中国2005年流行麻疹野病毒H_(1a)基因亚型血凝素基因和氨基酸特征分析

Hemagglutinin Gene and Amino Acid Characterization Analysis of the H_(1a) Sub-genotype of Wild-type Measles Viruses Circulated in China in 2005

目的研究2005年引起中国麻疹流行的麻疹野病毒H1a基因亚型血凝素蛋白（HA）核苷酸和氨基酸特征及变异程度。方法从各省疾病预防控制中心麻疹实验室送检的2005年麻疹野病毒中选取4个H1a基因亚型代表株，并选取2004年河北省流行的1个Hh基因亚型代表株做对比分析。提取麻疹病毒核糖核酸（RNA），用逆转录一聚合酶链反应（RT—PCR）扩增出核蛋白（N）羧基末端（450nt）和HA蛋白编码区基因片段（1854nt），并对扩增产物进行核苷酸序列测定和分析，与GenBank收录的1993～1994年中国优势基因型代表株、中国疫苗株沪191（S191）和长47（C47）HA蛋白和核蛋白羧基末端构建基因亲缘性关系树，分析HA蛋白基因的核苷酸／氨基酸的同源性。结果5株分离株全部为H1基因型的H1a亚型。5株H1a亚型毒株的HA与中国疫苗株S191相比有94～96个核苷酸差异，28～30个氨基酸差异；与C47有94～98个核苷酸差异，28～30个氨基酸差异。5株Hh亚型HA第719位核苷酸由G—A，导致第240位的丝氨酸（S）突变成天门酰胺（N），致使HA蛋白的1个N型糖基化位点丢失。结论该研究表明，麻疹野病毒H1a亚型株的HA蛋白的核苷酸／氨基酸，与1993～1994年流行株相比未发生明显变异。但与S191和C4，相比有较大基因变异，丢失了个别中和抗原位点，但大部分中和抗原位点未发生变异。中国使用的疫苗对现流行的麻疹野病毒仍然具有保护作用，但初免成功后是否绝大部分人具有终身保护还有待进一步病毒学和流行病学论证。2005年麻疹流行与病毒本身的基因突变无明显关联，而是由易感人群的积累和人口流动导致广泛的传播所致。

Objective To study the genetic characterization and amino acid mutation of hemagglutinin protein of H1a sub-genotype of wild-type measles viruses circulated in 2005. Methods Four isolates of H1a measles viruses sent by Provincial Measles Laboratories and one Hebei H1a strain, which caused measles epdemic in Hebei at 2004, were selected for contrasting and analyzing. After extracted RNA from measles isolates,complete coding regions of hemagglutinin （1854nt） and 450 COOH terminal of nucleoprotein were amplified by RT-PCR and sequenced. Alignmented five strains of this study with Chinese vaccine strain （S191）, changchun-47（C47） and representative strains of China from 1993 to 1994 which submitted to Gen Bank, phylogenetic analysis and the diversity were done by Bioedit. Results The genotype of five selected strains is H1a. There are about 94～98 nucleotides and 28～30 amino acids difference between the and China vaccine strain S191, （247. 719th nucleotide was changed from suits in amino aci Furthermore, one five strains That the G to A red mutation from Ser to Asn. N-glycosylation site in 240th amino acids was losen because of the mutation. Conclusion The major neutralization sites have not apparent difference by comparing nucleotide/amino acid of haemagglutinin protein of measles viruses we studied and representative strains in 1993 - 1994. China vaccine strains S191 and C47 enable to effectively prevent measles virus which induce to prevail. It should be further studied by the datas from virology and epidemiology about whether people could gain the lifetime protection after the vaccination. The measles outbreak in 2005 is not obvious related with genetic mutation or because the accumulation of susceptible population and floating people lead to widespread transmission.