2010—2013年我国鸡传染性支气管炎病毒分离株S1基因分子特性分析

Characterization and analysis of the molecular characteristics of the S1 gene of isolated chicken infectious bronchitisviruse from 2010 to 2013 in China

为掌握近年来我国传染性支气管炎病毒的流行动态和变化规律,利用检测转化至克隆载体鸡传染性支气管炎病毒（IBV）S1基因序列,应用MEGA5分析软件进行聚类分析,并对瑞普生物疫病诊断研究服务中心2010—2013年间从我国野外分离并测定的30株传染性支气管炎的S1基因序列与常用疫苗毒株和GenBank中代表性IBV毒株的对应基因序列进行比较,结果发现：1）30株野外分离株可分为2个基因型：LX4型和TW型,分别占总数的93.3%和6.7%;2）LX4型分离株S1基因和氨基酸序列与常见疫苗毒株序列差别很大,同源性仅分别为77.6%~86.3%和75.8%~85.7%;3）分析S基因裂解位点时发现同一基因型毒株的裂解位点氨基酸序列高度趋同,且型间差异性较大。可见,近年来我国主要IBV分离株属于LX4型,并且彼此间亲缘关系较近,与我国现用传染性支气管炎主要弱毒疫苗和国外参考株属于不同的基因型,这可能是导致疫苗免疫失败,传染性支气管炎（IB）在鸡群中爆发的主要原因。该研究结果为筛选针对我国目前流行IBV毒株的疫苗株提供参考。

Infectious bronchitis virus（IBV）belongs to family Coronaviridae and genus Gammacoronavirus,which have caused huge economic losses in commercial chicken flocks of China.In order to expand the knowledge of the molecular features of the IBV circulating in China nowadays,thirty wild IBV strains in China were isolated between 2010 and 2013 by the Ringpu Diagnosis Research and Service Center.The S1 gene of these viruses was cloned,sequenced,and analyzed by DNASTAR and MEGA.Comparing with the regular commercial vaccine strains and representative IBV strains published in Genbank,It has been found that 1）these 30 isolated strains were divided into 2 genotypes：LX4 type and TW type,the percentages of them were 90% and 10% respectively;2）there was a significant difference of the nucleotide sequences and amino acid sequences between the LX4 type isolates and the regular vaccine strains,the homology percentages were 77.6%-86.3% and 75.8%-85.7% respectively;3）the amino acid sequences andcleavage sites were of high homology in S gene of the same genotype viruses,while they were quite different between different genotypes.Therefore,the main current epidemic IBV strains belong to LX4 type and were also different from the widely applied commercial vaccine strain viruses significantly.This might be the reason for the immunity failure and IB outbreaks of chicken flocks.This study did lay a foundation for the selection of a better and suitable IBV strain as a brand new vaccine virus in China.