

Summary: This study provides the first metagenomic analysis of the virome of two prevalent Arctic mosquito species, Aedes impiger and Aedes nigripes, sampled near Kangerlussuaq, Greenland. The research employed next-generation sequencing (NGS) to identify viruses present in pooled mosquito samples collected in July 2022 and July 2023. The findings reveal a diverse and, importantly, a unique virome in these Arctic mosquitoes compared to other Aedes species. The study highlights the critical need to understand these viromes in light of climate change, which is significantly impacting Arctic ecosystems and potentially increasing the risk of vector-borne disease emergence and spread.

Key Findings and Themes:

  1. Dominance of Aedes impiger: Contrary to previous assumptions that Aedes nigripes was the sole mosquito species in western Greenland, this study found Aedes impiger to be the predominant species collected at the Kangerlussuaq site.
  • Fact: "Where a definitive identification could be made, A. impiger was the most frequently sampled mosquito at the Kangerlussuaq site."
  • Fact: In 2023, "49 mosquitoes were identified as A. impiger (70%) and 16 as A. nigripes (23%)."
  1. Novel and Diverse Arctic Mosquito Virome: Metagenomic analysis identified a range of RNA viruses belonging to various families in both Aedes impiger and Aedes nigripes. Many of these viruses are novel and exhibit low sequence identity (sometimes as low as 34% at the amino acid level) when compared to previously published virus sequences from other mosquito species.
  • Quote: "Metagenomic analysis of RNA extracted from species pools detected a number of novel RNA viruses belonging to a range of different virus families, including Flaviviridae, Orthomyxoviridae, Bunyavirales, Totiviridae and Rhabdoviridae."
  • Quote: "However, the sequence identities when compared to previously published, were as low as 34% at the amino acid level."
  • Fact: "Within the family of Flaviviridae, two novel flavi-like virus sequences were identified, with their polyproteins displaying 35% similarity to the nearest published polyprotein..."
  • Fact: "Similarly, two novel orthomyxo-like sequences were identified within the family of Orthomoyxoviridae... Their nucleoprotein comprised only 36% identity to that of Byreska virus..."
  • Fact: "Within the order of Bunyavirales, we discovered two novel phasiviruses as well as two novel phasmaviruses."
  1. Uniqueness of the Arctic Mosquito Virome: A significant finding is the distinct virome of Aedes impiger and Aedes nigripes compared to other Aedes species, particularly Aedes aegypti, which has the most well-characterized virome. Only a small percentage of the identified viruses overlapped with those found in other Aedes species.
  • Quote: "To emphasize the uniqueness of the virome of A. impiger and A. nigripes, we compared our findings to a database of viruses published for other Aedes species... The heatmap... reveals that the majority of sequences derived from Greenland mosquitoes were unique to A. impiger and A. nigripes..."
  • Fact: "...only 36 (of a total of 94, 38%) assigned viruses overlapping with viruses published for other Aedes spp."
  • Fact: "Only 22 (23%) overlapped with Aedes aegypti..."
  • Quote: "This makes the virome composition of A. cantans the most similar published virome composition to that of the mosquitoes we sampled near Kangerlussuaq."
  1. Influence of Climate Change on Arctic Vector Ecology: The study explicitly links its findings to the dramatic effects of climate change on Arctic ecosystems, including the potential for shifts in vector distribution and an increased likelihood of vector-borne disease emergence in previously unaffected areas.
  • Quote: "Climate change is dramatically affecting vector ecology in extreme environments such as the Arctic."
  • Quote: "Global changes in climate are causing a shift in the distribution of vectors and increasing the likelihood of vector-borne disease outbreaks in regions that have not experienced such disease emergence."
  • Quote: "With rapid environmental change, and warming at twice the global average the ecology of Arctic insects will be dramatically affected."
  1. Potential for Zoonotic Transmission Risk: While the detected viruses are likely insect-specific, the study highlights the potential for Aedes impiger and Aedes nigripes to replicate viruses belonging to families with known zoonotic potential. The documented human feeding behavior of Aedes impiger further underscores this risk.
  • Quote: "Our findings further support the capability of A. nigripes and A. impiger to replicate viruses belonging to a range of different virus families, including (-)ssRNA, (+)ssRNA, dsRNA and retroviruses."
  • Quote: "Aedes impiger is known to feed on humans and can productively produce eggs and oviposit after a human blood meal. These observations indicate a realistic risk that these Arctic mosquitoes are capable of transmitting viruses with zoonotic potential."
  • Quote: "However, none of the viruses detected are closely related to known viruses with zoonotic potential and are likely insect-specific."
  1. Importance of Continued Research: The study emphasizes the limited knowledge about Arctic mosquito viromes and the need for further research, including larger datasets and functional characterization of the identified viruses, to better understand their potential impact on animal and public health in a changing climate.
  • Quote: "However, surprisingly little is known about the viruses harboured by this and other indigenous mosquito species."
  • Quote: "Due to our limited sample size, future studies are needed to explore the differences and similarities with the virome of other Aedes species in more depth, and to determine how significant the virome difference between A. impiger and A. nigripes is."
  • Quote: "Further studies will need to functionally characterise the viruses we detected, with regard to their replicative capabilities, potential to cause disease and impact on the replication and transmission of other, better characterized arboviruses."

Implications:

The discovery of a unique and diverse virome in Arctic mosquitoes in Greenland has significant implications for understanding the current and future risks of vector-borne diseases in the region. As climate change continues to alter Arctic ecosystems, the potential for the introduction...

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5 months ago
20 minutes

Vector Signals
Novel Quinolones Counteract Insecticide Resistance in Malaria Vectors (May 2025)

BRIEFING DOCUMENT: Novel Approach to Malaria Control Targeting Mosquito-Stage Plasmodium Parasites

Date: Received - 29 March 2025 | Accepted - 17 April 2025 | Published - 21 May 2025

Source: Excerpts from "In vivo screen of Plasmodium targets for mosquito-based malaria control" by Probst et al. (Published online xx xx xxxx, Nature) https://doi.org/10.1038/s41586-025-09039-2

Subject: Development and testing of novel antiparasitic compounds for incorporation into mosquito bed nets to combat insecticide resistance and reduce malaria transmission.

Summary:

This research presents a promising new strategy for malaria control by targeting the Plasmodium falciparum parasite directly within its mosquito vector (Anopheles species). Recognizing the growing challenge of insecticide resistance in mosquitoes, the study explores the potential of incorporating antiparasitic compounds into long-lasting insecticide-treated nets (LLINs). The authors performed an in vivo screen of 81 compounds, identifying 22 active against mosquito-stage parasites. Notably, endochin-like quinolones (ELQs) targeting the parasite's cytochrome bc1 complex (CytB) showed high potency and were further optimized through medicinal chemistry. Two lead ELQ compounds, ELQ-453 and ELQ-613, demonstrated potent, long-lasting activity when incorporated into bed net-like materials, including in insecticide-resistant mosquitoes. The study also highlights the potential of a dual-target strategy using a combination of Qo-site and Qi-site ELQ inhibitors to reduce the risk of resistance, as CytB mutants show impaired development in mosquitoes. This approach offers a complementary tool to existing malaria control strategies, particularly in areas with high insecticide resistance.

Key Themes and Important Ideas/Facts:

  1. Malaria Burden and the Challenge of Insecticide Resistance:
  • Malaria deaths have stalled in recent years, with an estimated 263 million cases and 597,000 deaths in 2023.
  • Vector control, particularly LLINs, has been crucial in reducing malaria prevalence, but widespread insecticide resistance in Anopheles vectors is jeopardizing their effectiveness.
  • "The decline in malaria deaths has recently stalled owing to several factors, including the widespread resistance of Anopheles vectors to the insecticides used in long-lasting insecticide-treated nets (LLINs)..."
  1. Targeting Mosquito-Stage Parasites as a Mitigation Strategy:
  • Directly killing parasites during their mosquito-stage development by incorporating antiparasitic compounds into LLINs can prevent onward transmission, even if insecticides lose efficacy.
  • This strategy avoids conferring fitness costs or selective pressure on the mosquito, thus preventing vector resistance to the antiparasitic compound.
  • "Interventions that directly target parasites in the mosquito represent a promising approach to disrupt parasite transmission and to reduce malaria burden..."
  • "Of note, the use of a Plasmodium-specific compound would not confer any fitness cost or selective pressure to the anopheline mosquito, which therefore avoids potential development of resistance by the vector."
  1. In Vivo Compound Screening and Identification of Key Targets:
  • An in vivo screen of 81 antiplasmodial compounds with diverse modes of action was performed in Anopheles gambiae mosquitoes.
  • 22 compounds spanning seven distinct P. falciparum targets significantly reduced parasite infection (oocyst prevalence) in the mosquito midgut.
  • Key identified targets included the ubiquinol oxidation (Qo) and ubiquinone reduction (Qi) sites of the P. falciparum cytochrome bc1 complex (CytB), the sodium-proton antiporter P-type ATPase 4 (ATP4), and eukaryotic elongation factor 2 (EF2).
  • "This screen ultimately identified 22 compounds that significantly reduced parasite infection, and these compounds spanned seven P. falciparum targets..."
  1. Endochin-Like Quinolones (ELQs) as Lead Compounds:
  • Endochin-like quinolones (ELQs) targeting CytB were among the most effective compounds in the topical screen.
  • ELQ-456 (targeting the CytB Qo-site) completely inhibited infection in topical applications.
  • ELQ-331 (targeting the CytB Qi-site) strongly reduced infection prevalence.
  • Medicinal chemistry was used to improve the antiparasitic activity of ELQ hits, particularly for uptake via tarsal contact (mosquito legs).
  1. Tarsal Contact Activity and the Importance of Compound Structure:
  • Tarsal contact assays, mimicking mosquito interaction with treated surfaces like bed nets, showed that most compounds active in topical application were inactive.
  • Only ELQ-456 initially showed significant activity in tarsal contact assays.
  • Modifications to the ELQ structure significantly enhanced tarsal-based efficacy. ELQ-453 (Qo-site inhibitor) and ELQ-613 (Qi-site inhibitor), with specific alkyl chain lengths, demonstrated potent activity after tarsal contact.
  • "Of the 13 compounds we tested in tarsal-contact assays, only our most potent hit in the topical screen, ELQ-456 (CytB Qo-site inhibitor) reduced infection (69.5% reduction in oocyst prevalence)."
  • "These results highlight that uptake through mosquito tarsi is strongly affected by the structure of the compound and is key to its activity against P. falciparum."
  1. ELQ Combination (ELQ-453 + ELQ-613) Enhances Potency and Longevity:
  • A combination of ELQ-453 and ELQ-613 showed increased potency compared to either compound alone in tarsal contact assays.
  • This combination significantly reduced oocyst size and sporozoite prevalence even when mosquitoes were exposed to the compounds after establishing infection (3 days post-infection), suggesting an extension of the extrinsic incubation period (EIP).
  • "These data demonstrate that a single, short period of mosquito contact with surfaces treated with the ELQ combination can both prevent establishment of infection and slow down ongoing infections, thereby extending the parasite developmental time in the mosquito..."
  1. Activity in Bed Net-Like Materials and Insecticide Resistance:
  • ELQ-453 and ELQ-613, alone and in combination, maintained their activity when incorporated into low-density polyethylene (LDPE) and high-density polyethylene (HDPE) films, mimicking bed net materials.
  • These films retained complete antiplasmodial activity for over a year when stored at room temperature.
  • Crucially, the ELQ combination was fully effective in insecticide-resistant A. gambiae strains, demonstrating its potential to circumvent insecticide resistance.
  • "Crucially, these films maintained their antiplasmodial activity when tested 1 year later after being stored at room temperature with light exposure and when tested in an insecticide-resistant A. gambiae strain..."
  1. Resistance Considerations and CytB Mutants:
  • Targeting the parasite during the mosquito stage (a bottleneck with lower parasite numbers) is likely to reduce the propensity for de novo resistance mutations.
  • A combination therapy targeting different sites in CytB (Qo and Qi) further mitigates the risk of resistance emergence and spread.
  • Drug selection experiments showed no cross-resistance between Qo-site an...
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5 months ago
24 minutes

