Jamestown Canyon Virus is transmissible byAedes aegyptiand is only moderately blocked byWolbachiaco-infection

Abstract

AbstractJamestown Canyon Virus (JCV), a negative-sense arbovirus, is increasingly common in the upper Midwest of the USA. Transmitted by a range of mosquito genera, JCV has at its primary amplifying host, white-tailed deer.Aedes aegyptiis the major transmitter globally of the positive-sense viruses dengue (DENV), Zika, chikungunya, and Yellow Fever.Ae. aegypti’sdistribution, once confined to the tropics, is expanding, in part due to climate change.Wolbachia, an insect endosymbiont, limits the replication of co-infecting viruses inside insects. The release and spread of the symbiont intoAe. aegyptipopulations has been effective in reducing transmission of dengue and other viruses to humans. The mechanism ofWolbachia-mediated viral blocking in vectors is still poorly understood, however. Here we explored JCV infection potential inAe. aegypti, the nature of the vector’s immune response, and interactions withWolbachiainfection. We show thatAe. aegyptiis highly competent for JCV, growing to substantial loads and rapidly reaching the saliva after an infectious blood meal. The mosquito immune system responds with strong induction of RNAi and JAK/STAT. Neither the direct effect of viral infection nor the energetic investment in immunity appears to affect mosquito longevity.Wolbachiainfection blocked JCV only in the early stages of infection.Wolbachia-induced immunity was small compared to that of JCV, suggesting innate immune priming does not likely explain blocking. We propose two models to explain whyWolbachia’sblocking of negative-sense viruses like JCV may be less than that of positive-sense viruses, relating to the slowdown of host protein synthesis and the triggering of interferon-like factors like Vago. In conclusion, we highlight the risk for increased human disease with the predicted future overlap ofAe. aegyptiand JCV ranges. We suggest that with moderateWolbachia-mediated blocking and distinct biology, negative-sense viruses represent a fruitful comparator model to other viruses for understanding blocking mechanisms in mosquitoes.Author SummaryJamestown Canyon Virus (JCV), a newly emerging virus in North America, causes disease when it spills out of its wild mammal hosts into human populations via the bite of infected mosquitoes. We show that the mosquitoAedes aegypti, known for transmitting many viral pathogens to humans globally, and whose distribution is creeping northward in the USA toward regions where JCV is present, is likely able to transmit the virus.Wolbachiais an endosymbiotic bacterium being released in wild mosquito populations of mosquitoes because it limits the replication of human viruses inside the mosquito, limiting their transmission to humans. We show thatWolbachiahas a limited ability to control the replication of JCV, which is likely becauseWolbachia-induced antiviral response is quite weak, and unique aspects of negative-sense virus biology make them less susceptible to blocking. Our findings suggest that JCV may serve as a comparative model to positive-sense viruses like dengue in dissecting the mechanism ofWolbachia-mediated virus blocking. It also warns that shifting mosquito distributions, as expected under a changing climate, could bring JCV and Aedes mosquitoes into greater contact, potentially increasing the incidence of JCV in humans.