B9-scFv neutralizes SARS-CoV but does not compete with ACE2.A, neutralization of viruses pseudotyped with SARS-CoV Spike protein (left; n = 9), SARS-CoV-2 (Wu-1/D614G; middle; n = 3), or VSV-G (right; n = 3) by the indicated concentrations CR3022-scFv or B9-scFv. Data are presented as mean ± SD. B, estimation of the IC50 of CR3022- (n = 3) or B9-scFv (n = 4) for the neutralization of SARS-CoV pseudotyped lentiviruses. Data are presented as mean ± SD. Estimated IC50 values are shown. C, FACS-based quantification of SARS-CoV RBD binding to hACE2 in the presence of the indicated concentrations of ACE2-Fc, B9-scFv, or CR3022-scFv (n = 4). Data are presented as mean ± SD, p = 0.0004 (unpaired Student’s t test). FACS, fluorescence-activated cell sorting, RBD, receptor-binding domain.