Three way interactions between Wolbachia, dengue virus, and their host, Aedes aegypti

Many vector-borne diseases, including dengue virus, have no vaccines or specific treatments, leaving vector control as the main tool to fight them. The intracellular bacterium Wolbachia has been proposed as a potential control agent for vector mosquitoes, including Aedes aegypti. Before Wolbachia can be used as a vector control tool, we must better understand the interactions between the bacterium, its host, and the pathogen it targets. We used a variety of techniques to activate or suppress the mosquito immune system, and measured the change in Wolbachia densities in both mosquito ovaries and carcasses using real-time quantitative PCR (qPCR). Simultaneously inducing both the Toll and Imd pathways leads to an increase in ovary Wolbachia densities while repressing the Imd pathway or infection with gram negative bacteria decreases Wolbachia densities in mosquito ovaries. No effects on Wolbachia densities in mosquito carcasses were observed. We also measured how infection by Wolbachia, dengue virus, or both affects the fitness of the mosquito host. Co-infected mosquitoes live longer than mosquitoes infected with only the virus. Neither virus nor Wolbachia infection affected the number of eggs laid or the egg hatch rate. We conclude that the mosquito immune system is can affect Wolbachia infection levels and Wolbachia infection can have a positive effect on mosquito life history, especially when the mosquito is also infected with dengue virus.