Veterinary Diagnostic Laboratory, Veterinary Diagnostic and Production Animal Medicine, Iowa State University, IA, USA.
Department of Veterinary and Biomedical Sciences, Animal Disease Research and Diagnostic Laboratory, South Dakota State University, Brookings, SD, USA.
Virus Res. 2022 Jun;314:198764. doi: 10.1016/j.virusres.2022.198764. Epub 2022 Apr 1.
Porcine circovirus type 3 (PCV3) is a non-enveloped, circular, single-stranded DNA virus in the family Circoviridae. This member of the genus Circovirus was initially described as affecting swine in 2016, and new research has provided further insight into its structural characteristics, disease presentations, pathogenesis, and immune response following infection. Therefore, this review aims to summarize advances in PCV3-related research about genomic characteristics epidemiology, pathogenesis, immune response, and the development of diagnostics. PCV3 has been detected globally and retrospectively in pigs of all ages and is associated with a range of clinical presentations, including multisystemic inflammatory syndrome, reproductive failure, porcine dermatitis and nephropathy syndrome, and subclinical infection. Experimental studies have successfully reproduced multisystemic inflammation but have not detected clinical disease. These findings, coupled with a large number of reports of coinfections coinciding with PCV3, may suggest that PCV3 infection alone may not be sufficient to cause evidenceable clinical disease. The pathogenesis of PCV3 has not been fully elucidated yet, and while receptors that facilitate cell-viral entry have not been identified, replication has been confirmed in a wide range of cell types, including trophoblasts, myocardiocytes, skin adipocytes, and neurons. PCV3 seems to evade the host immune response as evidenced by persistent viremia 42 days post-infection in experimental and longitudinal field studies despite a strong humoral response. Minimal differences in host cytokine profiles and peripheral cell-mediated responses have been observed, but certainly many questions still surround the mechanisms by which PCV3 evades the immune response. The epidemiology of PCV3 remains unclear, and the exact routes of transmission have not been described; but, PCV3 can be shed in oral fluids, nasal secretions, feces, colostrum, and semen, demonstrating the importance of lateral and vertical transmission. The detection of PCV3 in numerous domesticated and wild animal species, including cattle, dogs, mice, wild boar, chamois, roe deer, ticks, and mosquitoes, suggests the potential for multiple reservoirs and cross-species transmission. Current advances in PCV3 diagnostic tests have the ability to differentiate PCV3 from other PCVs and corroborate its presence within lesions. Given that the economic impact associated with PCV3 infection has not been assessed and the virus has the potential to emerge as a high-prevalence pathogen in the coming years, future research should focus on filling the knowledge gaps identified in this review.
猪圆环病毒 3 型（PCV3）是圆环病毒科的一种无包膜、环状、单链 DNA 病毒。这种圆环病毒属的成员最初于 2016 年被描述为影响猪，新的研究进一步深入了解了其结构特征、疾病表现、发病机制以及感染后的免疫反应。因此，本综述旨在总结 PCV3 相关研究的进展，包括基因组特征、流行病学、发病机制、免疫反应和诊断方法的发展。PCV3 已在全球范围内被检测到，并在各个年龄段的猪中进行了回顾性检测，与多种临床表现相关，包括多系统炎症综合征、繁殖失败、猪皮炎和肾病综合征以及亚临床感染。实验研究已成功复制了多系统炎症，但未检测到临床疾病。这些发现，加上大量同时伴有 PCV3 感染的合并感染报告，可能表明 PCV3 单独感染不足以引起明显的临床疾病。PCV3 的发病机制尚未完全阐明，虽然尚未确定有助于细胞-病毒进入的受体，但已在广泛的细胞类型中证实了复制，包括滋养层细胞、心肌细胞、皮肤脂肪细胞和神经元。PCV3 似乎逃避了宿主的免疫反应，尽管有强烈的体液反应，但在实验和纵向田间研究中，感染后 42 天仍持续出现病毒血症。尽管宿主细胞因子谱和外周细胞介导的反应差异很小，但 PCV3 逃避免疫反应的机制肯定仍存在许多问题。PCV3 的流行病学仍不清楚，确切的传播途径尚未描述；但是，PCV3 可以在口腔液、鼻分泌物、粪便、初乳和精液中排出，这表明了横向和垂直传播的重要性。PCV3 在许多家养和野生动物物种中的检测，包括牛、狗、鼠、野猪、岩羚羊、狍子、蜱和蚊子，表明存在多个储主和跨物种传播的可能性。PCV3 诊断检测的当前进展能够将 PCV3 与其他 PCV 区分开来，并证实其在病变中的存在。鉴于与 PCV3 感染相关的经济影响尚未评估，并且该病毒有可能在未来几年成为高流行病原体，未来的研究应侧重于填补本综述中确定的知识空白。
