Porcine epidemic diarrhea virus inhibits dsRNA-induced interferon-ß production in porcine intestinal epithelial cells by blockade of the RIG-I-mediated pathway

Cao, Liyan; Ge, Xuying; Gao, Yu; Herrler, Georg; Ren, Yudong; Ren, Xiaofeng; Li, Guangxing

PEDV impeded poly (I:C)-mediated activation of IRF-3, but not NF-κB IRF-3 and NF-κB are two essential IFN-β transcription factors. In unstimulated cells, IRF-3 is ubiquitously present in the cytoplasm as an inactive monomer, whereas NF-κB is present as a homodimer or heterodimer bound to the inhibitory proteins IκB in the cytoplasm [28] . Phosphorylation, which is a key step during IRF-3 and NF-κB activation, in turn, leads to nuclear translocation. Therefore, we evaluated whether PEDV infection induced IRF-3 and p65 activation by western blot analysis. Following PEDV infection, the whole cell extracts were prepared for the indicative times, in Fig. 2a , IRF-3 still existed in the cytoplasm, and the levels of IRF-3 protein was almost equal with mock-infected cells, while the phosphorylation of IRF-3 (p-IRF-3) did not detect in the PEDV infected cells in comparision to a obviously signal in poly (I:C)-transfected cells. On the contrary, compared with the amount of NF-κB subunit p65 in the cytoplasm, the phosphorylation of p65 (p-p65) increased with progression of PEDV infection in the nucleus. Meanwhile, the concentration of poly (I:C)induced p65 nuclear translocation was clearly increased. PEDV N protein was also detected in PEDV-infected cells. These data suggested that PEDV did not induce activation of IRF-3, but NF-κB.