Chimeric symbionts expressing a Wolbachia protein stimulate mosquito immunity and inhibit filarial parasite development

Wolbachia can reduce the capability of mosquitoes to transmit infectious diseases to humans and is currently exploited in campaigns for the control of arboviruses, like dengue and Zika. Under the assumption that Wolbachia-mediated activation of insect immunity plays a role in the reduction of mosquito vectorial capacity, we focused our attention on the Wolbachia surface protein (WSP), a potential inductor of innate immunity. We hypothesized that the heterologous expression of this protein in gut- and tissue-associated symbionts may reduce parasite transmission. We thus engineered the mosquito bacterial symbiont Asaia to express WSP (Asaia(WSP)). Asaia(WSP) induced activation of the host immune response in Aedes aegypti and Anopheles stephensi mosquitoes, and inhibited the development of the heartworm parasite Dirofilaria immitis in Ae. aegypti. These results consolidate previous evidence on the immune-stimulating property of WSP and make Asaia(WSP) worth of further investigations as a potential tool for the control of mosquito-borne diseases. Epis and Varotto-Boccazzi et al. show that Wolbachia surface protein (WSP) activates host innate immunity in mosquitoes, inhibiting the development of the heartworm parasite in its insect host. This study suggests the possibility that the WSP-expressing symbiont may be harnessed to control mosquito-borne diseases.