siRNA targeting vaccinia virus double-stranded RNA binding protein [E3L] exerts potent antiviral effects

The Vaccinia virus gene, E3L, encodes a double-stranded RNA [dsRNA]-binding protein. We hypothesized that, owing to the critical nature ofdsRNA in triggering host innate antiviral responses, E3L-specific small-interfering RNAs [siRNAs] should be effective antiviral agents againstpox viruses, for which Vaccinia virus is an appropriate surrogate. In this study, we have utilized two human cell types, namely, HeLa and 293T,one which responds to interferon [IFN]-β and the other produces and responds to IFN-β, respectively. The antiviral effects were equally robust inHeLa and 293T cells. However, in the case of 293T cells, several distinct features were observed, when IFN-β is activated in these cells. Vacciniavirus replication was inhibited by 97% and 98% as compared to control infection in HeLa and 293T cells transfected with E3L-specific siRNAs,respectively. These studies demonstrate the utility of E3L-specific siRNAs as potent antiviral agents for small pox and related pox viruses.