Supernatants from transfected cells were harvested and used to infect target 293T cells overexpressing the SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2) (292T/ACE2) (32, 33) in 96-well plates, and Gluc activity was measured at 24, 48, and 72 hours after infection (Figure 1B). Here, ACE2 is linked to infection.