Vector Signals
Blocking Malaria Transmission with PfPIMMS43 Nanobodies (April 2025)

Briefing Document: Nanobody-Mediated Blocking of Malaria Transmission Targeting PfPIMMS43

Source: Excerpts from "s42003-025-08033-8.pdf" (A Nature Portfolio journal; https://doi.org/10.1038/s42003-025-08033-8)
Authors: Chiamaka Valerie Ukegbu, et al.
Date: Received - 04 December 2024 | Accepted - 02 April 2025 | Published - 30 April 2025

Executive Summary:

This study explores a novel strategy to block malaria transmission by targeting the Plasmodium falciparum protein PfPIMMS43 using single-domain VHH antibodies, also known as nanobodies. PfPIMMS43 is a critical surface protein for the parasite's development within the mosquito, specifically during the transition from ookinete to oocyst, and aids in evading the mosquito's immune response. Building on previous research demonstrating the potential of polyclonal antibodies against PfPIMMS43, this study successfully developed and characterized high-affinity nanobodies derived from llamas. These nanobodies were shown to significantly reduce both the intensity and prevalence of P. falciparum infection in Anopheles mosquitoes using both laboratory and field strains of the parasite. The study mapped the binding epitopes of the nanobodies to conserved regions in the second half of PfPIMMS43, confirming epitope accessibility. These findings establish PfPIMMS43 as a promising target for malaria transmission-blocking interventions and propose an innovative strategy utilizing genetically modified mosquitoes expressing these nanobodies in conjunction with gene drive technology for enhanced malaria control and elimination efforts.

Key Themes and Important Ideas:

  1. Malaria Transmission as a Target: The study emphasizes the importance of targeting the parasite's development within the mosquito vector to interrupt the human-to-mosquito and mosquito-to-human transmission cycle. This is presented as a crucial approach to complement existing malaria control measures, especially in the face of challenges like insecticide failure, climate change, and funding limitations. The transition from ookinete to oocyst in the mosquito midgut is identified as a "key developmental bottleneck" for the parasite.
  2. PfPIMMS43 as a Critical Transmission Target: The research highlights PfPIMMS43 as an "indispensable" surface protein for P. falciparum ookinetes and sporozoites. It is crucial for the ookinete-to-oocyst transition and plays a role in the parasite's ability to "evade the mosquito immune responses," specifically the complement-like system in the hemolymph. Previous studies, including those by the authors, had already indicated the potential of polyclonal antibodies targeting this protein in reducing transmission.
  3. Nanobodies as a Promising Intervention Tool: The study focuses on the development and application of VHH domain nanobodies as an alternative and potentially superior approach to conventional antibodies for transmission blocking. Nanobodies, derived from camelids and sharks, are described as "smaller, more easily produced monoclonal, heavy-chain variable (VHH) domain antibodies." Their advantages include:
  • "small size (~15 kDa)"
  • "structural simplicity"
  • "strong binding affinity"
  • Easily bioengineered for targeting parasite antigens in mosquito vectors.
  1. Development and Characterization of PfPIMMS43 Nanobodies: High-affinity nanobodies targeting PfPIMMS43 were successfully generated by immunizing llamas with recombinant PfPIMMS43. Nine nanobodies were selected based on variations in their antigen-binding regions (CDR1-3). Four nanobodies (G9, E5, C12, and E2) exhibited high nanomolar binding affinities to recombinant PfPIMMS43 (3, 5, 6, and 8 nM, respectively). These four nanobodies were also able to detect endogenous PfPIMMS43 protein expressed by P. falciparum ookinetes in infected mosquito midguts.
  2. Significant Transmission Blocking Activity (TRA): The developed nanobodies demonstrated significant transmission-reducing activity in mosquito feeding assays.
  • In standard membrane feeding assays (SMFAs) using laboratory P. falciparum NF54 and An. coluzzii mosquitoes, the four high-affinity nanobodies (G9, E5, C12, and E2) significantly reduced oocyst numbers at a concentration of 100 µg/ml, with reductions ranging from 83% to 99%. Oocyst reduction was concentration-dependent.
  • In direct membrane feeding assays (DMFAs) using natural P. falciparum isolates from gametocytaemic children in Tanzania and local An. gambiae mosquitoes, G9 and E5 (the two nanobodies with the highest affinities to recombinant PfPIMMS43) also showed significant TRA, with reductions of 99% and 79% at 100 µg/ml, respectively. Both nanobodies significantly reduced mosquito infection prevalence in field conditions.
  1. Epitope Mapping and Structural Insights: Epitope mapping revealed that the four nanobodies bind to "conserved regions in the second half of PfPIMMS43," specifically beyond amino acid residue 258. This suggests the C-terminal half of the protein is more immunogenic. G9 and E5 appear to recognize similar conformational epitopes, while C12 and E2 bind to distinct linear epitopes closer to the C-terminus. Homology modeling of the G9-PfPIMMS43 interaction suggests that G9 binds primarily through its CDR2 and CDR3 domains, interacting with residues in a β-sheet and an adjacent α-helix in the PfPIMMS43 structure. The model also supports the hypothesis that PfPIMMS43 is largely intrinsically disordered, potentially facilitating immune evasion.
  2. Innovative Future Strategy: The study proposes a "novel approach" for malaria control: "genetically modifying mosquitoes to express nanobodies targeting key post-fertilization proteins such as PfPIMMS43, with the possibility of spreading these traits in wild populations via gene drive technologies." This strategy aims to overcome limitations of vaccine-induced antibodies, such as the challenge of achieving high and sustained titers against mosquito-stage antigens that are not naturally boosted in humans.
  3. Conservation and Potential Challenges of PfPIMMS43: While PfPIMMS43 is largely conserved across P. falciparum isolates from Africa, the study notes the presence of single nucleotide polymorphisms (SNPs) in the epitope recognized by G9 and E5. These SNPs (M307I, L311I, L355H, L355P) have "high fixation indices and signatures of positive selection," suggesting potential evolutionary adaptations of the parasite to evade immune detection. Further investigation into the impact of these alleles on nanobody recognition is deemed necessary for field applications.

Supporting Quotes:

  • "The transition from ookinete to oocyst is a critical step in the Plasmodium falciparum lifecycle and an important target for malaria transmission-blocking strategies."
  • "PfPIMMS43, a surface protein of P. falciparum ookinetes and sporozoites, is critical for this transition and aids the parasite in evading mosquito immune responses."
  • "Here, building on these findings, we have developed high-affinity single-domain VHH antibodies (nanobodies) derived from llama heavy-chain-only antibodies."
  • "Importantly, they significantly reduce infection intensity and prevalence of laboratory and field strains of P. falciparum in An. coluzzii and An. gambiae, respectively."
  • "These findings establish PfPIMMS43 as a promising transmission-blocking target."
  • "To enhance mala...
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6 months ago
12 minutes

Vector Signals
Nanofiber Encapsulation of Pseudomonas for Sustained Mosquito Larvicide Release (April 2025)

Briefing Document: Nanofiber Encapsulation of Pseudomonas aeruginosa for Sustained Mosquito Larvicide Release

Date: Received - 13 December 2024 | Accepted - 04 April 2025 | Published - 21 April 2025
Source: Excerpts from "Nanofiber encapsulation of Pseudomonas aeruginosa for the sustained release of mosquito larvicides" https://doi.org/10.1038/s41598-025-97400-w


1. Executive Summary:

This study investigates a novel approach for mosquito vector control using nanofiber encapsulation of the bacterium Pseudomonas aeruginosa. The research addresses the inadequacy of current vector control strategies in eliminating mosquito-borne diseases by developing a method for the sustained release of bacterial larvicides. P. aeruginosa was selected for its potent larvicide production compared to other tested Pseudomonas species. The study demonstrates that encapsulating P. aeruginosa in electrospun nanofibers protects the bacteria, mimicking natural biofilms, enhances their survival in aquatic environments, and allows for prolonged larvicide production without harming non-target organisms (guppy fish). This nanotechnology-based method shows promise for controlling mosquito larvae in various breeding habitats over extended periods, potentially reducing application frequency and costs.

2. Background and Problem Statement:

  • Mosquito-borne diseases (malaria, dengue, chikungunya, Zika, etc.) pose a significant global health threat, affecting hundreds of millions annually.
  • Existing vector control strategies, primarily chemical insecticides and environmental management, are often insufficient for complete vector elimination.
  • Increased insecticide resistance and environmental concerns associated with chemical methods necessitate the development of novel, sustainable approaches.
  • Biological control using bacteria like Bacillus thuringiensis var. israelensis and Bacillus sphaericus offers a safer alternative, but their efficacy depends on persistence in the environment.
  • Sustained-release formulations of microbial larvicides are highly desirable to reduce application frequency and costs.
  • Conventional immobilization techniques for sustained release often suffer from limitations like low diffusion and reduced microbial viability.

"Despite the rising global incidence of vector-borne diseases such as malaria, dengue, chikungunya, and Zika, existing vector control strategies remain inadequate for completely eliminating vectors from their breeding sites."

