Incucyte data for infected cell colonized with Wolbachia or uncolonized

The ability of the endosymbiont Wolbachia pipientis to restrict RNA
viruses is presently being leveraged to curb global transmission of
arbovirus-induced diseases. Past studies have shown that virus replication
is limited early in arthropod cells colonized by the bacterium, although
it is unclear if this phenomenon is replicated in mosquito cells that
first encounter viruses obtained through a vertebrate blood meal.
Furthermore, these cellular events neither explain how Wolbachia limits
dissemination of viruses between mosquito tissues, nor how it prevents
transmission of infectious viruses from mosquitoes to vertebrate host. In
this study, we try to address these issues using an array of mosquito cell
culture models, with an additional goal being to identify a common viral
target for pathogen blocking. Our results establish the viral RNA as a
cellular target for Wolbachia-mediated inhibition, with the incoming viral
RNA experiencing rapid turnover following internalization in cells. This
early block in replication in mosquito cells initially infected by the
virus thus consequently reduces the production of progeny viruses from
these same cells. However, this is not the only contributor to pathogen
blocking. We show that the presence of Wolbachia reduces the per-particle
infectivity of progeny viruses on naïve mosquito and vertebrate cells,
consequently limiting virus dissemination and transmission, respectively.
Importantly, we demonstrate that this aspect of pathogen blocking is
independent of any particular Wolbachia-host association and affects
viruses belonging to Togaviridae and Flaviviridae families of RNA viruses.
Finally, consistent with the idea of the viral RNA as a target, we find
that the encapsidated virion RNA is less infectious for viruses produced
from Wolbachia-colonized cells. Collectively, our findings present a
common mechanism of pathogen blocking in mosquitoes that establish a link
between virus inhibition in the cell to virus dissemination and
transmission.