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目的通过对人禽流感H5N1毒株PA基因序列的变异分析,揭示毒株PA基因特征、变异与进化。方法检测广东地区人禽流感H5N1毒株PA基因核苷酸序列,同时检索全球人禽流感H5N1毒株PA基因序列,采用MEGA4.0软件对检索的人禽流感H5N1毒株PA基因核苷酸序列进行比对和分析;并结合流行病学资料对变异毒株进行进化速度分析。结果PA蛋白呈酸性,等电点pH5.4。1997-2006年52株毒株PA基因核苷酸序列同源性分成两组,1997年毒株为第一组(G1),2003-2006年香港、越南、泰国、印尼、中国大陆毒株、土耳其、伊拉克、阿塞拜疆、埃及毒株为第二组(G2)。PA基因114个氨基酸位点置换,占15.9(114/716),其中2003-2006年毒株PA基因有17个氨基酸位点不同于1997年毒株。PA基因Ks值为30.9×10-6～46.1×10-6Nt/d,Ka值为4.50×10-6～8.13×10-6Nt/d;而PA基因的同义突变速度是错义突变速度的5.7～6.9倍,显示PA基因受到机体免疫压力较小;检验发现PA基因进化存在负选择性压力。PA基因中潜在的7个糖基化位点基本稳定,毒株IDNS-569H-06的PA基因半胱氨酸发生置换(S224C)。结论PA基因进化分成两系列,PA基因进化特点是自发突变较快,而受到机体免疫机制压力较小;A基因与其它多聚酶基因(PB2和PB1)比较,核苷酸序列同源性和进化在时间特征和地区特征方面具有一致性;来自中国大陆的毒株进化值得关注。人禽流感H5N1毒株PA基因在自然界变异频繁,可能影响HN毒株致病性和在人-人传播能力。
OBJECTIVE: To reveal the variation, evolution and evolution of the PA gene in the avian influenza virus (H5N1) strain by analyzing the variation of PA gene sequence. Methods The nucleotide sequence of PA gene of H5N1 strain in bird flu in Guangdong area was detected and the sequence of PA gene of H5N1 strain in the world was searched. The nucleotide sequence of PA gene in H5N1 strain of human bird flu was searched by MEGA4.0 software. Compared and analyzed; and the epidemiological data were used to analyze the evolution speed of the mutated strains. Results PA protein was acidic, isoelectric point pH 5.4.1997 - 2006 strains of PA gene nucleotide sequence homology was divided into two groups, in 1997 the first strain (G1), 2003-2006 The strains of Hong Kong, Vietnam, Thailand, Indonesia and Mainland China, Turkey, Iraq, Azerbaijan and Egypt are in the second group (G2). PA gene 114 amino acid substitutions, accounting for 15.9 (114/716), 2003-2006 strains of PA gene 17 amino acid sites different from the 1997 strain. The Ks value of PA gene was 30.9 × 10-6 ~ 46.1 × 10-6Nt / d, and the Ka value was 4.50 × 10-6 ~ 8.13 × 10-6Nt / d. The synonymous mutation rate of PA gene was the rate of missense mutation 5.7- to 6.9-fold, showing that the PA gene was less immune-challenged by the body; negative selection pressure was found on PA gene evolution. The potential seven glycosylation sites in PA gene were basically stable, and the PA gene cysteine in strain IDNS-569H-06 was substituted (S224C). Conclusion PA gene evolution is divided into two series. PA gene evolution is characterized by faster spontaneous mutation and less pressure on the body’s immune system. The homology and evolution of nucleotide sequence homology and evolution between A gene and other polymerase genes (PB2 and PB1) Temporal characteristics and regional characteristics of the consistency; strain evolution from mainland China deserves attention. Human bird flu H5N1 strain PA gene mutated frequently in nature, may affect the pathogenicity of HN strains and human-human transmission capacity.