2',5'-Oligoadenylate synthetase 1(OAS1) inhibits PRRSV replication in Marc-145 cells.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically destructive disease for global pig industry. Although its invasion mechanism is clear, the knowledge of pathogen and host interaction is less known. Here, we found that PPRSV infection led to induction of 2', 5'-oligoadenylate synthetase gene 1(OAS1), an important interferon-stimulated gene. More importantly, ectopic overexpression of OAS1 significantly restricted the replication of PRRSV in 24 and 36 h post-infection in Marc-145 cells, and indirect immunofluorescence assay with antibody against PRRSV N protein displayed significantly lower frequency of fluorescence stained cells and reduced cytopathogenic effects of PRRSV on OAS1-transfected Marc-145 cells. Meanwhile, knockdown of endogenous OAS1 increased the PRRSV ORF7 mRNA level to 1.6 and 1.7 times of that in control in 24 and 36 h post-infection of PRRSV, and led to approximate 5.5 times increase of the frequency of fluorescence positive cells compared to negative control (p < 0.01). The obtained results strongly support a direct restriction function of OAS1 to PRRSV replication, which may contribute to the antiviral effect of the interferon system on PRRSV replication.