鸡源H_9N_2亚型流行性感冒病毒神经氨酸酶基因序列分析

Sequence Analyses of Neuraminidase Genes of H_9N_2 Influenza Viruses Isolated from Chickens

对1996～2001年间自中国部分养鸡场发病鸡或死亡鸡分离鉴定的8株H9N2亚型禽流感病毒的神经氨酸酶基因(NA),进行了扩增和序列测定,并分析和比较了其核苷酸和氨基酸的同源性。结果表明,NA基因核苷酸和氨基酸同源性分别为97 1%～99 8%和95 7%～99 7%,说明NA基因稳定遗传,高度保守。与A/chicken/HongKong/G9/97相比较,发现中国大陆鸡源H9N2分离株的神经氨酸酶蛋白在其茎部的第63、64、65位点上都有3个氨基酸的丢失,而与中国邻近的韩国、巴基斯坦鸡源H9N2分离株的神经氨酸酶没有氨基酸的丢失,因此这些部位的氨基酸丢失可初步认为是中国大陆H9N2流感病毒分离株的一个标记。系统进化树分析表明,该8株病毒的NA基因属于相同的进化分支,即A/duck/HongKong/Y280/97-like分支,尚未发现NA基因属于A/quail/HongKong/G1/97-like分支的分离株。中国的H9N2分离株与韩国、巴基斯坦等地的H9N2分离株隶属于不同的进化亚分支,说明H9N2亚型禽流感的发生与流行和地域有一定的相关性。

The neuraminidase(NA)genes of 8 H_9N_2 influenza virus strains isolated from diseased chickens in different farms during 1996-2001 were amplified and sequenced.The nucleotide and deduced amino acid sequences of NA genes of these isolates were compared.The results showed that the homologies of nucleotides and amino acids of the isolates were 97.1%～99.8% and 95.7%～99.7%,respectively, indicating that NA genes of H_9N_2 influenza viruses isolated in China's Mainland were well conserved.NAs of the 8 strains had a deletion of 3 amino acid residues at positions 63-65 as compared to that of A/chicken/Hong Kong/G9/97,while those of Korea and Pakistan isolates had no deletion.Therefore,these deletions could be basically considered as a useful marker for China H_9N_2 isolates.Phylogenetic analyses showed NA genes of these isolates belonged to A/duck/Hong Kong/Y280/97-like virus lineage and that virus belonged to A/quail/Hong Kong/G1/97-like lineage was not found.The NA genes of the H_9N_2 viruses isolated in Korea and Pakistan belonged to different sublineage from those of the 8 isolates,suggesting that the geographical distribution plays a significant role in the evolution of the H_9N_2 influenza viruses.