中国1995～1999年鸡传染性支气管炎病毒地方分离株核蛋白基因的遗传变异分析

Genetic Variations of Nucleocapsid Gene of Infectious Bronchitis Virus Strains Isolated in China during 1995-1999

应用RT-PCR方法扩增到了我国1995～1999年10株IBV现地分离株的核蛋白基因片段，并将其进行了克隆、序列测定及分析。结果发现，10株IBV分离株核蛋白基因均含有一个长1230bp的ORF，编码由409个氨基酸残基组成的多肽，末发现碱基的插入和缺失。与GenBank中的20个IBV参考毒株核蛋白基因序列进行比较和分析，发现本研究分离的毒株主要分布于3个群中，该3群病毒主要包括我国IBV现地分离株。对n基因及其局部功能区序列比较发现，我国分离株与H120疫曲株N蛋白存在广泛的氨基酸变异。通过与s1基因系统发育进化树比较发现，我国IBV分离株存在基因重组现象。以上结果表明我国1995～1999年IBV毒株存在基因突，变和基因重组现象。

Nucleocapsid protein （N protein） genes of ten IBV strains isolated in China between 1995 and 1999 were amplified by reverse transcriptase-polymerase chain reaction （RT-PCR）, and then were cloned, sequenced and compared with 20 IBV reference strains. The results showed that all of the n genes of the ten isolates were composed of 1230 nucleotides, encoding a polypeptide of 409 amino acid residues. Deletion and insertion were not found in the n genes of the ten isolates. Phylogenetic tree based on amino acid sequences of n genes from ten IBV isolates and 20 reference IBV strains showed that the ten isolates were classified into three distinct clusters. IBV strains in the three clusters were isolated mainly in China. Furthermore, the phylogenetic tree also showed that recombination within the genome of IBV isolates may induce gene mutation of some Chinese IBV isolates. In addition, compared with the H120 vaccine strain, it was found that point mutations inducing the amino acid substitutions were common in n genes of the ten isolates. Taken together, these results suggested that gene mutation and recombination within the IBV genome existed in the Chinese IBV strains isolated between 1995 and 1999.