Construction and pathogenicity studies of a live vaccine against highly pathogenic H5N1 avian influenza virus A/Anhui/2/2005

The cold-adapted (ca) influenza A vaccine donor strain A/Ann Arbor/6/60ca (H2N2) posses the cold-adapted (ca), temperature-sensitive (ts) and attenuation phenotypes. In this study, the PB2, PB1, PA, NP, M, NS genes of influenza A/Ann Arbor/6/60ca (H2N2) virus and the HA and NA genes from influenza A/Anhui/2/2005 virus were cloned into vector pBD, respectively and co-transfected into Vero cells for rescuing the recombinant virus. The rescued virus was identified by RT-PCR and sequencing. The results showed that the rescued virus possessed ca and ts phenotypes and was no longer lethal for SPF chickens in artificial infection. This work lays the foundation for further evaluating the protective efficacy of the recombinant virus as a vaccine candidate in mice and nonhuman primate animal models.