Fig. 3: Functional characterization of anti-SARS-CoV-2 RBD memory antibodies from vaccinated mAb recipients.

a-c, Monoclonal antibody binding to WT RBD. a, Graph shows ELISA binding monoclonal antibodies derived from mAb recipients after serial dilution. Each curve represents one antibody. Green curves show EC50s <10 μg/ml, grey dashed lines EC50s >10 μg/ml, solid black lines are antibodies that were below or equal to a negative control anti-HIV1 antibody 3BNC117 (thick, white-dashed line). C144 (thick, red-dashed line) is positive control. b Summary of EC50s derived from (a) mAb recipients in green, and controls in blue for all antibodies irrespective of isotype. c, as in (b) but IgM and IgG analyzed independently. Grey shaded area between horizontal dotted lines indicates antibodies with EC50s >10 μg/ml (poor binding) and non-binding antibodies arbitrarily grouped at 10 and 20 μg/ml, respectively. Ring plots summarize the fraction of all antibodies tested for the respective groups (encircled number). d, Plots show IC50s for all monoclonal antibodies isolated from vaccinated mAb recipients (green) or controls (blue). Ring plots illustrate the fraction of non-neutralizing (IC50 > 1000 ng/ml) antibodies (black slices) among all antibodies tested for the respective group (encircled number). e, as in (d) but IgM and IgG antibodies analyzed independently. For panels b-e, red horizontal bars and numbers represent median values. Statistical significance was determined using the two-tailed Mann-Whitney test for b and d, whereas the Kruskal-Wallis test with subsequent Dunn’s correction for multiple comparisons was used for c and e. To compare fractions from ring plots, the Chi-squared contingency statistic was used in b and c, and Fisher’s exact test for d and e. All experiments were performed at least in duplicate.