2.1. Cell Culture

HEK293T (ATCC CRL-3216) and HEK293T-hACE2 cells [11] were grown in Dulbecco’s Modified Eagle Medium (DMEM; Sigma, Taufkirchen, Germany) supplemented with 10% foetal bovine serum (Sigma, Taufkirchen, Germany), 5% l-glutamine (200 mM; Lonza, Verviers, Belgium), and 1% penicillin/streptavidin (Fisher Scientific, Schwerte, Germany) at 37 °C under 5% CO₂. The medium for HEK293T-hACE2 cells was furthermore supplemented with 50 µg/mL Zeocin™ (Fisher Scientific, Schwerte, Germany).