FIG 4.
Time-of-drug-addition assay for PF-00835231, GC-376, remdesivir, and a neutralizing antibody in A549+ACE2 cells. (a) At the indicated time points, A549+ACE2 cells were infected with SARS-CoV-2 USA-WA1/2020, treated with 3 μM monoclonal neutralizing antibody (control for targeting attachment and entry), 10 μM the drug GC-376 (control drug for 3CLpro inhibition), 3 μM PF-00835231 (3CLpro inhibitor), or 10 μM remdesivir (RdRp inhibitor). At 12 h (one round of replication) cells were fixed and stained for SARS-CoV-2 N protein, and infected cells were quantified by high-content microscopy. Means ± SEM from n = 3 independent experiments. (b) Schematic of SARS-CoV-2 life cycle in A549+ACE2 cells. 3CLpro, 3C-like protease; RdRp, RNA-dependent RNA polymerase.