IFNB1 and infection: Nsp15-defective rIBV-nsp15-H238A robustly activates PKR, efficiently induces SGs formation, and strongly induced the transcription of IFN-β; but in SG core proteins-defective cells, either by rIBV-nsp15-H238A infection or poly I:C stimulation, the induction of IFN-β signaling is severely decreased.