Fig. 5

IFN-λ inhibits DENV-2 replication in a dose-dependent manner. C33-A cells were treated with increasing concentrations of IFN-α (a), IFN-λ1 (b) or IFN-λ2 (c) and then infected by DENV-2 (MOI = 0.1). Forty-eight hours post-infection, the viral titer was obtained by plaque assay. The doses used were 10–40 ng/mL for IFNλ1 or IFN-λ2 and 100–400 UI/ml for IFN-α. Plots show the percentage inhibition of the viral titer in each group compared to untreated cells. Dotted lines represent the IC50 values corresponding to IFN-λ1 = 8.705 ng/ml, IFN-λ2 = 8.24 ng/ml, IFN-α = 122–138 IU/ml. The points are representative of two independent experiments performed in triplicate. Experiments were fit to the Hill equation, using nonlinear regression to estimate the IC50 of IFN-λ1, IFN-λ2 or IFN-α (concentration of IFN that inhibited DENV-PFU production by 50 %, compared with parallel IFN free infected cultures). These IC50 values were considered for subsequent experimental procedures