Extended Data Fig. 8: Polyclonal epitope mapping of trimer-binding antibodies in a representative protected animal by negative-staining electron microscopy (NSEM).

The analysis was performed using purified Fab fragments isolated from serum collected from macaque V3 (subgroup 1) at week 58. The arrow heads point to the trimer-bound Fab fragments. Visualization of antibodies binding to: a. A region compatible with the CD4-BS deep in the inter-protomer groove; b. A region in the inter-protomer groove more distal from the trimer axis than the CD4-BS; c. A region(s) at the trimer apex targeted by 2 Fabs simultaneously; d. A region at the trimer apex compatible with the V2-glycan supersite targeted by a single Fab; e. A region at the trimer base, presumably constituted by neo-epitopes produced by gp41 truncation.