63株IBV分离株M基因的遗传变异与系统进化分析

摘要

对1993-2010年从中国不同地区分离的63株传染性支气管炎病毒(infectious bronchitis virus,IBV)野毒株,采用RT-PCR方法克隆测定所分离野毒株的M基因核苷酸序列,并与GenBank中公布的部分国内外IBV毒株的M基因序列进行比较分析,研究中国IBV的分子流行病学特点和分子遗传变异规律.结果显示,所测毒株M基因具有6种不同长度的开放阅读框,这些长度的差异是由于5'端的核苷酸插入或缺失造成的；N端含有1～2个N-糖基化位点,其中1个糖基化位点“AsnCys-Thr”(NCT)是高度保守的.63个IBV分离株间氨基酸序列相似性为88.9％～100％,分离株与参考株间相似性为87.2％～100％.系统进化分析结果显示,本研究的63个IBV分离株可分为9个基因型,2005-2010年IBV中国流行株大部分与Mass型疫苗株处于不同的基因型,而且氨基酸序列相似性都小于94％.%The M genes of 63 infectious bronchitis viruses strains isolated in China from 1993 to 2010 were cloned and sequenced by RT-PCR to investigate the molecular epidemiology and genetic variation. Their sequences were also compared with those published in GenBank. The results showed that the nucleotide sequences of M gene had 6 different lengths. The nucleotide different in length resulted from insertion or deletion at the 5' terminus of M gene. There were 1 or 2 N-glycosylation site at the N terminus of M gene. The N-glycosylation site Asn-Cys-Thr was most conservative. The amino acid sequence similarities of Mgenes of 63 isolates were 87. 2% to 100%. The amino acid sequence similarities of M genes of 63 isolates and referenced strains were 88. 9% to 100%. 9 gentypes could be found among 63 IBV isolates in this study by the phylogenetic analysis. Most of IBV strains isolated in China from 2005 to 2010 were in different genotypes from vaccine strains of mass-genotype. The amino acid sequence similarities of M genes of the isolates from 2005 to 2010 and vaccine strains of mass-genotype were less than 94%.