e. SARS-CoV (I-II) and SARS-CoV-2 (III-IV) S-mediated syncytium formation on 293T/ACE2 cells at 48 h. f. SARS-CoV (I-II) and SARS-CoV-2 (III-IV) S-mediated syncytium formation on Huh-7 cells at 48 h. Scale bar equals 400 μm in d-f. 