Abstract: The aim of this study was to investigate the effect of porcine deltacoronavirus(PDCoV) infected neonatal piglet on small intestinal goblet cells (GC). Six neonatal piglets without colostrum were randomly divided into infection group (n=3) and control group (n=3). After acclimation for 48 h, the infected group was inoculated orally with a PDCoV-CHN-HG-2017 preparation with a titer of 1×10⁵TCID₅₀·mL^-1 (5 mL per pig), while the mock-infected group was inoculated with 5 mL of maintenance medium. Clinical signs were monitored hourly. The infected piglets developed typical symptoms, such as diarrhea, dehydration and lethargy, from 22 to 70 hours post inoculation (hpi). Piglets were euthanized at 22, 39 and 70 hpi after the onset of clinical symptoms. At the same time point, one piglet was treated in the control group. HE staining, PAS staining and AB staining were used to observe the histopathological changes and the number of GC in the small intestine of piglets. Fluorescent quantitative PCR and ELISA were used to detect the transcriptional quantity and content of mucoprotein-2 (MUC2) and hairy and enhancer of split-1 (Hes1) in small intestine of neonatal piglets. The results showed that piglets in the infected group had different degree of damage to the mucosal structure of small intestine compared with piglets in the control group, the villus length were significantly decreased (P<0.05), the ratio of VH:CD significantly decreased (P<0.05). Compared with the control group, the number of GC in each segment of small intestine of infected piglets was significantly reduced. The results of PAS staining and AB staining were consistent. Compared with the control group, the transcription and content of Hes1 mRNA in each segment of the small intestine of piglets in the infected group were all increased, and there were significant differences in the transcription of Hes1 in jejunum and ileum (P<0.01 or P<0.05), and there were significant differences in the content of Hes1 mRNA in the duodenum and ileum (P<0.01). Compared with the control group, the transcription and content of MUC2 mRNA in each segment of the small intestine of infected piglets were reduced, and the differences were significant in the duodenum and ileum (P<0.05, P<0.01 or P<0.001). In summary, the number of small intestinal GC was significantly reduced after PDCoV infection in neonatal piglets. PDCoV infection in piglets may inhibit the formation and secretion of GC in the small intestine by activating the Notch signaling pathway in the intestine to enhance the expression of target gene Hes1, resulting in a decrease in the number of GC and the expression of MUC2.

Key words: PDCoV, piglet, goblet cell, small intestine, Hes1, MUC2