3. Key Findings and Concepts:

  • Superiority of Pseudomonas aeruginosa: Among the tested Pseudomonas species (P. fluorescens and P. putida), P. aeruginosa demonstrated the most potent larvicidal activity against four major mosquito vectors: Aedes aegypti, Culex quinquefasciatus, Cx. tritaeniorhynchus, and Anopheles stephensi.
  • "During the initial screening, Pseudomonas aeruginosa proved to be more effective than the other two tested species, P. fluorescens and P. putida, in producing potent larvicides and was therefore selected for nanofiber encapsulation studies."
  • Nanofiber Encapsulation Technique: Electrospinning was used to create a thin fibrous material at the nanoscale (1 nm - 1 µm) from Pluronic F127 dimethacrylate (F127-DM) and polyethylene oxide (PEO) to encapsulate and immobilize live P. aeruginosa bacteria.
  • "In the present study, we rectified the shortcomings of conventional immobilization by developing a thin fibrous material at the nanoscale level (typically between 1 nm and 1 µm) using electrospinning to encapsulate and immobilize live bacteria."
  • Protection and Sustained Release: Nanofiber encapsulation shields the bacterial cells from environmental stress, mimicking natural biofilms, thereby enhancing their survival and prolonging larvicide production. The cross-linking of the nanofibers prevents their rapid dissolution in water.
  • "This study aimed to encapsulate larvicide-producing bacteria in nanofibers designed to shield bacterial cells from environmental stress—mimicking natural biofilms—thereby enhancing their survival in aquatic habitats and prolonging larvicide production."
  • Efficacy in Batch Systems (Container Breeding Habitats): Nanofiber-encapsulated P. aeruginosa demonstrated sustained larvicidal activity in batch systems (simulating stagnant water bodies). The spent water containing released metabolites remained lethal to all four tested mosquito species for at least 8 days.
  • "In the batch system, the spent water with metabolites of P. aeruginosa was lethal to all the tested species of larvae, such as Ae. aegypti, An. stephensi, Cx. tritaeniorhynchus, and Cx. quinquefasciatus, to varying degrees... The larvicidal potency of the spent water either remained the same as observed on the first day or increased during the subsequent days of incubation."
  • Reduced Efficacy in Continuous Systems (Flowing Water Habitats): In continuous flow systems (simulating paddy fields or tanks with water inflow), the larvicidal efficacy of the released metabolites declined over subsequent days, suggesting this method might be less effective in such environments.
  • "However, in a continuous system, although the 100% mortality of the tested larvae, Ae. aegypti and An. stephensi was recorded on the first day, but the efficacy declined on subsequent days."
  • Optimal Nanofiber Quantity: 1 gram of P. aeruginosa-encapsulated nanofiber per 1 liter of water was sufficient to produce larvicidal metabolites capable of causing 100% mortality in Ae. aegypti larvae within 24 hours.
  • "Our present study showed that even 1 g of P. aeruginosa-encapsulated nanofiber was sufficient to produce larvicidal exotoxin metabolites that can kill all the available mosquito larvae in 1 L of medium or water."
  • Viability and Cell Washout: The encapsulated bacteria remained viable within the nanofibers, and no significant release or washout of free bacterial cells into the surrounding water was detected.
  • "As there were no bacterial colonies appeared in the agar plates inoculated with the spent water of the nanofiber encapsulated P. aeruginosa, it is confirmed that there were no free bacteria released from the encapsulated fiber into the spent water..."
  • Storage Stability: Nanofiber-encapsulated P. aeruginosa retained its larvicidal efficacy for up to one month when stored at 3°C. However, efficacy declined with longer storage periods.
  • "The larvicidal efficacy of the spent water collected from the nanofibers stored for up to 1 month had killed 100% of the larvae of Ae. aegypti at 100% concentration... However, storage of bacteria-encapsulated fiber beyond 1 month shows declining efficacy..."
  • Non-Target Organism Safety: The metabolites released by the nanofiber-encapsulated P. aeruginosa showed no mortality in guppy fish (Poecilia reticulata) at concentrations effective against mosquito larvae, indicating target-specificity.
  • "No mortality was observed in the guppy fishes (P. reticulata) used as non-target organisms during the three days of the experiment..."
  • Identified Larvicidal Compounds: GC-MS analysis of the spent water identified several compounds released by the encapsulated bacteria, with oleic acid, octadecanoic acid, and 2-methyl-Z,Z-3, 13-Octadecadienol being the major constituents. These compounds, including fatty acids, have been previously reported to hav...
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6 months ago
13 minutes

Vector Signals
Predicting Aedes Albopictus Spread in Europe via Climate and Population (April 2025)

Population Dependent Diffusion Model for Aedes Albopictus Spread in Europe

Source: Barman et al., "A climate and population dependent diffusion model forecasts the spread of Aedes Albopictus mosquitoes in Europe," Nature Portfolio journal, 2025, https://doi.org/10.1038/s43247-025-02199-z

Date: Received - 25 November 2024 | Accepted - 07 March 2025 | Published - 09 April 2025


Key Themes and Important Ideas/Facts:

This paper presents a novel spatio-temporal diffusion model that accurately forecasts the spread of Aedes albopictus mosquitoes in Europe by simultaneously considering climate suitability and human population factors. Ae. albopictus is a crucial vector for several arboviruses, including Dengue, Chikungunya, Zika, and Yellow Fever. The study highlights the increasing risk of autochthonous (local) transmission of these diseases in Europe due to the mosquito's expanding range, driven by environmental changes and global interconnectedness.

1. Predictable Spread of Ae. albopictus:

  • The core finding is that the expansion of Ae. albopictus in Europe is predictable by integrating climate suitability and human population predictors within a single spatio-temporal diffusion model.
  • The model demonstrates high accuracy in predicting areas of presence and absence (99% and 79% respectively).
  • This predictability allows for anticipating future outbreaks by understanding the interplay between vector suitability and introduction.
  • Quote: "These results show that the expansion of Ae. albopictus in Europe is predictable and provide a basis for anticipating future outbreaks in situations of dependent interacting co-drivers."

2. Drivers of Ae. albopictus Expansion:

  • The study confirms that climate change (suitable climatic conditions), urbanization, and human population mobility are key factors facilitating the invasion of new habitats by this species.
  • Quote: "Suitable climatic conditions favoured by climate change, urbanisation, and human populationmobility, seems to have facilitated the expansion of this invasive mosquito species into novel habitats."
  • The passive transport of eggs through global travel and trade (e.g., used tires, lucky bamboo) and ground vehicles contributes significantly to its spread along transportation corridors.
  • The mosquito's ecological and physiological plasticity (e.g., adaptation to cold, desiccation-resistant eggs, domestic container-breeding) enables its rapid and widespread expansion.

3. Model Development and Performance:

  • The researchers developed a "highly predictive spatio-temporal vector diffusion model" that integrates climate suitability (temperature, humidity) and human population data.
  • The model is a generalized additive mixed (GAM) model fitted within a Bayesian framework (INLA).
  • It accounts for both short-range spread (geographical proximity) and potential long-range spread influenced by human population.
  • The model demonstrates good overall performance, with AUC values around 0.80 for predicting new establishments in previously uncolonized areas.
  • Quote: "Notably, model evaluation reveals that new introduction of Ae. albopictus into naïve areas, are very well predicted, which has not been achieved before with this type of model."
  • Two versions of the model were calibrated: one using raw climate and population covariates, and another using a mechanistic mosquito life cycle model output as a covariate. Both showed similar predictive performance.

4. Key Covariates and Their Influence:

  • Temperature: Median temperature (up to 24°C) shows a strong positive correlation with Ae. albopictus presence, decreasing at higher temperatures. Minimum temperature is positively correlated when median temperatures are high.
  • Relative Humidity: Low relative humidity is negatively correlated with Ae. albopictus presence.
  • Proximity: Geographical proximity to already established areas has a substantial impact on the spread, modeled through a spatio-temporal diffusion process.
  • Human Population: Higher population density is associated with a higher likelihood of Ae. albopictus presence, likely reflecting increased introduction opportunities via human mobility, although the measured effect size was relatively small compared to climate factors.
  • Human mobility modeled explicitly using a radiation model did not significantly improve model fit, suggesting that local diffusion and the human population covariate together can effectively capture its impact.

5. Implications for Public Health:

  • The model can be a valuable tool for preparedness and response to Aedes-borne infections by identifying high-risk areas for new introductions.
  • Quote: "This model can be integrated into early warning systems and help delineate areas at risk for the introduction and establishment of Ae. albo-pictus."
  • Predictions can help target awareness and prevention messages to susceptible populations and guide vector control efforts.
  • The model can also inform healthcare system preparedness for potential epidemics and the strategic deployment of available arboviral vaccines (Dengue and Chikungunya).
  • The framework could be adapted for other regions and vector-borne diseases.

6. Limitations:

  • Regional differences in Ae. albopictus surveillance efforts and data quality across Europe might influence the model's inferences.
  • The use of yearly presence/absence data at a relatively coarse spatial resolution (NUTS3/GAUL) limits the granularity of the inference.
  • The model showed slightly reduced predictive performance in the south-west geographical region (Iberian Peninsula), potentially due to a high number of regions with "no data."
  • Quote: "Limitations of inferences drawn from the model come partly from Ae. albopictus surveillance, where we have regional differences in surveillance efforts across countries..."

7. Future Directions and Solutions:

  • Addressing data gaps, particularly in regions with poor data quality, could improve model performance.
  • Integrating data from Citizen Science initiatives like MosquitoAlert could complement traditional surveillance data and enhance model validation.
  • The model framework can be further developed into operational early warning systems and climate services to enhance public health preparedness.

In Conclusion:

This research provides a significant advancement in our ability to predict the spread of Aedes albopictus in Europe. By simultaneously modeling climate suitability and human population dynamics within a diffusion framework, the developed model offers a robust and accurate tool for public health authorities to anticipate new establishments of this key vector and implement targeted interventions to mitigate the risk of arbovirus outbreaks. The findings underscore the importance of considering both environmental and human factors in understanding and predicting the spread of invasive disease vectors.

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7 months ago
12 minutes

Vector Signals
Malaria Transmission: Parasite and Vector Circadian Clock Coordination (April 2025)

Parasite and Vector Circadian Clocks Mediate Efficient Malaria Transmission

Source: Bento et al., "Parasite and vector circadian clocks mediate efficient malaria transmission," Nature Microbiology, Published online 31 March 2025, https://doi.org/10.1038/s41564-025-01949-1

Date: Received: 03 September 2024 | Accepted: 26 March 2025 | Published: 04 April 2025

Key Themes:

This study uncovers a critical tripartite relationship between the Anopheles mosquito vector, the Plasmodium malaria parasite, and the mammalian host, highlighting the significant role of their respective circadian clocks in mediating efficient malaria transmission. The research demonstrates that both the mosquito salivary glands and the resident sporozoite parasite exhibit substantial circadian transcriptional activity, preparing them for the nocturnal blood-feeding behavior of the mosquito and subsequent host infection. The alignment of these circadian rhythms, particularly during nighttime, is shown to be crucial for maximizing transmission efficiency.

Most Important Ideas and Facts:

  1. Circadian Rhythms in Mosquito Salivary Glands:
  • Approximately half of the Anopheles stephensi mosquito salivary gland transcriptome displays circadian expression.
  • Genes essential for efficient bloodmeals, such as those encoding anti-blood clotting factors (e.g., anophelin/cEF, aegyptin), vasodilators (Peroxidase 5B), and anti-inflammatory proteins (D7 long form L2), exhibit rhythmic expression, peaking around the times when mosquitoes prefer to feed.
  • The study found that mosquitoes prefer to feed and ingest more blood at nighttime, as demonstrated by higher hemoglobin levels in their midguts after nocturnal feeding ("measuring haemoglobin levels, we demonstrate that mosquitos prefer to feed and ingest more blood at nighttime").
  • Circadian clock genes (Clock, Cycle, Period, Vrille) are also rhythmically expressed in the salivary glands, suggesting an internal clock regulating these transcriptional changes.
  • This rhythmic expression in salivary glands occurs independently of light/dark cycles (LD vs. constant dark DD), indicating genuine circadian control ("Genes in the salivary glands of infected mosquitos cycled independently of the mosquito light/dark schedule (LD versus DD), suggesting that they are under circadian control and that the time of day (rather than light) is the main driver of transcriptional fluctuations in mosquito salivary glands").
  • Proteomics analysis confirmed rhythmic abundance of some salivary gland proteins, including those involved in glycolysis.
  1. Circadian Rhythms in Salivary-Gland Sporozoites:
  • A substantial subset (12-20%) of the Plasmodium berghei sporozoite transcriptome within the mosquito salivary glands also exhibits circadian cycling.
  • This finding challenges the traditional view of salivary-gland sporozoites as transcriptionally quiescent ("Notably, we show a substantial subset of the salivary-gland-resident parasite transcriptome cycling throughout the day, indicating that this stage is not transcriptionally quiescent.").
  • Sporozoite genes involved in motility, such as myosin A and thrombospondin-related sporozoite protein (TRSP), show rhythmic expression, potentially modulating their ability to initiate infection at different times of day ("Among the sporozoite genes undergoing rhythmic expression are those involved in parasite motility, potentially modulating the ability to initiate infection at different times of day.").
  • Other cycling sporozoite genes include apical membrane antigen 1 (AMA1), circumsporozoite protein (CSP), and plasmepsin X, all implicated in invasion and host interaction.
  • The rhythmic gene expression in sporozoites is not due to cell division within the salivary glands, as confirmed by EdU incorporation assays ("Taken together, our results show that the transcriptional daily rhythms identified in sporozoites are not a consequence of cell divi-sion but instead resemble a robust circadian rhythm.").
  1. Alignment of Rhythms for Efficient Transmission:
  • The study proposes a "circadian tripartite relationship" between the vector, parasite, and mammalian host that modulates malaria transmission efficiency.
  • Increased mosquito biting and blood ingestion occur at nighttime, aligning with the peak expression of bloodmeal-related genes in the salivary glands.
  • Sporozoite motility-associated genes peak in the early morning, potentially preparing them for transmission during the mosquito's nighttime feeding.
  • Experimental infections in mice demonstrated that parasite load in the liver was significantly higher when infection was initiated during the nighttime (using both nighttime sporozoites and mice) compared to daytime infections. This effect was abolished when the rhythms of sporozoites and mice were mismatched ("We observed a reduced parasite load in the livers of mice when infection was initiated during the daytime (using daytime sporozoites and mice) compared with nighttime infections (using nighttime sporozoites and mice; Fig. 4f). By contrast, this increase in parasite load was abolished when the biological timing of the sporozoites and that of the mice were mismatched...").
  • In vitro experiments with hepatocytes showed that parasite infection was significantly increased at night when the host cell circadian rhythms were synchronized with the time of sporozoite addition ("When the hepatocyte population was synchronous and matched the time with sporozoites, there was a significant increase in infection at night...").
  1. Implications for Disease Intervention:
  • Understanding this intricate circadian interplay could lead to novel strategies for combating malaria transmission, potentially by disrupting the synchronized rhythms.
  • The findings may have broader implications for other vector-borne diseases like Zika and dengue, which might also exhibit daily rhythms in transmission.
  • The timing of mosquito biting and the establishment of host infections are highlighted as important factors in malaria transmission biology.

