ACE2 and infection: The relative infectivity of SARS-CoV, SARS-CoV-2, and VSV pseudotypes in 293T/ACE2 cells, as compared with the background control, was plotted in Figure 1C, showing that lentiviral SARS-CoV-2 S pseudotypes consistently produced a luciferase signal 50- to 100-fold above background at 2–3 days after infection.