Fig. 5: OC43 neutralization and correlations with serum IgG titers.

a Serum OC43 neutralization potential was determined using 50% focus reduction neutralization tests (FRNT50) and compared between pre- (blue) and end-pandemic (red) donors. Statistical significance was determined by Mann–Whitney U-test. b Linear regression analysis between serum OC43 neutralization titers and OC43 IgG binding titers (pre-pandemic, blue) or OC43 and SARS-CoV-2 IgG binding titers (end-pandemic, red). The regression line and 95% confidence interval are plotted for significant correlations (p < 0.05). c The OC43 neutralization titers of sera depleted of OC43 S1-specific antibodies (left panel) (Wilcoxon paired t-test), and sera depleted for OC43 S2- or SARS-CoV-2 S2-specific antibodies (right panel), normalized to mock-depleted sera are shown. Statistical significance was determined between the original titers by one-way ANOVA with Geisser-Greenhouse correction. d IgG B-cell culture supernatants that were OC43 S1-specific, S2-specific, or SARS-CoV-2/OC43 S2-cross-reactive were tested in a OC43 focus reduction assay and compared with non-reactive controls (unpaired Student’s t-test). Significant differences were plotted as *p < 0.05, **p < 0.01 and ***p < 0.001.