Synergic and antagonistic effect of small hairpin RNAs targeting the NS gene of the influenza A virus in cells and mice

Abstract In the present study, we demonstrate the effect of individual and mixtures of shRNAs targeting the NS gene to treat an established infection of influenza A virus (IAV). We prepared 10 shRNAs targeting the NS gene of the IAV, and these shRNAs were tested individually or in mixtures 16 h after infection. Our results revealed: (i) shRNA targeting the NS1 transcript decreased the virus titre up to 21% ( P in vitro ; (iv) a mixture of individually inactive shRNAs targeting the NEP transcript significantly inhibited the replication of IAV in vitro ; (v) the activities of the individual shRNAs in vivo predominantly corresponded to their activities in vitro ; (vi) a synergistic effect of the shRNAs was observed in vivo ; and (vii) a shRNA targeting the region common to both the NS1 and NEP transcripts, shNS593, exhibited the strongest inhibition and reduced the virus titre up to 16.4% in vitro , prolonged the survival of the mice by three days and abolished the protective effect of other shRNAs in vivo . shRNAs inhibited influenza virus infection in a gene-specific manner. NS1 mRNA was significantly reduced in lungs treated with shRNAs and the levels of RIG-1, IFN-α, IFN-β and IFN-γ mRNAs shRNAs were not altered.