A limited role for autophagy during arbovirus infection of mosquito cells

Abstract

Macroautophagy is an evolutionarily conserved cellular process critical for maintaining cellular homeostasis. It can additionally function as an innate immune response to viral infection as has been demonstrated for a number of arthropod-borne (arbo-) viruses. Arboviruses are maintained in a transmission cycle between vertebrate hosts and invertebrate vectors yet the majority of studies assessing autophagy-arbovirus interactions have been limited to the mammalian host. Therefore we evaluated the role of autophagy during arbovirus infection of the invertebrate vector using the tractable Aag2 Aedes aegypti mosquito cell culture system. Our data demonstrates that autophagy is significantly induced in mosquito cells upon infection with two flaviviruses, dengue virus (DENV) and Zika virus (ZIKV), as well as an unrelated mosquito-borne virus, chikungunya virus (CHIKV; Togaviridae). While assessing the role of autophagy during arbovirus infection, we observed a somewhat paradoxical outcome. Both induction and suppression of autophagy via torin 1 and spautin-1, respectively, resulted in increased viral titers for all three viruses, yet suppression of autophagy-related genes had no effect. Interestingly, chemical modulators of autophagy had either no effect or opposite effects in another widely used mosquito cell line, C6/36 Aedes albopictus cells. Together, our data reveals a limited role for autophagy during arbovirus infection of mosquito cells. Further, our findings suggest that commonly used chemical modulators of autophagy alter mosquito cells in such a way as to promote viral replication; however, it is unclear if this occurs directly through autophagic manipulation or other means.\n\nAuthor SummaryArthropod-borne (arbo) viruses, specifically those transmitted by Aedes aegypti mosquitoes, cause significant morbidity and mortality and pose a continued public health threat worldwide. Many of these viruses lack vaccines or therapeutics and current mosquito control strategies are underperforming. For these reasons, identifying vulnerabilities within the transmission cycle that can be targeted will be critical to the development of novel control interventions. Autophagy is a highly conserved cellular pathway and previous studies manipulating this pathway have shown promise in minimizing viral infections in mammalian hosts. In this study we examined arbovirus-autophagy interactions within vector mosquitoes. The goal was to elucidate the role of autophagy during infection of mosquitoes in hopes of identifying critical interactions that can be targeted by novel approaches to block infection of and transmission by vector mosquitoes.