H7N2禽流感病毒分离株血凝素蛋白全基因的序列分析

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

为进一步分析H7N2禽流感病毒(AIV)分离株血凝素(HA)基因的特性,参照已发表序列设计了1对引物,采用RT-PCR获得了1条约1.7 kb的DNA片段,测序后进行了同源性比较、HA基因系统发育进化树分析和氨基酸编码分析.结果表明,所测的2个分离株的HA基因全长1 664 bp,编码除信号肽以外的HA蛋白的全部544个氨基酸,其中包括HA1的323个氨基酸,HA2的221个氨基酸.2个分离株HA基因核苷酸序列的同源性为99.4%;与GenBank中AIV标准株A/Afri.Star./Eng-Q/983/79(H7N1)的同源性最高,分别为99.4%和99.0%;与美国A/Chicken/NewYork/13142-5/94(H7N2)株同源性很低(仅65.0%),而与以色列、意大利H7N2 AIV的同源性较高(为96%～97%);2个分离株在HA基因进化树中均处于H7亚型AIV的欧亚群系分支内.推导氨基酸的序列分析表明,其HA蛋白裂解位点的氨基酸序列为-GR-GLF-,仅包含1个碱性氨基酸(R-)残基,符合低致病力AIV的基因特征.

In order to analyze sequence similarities of hemagglutinin （HA） gene among avian influenza virus （AIV） subtype HTN2 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.