Anti–dengue virus (DENV) activity of human OAS3 variants with variations at residues 18 and 381. A, Human T-REx 293 cells stably transfected with pcDNA5/TO vector, or pcDNA5/TO with 4 variants of OAS3 depending on amino acid at position 18 and 381, were cultured in the absence (−) or presence (+) of doxycycline (Dox; 1 µg/mL) for 16 hours. The cells were then infected with DENV-1 or DENV-2 (multiplicity of infection, 5) for 24 hours. Culture supernatants were collected for viral titration by plaque-forming assays. Viral titer of the controls (Dox negative), represented as a dashed line, were normalized to compare DENV-1 and DENV-2 infections. Viral titers (Dox positive) were normalized with respect to the control titer (Dox negative) for each experiment and then natural logarithm transformed. Viral titers are means ± SD of 3 independent experiments that have been natural logarithm transformed. Statistically significant differences are indicated. B and C, The cell lysates were harvested for Western blotting with antibodies against DENV NS3, hemagglutinin tag for OAS3 expression, and actin. Band density was quantified with ImageJ, and relative ratios of NS3 to actin are shown. Abbreviation: PFU, plaque-forming units.