广东人禽流感H5N1毒株M基因特性、进化和变异

通过对人禽流感H5N1毒株M基因序列的变异分析,揭示毒株M基因特征与进化。检测广东地区人禽流感H5N1毒株M基因核苷酸序列,同时检索全球人禽流感H5N1毒株M基因序列,采用DNAStar5.0软件对检索的人禽流感H5N1毒株M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。结果发现,1997~2006年53株毒株M1基因和51株毒株M2核苷酸序列同源性均分成两组,1997年毒株为第一组(GⅠ),2003~2006年香港、越南、泰国、印尼、中国大陆、土耳其、伊拉克、阿塞拜疆、埃及毒株为第二组(GⅡ)。M1基因20个氨基酸位点置换,占7.94%(20/252),其中2003~2006年毒株M1基因有9个氨基酸位点不同于1997年毒株;M2基因22个氨基酸置换,占22.7%,其中2003~2006年毒株M2基因有4个氨基酸不同于1997年毒株。M2基因Ks值为26.8×10-6~42.6×10-6Nt/d,Ka值为4.39×10-6~6.98×10-6Nt/d;而M1基因的同义突变速度均远高于错义突变速度,显示M1基因受到机体免疫压力较小;检验发现M1基因进化存在负选择性压力。2003~2006年毒株M1基因通过氨基酸S224N置换,增加一个糖基化位点NSS224-226;而来自印尼的8株毒株M2基因发生C50F置换,引起蛋白二级结构改变。1997年中国香港人禽流感毒株自当时出现后,便未在以后人禽流感疫情中出现。2003~2006年毒株M1基因增加糖基化位点NSS224-226,可能与毒株致病性有关。人禽流感H5N1毒株M基因在自然界变异频繁,可能影响H5N1毒株的人-人传播能力。

Characteristics, Evolution and Variation of M Genes of Human Avian H5N1 Strains in Guangdong

In order to reveal variation and evolution of M genes of human avian H5N1 influenza strains, the M genes of human avian H5N1 strains in Guangdong were sequenced and the M genes of global strains were searched out from Internet. They were analyzed by DNAStar 5. 0 and their revolutionary speeds were studied by means of combining the epidemiological data. It was found that M1 genes of 53 H5N1 strains and M2 genes of 51 strains during 1997-2006 were homologously classified into two groups: the strains from Hong Kong during 1997 (G I) were one group and the strains from Hong Kong, Vietnam, Thailand, Indonesia, China mainland, Turkey, Iraq, Azerbaijan, Egypt during 2003-2006 (G II ) were the another group. There were 20 substitutions of amino acids in M1 gene of all strains (7.94%, 20/252), where there were 9 amino acids in strains during 2003-2006 differing from the strains in 1997, meanwhile there were 22 substitutions of amino acids in M2 gene of all strains (22.7%, 22/97), where there were 4 amino acids in strains during 2003-2006 differing from the strains in 1997. In the synonymous variation, Ks values in M1 were 26.8 x 10(-6)-42.6 x 10(-6) Nt/d, and Ka values 4.39 x 10(-6)-6.98 x 10(-6) Nt/d, where there was more rapid speed of synonymous substitution than that of replacement, which showed that there existed less human immunological pressure and negative selective pressure by biological test. Ks values in M2 were 13.1 x 10(-6)-23.4 x 10(-6) Nt/ d, and Ka values 9.1 x 10(-6)-16.2 x 10(-6) Nt/d; where the ratios of Ks to Ka was 1.0-1.6 times as there was the neutral selective pressure in TL-676-05 strain. There was an amino acid substitution of S224, N in M1 gene of strains during 2003-2006 and an increas in a glycoprotein domain NSS224-226. The secondary structure of M2 protein varied as the substitution of C50 F of eight strains from Indonesia in 2005. The strains G I did not reemerge after Hong Kong human avian H5N1 influenza event. An increase of a glycoprotein domain NSS224-226 in M1 protein during 2003-2006 might be related with virus pathogenicity. Human avian H5N1 influenza M gene evolved frequently in nature, which might have an impact on its capacity of human-to-human transmission.