Porcine reproductive and respiratory syndrome virus (PRRSV) could be sensed by professional beta interferon-producing system and had mechanisms to inhibit this action in MARC-145 cells

Porcine reproductive and respiratory syndrome virus (PRRSV) causes an economically important disease in swine-producing area, and interferon beta (IFN-β) is the first responder against the animal virus infection. However, whether PRRSV could induce the production of IFN-β is controversial. In this paper, we first time found that PRRSV could phosphorylate IFN-regulatory factor 3 (IRF-3) and weakly activate the IFN-β promoter in MARC-145 cells in early infection, but the activations of IRF-3 and IFN-β promoter were rapidly inhibited in the following infection. Furthermore, which components or products of the invading PRRSV cause PRRSV to inhibit IFN-β promoter activity attracted our attentions. The obtained results showed that PRRSV nsp1 could inhibit Poly(I:C)-induced IFN-β promoter activity in MARC-145 cells by down-regulating the protein level of IRF-3 and inhibiting the phosphorylation of IRF-3. In conclusion, our results suggested that PRRSV could be sensed by professional IFN-β-producing system and had mechanisms to inhibit this action in MARC-145 cells.