Xu Tong, You Dong, Wu Fang, Zhu Ling, Sun Xian-Gang, Lai Si-Yuan, Ai Yan-Ru, Zhou Yuan-Cheng, Xu Zhi-Wen
College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.
College of Veterinary Medicine Sichuan Key Laboratory of Animal Epidemic Disease and Human Health, Sichuan Agricultural University, Chengdu, China.
Front Microbiol. 2022 Nov 3;13:1052533. doi: 10.3389/fmicb.2022.1052533. eCollection 2022.
Porcine circovirus 4 (PCV4) was identified in 2019 as a novel circovirus species and then proved to be pathogenic to piglets. However, there is a lack of its prevalence in the Southwest of China. To investigate whether PCV4 DNA existed in the Southwest of China, 374 samples were collected from diseased pigs during 2021-2022 and detected by a real-time PCR assay. The results showed that the positive rate of PCV4 was 1.34% (5/374) at sample level, and PCV4 was detected in two of 12 cities, demonstrating that PCV4 could be detected in pig farms in the Southwest of China, but its prevalence was low. Furthermore, one PCV4 strain (SC-GA2022ABTC) was sequenced in this study and shared a high identity (98.1-99.7%) with reference strains at the genome level. Combining genetic evolution analysis with amino acid sequence analysis, three genotypes PCV4a, PCV4b, and PCV4c were temporarily identified, and the SC-GA2022ABTC strain belonged to PCV4c with a specific amino acid pattern (239V for Rep protein, 27N, 28R, and 212M for Cap protein). Phylogenetic tree and amino acid alignment showed that PCV4 had an ancient ancestor with mink circovirus. In conclusion, the present study was the first to report the discovery and the evolutionary analysis of the PCV4 genome in pig herds of the Southwest of China and provide insight into the molecular epidemiology of PCV4.
猪圆环病毒4型（PCV4）于2019年被鉴定为一种新型圆环病毒，随后被证明对仔猪具有致病性。然而，在中国西南部地区缺乏其流行情况的相关研究。为了调查中国西南部地区是否存在PCV4 DNA，于2021年至2022年期间从患病猪中采集了374份样本，并通过实时荧光定量PCR检测。结果显示，样本水平上PCV4的阳性率为1.34%（5/374），在12个城市中的2个城市检测到了PCV4，表明在中国西南部地区的猪场中可以检测到PCV4，但其流行率较低。此外，本研究对一株PCV4毒株（SC-GA2022ABTC）进行了测序，在基因组水平上与参考毒株具有较高的同源性（98.1-99.7%）。结合遗传进化分析和氨基酸序列分析，暂时鉴定出三种PCV4基因型，即PCV4a、PCV4b和PCV4c，SC-GA2022ABTC毒株属于PCV4c，具有特定的氨基酸模式（Rep蛋白为239V，Cap蛋白为27N、28R和212M）。系统发育树和氨基酸比对显示，PCV4与水貂圆环病毒有一个共同的古老祖先。总之，本研究首次报道了中国西南部地区猪群中PCV4基因组的发现及进化分析，为PCV4的分子流行病学研究提供了依据。