Quotes Highlighting Key Findings:

  • "Here we show that approximately half of the mosquito salivary gland transcriptome, particularly genes essential for efficient bloodmeals such as anti-blood clotting factors, exhibits circadian expression."
  • "Notably, we show a substantial subset of the salivary-gland-resident parasite transcriptome cycling throughout the day, indicating that this stage is not transcriptionally quiescent."
  • "Our findings suggest a circadian tripartite relationship between the vector, parasite and mammalian host that together modulates malaria transmission."
  • "Together, our results suggest that the circadian regulation in both the mammalian host and the Anopheles mosquito vector has driven Plasmodium to evolve rhythms that align with both hosts, ensuring successful transmission."

Further Research Directions Identified:

  • Dissecting the specific contribution of each player's physiological rhythms and clock mechanisms to the observed phenomenon.
  • Investigating other layers of regulation (e.g., central brain-driven regulation) that shape the mosquito's feeding rhythm and influence salivary gland biology.
  • Characterizing mosquito circadian rhythms across the lifespan and across multiple bloodmeals.
  • Exploring the potential for tar...
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7 months ago
16 minutes

Vector Signals
Radiation Induces Alternative Splicing in Aedes aegypti (March 2025)

Briefing Document: Radiation-Induced Alternative Splicing in Aedes aegypti Mosquitoes

Source: Bendzus-Mendoza, H., Rodriguez, A., Debnath, T., Bailey, C. D., Luker, H. A., & Hansen, I. A. (2025). Radiation exposure induces genome-wide alternative splicing events in Aedes aegypti mosquitoes. Scientific Reports, 15, 5885.

Date of Publication: Received - 19 June 2024 | Accepted - 14 March 2025 | Published - 24 March 2025

Key Themes and Important Ideas/Facts:

This study investigates the impact of ionizing radiation on alternative splicing events (ASEs) in male Aedes aegypti mosquitoes, a crucial aspect for improving the sterile insect technique (SIT). The researchers compared RNA sequencing data from male mosquitoes irradiated with a standard dose of 50 Grey (Gy) of X-rays to that of un-irradiated control mosquitoes. Their findings reveal that radiation exposure induces significant changes in alternative splicing patterns across the mosquito genome, affecting genes involved in key biological processes.

1. Background and Motivation:

  • Aedes aegypti is a major vector for several deadly diseases, posing a significant public health threat. Controlling their populations is crucial.
  • "Aedes aegypti, the yellow fever mosquito, is the primary vector of several deadly diseases, including yellow fever, dengue fever, chikungunya, and Zika[1]. These insects are a major public health threat in many parts of the world, especially in tropical and subtropical regions[2,3]."
  • SIT, which involves releasing sterile males to mate with wild females, is an environmentally friendly method for controlling pest populations.
  • "An alternative method for controlling Ae. aegypti populations is the sterile insect technique (SIT)."
  • "SIT has been proven safe, effective, and environmentally friendly since it does not involve the use of pesticides. It is species-specific and does not make use of genetically modified organisms[10]."
  • Ionizing radiation is the preferred method for sterilizing male insects in SIT programs, typically using doses between 5 and 300 Gy depending on the species. The optimal dose for Ae. aegypti is 50 Gy.
  • "The use of ionizing radiation to sterilize male insects is the method of choice in many SIT programs[11]."
  • "The optimal radiation dosage for sterilizing male Ae. aegypti has been previously determined to be 50 Gy[16]."
  • A significant challenge with SIT is that while 50 Gy sterilizes males, it also reduces their fitness and lifespan, hindering their ability to compete with wild males.
  • "While irradiating mosquitoes with 50 Gy causes complete sterility, it still reduces male fitness and lifespan[17]. This is a problem because sterile males must successfully compete with wild males for SIT to be effective."
  • Previous research by the same group identified significant changes in gene expression (upregulation of DNA repair genes) in irradiated Ae. aegypti. This study focuses on the impact of radiation on alternative splicing.
  • "To better understand the impact of radiation exposure on mosquitoes, we previously investigated changes in the transcriptome of irradiated male Ae. aegypti. We found dramatic changes in the transcriptome, specifically a robust up-regulation of the transcription of DNA repair genes..."

2. Key Findings on Alternative Splicing Events (ASEs):

  • Radiation exposure significantly induced alternative splicing events in male Ae. aegypti.
  • "The results of our analysis of our dataset confirmed our hypothesis that radiation-exposure triggers specific and significant ASEs in mosquitoes."
  • The study identified 289 significantly differentially alternatively spliced events (FDR < 0.05 and |Δ PSI| > 0.1) in 181 unique genes after irradiation.
  • "In total, we detected 15,016 ASEs among the transcriptomes of irradiated and non-irradiated mosquitoes... 289 of these ASEs were significantly differentially alternatively spliced between both groups... with 181 unique genes undergoing ASEs..."
  • Five main types of ASEs were observed: alternative 3’ splice site (A3SS), alternative 5’ splice site (A5SS), mutually exclusive exon (MXE), retained intron (RI), and skipped exon (SE).
  • "Specifically, 88 events were classified as alternative 3’ splice site events (A3SS), 104 as alternative 5’ splice site events (A5SS), 17 as mutually exclusive exon events (MXE), 12 as retained intron (RI) events, and 68 as skipped exon events (SE)..."
  • A3SS, A5SS, and SE were the most prevalent types of ASEs induced by radiation. RI was the least common.
  • "Of these five, A3SS, A5SS, and SE are by far the most prevalent after irradiation treatment... In support of this notion, we found that RI is indeed the rarest type of ASE in our Ae. aegypti dataset."
  • These radiation-induced ASEs occurred genome-wide, affecting genes on all three chromosomes of Ae. aegypti.
  • "The genes that undergo significant ASEs after irradiation were mapped to the three chromosomes of Ae. aegypti... We found that all five ASEs occurred genome wide."

3. Functional Analysis of Alternatively Spliced Genes (ASGs):

  • Functional analysis of the 181 ASGs revealed their involvement in diverse biological processes, including:
  • Actin filament binding and other cytoskeletal-related processes.
  • Ubiquitin signaling processes (thiol-dependent deubiquitinase, deubiquitinase activity).
  • Calcium ion binding.
  • Phosphotransferase, kinase, and transferase activity.
  • Nucleotide and nucleoside phosphate biosynthetic processes.
  • Intracellular signal transduction, response to stimulus, and regulation of cellular processes.
  • KEGG pathway analysis highlighted significant enrichment in the:
  • Hippo signaling pathway: Involved in cell proliferation and apoptosis, and linked to radiation resistance in tumors. One identified ASG in this pathway is PP2A.
  • "Among the identified pathways, the HIPPO signaling pathway... emerged as the most abundant. These pathways play crucial roles in various cellular processes such as signal transduction, response to stimuli, and regulation of cellular activities[44–46]... One of the alternatively spliced genes that we identified in this pathway is PP2A, which is part of a regulatory complex within the Hippo pathway[53]."
  • Purine metabolism: Regulates DNA repair and has been implicated in promoting radiation resistance.
  • "The purine metabolism pathway regulates DNA repair, has been associated with cancer therapy, and implicated to promote radiation resistance[54,55]."
  • Notch signaling pathway: Involved in cell fate and associated with tumor cell proliferation and radiation resistance. NCSTN, an important regulator protein in this pathway, was found to be alternatively spliced.
  • "The Notch signaling pathway, another conserved pathway involved in cell fate, has been associated with tumor cell proliferation, and radiation resistance[56,57]. An important regulator protein, NCSTN[58], is also alternatively spliced upon radiation exposure."

4. Overlap with Differentially Expressed Genes (DEGs):

  • A cross-analysis with a previous study that identified DEGs after irradiation revealed that only a small number of genes (16) were both differentially expressed and alternatively spliced.
  • "As previously described by Pinch et al.[18], 149 genes were significantly differentially expressed between the non-irradiated and irradiated Ae. aegypti...
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7 months ago
20 minutes

Vector Signals
Mosquito Prefoldin Targeting Blocks Plasmodium Transmission (March 2025)

Briefing Document: Targeting the Mosquito Prefoldin–Chaperonin Complex to Block Plasmodium Transmission


Citation: Dong, Y., Kang, S., Sandiford, S.L. et al. Targeting the mosquito prefoldin–chaperonin complex blocks Plasmodium transmission. Nat Microbiol (2025). https://doi.org/10.1038/s41564-025-01947-3

Date: Received - 22 November 2024 | Accepted - 27 January 2025 | Published - 06 March 2025


Overview:

This study investigates the role of the conserved Anopheles mosquito prefoldin (PFDN)–chaperonin (CCT/TRiC) system as a potential target for blocking the transmission of multiple Plasmodium species. The researchers demonstrate that disrupting this protein folding complex in mosquitoes, either through gene silencing or antibody inhibition, significantly reduces Plasmodium infection intensity and prevalence. The mechanism of action involves compromising the integrity of the mosquito midgut, leading to immune activation and the disruption of the parasite's immune evasion strategies. The findings suggest that the PFDN–chaperonin complex, particularly the PFDN6 subunit, holds promise as a multispecies transmission-blocking vaccine (TBV) target.

