The cysteine protease domain of porcine reproductive and respiratory syndrome virus non-structural protein 2 antagonizes interferon regulatory factor 3 activation

There is growing evidence that porcine reproductive and respiratory syndrome virus (PRRSV) has developed mechanisms to subvert the host innate immune response PRRSV non-structural protein 2 (Nsp2) was suggested previously as a potential interferon (IFN) antagonist This study focused on Nsp2 to investigate its inhibitory mechanism of IFN induction It was demonstrated that Nsp2 strongly inhibited IFN-beta production by antagonizing activation of the IFN regulatory factor 3 (IRF-3) pathway induced by the Sendai virus (SeV) Further studies revealed that the cysteine protease domain (PL2) of Nsp2 was necessary for IFN antagonism Additionally, both full-length Nsp2 and the PL2 protease domain of Nsp2 were found to inhibit SeV-induced phosphorylation and nuclear translocation of IRF-3 These findings suggest that Nsp2 is likely to play an important role in subversion of IRF-3-dependent innate antiviral defences, providing a basis for elucidating the mechanisms underlying PRRSV pathogenesis