Assay for Antiviral Activity

BHK-21 cells or Vero E6 cells were seeded in six-well plates and allowed to adhere overnight. Montelukast sodium serially diluted in serum-free DMEM and 50 pfu of viruses were mixed and incubated 1 h at room temperature before being added to each well of cells. After incubation at 37°C for 2 h, the plaque assay was performed, and the plaques were visualized as described above. Curcumin, a reported antiviral drug (Mounce et al., 2017), was included as positive control. The percent inhibition by the montelukast was calculated, and the 50% inhibitory concentration (IC50) value was determined by using the software CalcuSyn (Chou and Talalay, 1984).