Main Themes and Important Ideas/Facts:

  • The Mosquito PFDN–Chaperonin Complex is Essential for Plasmodium Infection:
  • The Plasmodium infection cycle in mosquitoes relies on various host factors in the midgut.
  • The mosquito prefoldin complex is crucial for the proper folding of proteins and macromolecular complexes, including actin and tubulin, which are essential for cell division, motility, cytoskeletal stability, and signal transduction – all of which influence Plasmodium infection.
  • Silencing any of the six PFDN subunits (Pfdn1-6) or the CCT4 subunit via RNA interference significantly reduced Plasmodium falciparum oocyst loads in the Anopheles gambiae midgut.
  • "Silencing any prefoldin subunit or its CCT/TRiC partner via RNA interference reduces Plasmodium falciparum oocyst loads in the mosquito midgut..."
  • Co-silencing of different PFDN subunits did not have an additive effect, confirming that the complex functions as a unit in supporting parasite development.
  • Targeting PFDN6 with Antibodies Blocks Plasmodium Transmission:
  • Co-feeding mosquitoes with a PFDN6-specific antibody along with P. falciparum gametocytes resulted in a potent suppression of parasite infection at both the oocyst and sporozoite stages.
  • "Ingestion of purified anti-PFDN6 polyclonal antibody (IgG) resulted in a significant decrease in parasite loads (either at the oocyst or sporozoite stage) compared with control cohorts fed on rabbit anti-GFP antibody..."
  • The level of inhibition achieved with anti-PFDN6 antibodies was comparable to that of leading TBV candidates like Pfs230 and Pfs25, as well as antibodies targeting mosquito proteins AgAPN1 and FREP1.
  • Anti-PFDN6 antibody also effectively blocked P. falciparum transmission in Anopheles stephensi and Plasmodium vivax transmission in Anopheles dirus, indicating a broad-spectrum effect across different mosquito and parasite species.
  • Active immunization of mice with recombinant PFDN6 protein resulted in antibodies that, when mosquitoes fed on the immunized, infected mice, significantly reduced Plasmodium berghei oocyst infection intensity and prevalence, supporting its potential as a TBV target.
  • PFDN Supports Plasmodium Development After Ookinetes Invade the Midgut Epithelium:
  • Antibody blocking assays showed no significant difference in ookinete numbers in the midgut lumen at 24 hours post-infection, but a significant decrease in oocyst loads was observed at 36 hours and 8 days.
  • Injection of anti-PFDN6 antibody into the mosquito haemolymph also reduced oocyst numbers, suggesting an effect on the basal side of the midgut epithelium where oocysts develop.
  • "These results indicate that PFDN6 host factor function is exerted upon ookinete egress and oocyst formation on the basal side of the epithelium beneath the basal lamina."
  • PFDN6 distribution largely overlapped with actin in the midgut epithelium, but it did not co-localize directly with the parasites, suggesting an indirect role in parasite development.
  • Disruption of PFDN Compromises Midgut Integrity and Triggers Anti-Plasmodium Immunity:
  • Attempting to create a Pfdn6 knockout mosquito line resulted in pre-adult lethality, likely due to cytoskeletal and gut integrity issues.
  • Co-immunoprecipitation assays identified interactions between PFDN6 and actin, tubulin, and several extracellular matrix proteins, supporting its role in maintaining cellular and matrix integrity.
  • Silencing Pfdn6 or co-feeding with anti-PFDN6 antibodies led to a "leaky gut," characterized by increased permeability and bacterial leakage from the midgut lumen into the haemolymph.
  • "Interfering with the PFDN–CCT/TriC chaperonin complex results in a cascade of events, including compromised gut integrity and disrupted extracellular matrix organization. The increased gut permeability leads to bacterial leakage and systemic infection, ultimately augmenting antiplasmodial defences..."
  • Bacterial leakage triggered a stronger anti-Plasmodium immune response, with upregulation of key immune factors like Tep1, FBN9, and LRRD7.
  • The leaky gut condition also shortened mosquito lifespan in the presence of natural microbiota.
  • PFDN Facilitates Parasite Immune Evasion Through Laminin:
  • PFDN appears to be involved in maintaining the laminin coating on ookinetes and early oocysts, a basal lamina component previously shown to be important for parasite development and immune evasion.
  • Silencing laminin resulted in a significant decrease in oocyst numbers, similar to Pfdn6 silencing.
  • In Pfdn6-silenced mosquitoes, the laminin coating on parasites was compromised, leading to increased co-localization with the anti-Plasmodium factor Tep1.
  • Co-silencing of Pfdn6 and Tep1 negated the individual effects on parasite infection, suggesting that PFDN's host factor role involves limiting parasite accessibility to Tep1.
  • "These processes also compromise the parasite’s laminin-based immune evasion mechanism, enabling the primed immune system to attack it effectively."
  • PFDN as a Potential Transmission-Blocking Vaccine Target:
  • The high conservation of PFDN6 across mosquito species and its role as a host factor for multiple Plasmodium species make it a promising TBV target.
  • In silico analysis identified a potential unique B cell epitope on A. gambiae PFDN6 with low homology to human PFDN6, which could be explored to minimize cross-reactivity concerns.
  • The authors suggest that a multivalent vaccine targeting several PFDN–CCT/TriC complex epitopes could be a strategy to mitigate potential selective pressure.
  • Conditional genetic inactivation of the PFDN–CCT/TriC complex via gene-drive mechanisms is also proposed as a potential malaria control strategy.

Quotes Highlighting Key Findings:

  • "Here we show that the PFDN–CCT/TriC (T-complex protein ring complex) chaperonin complex serves as a host factor system for multiple Plasmodium species in all tested Anopheles species."
  • "In summary, we show here that the role of the PFDN–CCT/TriC chaperonin complex Plasmodium host factor is based on maintaining midgut epithelial and extracellular matrix and basal lamina integrity that (1) limits the leakage of midgut microbiota into the haemolymph, where it can prime anti-Plasmodium immunity; (...
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8 months ago
19 minutes

Vector Signals
Engineered Bacteria Combat Concurrent Malaria and Arbovirus Transmission (March 2025)

Briefing Document: Engineered Symbionts for Concurrent Malaria and Arbovirus Transmission Control


Citation: Hu, W., Gao, H., Cui, C. et al. Harnessing engineered symbionts to combat concurrent malaria and arboviruses transmission. Nat Commun 16, 2104 (2025). https://doi.org/10.1038/s41467-025-57343-2

Dates: Received - 27 July 2024 | Accepted - 19 February 2025 | Published - 01 March 2025

Prepared for: Saleh Lab


Executive Summary:

This research presents a novel paratransgenesis strategy utilizing engineered symbiotic bacteria (Serratia AS1) in mosquitoes to simultaneously combat the transmission of malaria parasites (transmitted by Anopheles mosquitoes) and arboviruses like dengue and Zika (transmitted by Aedes mosquitoes). The study demonstrates the successful engineering of Serratia AS1 to express anti-Plasmodium and anti-arbovirus effector proteins under the control of a blood-induced promoter. Both laboratory and semi-natural field-cage experiments show that these engineered bacteria effectively spread through mosquito populations and significantly inhibit pathogen infections in both Anopheles and Aedes mosquitoes, including reducing co-infection rates of dengue and Zika viruses. This work lays the groundwork for a promising tool to address the growing challenge of concurrent mosquito-borne disease outbreaks.

Main Themes and Important Ideas/Facts:

  1. The Growing Threat of Concurrent Mosquito-Borne Diseases:
  • More than half of the global population lives in areas at risk of contracting two or more major mosquito-borne diseases.
  • The geographic distributions of Anopheles (malaria) and Aedes (arboviruses) mosquitoes are increasingly overlapping, leading to co-existence and potential co-infection scenarios.
  • Co-infections of malaria and arboviruses (dengue, Zika, chikungunya) have been reported in various regions.
  • Co-circulation and simultaneous co-infection of multiple arboviruses are also prevalent.
  • These concurrent infections pose complex challenges for disease surveillance, diagnosis, and treatment.
  • "The overlapping distributions highlight the inevitable co-existence and potential co-infection of malaria and arboviruses, or multiple arboviruses, in single host. Such scenarios pose complex and multifaceted public health challenges."
  1. Limitations of Current Mosquito Control Strategies:
  • Reliance on mosquito management is hampered by widespread insecticide resistance.
  • Behavioral changes in Anopheles mosquitoes (e.g., outdoor biting) and antimalarial drug resistance have stalled progress in malaria control.
  • Current global outbreaks highlight the inadequacies of existing control tools.
  • "This situation underscores the urgent need for innovative intervention strategies to tackle the concurrent transmission of malaria and arbovirus diseases."
  1. Paratransgenesis as a Promising Innovative Strategy:
  • Paratransgenesis, utilizing genetically manipulated symbionts to inhibit pathogens, is an attractive approach.
  • While promising for malaria, its effectiveness against arboviruses and its potential to simultaneously target both requires further exploration.
  • "Here, we explore the potential of parastransgenesis strategy to concurrently inhibit the transmission of Plasmodium and arboviruses by Anopheles and Aedes mosquitoes, respectively."
  1. Identification and Engineering of Serratia AS1 as a Multifunctional Symbiont:
  • The symbiotic bacterium Serratia AS1 efficiently spreads through both Anopheles and Aedes mosquito populations (horizontally and vertically).
  • Laboratory cage experiments confirmed efficient spread in An. stephensi and Ae. aegypti.
  • Serratia AS1 proliferates in the mosquito midgut after a blood meal without significant fitness costs to the mosquitoes.
  • Wild-type Serratia AS1 did not significantly affect dengue virus infection in Ae. aegypti, making it a suitable chassis for engineering.
  • "...indicating that Serratia AS1 can efficiently spread throughout these two mosquito populations."
  • "...without causing obvious negative impact on fitness costs in both the mosquito species..."
  1. Development of Engineered Serratia AS1 Strains Expressing Anti-Pathogen Effectors:
  • The study engineered Serratia AS1 to co-express anti-Plasmodium peptides (Shiva1, scorpine) and anti-arbovirus peptides (DN59, Z2) using the efficient HlyA secretion system.
  • The initial construct (AS1-DK) with constitutive expression (using pnptII promoter) showed strong inhibition of P. berghei in Anopheles and DENV2 in Aedes.
  • "We found that AS1-DK strongly inhibited P. berghei ANKA (Pb ANKA) development in An. stephensi mosquitoes...and DENV2 infection in Ae. aegypti mosquitoes."
  1. Importance and Identification of a Blood-Induced Promoter (LipA):
  • Constitutive expression of effectors can impose fitness burdens on bacteria and potentially affect mosquitoes or lead to resistance.
  • Blood-inducible promoters are advantageous as effector expression is activated only upon blood meal ingestion, coinciding with pathogen entry.
  • A comprehensive analysis of Serratia transcriptional and proteomic data identified several blood-induced promoters.
  • The LipA promoter demonstrated the strongest inducible activity and the highest stringency for blood-induced expression.
  • "Notably, the LipA promoter showed the strongest activity, coupled with the highest stringency for blood-induced expression."
  1. Enhanced Pathogen Inhibition with LipA-Controlled Effector Expression (AS1-TK):
  • An engineered strain (AS1-TK) utilizing the LipA promoter to drive the expression of scorpine, Shiva1, DN59 (two copies), and Z2 (two copies) was developed.
  • AS1-TK strongly inhibited P. falciparum and P. berghei infection in Anopheles.
  • AS1-TK effectively inhibited both DENV2 and Zika virus infections in Ae. aegypti.
  • AS1-TK did not impose obvious fitness costs in either mosquito species.
  • "The recombinant strain AS1-TK strongly inhibit development of the human malaria parasite P. falciparum NF54 infection...and rodent malaria parasite P. berghei ANKA...in An. stephensi mosquitoes. Moreover, AS1-TK effectively inhibit both DENV2...and Zika virus infections...in Ae. aegypti mosquitoes..."
  1. Efficacy of AS1-TK in Semi-Natural Field-Cage Conditions:
  • Outdoor field-cage experiments demonstrated that AS1-TK efficiently colonized both An. stephensi and Ae. aegypti mosquitoes under semi-natural conditions.
  • Colonized female mosquitoes showed strong inhibition of P. berghei infection.
  • AS1-TK effectively inhibited all four serotypes of dengue viruses and Zika virus infection in Ae. aegypti in the field-cage setting.
  • "The outdoor field-cage experiments showed that the recombinant AS1-TK strain efficiently colonized both An. stephensi and Ae. aegypti mosquitoes..."
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8 months ago
22 minutes

