Figure 5.

Entry driven by the S proteins of the SARS-CoV-2 variants can be blocked with soluble ACE2, protease inhibitors targeting TMPRSS2, and a membrane fusion inhibitor

Top row, left panel: S protein-bearing particles were incubated with different concentrations of soluble ACE2 (30 min, 37°C) before being inoculated onto Caco-2 cells. Top row, middle and right panel: Caco-2 target cells were pre-incubated with different concentrations of serine protease inhibitor (Camostat or Nafamostat; 1 h, 37°C) before being inoculated with particles harboring the indicated S proteins. Bottom row, both panels: the peptidic fusion inhibitor EK-1 and its improved lipidated derivate EK-1-C4 were incubated with particles at indicated concentrations (30 min, 37°C) and then added to Caco-2 cells. All panels: transduction efficiency was quantified by measuring virus-encoded luciferase activity in cell lysates at 16–20 h post-transduction. For normalization, SARS-CoV-2 S protein-driven entry in the absence of soluble ACE2 or inhibitor was set as 0% inhibition. Presented are the average (mean) data from three biological replicates (each performed with technical triplicates [EK-1, EK-1-C4] or quadruplicates [soluble ACE2, Camostat, Nafamostat]). Error bars indicate the SEM. Statistical significance of differences between WT and variant S proteins was analyzed by two-way ANOVA with Dunnett’s posttest (p > 0.05, not significant [not indicated]; p ≤ 0.05, *; p ≤ 0.01, **; p ≤ 0.001, ***).