Figure 3: Function of VP35 and VP24 variants in IFN antagonism.

(a) Relative inhibition of IFN-β production by VP35. 293 cells were transfected with expression plasmids encoding different variants of the EBOV VP35 or empty vector (control), and a luciferase-reporter plasmid under control of an IFN-β promoter. Twenty-four hours later, cells were transfected either with a plasmid encoding the RIG-I CARD domain (stimulated) or with empty vector (unstimulated). After further 24 h, cells were harvested and reporter activity was measured. Fold induction was calculated as the ratio of reporter activity in stimulated to unstimulated cells. The mean and s.d. of three independent experiments are shown. (b) Relative inhibition of IFN-β signalling by EBOV protein VP24. 293 cells were transfected with increasing amounts of expression plasmids encoding different variants of the EBOV protein VP24 or empty vector (control), and a luciferase-reporter plasmid under control of an ISRE. Twenty-four hours later, cell medium was replaced with either fresh medium (unstimulated) or medium containing 1,000 I.U. human IFN-β 1a (stimulated). After further 8 h, cells were harvested and reporter activity was measured. Fold induction was calculated as in a. The mean and s.d. of three independent experiments are shown.