传染性支气管炎病毒S1基因的遗传多样性

Genetic Diversity of Spike Protein S1 Gene of Avian Infectious Bronchitis Virus

为全面分析传染性支气管炎(IBV)流行株S1基因的遗传变异,结合1992-2008年间从山东乃至全国分离鉴定的IBV毒株,在进行抗原性研究的基础上,对17株IBV毒株分别进行了S1基因的克隆测序,并与GenBank中具有代表性的参考株进行同源比较,同时对其高变区HVRⅠ氨基酸基序进行分析。根据系统发育树,结合病毒发生的年代、地域和临床病理,将58株IBV国内外毒株初步分为6个基因型,其中,国内流行株主要涵盖5种基因型,大部分流行株属于基因Ⅴ型(北方株为主)和基因Ⅳ型(南方株为主),两种类型毒株相互交织,呈现复杂的流行形式。对IBV高变区HVRⅠ氨基酸基序分析表明,多数毒株存在不同程度的点突变,尚有4株分离株在33位和34位之间有氨基酸残基的插入。S1基因的遗传变异具有多样性,与常规疫苗株和国外参考株相比,无论是核苷酸还是氨基酸均发生了较大的变异。不同IBV毒株S1基因片段与其全长之间遗传变异高度相关(r=0.968),但IBV流行株与疫苗株的遗传距离愈来愈远,彰显出IBV流行株在H120的免疫压力下,已经发生了较大程度的变异。

To assess the variation and evolution of S1 gene of the prevailing Infectious Bronchitis Virus（IBV） strains. 17 IBV isolates were identified from several Provinces including Shandong,Sichuan et al in China during 1992-2008,wherein the S1 genes were sequenced. Phylogenetic analysis and HVR I of these IBV isolates were compared and analyzed,together with the IBV reference strains published in GenBank. 58 IBV strains were divided into six genotypes on account of different times,areas and clinical pathologies. There were at least five genotypes in China up to now. In detail,genotype Ⅴand Ⅳ were the most important prevailing IBV genotypes in China recently. Genotype Ⅴ included most isolates from North area during 1992-2008,while the genotype Ⅳ were mainly isolated from South area during 2000-2008. Two kinds IBV strains were intercrossed mutually and displayed different epidemical forms,which would be a serious problem due to poultry transport. Importantly,the amino acid substitutions,insertions were also found in HVR I of these IBV isolates. Alignment analysis of the S1 nucleotide and deduced amino acids sequences showed that there were amounts of variations among circulating IBV strains,which indicated that the evolutions of IBV S1 genes were diverse. Nonetheless,there were good relationships among different segments of IBV strains （r = 0. 968） ,which could help us to have a better understanding to IBV. Furthermore,the distinctions among the prevailing strains and vaccine became more and more evident,which implied that there would be great variations in IBV isolates under the immune pressure due to the continuing H120 vaccination.