Impact of truncated NS1 proteins on IFN-β promoter activity. HEK-293TN cells were transiently transfected with IFN-β luciferase reporter plasmid, RIG-I and β-galactosidase expression plasmids, and vectors encoding full-length or truncated NS1 from C/JJ/50 or C/JHB/1/66, or empty pCI vector. 24 h post transfection, RIG-I was induced with poly(I:C) or vRNA, and eight hours post induction, luciferase activities of cell lysates were measured and normalised to β-galactosidase activities. Only full-length and N-terminally-truncated NS1 proteins inhibited reporter activity. Error bars indicate standard deviations.