Sexual transmission of Anopheles gambiae densovirus (AgDNV) leads to disseminated infection in mated females

Background: Anopheles gambiae densovirus (AgDNV) is an insect-specific, single-stranded DNA virus that infects An. gambiae sensu stricto (s.s.), the major mosquito species responsible for transmitting malaria parasites throughout sub-Saharan Africa. AgDNV is a benign virus that is very specific to its mosquito host and therefore has the potential to serve as a vector control tool via paratransgenesis (genetic modification of mosquito symbionts) to limit transmission of human pathogens. Prior to being engineered into a control tool, the natural transmission dynamics of AgDNV between An. gambiae mosquitoes needs to be fully understood. Additionally, improved knowledge of AgDNV infection in male mosquitoes is needed. In the study presented here, we examined the tissue tropism of AgDNV in the male reproductive tract and investigated both venereal and vertical transmission dynamics of the virus. Methods: Anopheles gambiae s.s. adult males were infected with AgDNV via microinjection, and reproductive tissues were collected and assayed for AgDNV using qPCR. Next, uninfected females were introduced to AgDNV-infected or control males and, after several nights of mating, both the spermatheca and female carcass were assessed for venereally transmitted AgDNV. Finally, F1 offspring of this cross were collected and assayed to quantify vertical transmission of the virus. Results: AgDNV infected the reproductive tract of male mosquitoes, including the testes and male accessory glands, without affecting mating rates. AgDNV-infected males venereally transmitted the virus to females, and these venereally infected females developed disseminated infection throughout the body. However, AgDNV was not vertically transmitted to the F1 offspring of this cross. Conclusions: Infected male releases could be an effective strategy to introduce AgDNV-based paratransgenic tools into naïve populations of An. gambiae s.s. females. Graphical Abstract: [Figure not available: see fulltext.].