Wolbachia wAlbB inhibit dengue and Zika infection in the mosquito Aedes aegypti with an Australian background

Abstract

Biological control of mosquito vectors using the insect-specific bacteria Wolbachia is an emerging strategy for the management of human arboviral diseases. We recently described the development of a strain of Ae. aegypti infected with the Wolbachia strain wAlbB (referred to as the wAlbB2-F4 strain) through simple backcrossing of wild type Australian mosquitoes with a wAlbB infected Ae. aegypti strain from the USA. Field releases of male wAlbB2-F4 mosquitoes resulted in the successful suppression of a wild population of mosquitoes in the trial sites by exploiting the strains Wolbachia-induced cytoplasmic incompatibility. We now demonstrate that the strain is resistant to infection by dengue and Zika viruses and is genetically similar to endemic Queensland populations. There was a fourfold reduction in the proportion of wAlbB2-F4 mosquitoes that became infected following a blood meal containing dengue 2 virus (16.7%) compared to wild type mosquitoes (69.2%) and a 6-7 fold reduction in the proportion of wAlbB2-F4 mosquitoes producing virus in saliva following a blood meal containing an epidemic strain of Zika virus (8.7% in comparison to 58.3% in wild type mosquitoes). Restriction-site Associated DNA (RAD) sequencing revealed that wAlbB2-F4 mosquitoes have > 98% Australian ancestry, confirming the successful introduction of the wAlbB2 infection into the Australian genomic background through backcrossing. Genotypic and phenotypic analyses showed the wAlbB2-F4 strain retains the insecticide susceptibility phenotype and genotype of the Australian mosquitoes. We demonstrate that the Wolbachia wAlbB2-F4, in addition to being suitable for suppression programs, can be effective in population replacement programs given its high inhibition of virus infection in mosquitoes. The ease at which a target mosquito population can be transfected with wAlbB2, while retaining genotypes and phenotypes of the target population, shows the robustness of this strain as a biocontrol agent against the Ae. aegypti mosquito itself as well as the pathogens it transmits. IMPORTANCEEpidemics of arthopod-borne virus (arbovirus) diseases affect millions of people and are becoming more frequent and widespread. A successful strategy to control these diseases is by infecting mosquito populations with benign, insect-specific Wolbachia bacteria that render mosquitoes refractory to infection with pathogenic arboviruses. Here we show that a strain of the major mosquito vector Ae. aegypti that was infected with Wolbachia following a simple back-cross mating procedure is refractory to infection with dengue and Zika viruses. Importantly, the genetic background of the strain is equivalent to the target population, which is important for persistence of the strain and regulatory approval.