The antiparasitic drug niclosamide inhibits dengue virus infection by interfering with endosomal acidification independent of mTOR
BHK-21 cells were inoculated with DENV2 (MOI = 1) for 2 h in the presence of niclosamide (Niclo, 5 μM), the protonophores CCCP (50 μM) and FCCP (5 μM), the V-ATPase inhibitor (Baf A1, 100 nM) or rapamycin (Rap, 200 ng/mL). (A) Representative ratiometric live cell imaging of acridine orange (AO) staining showing acidic compartments (red). Nuclei were stained with Hoechst 33258 (blue). (B) Representative Western blot showing viral E protein expression in DENV2 (MOI = 1)-infected BHK-21 cells for the indicated times. The relative ratio to β-actin is shown. (C) Representative immunostaining and the relative mean fluorescence intensity (MFI) of viral dsRNA (green) at 6 h post-infection. (D) Plaque assay showing the level of viral replication 24 h post-infection. DMSO was used as a solvent control. For all images, representative data were selectively obtained from three individual experiments. Quantitative data are depicted as the mean ± SD of three independent experiments. * P < 0.05, ** P < 0.01, and *** P < 0.001. ns, not significant.