Influence on apoptosis and type I interferon induction by overexpression of ORF 7a, ORF 7b, and ORF 7b with the Frankfurt-1-specific deletion. (A) Cleavage of procaspase 3 analyzed by Western blot on cell lysates 48 h after transfection with indicated plasmids or infection with Sendai virus (20 hemagglutinating units). (B) Interferon beta promoter-specific reporter gene expression (y-axis), shown as the factor of induction as compared to the mock-transfected, non-superinfected control (see below). The assay was done by transfection of HEK 293 cells with plasmids expressing either Ebolavirus VP35, ORF 7a, ORF 7b, or ORF 7b with a deletion corresponding to the ORF 7b deletion in Frankfurt-1 (x-axis), as well as reporter constructs for the interferon beta promoter (Firefly luciferase) and the SV40 promoter (Renilla luciferase). 24 h post transfection, cells were either superinfected with SeV (20 hemagglutinating units) or left uninfected. Interferon-specific reporter gene expression was determined 24 h after superinfection (black bars) or mock infection (grey bars). The experiment was done in triplicate and standard deviations are shown. To determine interferon-specific expression, the Firefly luminescence signal was divided by the Renilla luciferase signal.