Wolbachia impacts bluetongue and epizootic hemorrhagic disease virus replication in Culicoides sonorensis midge cells

Biting midges in the genus Culicoides are known to vector a number of veterinary pathogens including Blue Tongue Virus (BTV) and Epizootic Hemorrhagic Disease Virus (EHDV). Many of these pathogens lack effective therapeutic treatments or vaccines and the only effective approach to limit disease transmission is vector control. Current vector control for Culicoides midges is complicated by the biology of many Culicoides species and is not always effective at reducing midge populations and impacting disease transmission. The endosymbiont Wolbachia pipientis may offer an alternative control approach to limit disease transmission by impacting virus proliferation in the insect host. In this presentation, we discuss the transfection and characterization of Culicoides sonorensis cell lines with Wolbachia. In Wolbachia infected cell lines the expression of immune-related genes involved in the regulation of the IMD, Jak-Stat, and Toll innate immune pathways were significantly increased when compared to uninfected control cells, suggesting immune activation upon Wolbachia transfection. Following in vitro infection of Wolbachia infected cells with BTV and EHDV a decrease in virus proliferation was observed.  In addition, virus inoculation in Wolbachia infected cells was associated with a significant increase in expression of immune-regulated genes in BTV infected cells but not EHDV, suggesting specific virus-cell-Wolbachia interactions. We discuss the results in relation to the potential use of Wolbachia to limit transmission of pathogens vectored by Culicoides midges.