4株鸡肾型IBV陕西分离株3种主要结构蛋白基因的遗传变异分析

采用RT—PCR方法对近年来本实验室分离的4株肾型IBV陕西分离株的纤突蛋白S1基因、膜蛋白基因（M）和核蛋白基因（N）分别进行扩增，测序后进行遗传变异分析。结果显示：与肾型疫苗株w93相比，各分离株S1基因均存在广泛的点突变，并且都存在基因插入现象，分离株之间氨基酸同源性为75．8％～99．4％；M基因除了存在点突变外，W09和WNl2在其5’端还存在9个核苷酸的缺失，分离株之间氨基酸同源性为91．0％～99．6％；N基N无插入和缺失，但存在基因点突变，分离株之间氨基酸同源性为99．3％～99．5％。4株IBV分离株在S1、M和N基因氨基酸系统进化树上分属于不同的进化群，且都与较早的肾型IBV陕西分离株w118遗传距离较远。结果表明，4株鸡肾型IBV流行毒株的s1、M和N基因均存在不同程度变异，这可能是免疫鸡群肾型鸡传染性支气管炎长期流行的主要原因．

Genetic analysis of avian nephropathogenic infectious bronchitis virus isolated in Shaanxi province

In order （NIBV） in Shaan to understand the variation of avian nephropathogenic infe province, the S1,M and N genes of four isolates were ctious bronchitis vi amplified, cloned, rus se quenced for analyzing the genetic variation of IBV. In comparison with W93 vaccine strain, many point mutations occurred in the $1 gene in all viruses and gene insertions occurred in all of iso lates. Amino acid sequence homology of S1 gene among the four IBV isolates varied from 75.8% to 99. 4%. Mutations occurred in M gene, and gene deletions occurred in isolates of W09 and WN12. Amino acid sequence homology of M gene among the four IBV isolates varied from 91.0% to 99.6%. Deletion and insertion were not found in the N genes,but point mutations were found. Amino acid sequence homology of N gene among the four IBV isolates varied from 99. 3% to 99.5%. In the phylogenetic trees based on the deduced amino acid sequences of S1, M and N genes ,the four isolates were categorized into different branches, which suggested that the genes may develope recombination. Moreover,4 isolates had further relationship with Wl18 strain. The results indicated that the epidemic IBV strains in Shaanxi province had been mutated, which was probably the leading reason of immunization failure