Figure 4.

EM Reveals Distinct Predominant Epitopes Targeted by Convalescent Plasma Antibodies

(A) Side and top views for representative 3D reconstructions of four nsEMPEM datasets (S protein alone, S + COV21 Fabs, S + COV57 Fabs, S + COV107 Fabs). Bound Fabs observed in reconstructions from COV21 and COV57 plasmas are highlighted with false coloring as orange and green, respectively. No Fabs were observed in the reconstruction of COV107 Fabs plus S protein. Refined 3D models for SARS-CoV-2 S trimer-polyclonal Fab complexes from COV21 (B), and COV57 (C) were rigid-body fit with reference structures in Chimera (Goddard et al., 2007; Pettersen et al., 2004), displayed as cartoons (S1^A: blue, S1^B: red, S2: gray).

(B) For COV21, the volume was best-fitted with PDB 6VYB (SARS-CoV-2, one “up” S1^B conformation, inset). Overlay of PDB 6NB6 showed similarities in S1^B epitope targeting of COV21 Fab (orange) and the human SARS-CoV neutralizing antibody, S230 (magenta, cartoon).

(C) COV57 was fitted with PDB 6VXX (closed, prefusion conformation, inset). Fab density (green) was focused on the S1^A domain.

See also Figure S4.