4.4. Plaque Reduction Assay

Vero cells (4*10⁵ cells/well) were cultured in 12-well plates and incubated with 50 PFU (plaque forming unit) of HSV-1. The viral suspension was adsorbed on cells for 1 h at 37 °C. Next, the inoculum was removed and the NPRE or solvent (DMSO), diluted in medium containing 0.8% methylcellulose, was added at various concentrations (0.1, 0.2, 0.4, 0.6, 0.8 mg/mL). Acyclovir was used as positive control at the concentration of 20 µM. After 3 days, the virus plaques formed on Vero cell monolayers were visualized and counted by crystal violet staining at 10× magnification with an inverted microscope (Leica DMIL).