Sequencing analysis of NA gene of H7N2 AIV CK/HB/1/02 strain

The whole NA cDNA fragment of H7N2 AIV CK/HB/1/02 isolate was amplified by reverse transcription polymerase chain reaction(RT-PCR) with primers specific to the NA gene.The DNA fragment was sequenced and compared to the GenBank data.The 1 467 bp nucleotide sequence of NA gene was obtained,coding all the 469 amino acids of NA protein.The 61-65 amino acids of NA were -NITGI-,different from the special genetic marker of the Chinese H9N2 strains.NA gene of the isolate exhibits 93.3% homology with human influenza virus A/Leningrad/134/57(H2N2),89%-93% identity to Hong Kong H9N2 strains from duck,human and swine,85%-88% to H7N2 virus from U.S. and H9N2 virus from Beijing,Guangdong of China and South Korea.The isolate is situated in the Euro-Asia branch of the N2 phylogenetic tree and close to human H2N2 virus,and is less related with H7N2 isolates from North America which is in a different branch.