Vector Signals
Mosquito Viral Tolerance Enhanced by Prolonged Heat Exposure (February 2025)

Briefing Document: Heat Exposure and Mosquito-Virus Interaction

Source: Perdomo, H. D., Khorramnejad, A., Cham, N. M., Kropf, A., Sogliani, D., & Bonizzoni, M. (2025). Prolonged exposure to heat enhances mosquito tolerance to viral infection. Communications Biology, 8(1), 761. https://doi.org/10.1038/s42003-025-07617-8

Dates: Received - 27 September 2024 | Accepted - 28 January 2025 | Published - 04 February 2025

Prepared for: Saleh Lab


Executive Summary:

This study investigates the impact of increased environmental temperature on the interaction between the mosquito species Aedes albopictus and the cell fusing agent virus (CFAV), an insect-specific virus. The researchers examined how short-term (one generation) and long-term (ten generations) exposure to a higher temperature (32°C/26°C day/night cycle) influences mosquito tolerance and resistance to CFAV infection, as well as their overall fitness. The key findings reveal that prolonged heat exposure leads to increased viral tolerance in mosquitoes without significant fitness costs, while short-term heat exposure results in increased resistance but at the expense of mosquito fitness. These findings have significant implications for understanding the effects of climate change on arbovirus transmission dynamics and the evolution of both mosquito vectors and the viruses they carry.

Main Themes and Important Ideas/Facts:

  • Climate Change and Arbovirus Transmission:
  • The study highlights the complex interplay between climate change, mosquito biology, and virus interactions, emphasizing the relevance of this research to the prevalence and transmission dynamics of arboviruses like dengue, Zika, and chikungunya, which threaten billions globally.
  • "Current anthropogenic climate change has profound and complex impli-cations for the prevalence and the transmission dynamics of arboviruses such as dengue, Zika and chikungunya, which are an impending risk for 3.9 billion people in tropical and subtropical areas of the world."
  • Rising temperatures are expected to shift the distribution and phenology of key arboviral vectors, Aedes aegypti and Aedes albopictus, further expanding disease risk.
  • While increased temperature is known to accelerate viral replication in mosquitoes, the impact of temperature on the mosquito's response to viruses has been largely unexplored.
  • Resistance vs. Tolerance in Mosquito Immunity:
  • The study distinguishes between two key immunological strategies in mosquitoes: resistance (limiting viral replication) and tolerance (controlling the cost of infection without reducing viral load).
  • The researchers employed a framework developed in plant pathology using reaction norms (measuring host longevity across pathogen doses) to differentiate between resistance and tolerance.
  • Resistance exerts strong selective pressure on viruses, while tolerance has neutral or even positive effects on them. Understanding the shift between these responses due to climate change is crucial for predicting viral transmission dynamics and long-term evolutionary impacts.
  • Experimental Design: Thermal Acclimation vs. Evolution:
  • The study mimicked both acute thermal fluctuations (heat waves) and gradual, prolonged warming by exposing Aedes albopictus mosquitoes to a hot thermal regime (32°C for 14 hours, 26°C for 10 hours) for one generation (warm-acclimated) or ten generations (warm-evolved).
  • These groups were compared to a control group maintained under standard laboratory conditions (28°C). All infected mosquitoes were kept at their rearing temperature post-infection.
  • Prolonged Heat Exposure Enhances Viral Tolerance:
  • Warm-evolved mosquitoes demonstrated increased tolerance to CFAV infection, meaning they could withstand higher viral loads without significant reductions in longevity.
  • "We show that the length of the thermal challenge influences the outcome of the infection with warm-evolvedmosquitoes beingmore tolerant to CFAV infection..."
  • Tolerance curves showed that warm-evolved mosquitoes had comparable vigour (survival time of uninfected hosts) to the standard group and the lowest severity (longevity at the highest viral load).
  • "Multi-generational exposure to heat imposes no cost on CFAV infected mosquitoes."
  • Short-Term Heat Exposure Enhances Viral Resistance but with Fitness Costs:
  • Warm-acclimated mosquitoes exhibited higher resistance to CFAV, showing lower viral prevalence and load at 3 days post-infection compared to both warm-evolved and standard mosquitoes.
  • "...warm-acclimatedmosquitoes being more resistant..."
  • However, this increased resistance came at a cost, as warm-acclimated mosquitoes displayed reduced longevity and fecundity, and increased sterility and infertility, even in the absence of viral infection, suggesting the thermal challenge itself is stressful.
  • "One generational exposure to heat...results in fitness costs and increased resistance to viral infection."
  • Implications for Arbovirus Transmission:
  • The shift towards tolerance in warm-evolved mosquitoes has significant implications for arbovirus transmission. While they may control viral replication less effectively (lower resistance), their ability to survive infection with higher viral loads could increase the likelihood of transmission over a longer period.
  • "Increased viral tolerance raises the likelihood of viral trans-mission in warm-evolved mosquitoes."
  • The study suggests that the duration of heat exposure is a critical factor in determining mosquito immune response and, consequently, arbovirus transmission dynamics.
  • Implications for Biological Control using Insect-Specific Viruses (ISVs):
  • The findings that temperature modulates CFAV prevalence and load have implications for the potential use of CFAV as a biological control agent against arboviruses.
  • Short-term heat fluctuations could negatively impact CFAV prevalence in mosquito populations, while prolonged warming might favor its persistence.
  • "Considering the potential application of CFAV as a biological control agent, our results support the conclusion that global warming could favour CFAV persistence, but unexpected thermal fluctuations could negatively impact its prevalence in mosquito populations."
  • Evolutionary Consequences of Resistance and Tolerance:
  • The study discusses the contrasting evolutionary pressures exerted by resistance and tolerance mechanisms on both mosquitoes and viruses.
  • Resistance can drive an "arms race" leading to rapid molecular evolution.
  • Tolerance, by minimizing the cost of infection, may reduce selective pressure on viruses, leading to different evolutionary trajectories.
  • The interplay and potential trade-offs between resistance and tolerance mechanisms are crucial for understanding the long-term co-evolution of vectors and viruses.

Quotes:

  • "These results highlight the importance of considering fluctuations in vector immunity in relation to the length of a thermal challenge to understand natural variation in vector response to viruses and frame realistic transmission models."
  • "Exposure to heat increases overall Ae. albopictus tolerance to CFAV infection, but the length of the thermal challenge alters mosquito fitness and influences the immunological response to CFAV."
  • "Thermal adaptation includesprofoundand...
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9 months ago
15 minutes

Vector Signals
Bunyavirus NSm: Key to Transmission Between Vertebrates and Mosquitoes (January 2025)

Briefing Document: NSm Protein's Critical Role in Bunyavirus Transmission


Citation: Terhzaz, S., Kerrigan, D., Almire, F. et al. NSm is a critical determinant for bunyavirus transmission between vertebrate and mosquito hosts. Nat Commun 16, 1214 (2025). https://doi.org/10.1038/s41467-024-54809-7

Date: Received - 03 May 2024 | Accepted - 21 November 2024 | Published - 31 January 2025

Prepared for: Saleh Lab


Key Themes:

  • NSm as a Unique Feature of Vector-Borne Bunyaviruses: The study establishes a strong correlation between the presence of the non-structural protein NSm and the ability of bunyaviruses to be transmitted by arthropod vectors (arboviruses). Non-arboviral bunyaviruses do not encode NSm.
  • NSm's Dispensability in Monolayer Cell Cultures: While essential for in vivo transmission, NSm is shown to be largely dispensable for viral replication in both mammalian and mosquito cell lines in vitro.
  • NSm's Crucial Role in Mosquito Midgut Infection and Dissemination: The research demonstrates that NSm is absolutely required for Bunyamwera virus (BUNV) to successfully infect the female Aedes aegypti mosquito following a blood meal. Specifically, it is critical for cell-to-cell spread and egress from the mosquito midgut, a major barrier to viral infection.
  • Midgut-Specific Requirement: The necessity of NSm is specific to the midgut. When this barrier is bypassed through intrathoracic injection, the NSm deletion mutant (BUN-ΔNSm) can effectively infect other mosquito tissues, including the salivary glands, and be transmitted in saliva.
  • NSm Facilitates Infection Foci Formation: In the midgut, BUNV-wt infection leads to the formation of large clusters of infected cells (infection foci), while BUN-ΔNSm remains confined to initially infected cells and fails to spread.
  • NSm Acts Early and Transiently at the Periphery of Infection Foci: Immunocytochemistry reveals that NSm protein is localized mainly at the periphery of infection foci in the midgut, suggesting an early and transient role in spreading to neighboring cells. It is also found on the surface of infected cells and at cell junctions.
  • Convergent Evolution of NSm: Phylogenetic analysis suggests that NSm has likely been acquired independently multiple times during the evolution of different bunyavirus families, indicating convergent evolution driven by the selective pressure of vector-borne transmission.
  • Implications for Vaccine Development: The identification of NSm as a critical determinant for mosquito infection and transmission suggests that viruses lacking NSm could be promising candidates for live-attenuated vaccines against mosquito-borne bunyaviruses, as they would have a reduced risk of spillover in vectors.

Most Important Ideas and Facts:

  • Exclusive Presence in Arboviruses: "Interestingly, this revealed a strong correlation between the presence of NSm and bunyaviruses vectored by arthropods (Fig. 1). Indeed, NSm is present in arbo-bunyaviruses only and all bunyaviruses transmitted by arthropods encode an NSm protein..." This highlights NSm as a potential signature for vector-borne transmission within the Bunyavirales order.
  • Dispensable for In Vitro Replication: "Across all the cell lines tested (Fig. S2b), the growth curves of BUNV wild type (BUNV-wt) and BUN-ΔNSm were not significantly different, showing that NSm is not required for viral repli-cation in mosquito cells." This indicates that NSm's function is specific to the in vivo environment of the mosquito.
  • Essential for Midgut Infection and Dissemination: "Taken together, these results revealed the crucial role of BUNV NSm in vivo as the deletion of NSm alone was sufficient to nearly abolish midgut infection and dissemination in the Ae. aegypti mosquito." This is the central finding of the study, establishing NSm's role in overcoming midgut barriers.
  • Midgut Bypass Eliminates NSm Requirement: "...we did not observe differences in the salivary glands at 3 and 9dpi, indicating that both BUNV-wt and BUN-ΔNSm equally disseminated to and infected the salivary glands, when bypassing the midgut barrier through intra-thoracic inoculation." This confirms that NSm's primary function in vivo is related to traversing the midgut.
  • Failure of Cell-to-Cell Spread in ΔNSm Virus: "By contrast, only a small number of individual midgut cells were positive for the viral N antigen at 72 h pbm after BUN-ΔNSm infection, showing that BUN-ΔNSm stays confined in the initially infected cells and does not spread to neighbouring cells to form large foci." This pinpoints the specific stage of infection where NSm is required.
  • Rescue of ΔNSm Phenotype by NSm Expression: "Taken together, our data show that the ectopic expression of the NSm gene significantly res-cued BUN-ΔNSm infection in Ae. aegypti, demonstrating that BUNV NSm is a crucial viral determinant necessary for the successful spread of infection in the mosquito midgut." This provides strong evidence that the observed defects are directly attributable to the absence of NSm.
  • NSm Localization at Infection Foci Periphery: "...the NSm protein was detected mainly at the periphery of foci (Fig. 7c–f, Fig. S5a, b), showing higher levels of expression in newly infected cells in these clusters." This suggests a dynamic role for NSm during the spread of infection.
  • Convergent Evolution Implication: "As NSm is present in bunyaviruses belonging to only a few viral genera, and which are dispersed across phylogenetically distinct families12, the 'law of parsimony' supports a convergent evolution with independent and repeated acquisitions of NSm in bunyaviruses." This highlights the evolutionary importance of NSm for arboviral transmission.

