Genome Interactions and Malaria transmission Efficiency in Anopheles gambiae – GIME

Anopheles gambiae is the most important vector species of human malaria that kills over one million people each year in sub-Saharan Africa. The malaria situation keeps worsening and there is an urgent need for new and efficient control strategies. The GIME project explores innovative molecular approaches to decipher host-parasite interactions that underlie the vectorial capacity with the ultimate goal to identify new targets to disrupt parasite development within the mosquito. Our project aims at investigating the impact of the mosquito aquatic environment on its vectorial capacity and particularly the role of bacterial communities present in larval habitats and mosquito midguts. The research activities will be achieved through collaboration with multidisciplinary teams, including fundamental research groups and laboratories from malaria endemic countries, thus strengthening tights between research groups from Northern and Southern countries. The GIME proposal will focus at i) characterization of microbiota in the mosquito larval habitats and midguts and ii) examination of the immune status of A. gambiae in natural populations to determine the effect of exposure to microbiota on the mosquito ability to sustain malaria parasite development. Field collections will be performed in malaria endemic areas in Cameroon, where diverse environmental features will be screened. Water samples will be obtained from A. gambiae larval habitats and midguts will be dissected from the mosquitoes breeding in the same sites. We will use the 454 sequencing approach that allows accurate identification of the microbial communities in complex biological samples. Bacteria will be studied for their ability to stably colonize the mosquito midguts. We will further investigate to what extent larval breeding sites impact on the susceptibility of A. gambiae to P. falciparum. For this purpose, we will use natural isolates of P. falciparum to infect field populations of A. gambiae and artificial membrane feeding will be carried out in Cameroon using standardized methodologies. Infected mosquitoes will be dissected 8 days after infection for oocyst counts and parasite quantification using qPCR. Non-parametrical statistical methods will be used for comparison of infection levels between different study sites. A meta-analysis approach will be performed to correlate genome*genome interactions that underlie the mosquito capacity to sustain malaria parasite development. The mosquito immune responses will be examined in larvae and adults collected in natural larval habitats of distinct ecological features. Transcriptional analysis of immune genes by qRT-PCR will identify biotic components of the larval habitats that modulate mosquito immunity and impact on vectorial capacity. The GIME project should increase our knowledge on the interactions between the mosquito vector and P. falciparum. These studies, performed mostly in the natural environment, will address the role of microbiota in modulation of the mosquito immune responses. So far, this was mostly addressed in laboratory set-ups using model bacterial species like E. coli and S. aureus, which are not natural mosquito pathogens. Additionally, our results will provide a deeper understanding of understudied larval immune system, particularly on the immune signaling pathways regulating responses against bacteria. We will also determine whether larval immune history affects susceptibility of adults to malaria parasites. Finally, we aim at identifying bacterial species in the mosquito larval habitats that could render females refractory to malaria, thus opening new perspectives for malaria control strategies.