Fig. 2: CV3-25 binds to a linear peptide encompassing the C-terminus of the stem helix.
From: Structural definition of a pan-sarbecovirus neutralizing epitope on the spike S2 subunit
a Representative 2D class averages of CV3-25 IgG bound to SARS-CoV-2 6P-D614G S protein by negative stain electron microscopy. A single Fab of the IgG—highlighted in teal—can be seen bound to the lower S2 domain of the S protein. The red circle highlights the fullly IgG visible in 2D. Images without highlights are shown in the left column for comparison. b Segmented 3D reconstruction of a CV3-25 Fab (dark green) bound to the lower S2 domain of the S protein. Binding of the B6 (c), CC40.8 (d), and CV30 (e) mAbs to SARS-CoV-2 S6P alone or a SARS-CoV-2 S6P-CV3-25 complex as indicated. f Alignment of a set of 15mer peptides that overlap by 11 amino acids spanning residues 1133–1171 of the SARS-CoV-2 spike protein. The region that corresponds to the stem helix in the prefusion wild-type spike protein (based on the 6XR8) is shown in bold. g CV3-25 was tested for binding to the peptides in (e), and to a 15mer peptide derived from an HIV-1 Env protein. h CV2-10, which also binds to S2, but does not compete with CV3-25 was tested for binding to the peptides in (f). Each data point represents a technical replicate conducted in duplicate in (g) and (h). CV3-25 Fab binding was measured to the SARS-CoV-2 stem helix peptide: 1145-LDSFKEELDKYFKNHTSPDVDLG-1167 (i) or a stabilized SARS-CoV-2 spike protein by BLI (j).
