Effect of Wolbachia on replication of West Nile Virus in mosquito cell line and adult mosquitoes

Wolbachia as an endosymbiont is widespread in insects and other arthropods and is best known for reproductive manipulations of the host. Recently, it has been shown that wMelpop and wMel strains of Wolbachia inhibit replication of several RNA viruses, including Dengue virus, and other vector-borne pathogens (e.g. Plasmodium and filarial nematodes) in mosquitoes providing an alternative approach to limit transmission of vector-borne pathogens. In this study, we tested the effect of Wolbachia on the replication of West Nile Virus (WNV). Surprisingly, accumulation of the genomic RNA of WNV for all the three strains of WNV tested (New York 99, Kunjin and New South Wales) was enhanced in Wolbachia-infected Aedes aegypti cells (Aag2). However, the amount of secreted virus was significantly reduced in the presence of Wolbachia. Intrathoracic injections showed that replication of WNV in A. aegypti mosquitoes infected with wMel strain of Wolbachia was not inhibited; while wMelPop strain of Wolbachia significantly reduced replication of WNV in mosquitoes. Further, when wMelPop mosquitoes were orally inoculated with WNV, virus infection, transmission and dissemination rates were very low in Wolbachia-free mosquitoes and these were completely inhibited in the presence of Wolbachia. The results suggest that (i) despite enhancement of viral genomic RNA replication in the Wolbachia-infected cell line, production of secreted virus was significantly inhibited, (ii) the anti-viral effect in intrathoracically-infected mosquitoes depends on the strain of Wolbachia, and (iii) replication of the virus in orally infected mosquitoes was completely inhibited in wMelPop strain of Wolbachia