Fig. 2. Epitope binning and SARS-CoV-2 neutralization.

a Biolayer interferometry (BLI) was applied for the epitope binning experiments. Representative assay results are shown for MD65 mAb. The purified antibody was biotinylated, immobilized on streptavidin sensor and saturated with RBD. The complex was then incubated for 300 s with each one of the indicated antibodies. Time 0 represents the binding to the MD65-RBD complex. b Complete epitope binning of the eight selected MD monoclonal antibodies. Binding was evaluated by the ability of each pair of antibodies to simultaneously bind RBD, using biolayer interferometry. The matrix presents the concluded epitope specificity on the basis of the various competition experiments; see Supplementary Fig. 3 for the detailed competition profiles obtained by the binning experiments. c Four noncompeting RBD binding epitopes were identified and accordingly classified into four groups: I (blue), II (green), III (pink) and IV (yellow). d SARS-CoV-2 in vitro neutralization using plaque reduction neutralization test (PRNT). Neutralization potency was determined by the ability of each antibody (at indicated concentrations) to reduce plaques formation; results are expressed as percent inhibition of control without Ab. The values represent average of duplicates. e Binding of human ACE2 to RBD in the presence of neutralizing antibodies (representing each of the epitope groups) was tested by BLI. Each of the biotinylated antibodies was immobilized on streptavidin sensor, saturated with RBD, washed and incubated with recombinant human ACE2 for 300 s. Time 0 represents the binding of the ACE2 to the antibody-RBD complex.