Antisense oligonucleotides targeting the RNA binding region of the NP gene inhibit replication of highly pathogenic avian influenza virus H5N1.

The H5N1 avian influenza virus (AIV) causes widespread infections in bird and human respiratory tracts, and vaccines and drug therapy are limited in their effectiveness. Recent studies of AIV structures have been published and provide new targets for designing antiviral drugs such as antisense oligonucleotides (AS ODNs), which effectively inhibit gene replication. In this study, we designed and synthesized three AS ODNs (NP267, NP628, NP749) that were specific for the RNA binding region of nucleoprotein (NP) based on AIV structure. Results showed that all three AS ODNs could inhibit viral replication in MDCK cells. The NP628 showed the best antiviral effect of all through viral titers, quantitative RT-PCR and indirect immunofluorescence (IFA) assays. In addition, the liposome mediated NP628 could partially protect the mice from a lethal H5N1 influenza virus challenge. Moreover, the NP628 group had a lower viral titer and lung index in the infected mice when compared with the viral control. Our results showed that AS ODN targeting of the AIV NP gene could potently inhibit AIV H5N1 reproduction, thus, formulating a candidate for an emergent therapeutic drug for the pathogenic H5N1 influenza virus infection.