IFNB1 and infection: Therefore, we measured P, M, and P–M mRNAs transcribed from VSV-IFNβ or VSV-IFNβ-IGR P/MC-U, upon infection of B16 and Hep3BP, or B16-CSDE1C-T and Hep3B-CSDE1C-T, cells within 6 h of infection, which represents an early stage of replication (Fig. 3).