-induced inhibition of O'nyong nyong virus in mosquitoes is mediated by Toll signaling and modulated by cholesterol.

Enhanced host immunity and competition for metabolic resources are two main competing hypotheses for the mechanism of -mediated pathogen inhibition in arthropods. Using an mosquito - somatic infection - O'nyong nyong virus (ONNV) model, we demonstrate that the mechanism underpinning -mediated virus inhibition is up-regulation of the Toll innate immune pathway. However, the viral inhibitory properties of were abolished by cholesterol supplementation. This result was due to -dependent cholesterol-mediated suppression of Toll signaling rather than competition for cholesterol between and virus. The inhibitory effect of cholesterol was specific to -infected mosquitoes and cells. These data indicate that both and cholesterol influence Toll immune signaling in mosquitoes in a complex manner and provide a functional link between the host immunity and metabolic competition hypotheses for explaining -mediated pathogen interference in mosquitoes. In addition, these results provide a mechanistic understanding of the mode of action of -induced pathogen blocking in Anophelines, which is critical to evaluate the long-term efficacy of control strategies for malaria and -transmitted arboviruses.