Application of RNA interference methodology to inhibit avian influenza virus replication in vitro
RNA interference (RNAi) is a novel, gene silencing technique that could be valuable in creating alternatives to antiviral treatments/vaccines and producing virus resistant phenotypes in livestock. Nine anti-influenza shRNA expressed using human H1 promoter and targeting exogenous nucleocapsid protein (NP) and acidic component of polymerase complex (PA) genes of A/Quail/Italy/1117/65 strain of avian influenza virus were tested in chicken hepatoma (CH-SAH) and Madin Darby canine kidney (MDCK) cells. All constructs led to a significant decrease in virus infective titer (up to 500 fold reduction in CH-SAH cells and up to 107 fold in MDCK cells) and in viral mRNA (up to 80% in CH-SAH and up to 95% in MDCK cells). In CH-SAH cells, in contrast to MDCK cells, the plasmids did not induce any interferon (IFN) induction. In addition, in this cell line interferon-responsive genes (OASL, IFN-[beta]) were suppressed after the avian influenza virus infection. The RNAi efficiency was much higher in MDCK cells, which might be explained by a synergistic effect of the RNAi and strong IFN response and by difference in strength of the human H1 promoter in mammalian and avian cells. In the future, the developed anti influenza shRNA constructs can be used as aerosol delivered prophylactic/therapeutic drugs or for production of influenza resistant transgenic chickens.