Pathogenicity and Molecular Characterization of the H5N1 Influenza Virus Isolated from the First Human Case in Zhejiang Province
Abstract: In order to confirm the etiology of the first suspected human case of the highly-pathogenic avian influenza virus and to perform the pathogenicity studies, a tracheal aspirate specimen was tested by RT-PCR, Real-time PCR and virus isolation. In addition, the HI (hemagglutination-inhibition) antibody in serum samples was assayed. The results showed that RNA extracted from the tracheal aspirate specimen was positive for H5N1 avian influenza virus and influenza virus type A. The H5N1 avian influenza virus was named A/Zhejiang/16/06 (H5N1). The titers of HI antibody for H5N1 avian influenza virus were 1: 320 and 1: 640, respectively. Both the pathogenic and serologic tests confirmed the human case of H5N1 avian influenza virus infection. The results of HA (hemagglutination) gene sequencing revealed that there were multiple basic amino acids at the cleavage site of HA gene associated with highly pathogenic H5 avian virus. The HA、NA、PB2、NP、M and NS genes were all of avian origin and were very similar to that of H5N1 avian influenza virus isolated from Fujian and Anhui provinces in 2005. However, there were obviously differences compared with the strains isolated from Vietnam、Thailand and Hong Kong in 1997.