Quotes:

  • "Here we show that only vector-borne bunyaviruses express a non-structural protein, NSm, whose function has so far remained largely elusive."
  • "Using as experimental system Bunyamwera virus (BUNV) and its invertebrate host, Aedes aegypti, we show that NSm is dis-pensable for viral replication in mosquito cells in vitro but is absolutely required for successful infection in the female mosquito following a blood meal."
  • "More specifically, NSm is required for cell-to-cell spread and egress from the mosquito midgut, a known barrier to viral infection."
  • "Notably, the requirement for NSm is specific to the midgut; bypassing this barrier by experimental intrathoracic infection of the mosquito eliminates the necessity of NSm for virus spread in other tissues, including the salivary glands."
  • "Overall, we unveiled a key evolutionary process that allows the transmission of vector-borne bunyaviruses between arthropod and vertebrate hosts."
  • "Our study reveals that NSm was acquired during the evolution of vector-borne bunyaviruses, and it is a critical determinant allowing virus transmission between vertebrate and arthropod hosts."
  • "Thus, our findings demonstrate that the NSm protein is involved in cell-to-cell spread specifically in themidgut and it is therefore a key viral determinant for successful infection of bunya-viruses transmitted via a blood meal."
  • "Since live-attenuated vaccine strains against arboviruses should not spillover in the vectors... the elucidation of the function of NSm as a crucial viral determinant for mosquito...
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9 months ago
19 minutes

Vector Signals
Zika Virus Alters Human Skin to Attract Mosquito Vectors (January 2025)

Detailed Briefing Document: Zika Virus Modulation of Human Fibroblasts Enhances Transmission Success

Source: Mozūraitis, R., Cirksena, K., Raftari, M., et al. (2025). Zika virus modulates human fibroblasts to enhance transmission success in a controlled lab-setting. Communications Biology, 8(1), 754. https://doi.org/10.1038/s42003-025-07543-9

Date of Briefing: Received - 02 July 2024 | Accepted - 14 January 2025 | Published - 30 January 2025


1. Executive Summary:

This study investigates how Zika virus (ZIKV) infection of human dermal fibroblasts alters the release of volatile organic compounds (VOCs) and how these changes impact the host-seeking and feeding behavior of its mosquito vector, Aedes aegypti. The researchers demonstrate that ZIKV infection leads to significant alterations in the VOC profile of infected fibroblasts at both the invasion and transmission stages. These altered VOCs enhance the attraction of Ae. aegypti mosquitoes, increase their blood meal size, and even positively influence mosquito fecundity and survival. Furthermore, the study utilizes transcriptomic and proteomic meta-analyses to reveal that ZIKV infection modulates the expression of genes and proteins involved in lipid metabolism and transport in human host cells, potentially driving the observed changes in VOC production. The findings suggest that ZIKV actively manipulates its vertebrate host to promote its transmission by enhancing the attractiveness and feeding efficiency of its mosquito vector.

2. Main Themes and Important Ideas/Facts:

  • ZIKV alters the VOC profile of infected human dermal fibroblasts:
  • The study found significant differences in the VOCs released by human dermal fibroblasts when infected with ZIKV compared to uninfected cells.
  • At the invasion stage of ZIKV infection, fourteen VOCs were significantly increased, with the largest increase observed for 2,4-dimethyl-1-heptane. Five VOCs were significantly decreased.
  • At the transmission stage, all eight significantly altered VOCs were increased compared to healthy cells. The largest increases were seen in sulcatone, decanal, dodecanal, and 2-methyl-1-pentene.
  • Quote: "We found that ZIKV infection altered the volatome of human dermal fibroblasts (Supplementary Fig. 1a, c, SupplementaryTable 1, and SupplementaryData file 1)."
  • ZIKV-induced VOCs enhance Ae. aegypti host-seeking behavior:
  • Using a Y-tube olfactometer, the researchers demonstrated that synthetic blends of VOCs mimicking those emitted by ZIKV-infected fibroblasts at both invasion and transmission stages significantly attracted Ae. aegypti females.
  • Notably, Anopheles gambiae (a mosquito species that does not transmit ZIKV) did not show a preference for these blends.
  • Wind tunnel experiments with individual synthetic VOCs and blends confirmed the increased attractiveness of ZIKV-related odors to Ae. aegypti. Dodecanal, 2-methyl-1-pentene, and 4-methylheptane showed the highest single-compound efficiency.
  • Quote: "Using a Y-tube olfactometer, we demonstrated that olfactory active volatiles tested in the blends representing emissions from fibroblasts infected with ZIKV at invasive (invasion blend) and transmission (transmission blend) stages significantly attracted Ae. aegypti females."
  • ZIKV-induced VOCs increase Ae. aegypti blood-feeding behavior:
  • Mosquitoes exposed to ZIKV-related odor blends (both invasion and transmission) took significantly larger blood meals compared to those exposed to blood alone. Blood meal size was more than doubled with the invasion blend and tripled with the transmission blend.
  • A higher proportion of mosquitoes exhibited persistent feeding behavior (landing and feeding) when ZIKV-related odors were present near the blood source.
  • Quote: "The invasion and transmission blends modified the blood-feeding behaviour of mated five to sevendays old Ae. aegypti females, as the amount of blood meal obtained by females were more than doubled and tripled when fed on blood with nearby located invasion and transmission blends, respectively, compared to control blood in the absence of ZIKV related-odour."
  • ZIKV-induced VOCs enhance mosquito fitness (fecundity and survival):
  • The study found that exposure to ZIKV-related odors not only increased blood meal size but also positively impacted mosquito fecundity (number of eggs laid) and survival.
  • Quote: "Interestingly, both mosquito fecundity and survival were also enhanced by the ZIKV induced odour (Fig. 3f, g)."
  • ZIKV manipulates host cell's transcriptome and proteome:
  • RNA sequencing analysis of infected fibroblasts revealed significant alterations in the expression of 401 transcripts, with the largest changes observed at 24 hours post-infection (transmission stage). Enrichment analysis pointed towards antiviral defense mechanisms and changes in lipoprotein metabolic processes.
  • Meta-proteome analysis of multiple published studies identified 2,801 enzymes affected by ZIKV infection, with enrichment observed in enzymes involved in response to oxidative stress and fatty acid derivative metabolic processes.
  • Specifically, enzymes associated with the oxidative and reductive degradation of lipids and fatty acids, potentially leading to the production of the identified VOCs, were upregulated upon ZIKV infection.
  • Quote: "In sum, -omics meta-analyses reveal ZIKV-induced upregulation of lipoprotein and lipid metabolism enzymes that potentially are linked to Virus Induced Mosquito Attractant (VIMA)-VOCs release."
  • Potential mechanisms for VOC production:
  • The researchers suggest that the increased emission of oxidized compounds (alcohols and carbonyls) is likely associated with induced oxidative stress during viral infection.
  • Hydrocarbons are likely produced by oxidative fragmentation of lipids.
  • The study identifies potential enzymes involved in fatty acid metabolism and modification, including those responsible for methyl branching and the formation of alkanes and alkenes, although the complete biosynthetic pathway remains to be fully elucidated in human fibroblasts.
  • The increased expression of apolipoprotein L genes during the transmission stage might indirectly contribute to the enhanced feeding persistency of mosquitoes by increasing lipid transport and fragmentation.
  • Implications for arbovirus transmission and control:
  • The study highlights a novel mechanism by which an arbovirus manipulates its vertebrate host to enhance its transmission success by making the host more attractive to the vector and increasing the likelihood of a successful blood meal.
  • The findings suggest potential for developing novel vector control strategies, such as using the identified attractive VOCs for baiting and lethal trapping of Ae. aegypti mosquitoes.
  • Quote: "There are potentially profound implications of this previously unknown set of arboviral manipulations of its vertebrate host in manners that provoke transmission-enhancing behaviours in its invertebrate host. Among these are exploitation against arboviral transmission success by efficient baiting and lethal trapping as a more effective, sustainable, and environmentally benign approach to the very difficult problem of mosquito control."

3. Methodology:

The study employed a multi-faceted approach, including:

  • In vitro...
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9 months ago
19 minutes

Vector Signals
Mosquito Hsf1-sHsp Cascade: A Pan-Antiviral Defense (January 2025)

Briefing Document: Pan-Antiviral Activity of the Hsf1-sHsp Cascade in Mosquito Cells


Source: Qu, J., Schinkel, M., Chiggiato, L., Machado, S. R., Overheul, G. J., Miesen, P., & van Rij, R. P. (2025). The Hsf1-sHsp cascade has pan-antiviral activity in mosquito cells. Nature Communications Biology, 8(1), 74. https://doi.org/10.1038/s42003-024-07435-4

Date: Received - 05 July 2023 | Accepted - 20 December 2024 | Published - 25 January 2025


1. Executive Summary:

This research paper investigates the antiviral immune responses in Aedes aegypti mosquitoes, a primary vector for several arboviruses. Through multi-omics data integration, the study identifies a novel early-responsive antiviral cascade involving heat shock factor 1 (Hsf1) and a cluster of eight small heat shock protein (sHsp) genes. This "Hsf1-sHsp cascade" demonstrates pan-antiviral activity against multiple arboviruses, including chikungunya, Sindbis, dengue, and the insect-specific Agua Salud alphavirus in Ae. aegypti cells, and also against chikungunya and O’nyong-nyong viruses in other mosquito species (Aedes albopictus and Anopheles gambiae cells). The findings suggest that Hsf1 could be a promising target for developing novel intervention strategies to limit arbovirus transmission by mosquitoes.

