一株重组鸡传染性支气管炎病毒的分离及结构蛋白基因变异和血清型分析

Isolation and Analysis of Structural Protein Genes Variation and Serotype of a Recombinant Strain of Chicken Infectious Bronchitis Virus

为进一步了解鸡传染性支气管炎病毒(IBV)流行株的遗传变异情况,对2013年从免疫失败的广西某鸡场中分离到的一株IBV(GX-NN130048)进行S1、E、M和N基因的扩增、测序、相似性比较、系统进化树绘制和重组分析以及血清型鉴定。基因序列分析结果表明,分离株GX-NN130048的S蛋白裂解位点序列为RRSRR,S1、E、M和N基因与参考株核苷酸相似性分别在60.8%~90.1%、81.0%~94.2%、86.1%~93.8%和86.0%~93.3%;进化树分析显示,分离株GX-NN130048的S1基因与疫苗毒株4/91同属一群,而E、M和N基因则与毒株LX4属于同一群;重组分析显示,分离株GX-NN130048的S1基因来源于疫苗毒株4/91和GX-HC1006野毒株(LX4型)的重组;血清型分析表明,该分离株的血清型不同于疫苗株H120和4/91。研究表明分离株GX-NN130048是一株重组毒株,其结构基因和血清型均发生变异。本研究再次提供证据说明,疫苗株4/91越来越多参与到IBV流行株通过基因重组导致的遗传变异事件当中,并可能由此导致新血清型的出现。这可能是现场免疫失败的一个主要原因。有必要继续加强对IBV的监测和新疫苗的研发。

In order to further understand the genetic variation of circulating infectious bronchitis virus(IBV),S1,E,M and N genes of an IBV strain(GX-NN130048),which was isolated from chickens with immunoprophylaxis defeat in Guangxi,were amplified by reverse transcriptase polymerase chain reaction(RT-PCR),and then cloned,sequenced,and similarity comparison,phylogenetic tree,recombination and serotype analysis were conducted.The results showed that the gene sequence of cleavage site within S protein of GX-NN130048 was RRSRR.The nucleotide similarities of S1,E,M and N genes with those of other reference strains were 60.8%-90.1%,81.0%-94.2%,86.1%-93.8%and 86.0%-93.3%,respectively.According to the phylogenetic tree analysis,it was clustered into 4/91-type based on S1 gene,while its E,Mand Ngenes belonged to LX4-type.Recombination event was detected in S1 gene,which was a recombinant between vaccine strain 4/91 and isolate GX-HC1006(LX4-type).The serotype analysis revealed that the serotype of GX-NN130048 was different from vaccine strains H120 and 4/91.The results indicated thatisolate GX-NN130048 was a recombinant strain and variation existed both in structural genes and serotype.Our results also provide the evidence that the vaccine strain 4/91 has been increasingly involved in genetic variation of IBV epidemic strains,which may lead to the emergence of new serotype,and that may be one of the main causes of vaccine break in the field.Therefore,it is necessary to strengthen the monitoring of IBV field isolates and development of new vaccines.