An RNAi Therapy That Attenuates Multi-Organ Viremia and Improves Animal Survival in a Lethal EMCV Challenge Model.

Encephalomyocarditis virus (EMCV) is an important zoonotic pathogen that infects many animals with mild symptoms. However, swine is the most receptive host and causes acute and lethal myocarditis and/or encephalitis, and induces sudden death in piglets. There are currently no approved antivirals against EMCV. In recent years, antiviral therapies based on small interfering RNA (siRNA) have been rapidly developed as effective alternative therapies. In this study, we designed siRNAs targeting highly conserved regions in the EMCV genome coinciding with VP2 and 3C genes. We show that these siRNAs were non-immunostimulatory and significantly inhibited EMCV replication in vitro. The siRNAs were then complexed in liposomes before testing in a lethal EMCV mouse model in vivo. Both prophylactic and therapeutic intravenous delivery of siRNAs ameliorated viral infection in multiple organs and improved animal survival. This is the first demonstration of the use of a liposomal delivery platform to deliver highly conserved anti-EMCV siRNAs for EMCV antiviral therapy in vivo.