IFN-β1 mRNA was induced prominently and time-dependently in MRC-5 cells during the 3 days after infection with HCoV-OC45, and then reduced at 4 dpi; by contrast, no IFN-β1 mRNA was detected in virus-infected cells that were treated with kurarinone (Figure 2E). This evidence concerns the gene IFNB1 and infection.