Sindbis virus suppresses dengue-4 virus in cell culture and reduces vector competence for dengue-4 virus

Mosquito-borne viruses are important public health challenges throughout the world. Many of these viruses have overlapping geographic distribution and may share common vectors. We examined how Sindbis virus (SINV, Togaviridae: Alphavirus) influences vector competence of Aedes albopictus for dengue-4 virus (DENV-4, Flaviviridae: Flavivirus) as well as its replication in C6/36 Ae. albopictus cells. As expected, cytopathic effects were observed when C6/36 cells were inoculated with either SINV alone or SINV and DENV-4 coinfections and superinfections but not when inoculated with DENV-4 alone. DENV-4 titers in C6/36 cells were significantly higher in the absence than in the presence of SINV. Ae. albopictus adult females simultaneously infected with SINV and DENV-4 had significantly lower DENV-4 infection and dissemination rates compared to those infected with DENV-4 alone. These findings demonstrate the potential for viral coinfections to influence arbovirus transmission dynamics in regions where multiple viruses co-occur and share common vectors.