Figure 4. 3BC315 binding to BG505 Env analysed by SPR.

(a) The epitopes of 35O22 and 3BC315 are shaded on the surface of an unliganded SOSIP.664 cryo-EM structure (EMDB ID: 5782). The epitopes of 3BC315 (light blue) and 35O22 (pink) extensively overlap (navy). (b) 35O22 (pink) and 3BC315 (blue) bind the trimer from two different approach angles despite a large overlap in their epitopes. (c) SPR analysis of sequential antibody binding to BG505 SOSIP.664_293T trimer. The sequential-injection curve is colour-coded with the label of its first Ab. The single-injection curve for the second Ab in the sequential injection is superimposed on its corresponding curve in the second injection in a different colour. The curves are displayed in the same order as shown in the matrix to the right. The matrix diagram gives the binding of the second Ab in a sequential injection relative to its binding when injected alone (% of plateau colour-coded as shown in key at the bottom). The values are the means of two replicate experiments with s.e.m. values <5% of the means. (d) The 3BC315 IgG reactivity with BG505 SOSIP.664_293T trimer, gp120–gp41_ECTO-293T protomer and gp120_293T monomer is shown. All gp140 constructs shown here have the SOS and IP mutations. (e) The 3BC315 IgG reactivity with equivalent amounts of 293T-produced BG505 SOSIP trimers and cleavage-modified variants. Variants containing the R6 motif are fully cleaved, whereas those with SEKS are uncleaved.