Genetic Diversity and Positive Selection Analysis of Classical Swine Fever Virus Envelope Protein Gene E2 in East China under C-Strain Vaccination.
Genetic Diversity and Positive Selection Analysis of Classical Swine Fever Virus Envelope Protein Gene E2 in East China under C-Strain Vaccination.
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DOI：
10.3389/fmicb.2016.00085
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发表时间：
2016
影响因子：
5.2
通讯作者：
Liu S
中科院分区：
文献类型：
--
作者：
Hu D;Lv L;Gu J;Chen T;Xiao Y;Liu S
猪瘟病毒（classical swine fever virus，CSFV）是一种严重危害人类健康的传染病。C-菌株疫苗接种是控制这种疾病的最有效方法之一。自2014年以来，在中国一些接种C株疫苗的省份发生了散发性CSF疫情。为阐明该病的病因，对169份临床标本的25个猪瘟病毒E2基因进行了克隆和序列测定。系统发育分析表明，所有25个菌株属于亚基因型2.1。25个分离物中有23个聚在一个新定义的亚基因型，2.1d，并共享一些一致的分子特征。为了确定完整的E2基因是否处于正选择压力下，我们使用逐位点分析来鉴定经历进化选择的特定密码子，发现了7个正选择密码子，在E2蛋白氨基末端的抗原性相关结构域B/C中鉴定了3个正选择位点（氨基酸17、34和72）。另外，另一个正选择位点（氨基酸200）表现出从亲水性到疏水性的极性变化，这可能改变了CSFV的抗原性和毒力。结果表明，山东省流行的猪瘟病毒主要聚集在2.1d亚型。这些正选择位点的鉴定有助于揭示毒力或致病性的分子决定因素，并有助于阐明华东地区猪瘟病毒进化的驱动力。
Classical swine fever virus (CSFV) causes an economically important and highly contagious disease of pigs worldwide. C-strain vaccination is one of the most effective ways to contain this disease. Since 2014, sporadic CSF outbreaks have been occurring in some C-strain vaccinated provinces of China. To decipher the disease etiology, 25 CSFV E2 genes from 169 clinical samples were cloned and sequenced. Phylogenetic analyses revealed that all 25 isolates belonged to subgenotype 2.1. Twenty-three of the 25 isolates were clustered in a newly defined subgenotype, 2.1d, and shared some consistent molecular characteristics. To determine whether the complete E2 gene was under positive selection pressure, we used a site-by-site analysis to identify specific codons that underwent evolutionary selection, and seven positively selected codons were found. Three positively selected sites (amino acids 17, 34, and 72) were identified in antigenicity-relevant domains B/C of the amino-terminal half of the E2 protein. In addition, another positively selected site (amino acid 200) exhibited a polarity change from hydrophilic to hydrophobic, which may change the antigenicity and virulence of CSFV. The results indicate that the circulating CSFV strains in Shandong province were mostly clustered in subgenotype 2.1d. Moreover, the identification of these positively selected sites could help to reveal molecular determinants of virulence or pathogenesis, and to clarify the driving force of CSFV evolution in East China.