Fig. 1

ALT inhibited VZV replication in vitro. (A) A primary screen of 50 natural compounds against VZV infection at 10µM. Arrow indicated that ALT with optimal inhibition efficacy (86.6%) was selected. (B) Chemical structure of alantolactone. (C) and (D) Cell viability was measured in ARPE and WI-38 cells after being treated with ALT for 4 days. Cells were treated with ALT at the indicated concentrations. Cell viability was analyzed by CCK-8 assays. The half-maximal cytotoxicity concentration (CC50) was determined based on the results of the cell viability assay according to nonlinear trajectory analysis using GraphPad Prism. (E) Effects of ALT on morphological changes with or without VZV infection. ARPE-19 and WI-38 cells were infected with VZV at an MOI of 0.04, and typical CPE and green fluorescent plaques were observed at 4 days post infection (dpi). In the ALT treatment group, cells were pretreated with ALT at the indicated concentrations 1 h before VZV infection. (F) Plaque assays were performed according to materials and methods. (G) and (H) VZV virus titers of each group were calculated. The experiments were duplicated at least three times. (I) and (J) The falf-maximal inhibitory concentration (IC50) was determined based on the results of the Plaque assays according to nonlinear trajectory analysis using GraphPad Prism. P values were calculated with one-way ANOVA. ( *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001)