牦牛源牛凸隆病毒的检测及其基因组特征

Detection and Genomic Characteristics of Bovine Torovirus in Yak

本研究旨在证实青藏高原牦牛中牛凸隆病毒(bovine torovirus,BToV)的存在,并分析其基因组特征。采用RT-PCR方法检测西藏、青海、四川藏区的犊牦牛腹泻粪便中BToV,并扩增基因组。结果从145份样本中检出10份BToV阳性,平均阳性率约为6.9%,其中西藏、青海、四川藏区的阳性率分别约为11.8%、8.9%、3.0%。成功获得1个长为28314 bp的牦牛源BToV基因组,GC含量为36.31%,与GenBank中已有的5个BToV基因组的核苷酸相似性为82%~97%,与国内BToV基因组SC2的相似性最高且遗传关系最近。本研究中BToV基因组的S基因与GenBank中已有的14个完整BToV-S基因相比,存在8个独特的氨基酸变异,其中,6个位于S1结构域,2个位于S2结构域,且在222—2473 bp发生区域重组事件。本研究证明BToV在牦牛中的存在,并且地域分布广泛,获得了牦牛源Ⅲ型BToV基因组,报道了BToV的S基因重组事件,有助于进一步了解BToV的分子特征和遗传进化。

The purpose of this study was to investigate the presence of bovine torovirus(BToV)in yak in Qinghai-Tibetan Plateau and to analyze the characteristics of the BToV genome.An RT-PCR assay was used to detect BToV from clinical samples from Tibet,Qinghai and Sichuan,and the BToV genome was further amplified from the positive sample.Approximate 6.9%(10/145)diarrheic samples were detected as BToV positive,and the positive rate in Tibet,Qinghai and Sichuan was 11.8%,8.9%and 3.0%respectively.Moreover,a complete BToV genomic sequence was obtained from a positive sample,which was 28314 nucleotides in length with a GC content of 36.31%.The genome in this study shared 82%-97%nucleotide sequence identity with the 5 BToV genomic sequences in the GenBank database.It shared the highest sequence identity and the closest genetic relationship with the native BToV genome SC2.Compared with all 14 complete BToV-S gene sequences in the GenBank database,the S gene of the BToV genome in this study had 8 unique amino acid variations which include 6 variations in the S1 domain and 2 variations in the S2 domain.Besides,a recombinant event was predicted in the region of 222-2473 bp of the S gene.In conclusion,this research revealed that BToV could infect yak with wide geographical distribution.Furthermore,a genotypeⅢBToV genome was obtained,and a recombinant event was predicted in its S gene.The results of this study would be helpful for a better understanding of BToV’s molecular characteristics and genetic evolution.