IFIH1 and infection: As illustrated in Figure 2, the transcript and protein levels of IFN-α, IFN-β, RIG-I, MDA5, MAVS, TRAF3, TBK1, and IRF3 in the PRRSV-ICs-infected cell group were significantly diminished at 12 h and 24 h post-infection compared to those in the PRRSV-PNI-infected cell group (Figure 2a–p,r).