International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou 450046, People's Republic of China.
International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou 450046, People's Republic of China.
Comp Immunol Microbiol Infect Dis. 2023 Jul;98:102009. doi: 10.1016/j.cimid.2023.102009. Epub 2023 Jun 22.
Porcine circovirus 4 (PCV4) is a recently discovered circovirus that was first reported in 2019 in several pigs with severe clinical disease in Hunan province of China, and also identified in pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV). To further investigate the epidemic profile and genetic characteristics of the two viruses, 150 clinical samples were collected from 9 swine farms in Shaanxi and Henan provinces of China, and a SYBR Green I-based duplex quantitative real-time polymerase chain reaction (qPCR) was developed for detecting PCV4 and PRRSV simultaneously. The results showed the limits of detection were 41.1 copies/μL and 81.5 copies/μL for PCV4 and PRRSV, respectively. The detection rates of PCV4 and PRRSV were 8.00% (12/150) and 12.00% (18/150) respectively, and a case of co-infection with PCV4 and PRRSV was found in the lung tissue of a suckling pig with respiratory symptom. Subsequently, the complete genomic sequences of five PCV4 strains were obtained, of which one PCV4 strain (SX-ZX) was from Shaanxi province, and these strains were 1770 nucleotides in length and had 97.7%-99.4% genomic identity with 59 PCV4 reference strains. The genome characteristic of the SX-ZX strain was evaluated from three aspects, a "stem-loop" structure, ORF1 and ORF2. As essential elements for the replication, the 17-bp iterative sequence was predicted as the stem structure, in which three non-tandem hexamers were found at downstream with H1/H2 (12-CGGCACACTTCGGCAC-27) as the minimal binding site. Three of the five PCV4 strains were clustered into PCV4b, which was composed of Suidae, fox, dairy cow, dog and raccoon dog. Phylogenetic analysis revealed that seven PRRSV strains from the present study were clustered into the PRRSV-2 genotype. Collectively, these data extend our understanding of the genome characteristic of PCV4 as well as the molecular epidemiology and the genetic profile of PCV4 and PRRSV.
猪圆环病毒 4 型（PCV4）是一种新发现的圆环病毒，于 2019 年在中国湖南省出现严重临床疾病的几头猪中首次报道，也在感染猪繁殖与呼吸综合征病毒（PRRSV）的猪中鉴定出来。为了进一步调查这两种病毒的流行情况和遗传特征，从中国陕西省和河南省的 9 个猪场采集了 150 份临床样本，并建立了一种基于 SYBR Green I 的双重实时荧光定量 PCR（qPCR）来同时检测 PCV4 和 PRRSV。结果表明，PCV4 和 PRRSV 的检测限分别为 41.1 拷贝/μL 和 81.5 拷贝/μL。PCV4 和 PRRSV 的检测率分别为 8.00%（12/150）和 12.00%（18/150），在一头有呼吸症状的哺乳仔猪的肺组织中发现了一例 PCV4 和 PRRSV 混合感染。随后，获得了 5 株 PCV4 全长基因组序列，其中一株 PCV4 株（SX-ZX）来自陕西省，这些序列长 1770 个核苷酸，与 59 株 PCV4 参考株的基因组同一性为 97.7%-99.4%。从“茎-环”结构、ORF1 和 ORF2 三个方面对 SX-ZX 株的基因组特征进行了评估。作为复制的必需元件，预测 17 个碱基的迭代序列为茎结构，在其下游发现三个非串联六聚体，最小结合位点为 H1/H2（12-CGGCACACTTCGGCAC-27）。这 5 株 PCV4 中有 3 株聚为 PCV4b，该亚群包含了猪、狐狸、奶牛、狗和貉。系统进化分析显示，本研究中的 7 株 PRRSV 株聚为 PRRSV-2 基因型。总之，这些数据扩展了我们对 PCV4 基因组特征以及 PCV4 和 PRRSV 的分子流行病学和遗传特征的认识。
