Davies Brendan, Wang Xiong, Dvorak Cheryl M T, Marthaler Douglas, Murtaugh Michael P
Departments of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN 55108, United States.
Departments of Veterinary Population Medicine, University of Minnesota, St. Paul, MN 55108, United States.
Virus Res. 2016 Jun 2;217:32-7. doi: 10.1016/j.virusres.2016.02.010. Epub 2016 Mar 3.
Porcine circovirus 2 (PCV2) was prevalent in swine in the United States before PCV2-associated disease (PCVAD) appeared in 2006. Limited nucleotide sequencing of open reading frame 2 (ORF2) encoding capsid, the only structural protein, revealed the presence of two genotypes, PCV2a and PCV2b. Later, PCV2c and mutant PCV2b, or PCV2d, were also described. However, extensive PCV2 ORF2 sequence databases in veterinary diagnostic laboratories have not been analyzed systematically to determine the genetic diversity of field isolates. Here, we interrogated >1100 PCV2 ORF2 nucleotide sequences to assess population diversity and genetic variation. We detected a novel PCV2 genotype that is substantially different, primarily in ORF2, from all known PCV2. Notably, ORF2 contains a unique carboxyl terminal amino acid insertion resulting in a 238 amino acid ORF2. All other PCV2 ORF2 proteins are 233 or 234 aa in length. Phylogenetic analysis indicates that it is more ancient than other PCV2 genotypes. The findings demonstrate the value of analyzing routine diagnostic laboratory sequence databases in population genetic analyses of animal pathogens.
在2006年猪圆环病毒2型相关疾病（PCVAD）出现之前，猪圆环病毒2型（PCV2）在美国的猪群中就已普遍存在。对编码唯一结构蛋白衣壳的开放阅读框2（ORF2）进行的有限核苷酸测序显示存在两种基因型，即PCV2a和PCV2b。后来，也发现了PCV2c以及突变型PCV2b，即PCV2d。然而，兽医诊断实验室中广泛的PCV2 ORF2序列数据库尚未得到系统分析，以确定田间分离株的遗传多样性。在此，我们对1100多条PCV2 ORF2核苷酸序列进行了研究，以评估群体多样性和遗传变异。我们检测到一种新型PCV2基因型，其与所有已知PCV2在主要在ORF2方面存在显著差异。值得注意的是，ORF2包含一个独特的羧基末端氨基酸插入，导致ORF2有238个氨基酸。所有其他PCV2 ORF2蛋白长度为233或234个氨基酸。系统发育分析表明，它比其他PCV2基因型更为古老。这些发现证明了在动物病原体群体遗传分析中分析常规诊断实验室序列数据库的价值。
