Figure S1.

Sorting strategy for SARS-CoV-2-specific memory B cells and characterization of monoclonal antibodies, related to Figure 1

(A) Representative flow cytometry plots showing CD19⁺, CD27⁺, SARS-CoV-2 S-binding B cells from a convalescent subject (C12, top row) and a pre-pandemic control (bottom row). PBMCs were pre-enriched with CD19 magnetic beads then gated on live IgD⁻IgM-IgG⁺CD27⁺ and finally on S (B) Representative flow cytometry plots showing S-positive, RBD-negative B cells for three convalescent subjects and a pre-pandemic control, sorted as in (A) except for the S gate. (C) Representative flow plot of mAb supernatant bound to SARS-CoV-2 S on HEK293T cells. Cells were gated on DAPI⁻GFP⁺ population. (D) Representative flow plot of mAb supernatant bound to SARS-CoV-2 RBD on yeast. cMyc tag indicated yeast that expressed RBD. (E) Representative flow plot of mAb supernatant bound to SARS-CoV-2 NTD on yeast. cMyc tag indicated yeast that expressed NTD. See Figure 1C for the screening color scheme. (F) Bar graph of Log₁₀(EC₅₀) of antibodies targeting RBD, NTD and S2 using ELISA and cell-based assay. EC₅₀ (μg/mL), RBD (n = 23), NTD clusters (n = 15) and S2 (n = 15). ^∗∗∗p < 0.001, ^∗∗∗∗p < 0.0001; Paired nonparametric Wilcoxon test. Data are mean values ± SEM (G) Dot plot of Log₁₀(EC₅₀) of antibodies in the indicated bins by cell-based assay. Antibodies are from subjects G32 and C41, sorted with S. Each dot represents one monoclonal antibody. EC₅₀ (μg/mL), 13-39 days (n = 13), 40-63 days (n = 8). No significance; nonparametric Mann-Whitney test. Data are mean values ± SEM.