enhances insect-specific flavivirus infection in mosquitoes.

Mosquitoes transmit a diverse group of human flaviviruses including West Nile, dengue, yellow fever, and Zika viruses. Mosquitoes are also naturally infected with insect-specific flaviviruses (ISFs), a subgroup of the family not capable of infecting vertebrates. Although ISFs are not medically important, they are capable of altering the mosquito's susceptibility to flaviviruses and may alter host fitness. is an endosymbiotic bacterium of insects that when present in mosquitoes limits the replication of co-infecting pathogens, including flaviviruses. Artificially created -infected mosquitoes are being released into the wild in a series of trials around the globe with the hope of interrupting dengue and Zika virus transmission from mosquitoes to humans. Our work investigated the effect of on ISF infection in wild-caught mosquitoes from field release zones. All field mosquitoes were screened for the presence of ISFs using general degenerate flavivirus primers and their PCR amplicons sequenced. ISFs were found to be common and widely distributed in populations. Field mosquitoes consistently had higher ISF infection rates and viral loads compared to laboratory colony material indicating that environmental conditions may modulate ISF infection in . Surprisingly, higher ISF infection rates and loads were found in -infected mosquitoes compared to the free mosquitoes. Our findings demonstrate that the symbiont is capable of manipulating the mosquito virome and that -mediated viral inhibition is not universal for flaviviruses. This may have implications for the based DENV control strategy if ISFs confer fitness effects or alter mosquito susceptibility to other flaviviruses.