Rodrigues I L F, Cruz A C M, Souza A E, Knackfuss F B, Costa C H C, Lago B V, Silveira R L, Castro T X
Department of Microbiology and Parasitology, Biomedical Institute, Fluminense Federal University, Rua Prof. Hernani Melo, 101, Niterói, Rio de Janeiro, 24210-130, Brazil.
Universidade do Grande Rio/UNIGRANRIO, School of Health Sciences, Rua Professor José de Souza Herdy, 1160, 25 de Agosto, Duque de Caxias, RJ, 25071-202, Brazil.
Arch Virol. 2025 Apr 9;170(5):97. doi: 10.1007/s00705-025-06276-8.
Porcine circovirus type 2 (PCV2) is a common virus that infects pigs. It exhibits marked genetic variability, which is affected by factors such as vaccination and commercial trade. In this study, a retrospective analysis of PCV2 was performed based on molecular characterization, Bayesian inference, and haplotype networks in tissue samples obtained from Brazilian pig herds from 1967 to 2018. A nested PCR targeting a 225-nucleotide fragment of the PCV2 capsid gene was performed, followed by bidirectional sequencing. Out of 178 samples tested, 39 (21.9%) were positive for PCV2. Phylogenetic analysis showed that strains from this study collected before the introduction of a PCV2 vaccine clustered with genotype 2d reference strains. The mean substitution rate was 1.54 × 10 substitutions per site per year (s/s/y). The haplotype diversity of PCV2 was 0.98, which shows a high mutation rate compatible with the topology found in the haplotype network. Our study shows that most of the Brazilian isolates, including those obtained before the introduction of the PCV2 vaccine, were similar to PCV2d reference strains, suggesting that this genotype was already circulating before the introduction of the vaccine in Brazil. One of the PCV2 sequences was from an isolate from 1967, making it the oldest sequenced isolate from the Americas, and the second oldest worldwide. Phylogenetic analysis and haplotype network analysis indicated a high degree of diversity of PCV2 as well as a high rate of evolution. These results increase our knowledge about the genetic diversity, evolution, and dispersal patterns of PCV2 in Brazil.
猪圆环病毒2型（PCV2）是一种常见的感染猪的病毒。它表现出显著的遗传变异性，这受到疫苗接种和商业贸易等因素的影响。在本研究中，基于对1967年至2018年从巴西猪群采集的组织样本进行分子特征分析、贝叶斯推断和单倍型网络分析，对PCV2进行了回顾性分析。进行了针对PCV2衣壳基因225个核苷酸片段的巢式PCR，随后进行双向测序。在178个检测样本中，39个（21.9%）PCV2呈阳性。系统发育分析表明，本研究中在引入PCV2疫苗之前收集的毒株与2d基因型参考毒株聚类。平均替换率为每年每个位点1.54×10个替换（s/s/y）。PCV2的单倍型多样性为0.98，这表明其突变率较高，与单倍型网络中发现的拓扑结构相符。我们的研究表明，大多数巴西分离株，包括在引入PCV2疫苗之前获得的分离株，与PCV2d参考毒株相似，这表明该基因型在巴西引入疫苗之前就已经在传播。其中一个PCV2序列来自1967年的一个分离株，使其成为美洲最古老的测序分离株，也是全球第二古老的分离株。系统发育分析和单倍型网络分析表明PCV2具有高度的多样性以及较高的进化速率。这些结果增加了我们对PCV2在巴西的遗传多样性、进化和传播模式的了解。
