Therapeutic Effect of Duck Interferon-Alpha Against H5N1 Highly Pathogenic Avian Influenza Virus Infection in Peking Ducks

The antiviral cytokine interferon-alpha (IFN-) plays a critical role in the innate immune system. Previous studies have shown that recombinant chicken IFN- inhibits avian influenza virus (AIV) replication in vivo; however, the antiviral effect of recombinant duck IFN- (rDuIFN-) on highly pathogenic AIV remains unknown. In this study, the duck IFN- gene was cloned, expressed, and purified. The antiviral effects of the resulting rDuIFN- were further evaluated in vitro and in vivo. Our results showed that rDuIFN- inhibited the replication of vesicular stomatitis virus (VSV) and AIV in duck embryo fibroblasts in vitro, with antiviral activities against VSV and AIV of 2.1x10(5) and 4.1x10(5) U/mg, respectively. We next investigated the anti-H5N1 AIV effect of intramuscular injection of rDuIFN- in vivo. rDuIFN- reduced viral titers in the brains, lungs, and spleens of 2-day-old (2D) ducks compared with that in the virus-challenged control group, and pretreatment with rDuIFN- reduced mortality from 60% to 10% in 2D ducks. Moreover, rDuIFN- increased the expression of IFN-stimulated genes in the brains and spleens of 2D ducks. Our results demonstrate that rDuIFN- blocks VSV and H5N1 influenza virus infection in vitro and exhibits antiviral effects against H5N1 influenza virus infection in 2D ducks.