Institute of Virology, Wenzhou University, Wenzhou, China.
Institute of Military Veterinary Medicine, Academy of Military Sciences, Changchun, China.
Transbound Emerg Dis. 2021 Mar;68(2):289-295. doi: 10.1111/tbed.13731. Epub 2020 Jul 30.
In this study, we detected a circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA virus (named Po-Circo-like (PCL) virus) in intestinal tissue samples of pigs, and the complete genome sequences of three strains (named PCL viruses GX14, GX15 and GX19) were obtained. Unlike PCL virus strains 21 and 22, whose genome sequences have 3,912 and 3,923 nucleotides (nt), respectively, the strains revealed in this study have a circular genome with 3,944 nt and five major open reading frames (ORFs). Among these ORFs, ORF1 encodes the Rep and not the typical capsid protein encoded in PCV. Furthermore, the strains in this study share 79.2%-96.0% nucleic acid identity and 83.0%-98.1% amino acid identity with ORF1 of the reference strains. Moreover, the Rep of the PCL virus in this study shared 19.9%-22.2% (<30%) identity of its amino acid sequence with PCV but shared 34.9%-94.8% (>30%) identity of its amino acid sequence with sequences of five proteins that are expressed by the family Kirkoviridae. [Correction added on 24 December 2020 after first online publication: The preceding sentence has been corrected in this version.] Interestingly, the stem loop of the PCL virus has one nucleotide substitution, T1328G. The Bo-Circo-like CH strain shares high nucleic acid and amino acid similarity (>80%) with the PCL virus. Moreover, Bo-Circo-like CH and GX-19 had similar stem-loop sequences. The PCL virus might therefore be transmitted to non-porcine hosts by cross-species transmission routes. Phylogenetic analysis classified the PCL virus into the new family Kirkoviridae and indicated its close relationship with the Bo-Circo-like virus. A phylogenetic divergence analysis based on the rep gene classified all PCL virus strains into two genotypes (PCLa and PCLb). In conclusion, the present study is the first detailed report of the PCL virus, which is a potential new virus in pigs that might be involved in cross-species transmission. Further investigation is needed to determine the pathogenesis of this virus and its epidemiologic impact.
在这项研究中，我们在猪的肠道组织样本中检测到了一种环状复制相关蛋白（Rep）编码的单链（CRESS）DNA 病毒（命名为 Po-Circo-like（PCL）病毒），并获得了三个毒株（命名为 PCL 病毒 GX14、GX15 和 GX19）的完整基因组序列。与基因组序列分别为 3912 个和 3923 个核苷酸（nt）的 PCL 病毒株 21 和 22 不同，本研究中发现的毒株具有 3944 个核苷酸和五个主要开放阅读框（ORF）的环状基因组。在这些 ORF 中，ORF1 编码 Rep，而不是 PCV 中编码典型衣壳蛋白的基因。此外，本研究中的毒株与参考株的 ORF1 的核酸同源性为 79.2%-96.0%，氨基酸同源性为 83.0%-98.1%。此外，本研究中的 PCL 病毒 Rep 与其氨基酸序列与 PCV 的同一性<30%，但与其家族 Kirkoviridae 表达的五种蛋白的氨基酸序列的同一性>30%。[2020 年 12 月 24 日首次在线发表后添加的更正：此版本中已更正了前一句话。]有趣的是，PCL 病毒的茎环有一个核苷酸取代，T1328G。Bo-Circo-like CH 株与 PCL 病毒具有高核酸和氨基酸相似性（>80%）。此外，Bo-Circo-like CH 和 GX-19 具有相似的茎环序列。因此，PCL 病毒可能通过跨物种传播途径传播给非猪宿主。系统发育分析将 PCL 病毒归类为新的 Kirkoviridae 科，并表明其与 Bo-Circo-like 病毒密切相关。基于 rep 基因的系统发育分歧分析将所有 PCL 病毒株分为两种基因型（PCLa 和 PCLb）。总之，本研究首次详细报道了 PCL 病毒，这是一种可能涉及跨物种传播的猪的潜在新病毒。需要进一步研究以确定该病毒的发病机制及其流行病学影响。
