Sindbis virus-induced silencing of dengue viruses in mosquitoes

Aedes aegypti were injected intrathoracically with double subgenomic Sindbi s (dsSIN) viruses with inserted sequences derived from the genome of one or more of the four dengue (DEN) virus serotypes. Mosquitoes were highly resi stant to challenge with homologous DEN viruses from which the effector sequ ences were derived, and resistance to DEN viruses was independent of the or ientation of the effector RNA. dsSIN viruses designed to express RNA derive d 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 challe nged at 2, 5 or 8 days after the initial dsSIN virus infections, even thoug h the dsSIN-derived RNA had sharply declined at the later time points. Init iation of resistance occurred prior to or within the first 8 h after challe nge with DEN-2 virus. We conclude that DEN viruses are inhibited by a mecha nism similar to post-transcriptional gene silencing (PTGS) or RNA interfere nce (RNAi) phenomena described in plants and invertebrates, respectively. T he potential occurrence of PTGS or RNAi in mosquitoes and mosquito cells su ggests new ways of inhibiting the replication of arthropod-borne viruses in mosquito vectors, studying vector-virus interactions, and silencing endoge nous mosquito genes.