Porcine epidemic diarrhea virus nsp4 induces pro-inflammatory cytokine and chemokine expression inhibiting viral replication in vitro.

Porcine epidemic diarrhea virus (PEDV) causes severe economic loss in the pig industry each year. To better understand the relationship between cytokines and PEDV replication, in this study, pro-inflammatory cytokine and chemokine expression profiles in Vero cells infected with PEDV were analyzed. Real-time quantitative PCR assay indicated that IL-1α, IL-1β, TNF-α, CCL2, CCL5 and CXCL8 expression levels were significantly upregulated. Moreover, overexpression and siRNA silencing assays showed that overexpression of IL-1α, IL-1β, TNF-α, CCL2, CCL5 and CXCL8 could significantly inhibit PEDV replication, while silencing of IL-1α, IL-1β, TNF-α, CCL2, CCL5 and CXCL8 could significantly promote PEDV replication. Finally, a dual-luciferase reporter assay showed that nsp4 contributed to the expression of IL-1α, IL-1β, TNF-α, CCL2, CCL5 and CXCL8 via the NF-κB pathway. Together, these data determined that PEDV nsp4 could upregulate pro-inflammatory cytokine and chemokine expression, inhibiting viral replication in vitro. These results provided novel insights for understanding the roles of cytokines in PEDV replication.