Figure 3.
S20 inhibits at early times during infection and is effective against HA-mediated viral entry. (a) Time-of-addition assay for inhibition of influenza A/WSN/33 virus by S20. A549 cells were infected with influenza virus A/WSN/33 (MOI = 1). Compound S20 was present in the culture medium 2 h before infection or added to the medium at the indicated time points postinfection at its CC10 concentration. Viral titers were determined 24 h postinfection by plaque assay. The assay was performed in triplicate; results are presented as the mean ± SD. (b) Inhibitory activity of S20 at the indicated concentrations on infection of A549 cells with luciferase-expressing lentiviruses pseudotyped with VSV-G or WSN HA and NA. The non-entry inhibitor A3 has no effect on the pseudotyped particle system and served as a negative control. The samples were tested in triplicate, and the data are presented as the mean ± SD.