Sequence analysis of HA gene of H7N2 avian influenza virus isolates from chickens

In order to analyze sequence similarities of hemagglutinin(HA) gene among avian influenza virus(AIV) subtype H7N2 isolates,1.7kb DNA fragments were amplified with primers specific to HA gene by RT-PCR,and the DNA fragments were sequenced subsequently and compared with GenBank data.A 1664bp nucleotides sequence of HA gene was obtained,which encodes all the 544 amino acids(no signal peptides) of HA protein,including 323 amino acids for HA1 and 221 amino acids for HA2.HA gene of the two isolates shared 99.4% nucleotide sequence identity,and 99.0%-99.4% identity to A/Afri.Star./ Eng-Q/983/79(H7N1) virus,65.0% to A/Chicken/NewYork/13142-5/94(H7N2),and 96.0%-97.0% to other H7N2 viruses isolated from Italy and Israel.Both of these two H7N2 isolates were(situated) in the Euro-Asia branch of the HA phylogenetic tree of H7 subtype.The single basic amino acid at the cleavage site of HA implies the low pathogenic characteristics of the virus isolates.