Zhang Yuhan, Liu Kang, Chen Longfei, Yuan Meng, Lu Hongyu, Xiao Shaobo, Fang Liurong
National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070, China.
Viruses. 2025 May 12;17(5):695. doi: 10.3390/v17050695.
Porcine deltacoronavirus (PDCoV) is a newly discovered enteropathogenic coronavirus primarily responsible for diarrhea and mortality in piglets, with the potential to infect humans, thereby posing a significant threat to both human health and the global pig industry. Currently, there is no commercially available live-attenuated vaccine for PDCoV. In this study, an isolated virulent PDCoV strain, DHeB1, was continuously passaged in LLC-PK1 cells for up to 110 passages. The virus growth kinetics in cell culture and complete genome sequences of various passages (F11, F40, F70, F90, and F110) were determined. The results indicated significant increases in virus titers at passages F40 and F90. Sequence analysis revealed that only a few single-nucleotide mutations (some of which resulted in amino acid changes) and one nucleotide insertion were observed throughout successive passages. Notably, the eight and seven amino acid mutations that emerged in F40 and F70, respectively, remained stable in subsequent passages and were predominantly located in the S glycoprotein. The pathogenicity of F11, F40, F70, and F90 was assessed in 5-day-old piglets, revealing markedly reduced clinical symptoms, histopathological lesions, and intestinal PDCoV antigen distributions in piglets inoculated with F70 or F90. Importantly, F90 exhibited little to no virulence in piglets. The immunogenicity of F70, F90, and F110 was further evaluated in weaned piglets, with results indicating that the neutralizing antibody titers induced by F70 and F90 were comparable and significantly higher than those induced by F110. Collectively, these findings suggest that the PDCoV strain DHeB1 has been attenuated and can be used to develop a live-attenuated vaccine against PDCoV.
猪德尔塔冠状病毒（PDCoV）是一种新发现的肠道致病性冠状病毒，主要导致仔猪腹泻和死亡，有可能感染人类，从而对人类健康和全球养猪业构成重大威胁。目前，尚无用于PDCoV的商业化减毒活疫苗。在本研究中，一株分离的强毒PDCoV毒株DHeB1在LLC-PK1细胞中连续传代至110代。测定了细胞培养中的病毒生长动力学以及各代（F11、F40、F70、F90和F110）的完整基因组序列。结果表明，在F40和F90代时病毒滴度显著增加。序列分析显示，在连续传代过程中仅观察到少数单核苷酸突变（其中一些导致氨基酸变化）和一个核苷酸插入。值得注意的是，分别在F40和F70代出现的8个和7个氨基酸突变在后续传代中保持稳定，且主要位于S糖蛋白中。对5日龄仔猪评估了F11、F40、F70和F90的致病性，结果显示，接种F70或F90的仔猪临床症状、组织病理学病变和肠道PDCoV抗原分布明显减轻。重要的是，F90在仔猪中几乎没有毒力。在断奶仔猪中进一步评估了F70、F90和F110的免疫原性，结果表明F70和F90诱导的中和抗体滴度相当，且显著高于F110诱导的中和抗体滴度。总体而言，这些发现表明PDCoV毒株DHeB1已被减毒，可用于开发抗PDCoV的减毒活疫苗。
