中国1995～2004年鸡传染性支气管炎病毒地方分离株膜蛋白基因的遗传变异分析

应用RT-PCR方法扩增到了我国1995～2004年20株IBV现地分离株的膜蛋白(Membrane,M)基因片段.序列测定表明,20株IBV分离株M基因开放阅读框由672～681bp组成,编码由223～226个氨基酸残基组成的多肽.与我国分离株LX4相比,M基因推导氨基酸序列的变异主要发生在2～17位、221～223位,其中4～6位存在氨基酸的插入和缺失,导致IBV毒株间M蛋白糖基化位点的差异.与GenBank中34株IBV参考毒株M蛋白基因推导氨基酸序列进行比较和分析,系统进化关系显示54株IBV毒株分属于5个进化群.我国IBV分离株M基因在进化关系上较为独立,主要分布在第Ⅱ群和第Ⅳ群,其中第Ⅱ群分离株和中国台湾毒株进化关系密切.此外,参考IBV国内分离株S1基因及N基因系统发育进化树的研究结果,并与M基因进行比较,表明我国IBV也存在着基因重组现象,尤其是疫苗毒和流行毒之间的重组.

Genetic Variations of Membrane Gene of Infectious Bronchitis Virus Strains Isolated in China between 1995 and 2004

Membrane (M) protein genes of 20 infectious bronchitis virus (IBV) strains isolated in China between 1995 and 2004 were sequenced and analyzed. The M genes of twenty isolates were composed of 672 to 681 nucleotides, encoding polypeptides of 223 to 226 amino acid residues. Variations of the deduced amino acids of M gene mainly occurred at positions 2 to 17 and 221 to 233, comparing with that of the IBV strain LX4. There were deletions or insertions in the M gene of Chinese isolates at amino acid position 2 to 6, leading to the loss or gain of a glycosylation site. Phylogenetic tree based on amino acid sequences of M genes from 20 Chinese isolates and 34 reference strains showed that they were classified into five distinct clusters. Most of the Chinese IBV strains were included in clusters II and IV, forming distinct groups. The isolates in cluster II showed a close evolutionary relationship with Taiwan isolates. Furthermore, recombination especially the recombination between field isolates and vaccine strains had been observed while comparing the phylogeny of M genes with those of S1 and N genes.