Isolation, characterization and transcriptome analysis of porcine deltacoronavirus strain HNZK-02 from Henan Province, China

Porcine deltacoronavirus (PDCoV), an emerging porcine enteropathogenic coronavirus, causes acute watery diarrhea and vomiting in piglets. Here, we isolated a strain of PDCoV from intestinal content of a piglet with severe watery diarrhea on a farm located in Henan Province, named PDCoV strain HNZK-02. Subsequently, the complete genomes of cell-cultured PDCoV HNZK-02 passage 5 and 15 were sequenced and analyzed. There was a continuous 3-nucleotide deletion and 7 amino acid changes in S genes when compared with the other reported PDCoVs. RNA sequencing (RNA-seq)-based transcriptome analysis was used to quantitatively identify differentially expressed genes after PDCoV infection in ST cells. In total, 523 differentially expressed genes (DEGs) were identified, including 62 upregulated genes and 457 downregulated genes. The 62 upregulated genes were associated with TNF signaling pathway, cytokine-cytokine receptor interaction, Toll-like receptor signaling pathway, IL-17 signaling, chemokine signaling pathway and NF-κB signaling pathway. The significant expressing changed genes, including three antiviral genes (Mx1, OASL, OAS1) and three inflammatory chemokine related genes (CCL5, CXCL8, CXCL10) were further validated using quantitative real-time RT-PCR (qRT-PCR) assay. It showed the consistent expression patterns of the candidate genes with those from RNA-seq. Our results demonstrated that PDCoV infection activates NF-κB signaling pathway and leads to the expression of inflammatory factors, which may be related to TLRs but TLR2 is not a critical factor.In general, these results can help us to confirm the molecular regulation mechanism and also provide us a comprehensive resource of PDCoV infection.