Sindbis virus-induced silencing of dengue viruses in mosquitoes

Aedes aegypti were injected intrathoracically with double subgenomic Sindbis (dsSIN) viruses with inserted sequences derived from the genome of one or more of the four dengue (DEN) virus serotypes. Mosquitoes were highly resistant to challenge with homologous DEN viruses from which the effector sequences were derived, and resistance to DEN viruses was independent of the orientation of the effector RNA. dsSIN viruses designed to express RNA derived from the premembrane coding region of DEN-2 prevented the accumulation of DEN2 RNA, and C6/36 cells were highly resistant to DEN-2 virus when challenged at 2, 5 or 8 days after the initial dsSIN virus infections, even though the dsSIN-derived RNA had sharply declined at the later time points. Initiation of resistance occurred prior to or within the first 8 h after challenge with DEN-2 virus. We conclude that DEN viruses are inhibited by a mechanism similar to post-transcriptional gene silencing (PTGS) or RNA interference (RNAi) phenomena described in plants and invertebrates, respectively. The potential occurrence of PTGS or RNAi in mosquitoes and mosquito cells suggests new ways of inhibiting the replication of arthropod-borne viruses in mosquito vectors, studying vector-virus interactions, and silencing endogenous mosquito genes.