IFNB1 and infection: Infection with MERS-CoV-MA-Δ4b and MERS-CoV-mNLS led to reduced levels of IFN-β and IL-6 compared to MERS-CoV-MA-WT at 4 and 6 dpi, suggesting that the nuclear localization of 4b was necessary in vivo to induce the expression of IFN-β and IL-6.