Effect of treatment of cells or virus with 3b before and during infection. Pretreatment of cells: Vero cells were incubated with maintenance medium containing or not 100 μM 3b for 2 h at 37°C, then compound was removed and cells were infected with DENV-2. Virus yields were determined at 48 h p.i. Pretreatment of virus: DENV-2 suspensions were incubated with MEM containing or not 100 μM 3b for 1.5 h at 37°C and then remaining infectivity was determined by plaque assay. Treatment during infection: Compound was added to Vero cells after virus adsorption and maintained for 48 h at 37°C, when virus yields were determined. Results are expressed as percent of remaining infectivity in compound-treated samples compared to untreated ones. Each value is the mean of triplicate assays ± standard deviation.