He Wenlong, Peng Qi, Li Jizong, Huang Jin, Cai Xuhang, Li Siyuan, Zhang Baotai, Xiao Li, Gao Jie, Wang Chuanhong, Qian Jiali, Gu Laqiang, Wang Rui, Tang Xuechao, Li Kemang, Song Xu, Zhou Jinzhu, Zhu Mingjun, Li Bin
College of Veterinary Medicine, Hebei Agricultural University, Baoding 071001, China.
Nanchang City Key Laboratory of Animal Virus and Genetic Engineering, Nanchang 330045, China.
Transbound Emerg Dis. 2023 Mar 31;2023:2830485. doi: 10.1155/2023/2830485. eCollection 2023.
Porcine deltacoronavirus (PDCoV) is an emerging swine coronavirus that causes severe diarrhea to pigs of all ages, especially the suckling piglets under one-week-old. We previously isolated a highly pathogenic PDCoV strain, CZ2020, from a diarrheal piglet and have passaged it for over 100 passages. The adaptability of the CZ2020 increased gradually as the passage increased. Amino acid mutations were observed in pp1a, pp1ab, spike, envelop, and membrane proteins, and the spike protein accounts for 66.7% of all amino acid mutations. Then, the high passage strains, CZ2020-F80 and CZ2020-F100, were selected for evaluation of the pathogenicity in three-day-old piglets to examine whether these amino acid changes affected their virulence. At 2 days postchallenge (DPC), 2/5 piglets started to show typical diarrhea, and at 4 DPC, severe diarrhea was observed in the CZ2020-challenged piglets. Viral RNA could be detected at 1 DPC in rectal swabs and reached its highest at 4 DPC in the CZ2020-challenged group. CZ2020-F80- and CZ2020-F100-challenged groups have one piglet exhibiting mild diarrhea at 4 and 6 DPC, respectively. Compared with the CZ2020-challenged group, the piglets in CZ2020-F80- and F100-challenged groups had lower viral loads in rectal swabs, intestines, and other organs. No obvious histopathological lesions were observed in the intestines of CZ2020-F80- and F100-challenged piglets. Virulent PDCoV infection could also induce strong interferons and proinflammatory cytokines and . These data indicate that the strains, CZ2020-F80 and CZ2020-F100, were significantly attenuated via serial passaging and have the potential for developing attenuated vaccine candidates.
猪德尔塔冠状病毒（PDCoV）是一种新出现的猪冠状病毒，可导致各年龄段猪出现严重腹泻，尤其是1周龄以下的哺乳仔猪。我们之前从一头腹泻仔猪中分离出一株高致病性PDCoV毒株CZ2020，并对其进行了100多代传代。随着传代次数增加，CZ2020的适应性逐渐增强。在pp1a、pp1ab、刺突、包膜和膜蛋白中观察到氨基酸突变，其中刺突蛋白的氨基酸突变占所有氨基酸突变的66.7%。然后，选择高代毒株CZ2020-F80和CZ2020-F100评估其对3日龄仔猪的致病性，以检查这些氨基酸变化是否影响其毒力。攻毒后2天（DPC），2/5的仔猪开始出现典型腹泻，在4 DPC时，CZ2020攻毒组的仔猪出现严重腹泻。在CZ2020攻毒组中，直肠拭子在攻毒后1天可检测到病毒RNA，并在4 DPC时达到最高水平。CZ2020-F80和CZ2020-F100攻毒组分别有1头仔猪在4和6 DPC时出现轻度腹泻。与CZ2020攻毒组相比，CZ2020-F80和F100攻毒组仔猪的直肠拭子、肠道和其他器官中的病毒载量较低。在CZ2020-F80和F100攻毒组仔猪的肠道中未观察到明显的组织病理学病变。强毒株PDCoV感染也可诱导产生强烈的干扰素和促炎细胞因子。这些数据表明，CZ2020-F80和CZ2020-F100毒株通过连续传代显著减毒，具有开发减毒候选疫苗的潜力。
