Insulin/insulin growth factor signaling (IIS) pathway modulates immunity in Anopheles stephensi mosquitoes following bacterial infection

Abstract

Malaria remains one of the most devastating diseases worldwide, causing 450,000 deaths every year. Given the lack of an effective vaccine against Plasmodium and the increased resistance of this parasite to the current drugs and of Anopheles mosquitoes to insecticides, there is an urgent need for the development of novel control strategies to control malaria's transmission. The insulin/insulin growth factor signaling (IIS) pathway is highly conserved and has shown to regulate lifespan, metabolism, immunity and pathogen resistance. We previously showed that overexpression of Akt, a key molecule of the IIS in the fat body of Anopheles stephensi, extended lifespan and had no impact on reproduction for the first and second reproductive cycle. To further explore the role of IIS beyond lifespan and reproduction, we looked to determine IIS's role in controlling immunity by analyzing the antimicrobial transcript expression in young transgenic females compared to non-transgenic females in response to infection with E. coli and B. subtilus. We also analyzed the survival rate of both transgenic and non-transgenic mosquitoes in in response to infection with E. coli and B. subtilus. We observed that IIS influenced mosquito antimicrobial transcript gene expression and mortality rate in response to E. coli and B. subtilus. Our data suggested that overexpression of the IIS in a mosquito’s fat body altered innate immunity genes and the mosquito’s survival rate.