Fig. 8.

Impact of the cathepsin B/L inhibitor MDL 28170 on virus–cell (left panel) and cell–cell fusion (right panel) driven by wt SARS-S and SARS-S mutant T760R. Left panel: 293T target cells were pre-incubated with the indicated concentrations of MDL 28170 for 1 h and thereafter infected in quadruplicateswith infectivity-normalized pseudotypes bearing the indicated S-proteins. Luciferase activities in cell lysates were determined at 72 h post infection. The results of a representative experiment carried out in triplicates are shown and were confirmed in two separate experiments. Right panel: 293T target cells transfected with gal5-luc and either pcDNA3 (control) or ACE2 were mixed with effector cells expressing GAL-VP16 in combination with the indicated S-proteins. After mixing, cells were either left untreated or treated with 1 μM MDL 28170. Luciferase activities were determined two days after mixing. The results of a representative experiment are shown; comparable results were obtained in an independent experiment. Error bars indicate SD.