A single-cell atlas of theCulex tarsalismidgut during West Nile virus infection

Abstract

The mosquito midgut functions as a key interface between pathogen and vector. However, studies of midgut physiology and associated virus infection dynamics are scarce, and inCulex tarsalis- an extremely efficient vector of West Nile virus (WNV) - nonexistent. We performed single-cell RNA sequencing onCx. tarsalismidguts, defined multiple cell types, and determined whether specific cell types are more permissive to WNV infection. We identified 20 cell states comprised of 8 distinct cell types, consistent with existing descriptions ofDrosophilaandAedes aegyptimidgut physiology. Most midgut cell populations were permissive to WNV infection. However, there were higher levels of WNV RNA (vRNA) in enteroendocrine cells and cells enriched for mitochondrial genes, suggesting enhanced replication in these populations. In contrast, proliferating intestinal stem cell (ISC) populations had the lowest levels of vRNA, a finding consistent with studies suggesting ISC proliferation in the midgut is involved in viral control. Notably, we did not detect significant WNV-infection induced upregulation of canonical mosquito antiviral immune genes (e.g., AGO2, R2D2, etc.) at the whole-midgut level. Rather, we observed a significant positive correlation between immune gene expression levels and vRNA in individual cells, suggesting that within midgut cells, high levels of vRNA may trigger antiviral responses. Our findings establish aCx. tarsalismidgut cell atlas, and provide insight into midgut infection dynamics of WNV by characterizing cell-type specific enhancement/restriction of, and immune response to, infection at the single-cell level.