禽传染性支气管炎病毒鸡胚连续传代后3'端7 kb编码区核酸变异特性

The characteristics of altered 3'-7 kb regions of an IBV strain after serial passage in embryos

CK/CH/LHLJ/04V在鸡胚上连续传代后,其致病力、免疫原性和组织嗜性均发生了改变。为了研究其生物学特性变化的分子特征,通过RT-PCR的方法扩增出4个不同代次(P3、P40、P70、P110)的毒株的3'端7kb区域,克隆于pMD18-T中进行测序。序列分析表明CK/CH/LHLJ/04V病毒群中含有基因突变的各种亚群。3'端7kb区域的氨基酸替换主要发生在S蛋白。P3和P40中,S1亚基中的氨基酸替换,同样发生在病毒传代过程中的其它亚群中。但是P70和P110中的另一些氨基酸替换却仅发生在某些亚群中。P70和P110的大部分亚群中,3'非编码区出现109bp的缺失,这可能与病毒的复制、转录和致病力有关。病毒3'端7kb区域的变化很可能导致了病毒毒力的减弱、免疫原性的降低和组织嗜性的变化。

The characteristics of 3＇-7 kb regions of chicken infectious bronchitis virus（IBV） CK/CH/LHLJ/04V strain were altered after serial passages in chicken embryos. In this study,the 3＇-7 kb regions of four passaged IBV（P3,P40,P70 and P110） were amplified by RT-PCR and sequenced. The results showed that the CK/CH/LHLJ/04V virus population contained subpopulations with a mixture of genetic mutants. Deduced amino-acid substitutions were observed in the 3＇-7 kb region,primarily in the spike（S） protein. Substitutions in the S1 subunit between P3 and P40 were also shown in all subpopulations in a virus passage. Other substitutions between P70 and P110 were only found in some subpopulations of the virus passages. A 109 bp deletion in the 3＇-UTR was founded in most subpopulations of P70 and P110,and might be related to virus replication,transcription and pathogenicity. The changes of the 3＇-7 kb of the virus were possibly responsible for virus attenuation,immunogenicity decrease and tissue tropism changes. But we cannot exclude the possibility that other regions of the genome may also be involved in those phenotype changes.