Exploring the tripartite interaction of Aedes aegypti, arboviruses and Wolbachia: effects on mosquito biology and maintenance of virus-blocking phenotype

• Applicant: Professor Dr. Rafael Maciel-de-Freitas, Ph.D.
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens ; Virology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462609027

The Aedes aegypti (Diptera: Culicidae) mosquito is the primary vector of arboviruses as dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV). Traditional vector control methods have limited efficacy, what makes the development of supplementary approaches continuously encouraged. Wolbachia is a maternally inherited endosymbiont that when transinfected into Ae. aegypti is able to block the aforementioned arboviruses. The deployment of Ae. aegypti transinfected with the Wolbachia strains wMel (from Drosophila melanogaster) or wAlbB (from Ae. albopictus) are ongoing in 14 countries simultaneously. The aim is to replace natural populations highly competent to arboviruses by Wolbachia-infected individuals with reduced vector competence. The principal aim of this research project is to explore the tripartite interaction of mosquito-viruses-Wolbachia by three specific objectives, using wild, wMel and wAlbB Ae. aegypti. In Aim1 we will investigate whether Wolbachia influences the reproductive tactics of Ae. aegypti. Life-history traits of blood-fed females as wing length (using a grade slide in millimeters), blood meal size (by quantification of hematin on feces after producing a standard curve with known amounts of hematin), mean egg mass (weighted individually in a precision balance), number of eggs and Wolbachia density (RT-qPCR) will be compared among groups using a path analysis to discern the causal direction of effects. In Aim2, we will estimate the Wolbachia blocking ability to DENV, ZIKV and CHIKV at fluctuating temperature of 21 +/- 5 oC and 27 +/- 5 oC. At 7 and14 dpi, the (a) infection rate (proportion of females with infected bodies); (b) dissemination rate (proportion of females with infectious heads); (c) transmission rate (proportion of females with infectious viral particles in saliva), and (d) transmission efficiency (proportion of females with virus in saliva among all those orally challenged) will be assessed for each combination. Around 20-30% of Wolbachia-infected Ae. aegypti still salivate DENV particles, despite the presence of Wolbachia in high densities at the salivary gland, i.e., DENV leaks through saliva in around one quarter of Wolbachia-infected Ae. aegypti. In Aim3 we will test whether Wolbachia presence can differently affect the diversity of DENV quasispecies through the analysis of saliva at 14dpi of Wolbachia-infected and non-infected (wild) mosquitoes. Next-Generation Sequencing analysis of full-length viral genome variants of DENV before a blood meal and after salivation will also be analyzed among wild, wMel and wAlbB to infer whether Wolbachia would act as a biological filter and select specific variants of DENV. By collecting such information for the first time, we will investigate research gaps on the tripartite interactions involving Ae. aegypti, three different arboviruses and two Wolbachia strains aiming to better understand how host phenotype and disease transmission can be shaped by the endosymbiont bact

• DFG Programme: Research Grants