FIG 4.
Antiviral time-of-addition assay. MRC5 cells were infected with AD169IE2-YFP (MOI, 3) at time zero and treated with a single dose of each compound (cymarin, 500 nM; K-strophanthin, 500 nM; mansonin, 5,000 nM; strophanthidin, 5,000 nM; glucostrebloside, 5,000 nM; strogoside, 5,000 nM; strophanthidol, 5,000 nM; ouabain, 50 nM; β-antiarin, 50 nM; or convallatoxin, 50 nM) at various times relative to infection (−1 hpi to 8 hpi). At 18 hpi, the number of YFP+ cells was determined using an Acumen eX3 cytometer. The relative maximal inhibition was determined based on the 0-hpi sample as 100% relative maximal inhibition. The error bars represent standard errors of the mean. Statistical significance was determined by a two-tailed t test of means; *, P < 0.05; **, P < 0.01; ***, P < 0.001.