Following virus infection, expression of IFN-β (measured by enzyme-linked immunosorbent assay [ELISA]) and the mRNA level of the IFN-stimulated gene 56 (ISG56, measured by RT-qPCR) were increased approximately twofold as compared to WT cells (Fig. 3 J and K) without a detectable change in Ifnb1 mRNA levels (SI Appendix, Fig. S5B). This evidence concerns the gene IFNB1 and viral infectious disease.