Figure 1.
Anti-MERS-CoV activity of the cardiotonic steroids digitoxin, bufalin, cinobufagin, telocinobufagin, bufotalin, cinobufotalin, and resibufogenin. (A) The dose–response curve analysis by immunofluorescence staining was performed to determine the antiviral effect of the cardiotonic steroids, ranging between 0.001 and 10 μM in Vero cells. (B) The dose–response curve analysis of the viral cytopathic effect was performed to determine the antiviral effects of cardiotonic steroids, ranging between 0.01 and 10 μM in Calu-3 cells. Inhibition of MERS-CoV infection (%; blue circles) and cell viability (%; red squares) were indicated. The IC50 values were calculated using non-linear regression analysis. The data represent duplicate experiments and are presented as the mean ± SEM.