Porcine epidemic diarrhea virus (PEDV) is an enveloped, single-stranded positive-sense RNA virus that belongs to a porcine entero-pathogenic alphacoronavirus, causing lethal watery diarrhea in piglets. Despite existing study reports the sole accessory protein ORF3 identified as NF-κB antagonist, the contribution of PEDV ORF3 to production of the pro-inflammatory cytokines mediated by NF-κB signaling remains largely unknown. Thus in this present study, we showed that PEDV ORF3 protein significantly inhibited the productions of pro-inflammatory cytokines interleukin-6 (IL-6) and IL-8. The phosphorylation of IκBα was inhibited by ORF3 protein, but no degradation of IκBα was induced in ORF3-expressing cells. Furthermore, PEDV ORF3 inhibited NF-κB activation through preventing nuclear factor p65 phosphorylation and down-regulating p65 expression level, as well as interfering nuclear translocation of p65, eventually resulting into the inhibition of IL-6 and IL-8 production. Our study definitely links PEDV ORF3 to inhibition of pro-inflammatory cytokines production, which will provide new insight into the molecular mechanisms of NF-κB activity inhibited by PEDV proteins to facilitate virus evasion of host innate immune.

猪流行性腹泻病毒（PEDV）是一种有包膜的单链正义RNA病毒，属于猪肠道致病性α冠状病毒导致仔猪致命的水样腹泻。尽管现有研究报道了唯一的辅助蛋白ORF3被鉴定为NF-κB拮抗剂，但PEDV ORF3对由NF-κB信号介导的促炎性细胞因子产生的贡献仍然未知。因此，在本研究中，我们表明PEDV ORF3蛋白显着抑制促炎细胞因子白介素6（IL-6）和IL-8的产生。IκBα的磷酸化被ORF3蛋白抑制，但是在表达ORF3的细胞中没有诱导IκBα的降解。此外，PEDV ORF3通过阻止核因子p65磷酸化和下调p65表达水平，以及干扰p65的核易位，抑制NF-κB活化，最终导致IL-6和IL-8产生受到抑制。