Exposure to West Nile Virus Increases Bacterial Diversity and Immune Gene Expression in Culex pipiens.

Steven Zink,Laura Kramer,Greta Van Slyke,Michael Palumbo,Alexander Ciota

doi:10.3390/v7102886

Abstract

Complex interactions between microbial residents of mosquitoes and arboviruses are likely to influence many aspects of vectorial capacity and could potentially have profound effects on patterns of arbovirus transmission. Such interactions have not been well studied for West Nile virus (WNV; Flaviviridae, Flavivirus) and Culex spp. mosquitoes. We utilized next-generation sequencing of 16S ribosomal RNA bacterial genes derived from Culex pipiens Linnaeus following WNV exposure and/or infection and compared bacterial populations and broad immune responses to unexposed mosquitoes. Our results demonstrate that WNV infection increases the diversity of bacterial populations and is associated with up-regulation of classical invertebrate immune pathways including RNA interference (RNAi), Toll, and Jak-STAT (Janus kinase-Signal Transducer and Activator of Transcription). In addition, WNV exposure alone, without the establishment of infection, results in similar alterations to microbial and immune signatures, although to a lesser extent. Multiple bacterial genera were found in greater abundance in WNV-exposed and/or infected mosquitoes, yet the most consistent and notable was the genus Serratia.

Highlights

West Nile virus (WNV; Flaviviridae, Flavivirus) is the most prevalent arthropod-borne virus in the U.S and the most geographically widespread arbovirus in the world
Experimental treatment was not associated with distinct phylogenetic signatures (Supplementary Figure S1), increased bacterial diversity was associated with WNV exposure and further elevated with WNV infection (Table 1; Supplementary Figure S2)
While just 0.36% of UNEXP sequences were identified as Serratia, 7.8% and 8.7% of the reads from WNVand WNV+ were identified as Serratia, respectively, representing a greater than 20-fold increase in proportion in WNV exposed groups relative to the UNEXP group

Summary

Introduction

West Nile virus (WNV; Flaviviridae, Flavivirus) is the most prevalent arthropod-borne virus (arbovirus) in the U.S and the most geographically widespread arbovirus in the world. The majority of WNV infections go undiagnosed, over 40,000 cases of disease and 1400 deaths have been attributed to WNV over the last 15 years in the U.S WNV is maintained in nature in an enzootic cycle between Culex spp. mosquitoes and birds. While the essential function of the nutrient rich blood meal is to facilitate egg development, it results in substantial alterations to microbial diversity and load [12]. These microbial alterations are, inherently bound to arbovirus exposure and infection

Methods

Results

Conclusion