Fig. 5: Characterization of S2 vaccine-induced B cells and mAbs.

a Schema of mice immunization. S2 VLP or control VLP (7.5 µg/mouse) combined with the AS03 adjuvant and Poly(I:C) were injected subcutaneously into BALB/c mice (n = 5 per group, 10–12 weeks old). Spleen samples were collected four weeks after immunization. Created in BioRender. Wilson, P. (2024) https://BioRender.com/a30b566. b Proportion of B cells binding to indicated subunit probes in each immunization group. The numbers of B cells analyzed are shown above each bar. c Number of somatic hypermutations or (d) complementarity determining region 3 (CDR3) amino acid length in the IGHV in each immunization group. Significance was assessed by one-way ANOVA followed by Dunnett’s test. e–g Probe binding profile of B cells against Wuhan-subunits or Human CoV spikes. Binding intensities are obtained by dividing the probe count by the CD79b count. The numbers in the center of the pie graphs indicate the number of B cells analyzed. The pink pie chart shows B cells that cross-reacted with SARS-CoV-2 and Human CoV, and the gray pie chart shows B cells that are specifically bound to either. h–j Number of strains bound by B-cell clones in mice immunized with VLP-CoV-2 S2, VLP-CoV-1 S2, and Wuhan Spike, respectively. 32 B cells were analyzed for 5h, 17 B cells for 5i, and 37 B cells for 5j. k Binding specificity of mAbs generated from S2 VLP immunized mice against Wuhan subunits, SARS-CoV-2 spikes, or Human CoV spikes. Binding data are represented as areas under the curve (AUC). l IC50 of the neutralization potencies of mAbs against SARS-CoV-2 spike pseudotyped viruses. m Activation of the ADCC signaling pathways. FcγR-mediated signaling activation in effector cells expressing human FcγRIIIa was induced by co-culture with Spike-expressing CHO cells. Signaling activation was measured in two technically independent experiments. The mAb clone 241-15-068 A 1E04 (anti-HA mAb) was used as a negative control. RLU, relative light unit.