Linking mosquito midgut and virus population biology at the molecular and cellular level
Date
2024
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Abstract
Vector competence (VC) refers to the efficiency of pathogen transmission by vectors. Each step in infection of a mosquito vector constitutes a barrier to transmission that may impose bottlenecks on virus populations. West Nile virus (WNV) is maintained by multiple mosquito species with varying VC. However, the extent that bottlenecks and VC are linked is poorly understood. Similarly, quantitative analyses of mosquito-imposed bottlenecks on virus populations are limited. We used molecularly barcoded WNV to quantify tissue-associated population bottlenecks in three variably competent WNV vectors. Our results confirm strong population bottlenecks during mosquito infection that are capable of dramatically reshaping virus population structure in a nonselective manner. In addition, we found that mosquitoes with differing VC uniquely shape WNV population structure: highly competent vectors are more likely to contribute to the maintenance of rare viral genotypes. These findings have important implications for arbovirus emergence and evolution. The mosquito midgut functions as a key interface between virus and vector. However, studies of midgut physiology and associated virus infection dynamics are scarce, and in Culex tarsalis - the primary vector of West Nile virus (WNV) in the contiguous United States - nonexistent. We performed single-cell RNA sequencing on dissociated, WNV-infected Cx. tarsalis midguts. We identified populations of distinct midgut cell-types consistent with existing descriptions of insect midgut physiology and found that all midgut cell populations were permissive to WNV infection. However, we observed high levels of viral RNA suggesting enhanced replication in enteroendocrine cells and cells enriched for mitochondrial genes. In addition, we found no significant upregulation of mosquito immune genes associated with WNV infection at the whole-midgut level, rather, a significant positive correlation between immune gene expression and WNV viral RNA load at the individual cell level. These findings illuminate the midgut infection dynamics of WNV, providing insight into cell-type specific enhancement of, and immune response to, WNV infection in a primary vector.
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Embargo expires: 05/20/2025.
Subject
vector biology
infectious disease
virus evolution