A549 cells were transfected with an expression construct encoding viperin using lipofectamine 2000 (Invitrogen, USA). Cells were selected using 500 mg/ml G418 and screened for viperin expression by immunoblotting. Cells were cultured overnight in 6 well plates before IFNb (Glycoferon, Singapore), at a final concentration of 500 U/ml, was added to each well while control wells remained untreated. Twelve hours post IFNb treatment, cells were infected with dengue virus (TSV01; MOI 1) for 48 hrs and the plaque assay was used to determine virus production.