Figure 5. Characterization of SFTSV L Endonuclease Inhibitors.

(A) FRET-based assays with SFTSV L 1–231 aa (black), HRTV L1–231 aa (red), or IAV PA 1–192 aa (blue) in the presence of 1 mM MnCl₂ and increasing concentrations of BXA. The dose-response curves were fit to yield IC₅₀ values using a nonlinear regression model. Experiments were carried out in triplicate and average data are shown with error bars representing the standard deviation.

(B) Plaque reduction assays for SFTSV (black) and HRTV (red). Plaques were counted by visual examination and the required concentration to reduce the 50% plaque number (EC₅₀) was calculated as relative to the control without BXA. Experiments were carried out in duplicate and average data are shown with error bars representing the standard deviation.

(C and D) Virus growth inhibition assays of (C) SFTSV or (D) HRTV in the presence of BXA. BXA concentrations used are as follows: 1000 nM, square; 500 nM, diamond; 250 nM, hexagon; 125 nM, down triangle; 62.5 nM, cross; and 0 nM, star. The virus yield was visualized by immunostaining and expressed as TCID₅₀/mL using the Reed-Muench method. Experiments were carried out in duplicate.