Fig. 7: THX mice vaccinated with Pfizer COVID-19 mRNA mount a mature neutralizing antibody response to SARS-CoV-2 Spike S1 RBD.
a–g, THX mice were injected i.m. with Pfizer-BioNTech 162b2 COVID-19 mRNA vaccine (5 μg in 50 μl PBS) or nil (50 μl PBS) on day 0, boosted (5 μg in 50 μl PBS or 50 μl PBS) on day 21 and euthanized on day 28. a, Serum RBD-specific human antibodies in COVID-19 mRNA-vaccinated (n = 8) and non-vaccinated (nil, n = 8) THX mice by specific ELISA (titers expressed as optical density (OD) readings at different dilutions). b, Total and RBD-specific spleen huCD45+ cells, huB cells, huMBCs and huPBs/PCs in COVID-19 mRNA-vaccinated THX mice, as identified by binding of labeled SARS-CoV-2 Spike S1 RBD. c, Total and RBD-specific huIgM, huIgG and huIgA ASCs in spleen and BM of COVID-19 mRNA-vaccinated THX mice, as analyzed by specific ELISPOTs. Data in b and c are from one THX mouse representative of three THX mice. d, Dose-dependent neutralizing antibody activity of sera from COVID-19 mRNA-vaccinated THX mice (n = 4), as analyzed by EpigenTek and Cayman SARS-CoV-2-neutralizing antibody detection platforms. SARS-CoV-2-neutralizing humAb4 and humAb15 were provided as positive control by EpigenTek and Cayman. e, Point mutation frequencies (changes per base) in spleen huB cell huVHDJH-CH (huVHDJH-Cμ: 0.8 ± 0.01 × 10−2, huVHDJH-Cγ: 1.5 ± 0.2 × 10−2, huVHDJH-Cα1: 1.2 ± 0.1 × 10−2) transcripts of COVID-19 mRNA-vaccinated THX mice (n = 3, THX 477, 478, 479) depicted as scatterplots and pie charts. Each dot represents a single sequence and bars depict the mean with s.e.m. f, huVHDJH-CH B cell clones and intraclonal diversification in THX mice as in e, depicted by TreeMaps and phylogenetic trees. Individual rectangle or square (unique color) area reflects huB cell clone size. In THX 477, 478 and 479 mice, the three largest huVHDJH-Cμ, huVHDJH-Cγ and huVHDJH-Cα1 clones accounted for 4.7%, 3.9% and 2.8% of huVHDJH-Cμ huB cells, 22.0%, 16.1% and 36.9% of huVHDJH-Cγ huB cells and 42.8%, 40.7% and 22.5% of huVHDJH-Cα1 huB cells. g, Interplay of SHM and CSR shapes B cell stepwise intraclonal diversification in COVID-19 mRNA-vaccinated THX mice, as exemplified by genealogical trees outlining the evolution of two huB cell clones, one tracked from its huV3-53D1-26JH1-Cμ heavy-chain huB cell progenitor, the other from its huVκ3-11Jκ1-Cκ light-chain huB cell progenitor.
