Sindbis virus interferes with dengue 4 virus replication and its potential transmission by Aedes albopictus

Background: Mosquitoes transmit a number of arboviruses associated with disease outbreaks in humans and other animals. The majority of medically important arboviruses belong to three families: Togaviridae, Flaviviridae and Bunyaviridae. Several members of these families have overlapping distributions and share common vectors, increasing the potential for arboviral coinfections. This study examined how two model viruses: Sindbis virus (SINV, Togaviridae: Alphavirus) and dengue-4 virus (DENV-4, Flaviviridae: Flavivirus) may interact in C6/36 Aedes albopictus cells and in the mosquito vector Ae. albopictus. Methods: C6/36 cells were coinfected, superinfected, or singly infected with SINV and DENV-4 and the two viruses quantified at different time points. Four to seven day old adult females of Ae. albopictus were also fed blood containing one or both viruses and viral infection and dissemination rates determined. Results: Sindbis virus suppressed replication of DENV-4 in C6/36 Ae. albopictus cells with greater inhibition occurring when the two arboviruses were inoculated simultaneously compared to sequentially. In addition, Ae. albopictus simultaneously exposed to both arboviruses had significantly lower DENV-4 infection and population dissemination rates compared to those exposed to DENV-4 alone. Conclusion: These results suggest that certain Alphaviruses may interfere with DENV-4 transmission by suppressing its replication and increasing vector refractoriness. The findings provide important insights into the potential contribution of mixed arboviral infections to DENV transmission dynamics.