Fig. 4. Antibody functional activity by epitope specificities.

Monoclonal antibody epitope binning was completed using RBD and SARS-CoV-2 S protein as target antigens. (A) A total of three noncompeting epitopes for RBD (RBD-A, RBD-B, and RBD-C) and three noncompeting epitopes for S (S-A, S-B, and S-C) were identified. (B) MAbs were evaluated for binding to different target antigens (S, NTD, RBD, RBD-SD1, and RBD-SD1-2) by ELISA and apparent EC₅₀ values are reported in micrograms per milliliter. (C) MAbs were evaluated for neutralization of SARS-CoV-2 pseudovirus using HeLa-ACE2 target cells. Antibodies are grouped according to epitope specificities, and neutralization IC₅₀ values are reported in micrograms per milliliter. (D) The MNP is reported for each mAb and grouped by epitope specificity. MAbs were mixed with (E) S or (F) RBD protein and measured for binding to HeLa-ACE2 target cells as a measure of competition to the cell surface ACE-2 receptor. (G) mAb neutralization potencies (IC₅₀) are plotted as a function of dissociation constants (KD) measured by SPR to RBD target antigen.