Fig. 3|. Clonal analysis of germinal centre response to SARS-CoV-2 immunization.

a, Binding of monoclonal antibodies (mAbs) generated from germinal centre B cells to SARS-CoV-2 S, N-terminal domain (NTD) of S, RBD, or S proteins of betacoronavirus OC43 or HKU1, measured by ELISA. Results are from one experiment performed in duplicate. Baseline for area under the curve was set to the mean + three times the s.d. of background binding to bovine serum albumin. b, Clonal relationship of sequences from S-binding germinal centre-derived monoclonal antibodies (cyan) to sequences from bulk repertoire analysis of plasmablasts from PBMCs (red) and germinal centre B cells (blue) sorted 4 weeks after immunization. Each clone is visualized as a network in which each node represents a sequence and sequences are linked as a minimum spanning tree of the network. Symbol shape indicates sequence isotype: IgG (circle), IgA (star) and IgM (square); symbol size corresponds to sequence count. c, d, Comparison of nucleotide mutation frequency in IGHV genes of naive B cells sorted from individuals vaccinated with influenza virus vaccine¹⁹ (grey) to clonal relatives of S-binding monoclonal antibodies among plasmablasts sorted from PBMCs and germinal centre B cells 4 weeks after immunization (green) in indicated participants (c) and between clonal relatives of S-binding monoclonal antibodies cross-reactive (purple) or not (teal) to seasonal coronavirus S proteins among plasmablasts sorted from PBMCs and germinal centre B cells 4 weeks after immunization (d). Horizontal lines and error bars indicate the median and interquartile range. Sequence counts were 2,553 (naive), 199 (participant 07), 6 (participant 20), 240 (participant 22), 54 (cross-reactive) and 391 (not cross-reactive). P values from two-sided Kruskal–Wallis test with Dunn’s post-test between naive B cells and S-binding clones (c) or two-sided Mann–Whitney U test (d).