Nutrition impacts tolerance and resistance to bacterial infection in Aedes aegypti mosquitoes

Mosquito immunity is comprised of two responses: 1) resistance: the ability to directly limit pathogen levels, and 2) tolerance: the ability to limit the deleterious effects of infection. Immune tolerance is a critical but less well understood defense strategy utilized by disease vector mosquitoes during infection. Further, factors that may influence tradeoffs in resistance and tolerance are not well characterized. Here, we investigated the potential effect of nutrition on resistance and tolerance to E. coli in Aedes aegypti. We hypothesized that varying a mosquito’s sucrose meal (1% or 10%) or blood meal (present or absent) would influence tolerance and/or resistance to bacterial infection. We exposed adult Aedes aegypti females to various blood/sucrose diets, infected individuals with E. coli, then monitored population survival and median bacterial load by homogenizing and culturing mosquitoes over time. We then used a generalized linear model to test the effects of blood, sucrose, time, and bacterial load on survival. We interpreted a significant interaction between any factor and bacterial load to indicate that the factor affected tolerance. We also tested the effects of blood, sucrose, and time on bacterial load. Here, we interpreted any significant main effect to indicate the factor affected resistance. Preliminary analysis revealed that 1% sucrose significantly increases resistance, and a blood meal significantly increases tolerance. To our knowledge, these results are the first to show that blood, a unique nutritional resource, enhances tolerance to infection. Overall, this research will inform a more nuanced understanding of the interplay between insects, diet, and immunity.