[Objective] The study aimed to investigate the genetic variation characters of entire sequences between two H9N2 subtype avian influenza virus strains and other reference strains.[Method] The entire sequences of 8 genes were obtained by using RT-PCR,and these sequences were analyzed with that of six H9N2 subtype avian influenza isolates in homology comparison and genetic evolution relation.[Result] The results showed that the nucleotide sequence of entire gene of the strain shared 91.1%-95.4% homology with other seven reference strains,and PG08 shared the highest homology 91.3% with C/BJ/1/94;ZD06 shared the highest homology 92.3% with D/HK/Y280/97.HA cleavage sites of two H9N2 subtype avian influenza virus isolated strains were PARSSR/GLF,typical of mildly pathogenic avian influenza virus.[Conclusion] Phylogenetic tree for entire gene of eight strains showed that the genetic relationship was the closest between ZD06 and C/Pak/2/99 strains,which belonged to the Eurasian lineage;PG08 shared the highest homology 91.3% with ZD06,it may be the product of gene rearrangements of other sub-lines.
[ Objective] To determine the HA gene sequences of four H9N2 Avian influenza virus （AIV） strains and carry out comparative analysis so as to understand the difference and variation pattern of each strain from the angle of molecular biology and to know the distribution and epidemic law of H9N2 AIV. [Method] One pair of primers was designed referring to HA gene sequences of H9N2 AIV. The HA genes of A/Chicken/Hebei/WD/98 （H9N2; WD98 for short）, A/Chicken/Hebei/ZD/04 （H9N2; ZD04 for short））, A/Chicken/Beijing/MY/06 （H9N2; MY06 for short） ）, and A/Chicken/Beijing/PG/08 （H9N2; PG08 for short）） were amplified, cloned and sequenced. Then the HA gene sequences of these strains were compared with that of 10 H9N2 AIV stains in GenBank. [Result] The ORF of HA genes of the four strains was 1 683 bp in size, encoding 516 amino acids. The HA gene sequences of the four strains, WD98, MY06, PG08, and ZD04, were 82.6% -95.1%, 83.0% -99.0%, 82.7% -95.5%, and 81.3% -95.7% homologous to that of the 10 H9N2 AIV stains, respectively. And the homology of amino acid was respectively 86.6% -96.3%, 86.6% -97.9%, 87.0% -97.1%, and 86.9% -97.3%. [ Conclusion] The HA gene has greatly high homology among different strains.
