Figure 2.

Anti-SARS-CoV-2 RBD memory B cells after breakthrough infection. (A and B) The frequency (A) and the number (B) of WT RBD-specific B cells are indicated for young participants after Vax3 (n = 24) and elderly participants 8.5 mo after Vax3 (n = 7) or 3 mo after Vax4 (n = 24, in blue). (C) Pie charts show the distribution of IgG antibody sequences obtained from WT-specific memory B cells from five younger individuals assayed after the third mRNA dose (Vax3); two elderly individuals after Vax3, and three elderly individuals after Vax4 (see also Fig. S3 C). The number inside the circle indicates the number of sequences analyzed for the individual denoted above the circle. Pie slice size is proportional to the number of clonally related sequences. The black outline and associated numbers indicate the percentage of clonal sequences detected at each time point. Colored slices indicate persisting clones (same IGHV and IGLV genes, with highly similar CDR3s) found at more than one time point within the same individual. Gray slices indicate clones unique to the time point. White slices indicate sequences isolated only once per time point. (D) Circus plot depicts the relationship between antibodies that share V and J gene segment sequences at both IGH and IGL. Purple, green, and gray lines connect related clones, clones and singles, and singles to each other, respectively. (E and F) The Shannon-Weiner index for diversity analysis (E) and clonality analysis (F) of the sequences from C. All experiments were performed at least in duplicate and repeated twice. The elderly Vax4 value is shown in blue. Red bars and numbers in A, B, E, and F represent mean. Statistics in A and B were determined by two-tailed Kruskal–Wallis test with subsequent Dunn’s multiple-comparisons test and in E and F by two-tailed Mann–Whitney test.