IFNB1 and infection: Initially, we tested whether infection with PPRV stimulated the production of IFN-β, using PPRV-infected Vero-human-SLAM (VHS) cells which had previously been transfected with a reporter plasmid expressing luciferase under the control of the IFN-β promoter and a transfection control plasmid constitutively expressing β-galactosidase.