Monitoring and sequence analysis of HA genes of H9N2 subtype influenza virus in YunNan province from 2006-2007.

To investigate the epidemiology of H9N2 subtype avian influenza viruses in yunnan province,5728 samples from poultry and swine in difference places were randomly collect between June 2006 and April 2007.2 pairs of primer were designed and synthesized based on nucleoprotein(HA and NA)gene and variability of known H9N2 subtype avian influenza viruses.The 276 samples were infected with H9N2 subtype avian influenza viruses by RT-PC R.HA gene of 17 strains were cloned into PMD-18T vector.Sequence analysis shows that homology of HA gene of H9N2 subtype from different districts samples was between 92%-100%.The homology of HA gene of 12 strains is 97% as a branch,which HA of 556 amino acids in 11 strains existed the same four-amino-acids deletion in the HA stalk at 6-9aa and homology of HA gene encoding 560aa in other 5 strains is 98% as another a branch.The 17 of strains with H9N2 subtype influenza virus isolated is low homology comparing with abroad other domestic strains including in 1999,2000 and 2001 of Yunnan province(except Qa/ST3143/05,97%).There were no basic amino acid inserted into the cleavage sites of HA,and variation of amino acid at receptor binding sites either.The glycosylation site of HA in 4 strains existed variation with different modality.