Fig. 1.

Cell-based high-throughput screening of FDA-approved drug library identified benidipine hydrochloride as an inhibitor of SFTSV replication. a Cell-based high-throughput screening to identify inhibitors of SFTSV replication. b Analysis of screen reproducibility. Dots represent the inhibition rate (left) and cell survive rate (right) for each drug from two replicates of the screen. Red dots indicated 14 drugs that inhibited virus infection (inhibition rate > 70%) without causing significant cytotoxicity (survive rate > 70%). c Dose-dependent inhibitory effects of the seven selected compounds analyzed in Vero cells. Vero cell monolayers were treated with each drug at the indicated concentrations for 1 h, and then inoculated with SFTSV at MOI of 1. At 36 hpi, cells were fixed, and the infected cells were detected through immunofluorescence analysis using antibody against NP protein. The chemical structure of each compound is displayed. d Survival rate analysis of benidipine hydrochloride treatment in Vero cells. CC₅₀: 50% cytotoxic concentration. e Dose-dependent inhibition effects of benidipine hydrochloride on SFTSV infection. IC₅₀: 50% inhibitory concentration. f Inhibition effect of benidipine hydrochloride on the production of infectious SFTSV progeny virions in Vero cells. Vero cells were treated with serial concentrations of benidipine hydrochloride and infected with SFTSV, and virus titer in the supernatant at 16 hpi was determined. g Inhibition effect of benidipine hydrochloride on the production of infectious SFTSV progeny virions in Huh7 cells. Experiment in Huh7 cells was performed as described in f. h Inhibition effect of benidipine hydrochloride on intracellular SFTSV vRNA level in Huh7 cells. Huh7 cells were treated with serial concentrations of benidipine hydrochloride and infected with SFTSV. At 48 hpi, intracellular RNA was extracted and the vRNA level of SFTSV was measured with qRT-PCR. Comparison of mean values between benidipine hydrochloride-treated group and vehicle (DMSO) group (f–h) was analyzed by Student’s t-test. *P < 0.05; **P < 0.01; ***P < 0.001. R² (c, f–h) was estimated by nonlinear regression model (curve fit)