ACE2 and infection: To address this question, we repeated the experiment with Calu-3, 293T-ACE2, and Huh-7 cells and found that infection efficiencies in Calu-3 and Huh-7 cells were significantly decreased, while the decrease was not as significant in 293T-ACE2 cells (Fig. 5c, d and Supplementary 8c, d).