Although porcine deltacoronavirus (PDCoV) is a significant pandemic threat in the swine population and has caused significant economic losses, information regarding the immune response in conventionally weaned pigs infected with PDCoV is scarce. Hence, the immune response in conventionally weaned pigs infected with PDCoV was assessed after challenge and rechallenge. After the first challenge, obvious diarrhea and viral shedding developed successively in all pigs in the four inoculation dose groups from 3 to 14 days postinfection (dpi), and all pigs recovered (no clinical symptoms or viral shedding) by 21 dpi. All pigs in the four groups exhibited significantly increased PDCoV-specific IgG, IgA and virus-neutralizing (VN) antibody (Ab) titers and IFN-γ levels in the serum after the first challenge. All pigs were completely protected against rechallenge at 21 dpi. The serum levels of PDCoV-specific IgG, IgA, and VN Abs increased further after rechallenge. Notably, the IFN-γ level declined continuously after 7 dpi. In addition, the levels of PDCoV-specific IgG, IgA and VN Abs in saliva increased significantly after rechallenge and correlated well with the serum Ab titers. Furthermore, the appearance of clinical symptoms of PDCoV infection in conventionally weaned pigs was delayed with reduced inoculation doses. In summary, the data presented here offer important reference information for future PDCoV animal infection and vaccine-induced immunoprotection experiments.

中文翻译：

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感染猪三角洲冠状病毒的常规断奶猪的免疫反应评估。

尽管猪三角洲冠状病毒（PDCoV）对猪群来说是一种重大的流行病威胁，并造成了重大的经济损失，但有关感染 PDCoV 的传统断奶猪的免疫反应的信息却很少。因此，在攻击和再攻击后评估感染 PDCoV 的传统断奶猪的免疫反应。第一次攻击后，感染后3至14天（dpi），四个接种剂量组的所有猪相继出现明显的腹泻和病毒排出，到21dpi时所有猪均恢复（无临床症状或病毒排出）。第一次攻击后，四组所有猪的血清中 PDCoV 特异性 IgG、IgA 和病毒中和 (VN) 抗体 (Ab) 滴度以及 IFN-γ 水平均显着升高。所有猪在 21 dpi 时都完全免受再次攻击。再次攻击后，PDCoV 特异性 IgG、IgA 和 VN Ab 的血清水平进一步升高。值得注意的是，IFN-γ水平在7 dpi后持续下降。此外，再次攻击后唾液中 PDCoV 特异性 IgG、IgA 和 VN Ab 的水平显着增加，并且与血清 Ab 滴度密切相关。此外，随着接种剂量的减少，传统断奶仔猪出现PDCoV感染临床症状的时间也被推迟。总之，这里提供的数据为未来PDCoV动物感染和疫苗诱导的免疫保护实验提供了重要的参考信息。