2. Main Themes and Important Ideas:

  • Identification of a Novel Antiviral Cascade: The study reveals a previously uncharacterized early immune response in Ae. aegypti cells triggered by chikungunya virus (CHIKV) infection. This response involves the transcription factor Hsf1 activating the expression of eight sHsp genes located within a single topologically associated domain (TAD) in the mosquito genome.
  • "By integrating multi-omics data, we find that heat shock factor 1 (Hsf1) regulates eight small heat shock protein (sHsp) genes within one topologically associated domain in the genome of the Aedes aegypti mosquito."
  • Hsf1 Drives Early sHsp Expression: RNA-seq and chromatin profiling data indicate that Hsf1 binds to the promoter regions of these eight sHsp genes, leading to their rapid upregulation upon CHIKV infection. RNAi-mediated silencing of Hsf1 significantly diminished the induction of all eight sHsps, confirming its regulatory role.
  • "We found the DNA binding motif of the transcription factor heat shock factor 1 (Hsf1) to be highly enriched at promoter regions of these eight sHsp genes..."
  • "Hence, the Hsf1-sHsp cascade functions as an early transcriptional response to CHIKV infection in Aag2 cells."
  • The Hsf1-sHsp Cascade Exhibits Anti-CHIKV Activity: Silencing either Hsf1 or all eight sHsp genes using RNAi resulted in elevated CHIKV RNA levels in Ae. aegypti cells, indicating that this cascade plays a role in suppressing CHIKV replication.
  • "To explore the antiviral potential of the identified Hsf1-sHsp axis, we silenced Hsf1 using RNAi and observed elevated CHIKV RNA levels at 8 hpi..."
  • "...we therefore used two sets of dsRNA targeting the conserved Hsp20 domain to knock down all eight sHsp genes and observed significantly increased CHIKV RNA copies at 8 hpi..."
  • Modulation of Hsf1 Activity Impacts CHIKV Replication: Using a pharmacological inhibitor (KRIBB11) of Hsf1 led to increased CHIKV replication, while an activator (hsfa1) resulted in a significant reduction in viral RNA levels. Interestingly, DTHIB, reported as a human Hsf1 inhibitor, acted as an activator in mosquito cells and also repressed CHIKV replication, further supporting the antiviral role of the sHsps.
  • "KRIBB11 treatment significantly downregulated most sHsp genes after 12 h...led to more than 5-fold increase of viral RNA levels in Aag2 cells..."
  • "Hsfa1 treatment significantly increased Hsf1 expression and strongly activated all eight sHsp genes, leading to about a 25-fold reduction in CHIKV copies at 12 hpi..."
  • The Cascade Targets an Early Post-Entry Stage of Viral Replication: Time-of-addition assays with the Hsf1 activator and inhibitor suggest that the Hsf1-sHsp cascade interferes with an early stage of the CHIKV replication cycle, occurring around 4 hours post-infection, after virus entry but before significant RNA replication.
  • "When the Hsf activator hsf1a was added at time points before inoculation and up to 4 hpi, CHIKV replication was strongly inhibited..."
  • "This indicates that the Hsf1-sHsp cascade interacts with the early stage of CHIKV RNA replication but does not affect subsequent stages."
  • Pan-Antiviral Activity Across Multiple Arboviruses and Mosquito Species: The study demonstrates that the Hsf1-sHsp cascade is not specific to CHIKV. Activation of Hsf1 with hsfa1 reduced replication of Sindbis virus (SINV), Agua Salud alphavirus (ASALV), and dengue virus (DENV) in Ae. aegypti cells. Furthermore, activating the cascade showed antiviral effects against CHIKV in Aedes albopictus cells and the RNAi-deficient C6/36 cells, and against O’nyong-nyong virus (ONNV) in Anopheles gambiae cells.
  • "Consistently, KRIBB11 treatment led to increased virus replication for SINV and ASALV, whereas hsfa1 treatment significantly reduced virus replication for SINV, ASALV and DENV..."
  • "The fact that the heat shock response was antiviral in both U4.4 cells and the RNAi-deficient C6/36 cells indicates that the Hsf1-sHsps cascade functions independently of RNAi."
  • Hsf1 as a Potential Target for Intervention: The broad antiviral activity of the Hsf1-sHsp cascade across different arboviruses and mosquito vectors highlights Hsf1 as a promising target for developing novel strategies to block arbovirus transmission at the mosquito stage.
  • "Overall, our work uncovers an antiviral cascade Hsf1-sHsp and identifies Hsf1 as a potential target for developing transmission-blocking strategies against arboviruses at the mosquito stage."
  • "Considering the pan-antiviral activity of the Hsf1-sHsp cascade, our findings may open the way for the development of a broad-spectrum drug to prevent arbovirus transmission."
  • Potential Mechanism of Action: The study suggests that sHsps, known for maintaining protein homeostasis by preventing protein aggregation, might exert their antiviral effects by interacting with conserved viral or host protein complexes involved in early viral replication. Proteomic approaches are proposed to identify sHsp client proteins and elucidate the underlying mechanism.
  • "Our time-of-addition assays suggest that the response inhibits an early post-entry stage of the viral replication cycle."
  • "It has been suggested that sHsps maintain protein homeostasis by binding proteins in non-native conformations, thereby preventing substrate aggregation."

3. Implications and Future Directions:

  • The discovery of the Hsf1-sHsp cascade adds a new layer to our understanding of mosquito antiviral immunity, complementing the well-established role of RNAi and other innate immune pathways.
  • Targeting Hsf1 in mosquitoes could offer a novel, broad-spectrum approach to reduce the transmission of multiple medically important arboviruses. This strategy could potentially be less susceptible to viral resistance mechanisms compared to targeting specific viral proteins.
  • Further research is needed to validate the in vivo relevance of this cascade in whole mosquitoes and to understand the precise molecular mechanisms by which sHsps inhibit viral replication.
  • Investigating the interaction between the Hsf1-sHsp cascade and other m...
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9 months ago
12 minutes

Vector Signals
Toxic Seminal Proteins Reduce Female Insect Lifespan (January 2025)

Briefing Document: "Recombinant venom proteins in insect seminal fluid reduce female lifespan"

Source: Article "Recombinant venom proteins in insect seminal fluid reduce female lifespan" by Samuel J. Beach & Maciej Maselko, published in Nature Communications (DOI: 10.1038/s41467-024-54863-1).

Date: Current date (based on when the briefing document is created).

Prepared for: [Intended Audience - e.g., Pest Management Stakeholders, Research Community, Regulatory Bodies]

Executive Summary:

This research presents a novel genetic biocontrol technology termed the "toxic male technique" (TMT). The study demonstrates, using Drosophila melanogaster as a model, that genetically engineering males to express insecticidal venom proteins within their seminal fluid, which are then transferred to females during mating, significantly reduces the lifespan of the mated females. This intragenerational approach contrasts with existing mating-based genetic biocontrol technologies that primarily focus on reducing offspring viability or skewing sex ratios. Agent-based modeling of Aedes aegypti suggests that TMT has the potential to be significantly more effective in rapidly reducing blood-feeding rates, a key factor in disease transmission, compared to leading intergenerational biocontrol methods like female-specific Release of Insects carrying a Dominant Lethal gene (fsRIDL). TMT offers a promising avenue for rapidly controlling outbreaks of disease vectors and agricultural pests with potentially reduced reliance on chemical insecticides and lower risks of transgene persistence compared to gene drive technologies.

Main Themes and Important Ideas/Facts:

  • The Need for Alternative Pest Management Tools:
  • The emergence of insecticide resistance is a major challenge.
  • Current genetic biocontrol technologies (GBTs) have limitations, particularly a generational lag in their impact, leaving mated females capable of causing harm (e.g., disease transmission) in the interim.
  • The study highlights the significant human and economic costs associated with insect pests and the negative impacts of widespread insecticide use on non-target species and the environment.
  • "The emergence of insecticide resistance has increased the need for alternative pest management tools."
  • Introducing Intragenerational Genetic Biocontrol: The Toxic Male Technique (TMT):
  • TMT aims to directly reduce the lifespan of mated females by expressing toxic proteins in the male reproductive tract (male accessory glands - MAG) that are transferred during mating.
  • This is presented as the "first example of an intragenerational GBT."
  • "Here we describe the toxic male technique (TMT), which is—to the best of our knowledge—the first example of an intragenerational GBT. By genetically engineering pest species to express toxic, low molecular weight compounds within the MAG, the survival of mated females can be reduced (Fig. 1)."
  • Proof of Concept in Drosophila melanogaster:
  • Seven insect-specific venom proteins were selected based on criteria including invertebrate specificity, low mammalian toxicity, and low molecular weight.
  • MAG-specific expression was achieved using the antr-GAL4 driver in the UAS/GAL4 system.
  • Mating with males expressing Γ-CNTX-Pn1a (from a spider) or δ-AITX-Avd2a (from a sea anemone) significantly reduced the median lifespan of wild-type females by 37-64% compared to controls.
  • Increasing the ratio of TMT males to females (3:1) resulted in an even greater reduction in female lifespan (50% and 64% respectively).
  • "The median lifespans of wild-type females mated to two of the TMT strains are reduced by 37–64% after initial exposure compared to control females mated to wild type males."
  • Functionality and Specificity of Recombinant Venoms:
  • Functionality of the venom proteins was confirmed through ubiquitous expression assays, where functional venoms resulted in non-viable offspring.
  • The antr-GAL4 driver showed strong and specific expression in the male accessory glands with minimal off-target expression.
  • Single-pair courtship assays indicated that TMT males were able to court females as effectively as wild-type males, suggesting no significant impact on mating behavior.
  • However, competitive mating assays revealed reduced competitiveness of the transgenic males likely due to the GAL4-UAS genetic background.
  • Modeling the Impact on Aedes aegypti Populations:
  • Agent-based models simulating Aedes aegypti release programs compared TMT to SIT and fsRIDL.
  • The model predicted that TMT could reduce blood-feeding rates by a further 40-60% during release periods compared to fsRIDL.
  • TMT achieved faster population reduction (PR50 and PR95) compared to fsRIDL in the simulations.
  • The median number of gonotrophic cycles (related to disease transmission potential) was significantly lower in the TMT simulations.
  • "Agent-based models of Aedes aegypti predict that TMT could reduce rates of blood feeding by a further 40 – 60% during release periods compared to leading biocontrol technologies like fsRIDL."
  • Impact of Mating Lethality and Male Sterility in Models:
  • Simulations exploring reduced mating lethality showed that fertile TMT males required ≥80% mating lethality to outperform fsRIDL in reducing blood-feeding.
  • Sterile TMT males (combined with a sterility mechanism) only required ≥40% mating lethality to outperform fsRIDL.
  • This highlights the potential benefit of combining TMT with male sterilization to prevent transgene escape.
  • Sensitivity Analysis of Model Parameters:
  • Sensitivity analysis revealed that polyandry (multiple mating by females) and release ratio of TMT males had significant positive effects on TMT's relative performance.
  • Density-dependent mortality had a negative effect, although this could be mitigated by increased release ratios.
  • Higher rates of polyandry are predicted to enhance the effectiveness of TMT.
  • Potential and Future Directions of TMT:
  • TMT offers a rapid response to pest outbreaks, making it a potential alternative to chemical pesticides as a first-line response.
  • The taxonomic selectivity of venom proteins allows for targeted pest control.
  • Co-expression of multiple toxins could help prevent resistance.
  • Future research needs to focus on identifying optimal venom proteins (considering molecular weight and toxicity), improving expression levels, and engineering stable, conditional expression systems for mass rearing.
  • Determining the mating competitiveness of TMT males in target species under wild-type genetic backgrounds is crucial.
  • Further studies are needed to understand the epidemiological effects and the impact on non-target organisms.
  • "TMT is inherently self-limiting due to strong selection pressure against venom expression, which maybe advantageous from a regulatory perspective as, unlike GBT such as gene drives, there is little risk of substantial transgene introgression into non-target populations, and TMT transgenes are predicted to be rapidly lost from all populations in the absence of ongoing releases."

Quotes:

  • "Here, we demonstrate intra-generational genetic biocontrol, wherein mating with engineered males reduces female lifespan."
  • "The toxic male technique (TMT) involves the heterologous expres...
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10 months ago
21 minutes

Vector Signals
A private, AI-curated podcast delivering 15-20 minute deep dives into the latest Nature articles on mosquito-borne viruses and AI-driven therapeutic breakthroughs. Designed for the researchers of the Saleh Lab at Institut Pasteur, each episode distills cutting-edge science into accessible insights—so you can stay current, even during your busiest bench days.