Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus (CoV) that causes lethal watery diarrhea in neonatal pigs and poses economic and public health burdens. Currently, there are no effective antiviral agents against PDCoV. Curcumin is the active ingredient extracted from the rhizome of turmeric, which has a potential pharmacological value because it exhibits antiviral properties against several viruses. Here, we described the antiviral effect of curcumin against PDCoV. At first, the potential relationships between the active ingredients and the diarrhea-related targets were predicted through a network pharmacology analysis. Twenty-three nodes and 38 edges were obtained using a PPI analysis of eight compound-targets. The action target genes were closely related to the inflammatory and immune related signaling pathways, such as the TNF signaling pathway, Jak-STAT signaling pathway, and so on. Moreover, IL-6, NR3C2, BCHE and PTGS2 were identified as the most likely targets of curcumin by binding energy and 3D protein-ligand complex analysis. Furthermore, curcumin inhibited PDCoV replication in LLC-PK1 cells at the time of infection in a dose-dependent way. In poly (I:C) pretreated LLC-PK1 cells, PDCoV reduced IFN-β production via the RIG-I pathway to evade the host's antiviral innate immune response. Meanwhile, curcumin inhibited PDCoV-induced IFN-β secretion by inhibiting the RIG-I pathway and reduced inflammation by inhibiting IRF3 or NF-κB protein expression. Our study provides a potential strategy for the use of curcumin in preventing diarrhea caused by PDCoV in piglets.
Keywords: PDCoV; RIG-I; curcumin; molecular docking.