Rosario Karyna, Breitbart Mya, Harrach Balázs, Segalés Joaquim, Delwart Eric, Biagini Philippe, Varsani Arvind
College of Marine Science, University of South Florida, Saint Petersburg, FL, 33701, USA.
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary.
Arch Virol. 2017 May;162(5):1447-1463. doi: 10.1007/s00705-017-3247-y. Epub 2017 Feb 2.
The family Circoviridae contains viruses with covalently closed, circular, single-stranded DNA (ssDNA) genomes, including the smallest known autonomously replicating, capsid-encoding animal pathogens. Members of this family are known to cause fatal diseases in birds and pigs and have been historically classified in one of two genera: Circovirus, which contains avian and porcine pathogens, and Gyrovirus, which includes a single species (Chicken anemia virus). However, over the course of the past six years, viral metagenomic approaches as well as degenerate PCR detection in unconventional hosts and environmental samples have elucidated a broader host range, including fish, a diversity of mammals, and invertebrates, for members of the family Circoviridae. Notably, these methods have uncovered a distinct group of viruses that are closely related to members of the genus Circovirus and comprise a new genus, Cyclovirus. The discovery of new viruses and a re-evaluation of genomic features that characterize members of the Circoviridae prompted a revision of the classification criteria used for this family of animal viruses. Here we provide details on an updated Circoviridae taxonomy ratified by the International Committee on the Taxonomy of Viruses in 2016, which establishes the genus Cyclovirus and reassigns the genus Gyrovirus to the family Anelloviridae, a separate lineage of animal viruses that also contains circular ssDNA genomes. In addition, we provide a new species demarcation threshold of 80% genome-wide pairwise identity for members of the family Circoviridae, based on pairwise identity distribution analysis, and list guidelines to distinguish between members of this family and other eukaryotic viruses with circular, ssDNA genomes.
圆环病毒科包含具有共价闭合环状单链DNA（ssDNA）基因组的病毒，其中包括已知最小的自主复制、编码衣壳的动物病原体。已知该科成员可在鸟类和猪中引发致命疾病，历史上一直被归类于两个属之一：圆环病毒属，包含禽类和猪类病原体；环曲病毒属，仅包含一个种（鸡贫血病毒）。然而，在过去六年中，病毒宏基因组学方法以及在非常规宿主和环境样本中进行的简并PCR检测表明，圆环病毒科成员的宿主范围更广，包括鱼类、多种哺乳动物和无脊椎动物。值得注意的是，这些方法发现了一组与圆环病毒属成员密切相关的独特病毒，并将其归为一个新属，即环病毒属。新病毒的发现以及对圆环病毒科成员基因组特征的重新评估促使对该动物病毒科的分类标准进行修订。在此，我们详细介绍了2016年经国际病毒分类委员会批准的圆环病毒科最新分类法，该分类法确立了环病毒属，并将环曲病毒属重新归类到细小病毒科，后者是动物病毒的另一个谱系，也包含环状ssDNA基因组。此外，基于全基因组两两比对同一性分布分析，我们为圆环病毒科成员提供了一个新的种划分阈值，即全基因组两两同一性为80%，并列出了区分该科成员与其他具有环状ssDNA基因组的真核病毒的指导原则。
