传染性法氏囊病病毒B87株VP2基因克隆及序列分析

Cloning and sequencing of the VP2 gene of infectious bursal disease virus vaccine strain B87

目的获得传染性法氏囊病病毒(IBDV)B87株VP2基因,并对其序列进行分析。方法采用RT-PCR方法扩增传染性法氏囊病病毒B87株VP2基因,扩增产物提纯后克隆入pMD18-T载体,通过酶切、PCR和测序验证克隆,测序结果与GenBank下载的21株参考毒株VP2基因编码区全核苷酸序列进行比较。结果克隆的VP2基因序列长度为1536bp。所测B87株与Ⅰ型参考毒株的核苷酸同源性介于95.1%～99.2%之间,与Ⅱ型毒株的同源性仅为54.1%～54.7%。结论大多数IBDV强毒株、变异株、超强毒株与B87株的亲缘关系较远;诱导产生保护性中和抗体的VP2抗原决定簇的两个亲水区氨基酸变异较大,是逃避B87疫苗株的免疫保护、导致免疫失败而发生免疫鸡群传染性法氏囊病(IBD)流行的分子基础。

Objective To clone and sequence the VP2 gene of infectious bursal disease virus （1BDV） strain B87. Methods The VP2 gene of IBDV strain B87 was amplified by RT-PCR and cloned into a pMD18-T vector. After enzyme cutting, PCR and verifying the gene sequence, the sequence result was compared with 21 reference strains downloaded from GenBank. Results The sequence length of the VP2 gene is 1 536 bp, and the nucleotide homology of strain B87 compared with type I reference strain is 95.1%--99.2% but only 54. 1%--54.7% compared with type Ⅱ. Conclusion The majority of the virulent strain has a distant relationship to strain B87. The VP2 epitope can induce protective neutralizing antibodies because of two hydrophilic amino acids which have a large variation. This is also the molecular hasis of trying to escape the immune protection of vaccine strain B87 and what causes immune failure and the prevalence of IBD in immune chickens.