Wang Dongliang, Mai Jinhui, Lei Bo, Zhang Yingjie, Yang Yi, Wang Naidong
Hunan Provincial Key Laboratory of Protein Engineering in Animal Vaccines, Laboratory of Functional Proteomics, Research Center of Reverse Vaccinology, College of Veterinary Medicine, Hunan Agricultural University, Changsha, China.
Front Vet Sci. 2021 Aug 24;8:695466. doi: 10.3389/fvets.2021.695466. eCollection 2021.
Porcine circovirus type 4 (PCV4), a recently reported circovirus, was first identified in pigs with clinical signs similar to porcine dermatitis nephropathy syndrome (PDNS), in Hunan province, China, in 2019. More knowledge regarding the assembly of capsid protein (Cap) into virus-like particles (VLPs), their structure and antigenic properties, are needed to provide new knowledge for diagnosis and further characterization of PCV4. In this study, high-level expression of PCV4 Cap was achieved in with purified Cap self-assembling into VLPs (~20 nm) . Furthermore, these VLPs were internalized by PK15 and 3D4/21 cell lines. Significant structural differences between PCV4 and PCV2 capsids were demonstrated among loops (loop BC, CD, DE, EF, and GH), based on comparisons of 3D structures. In addition, five potential B cell epitopes identified were mostly located in surface-exposed loops of PCV4 capsid. Cross-reaction between PCV4 and PCV2 or PCV3 conferred by humoral immune responses was deemed unlikely on the basis of ELISA and Western blotting for assessment of VLPs and using PCV4 or PCV2 VLPs. In conclusion, these studies provided new knowledge regarding PCV4 capsid surface patterns. It is noteworthy that the PCV4 VLPs prepared in our study have much potential for development of serological diagnostics for PCV4 and to further characterize this virus.
猪圆环病毒4型（PCV4）是一种最近报道的圆环病毒，于2019年在中国湖南省首次在出现与猪皮炎肾病综合征（PDNS）相似临床症状的猪中被鉴定出来。需要更多关于衣壳蛋白（Cap）组装成病毒样颗粒（VLP）及其结构和抗原特性的知识，以为PCV4的诊断和进一步特征描述提供新知识。在本研究中，PCV4 Cap在[此处原文缺失具体表达系统]中实现了高水平表达，纯化后的Cap自组装成VLP（约20纳米）。此外，这些VLP被PK15和3D4/21细胞系内化。基于三维结构的比较，在环（环BC、CD、DE、EF和GH）之间证明了PCV4和PCV2衣壳之间存在显著的结构差异。此外，鉴定出的五个潜在B细胞表位大多位于PCV4衣壳的表面暴露环上。基于ELISA和Western印迹法对VLP进行评估，并使用PCV4或PCV2 VLP，认为PCV4与PCV2或PCV3之间由体液免疫反应引起的交叉反应不太可能。总之，这些研究提供了关于PCV4衣壳表面模式的新知识。值得注意的是，我们研究中制备的PCV4 VLP在开发PCV4血清学诊断方法和进一步表征这种病毒方面具有很大潜力。
