Wolbachia strain wAu differs in cellular perturbation and virus inhibition profiles from previously characterised Wolbachia strains

Abstract Some strains of the inherited bacterium Wolbachia have been shown to be effective at reducing the transmission of dengue and other positive-sense RNA viruses by Aedes aegypti in both laboratory and field settings and are being deployed for dengue control. The degree of virus inhibition varies between Wolbachia strains; density and tissue tropism can contribute to these differences but there are also indications that this is not the only factor involved: for example, strains wAu and wAlbA are maintained at similar densities but only wAu produces strong dengue inhibition. We previously reported perturbations in lipid transport dynamics, including sequestration of cholesterol in lipid droplets, with strains wMel / wMelPop in Ae. aegypti. Here we show that strain wAu does not produce the same cholesterol sequestration phenotype despite displaying strong virus inhibition and moreover, in contrast to wMel, wAu antiviral activity was not rescued by cyclodextrin treatment. To further investigate the cellular basis underlying these differences, proteomic analysis of midguts was carried out on Ae. aegypti lines and revealed that wAu-carrying midguts showed a distinct proteome when compared to Wolbachia-free, wMel- or wAlbA-carrying midguts, in particular with respect to lipid transport and metabolism. The data suggest a possible role for perturbed RNA processing pathways in wAu virus inhibition. Together these results indicate that wAu shows unique features in its inhibition of arboviruses compared to previously characterized Wolbachia strains. Author Summary Wolbachia endosymbionts can block transmission of dengue virus by Aedes aegypti mosquitoes, and Wolbachia release programs for dengue control are now being undertaken in several countries. Understanding the mechanisms of Wolbachia-mediated antiviral activity is important for maximizing the efficacy of this control approach. Using functional and proteomic analyses, this study indicates that different strains of Wolbachia perturb cellular functions in diverse ways and display different antiviral profiles. These differences raise the possibility that Wolbachia strain switching could be used to counteract viral escape mutations, should they arise and threaten the efficacy of dengue control programmes.