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

Abstract

Biological control of mosquito vectors using the endosymbiotic bacteria Wolbachia is an emerging strategy for the management of human arboviral diseases. We recently described the development of a strain of Aedes 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 wild populations of mosquitoes in the trial sites by exploiting the strain’s 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 susceptible phenotype and genotype of native Australian mosquitoes. We demonstrate that the Wolbachia wAlbB2-F4, in addition to being suitable for population suppression programs, can also be effective in population replacement programs given its inhibition of virus infection in mosquitoes. The ease at which a target mosquito population can be transfected with wAlbB2, while retaining the genotypes and phenotypes of the target population, shows the utility of this strain for controlling the Ae. aegypti mosquitoes and the pathogens they transmit.

Introduction of Aedes aegypti mosquitoes carrying wAlbB Wolbachia sharply decreases dengue incidence in disease hotspots

“…Releases of Wolbachia -carrying Ae . aegypti were first initiated in northeastern Australia in 2010 2 with the aim of replacing Wolbachia -free populations with populations carrying a high frequency of this bacterium, and thus decrease the transmission of DENV (e.g., 3 , 4 , 5 ). The initial releases were undertaken with a Wolbachia strain ( w Mel) that originated in Drosophila melanogaster .…”

Wolbachia wMel-mediated effects on dengue virus vertical transmission from Aedes aegypti to their offspring

“…A new approach, using the insect endosymbiont Wolbachia (wMel or wAlbB strains), is being applied to render Ae. aegypti populations much less competent at transmitting DENV between humans [19][20][21]. Wolbachia inhibits virus replication in mosquito cells via multiple mechanisms, including altering the intracellular environment, activating the innate immune system, and interacting with the cell machinery involved in RNA virus infection [22].…”

Operationalized releases ofwAlbBWolbachiainAedes aegyptilead to sharp decreases in dengue incidence dependent onWolbachiafrequency

“…Releases of Wolbachia-carrying Aedes aegypti mosquitoes were first initiated in north-eastern Australia in 2010 [1] with the aim of replacing Wolbachia-free populations with populations carrying a high frequency of this bacterium that can decrease the transmission of dengue and other arboviruses [e.g. 2,3,4]. The initial releases were undertaken with a Wolbachia strain (wMel) sourced from Drosophila melanogaster [1] but since that time releases have also been initiated with other Wolbachia including the wAlbB strain originating from Ae.…”