Fig. 1. Comparison of SARS-CoV-2 RBD-specific antibodies and SARS-CoV-2-specific T cell response in healthy controls and recovered children and adolescents. (A) Serological responses to recombinant RBD protein in 31 recovered COVID-19 patients with median 46.5 recovery days and ranging 29-219 days and 20 uninfected controls. Dash line indicated the anti-RBD IgG ratio reference obtained from uninfected controls. (B) Representative data of the T cell response towards SARS-CoV-2 peptide pools in controls and recovered patients. (C) Immunophenotyping of PBMCs for frequency of CD4+, CD8+, or CD69+ T cells, IFN-γ+ cells, and CD69+/IFN-γ+ double-positive cells from uninfected individuals (n=20) or convalescent children and adolescents (n=31). Data are presented as mean±SD and analyzed using two-sided Student’s t-test between control and patient groups. *p<0.05, **p<0.01, ***p<0.001
Fig. 2. Measurement of SARS-CoV-2-specific T cell response in recovered patients. Total T cell responses towards SARS-CoV-2 Membrane (M), Nuclear (N) and Spike (S) peptides and mixed peptide pools in stacked columns representing the summation of different measured immune subsets in CD4+ and CD8+ T cells after 16 hours of incubation of PBMCs from recovered patient. Data are expressed as mean±SD. Dash line in the stack columns indicated the corresponding reference CD4+ and CD8+ T cells response stimulated by different SARS-CoV-2 peptide in uninfected controls group.
Fig. 3. SARS-CoV-2-specific RBD and T cell responses over time.(A) Regression analysis of the measured RBD IgG ratio in convalescent serum was plotted against the post-infection time. The best fitting trendline is shown. The calculated t1/2 was 121.6 days and the estimated duration of antibodies was 7.9 months compared with the average basal level obtained from uninfected individuals. (B) Representative T cell subset frequencies in PBMC of recovered patients were plotted against the post-infection period showing a flat slope for (i) CD4+ and (ii) CD8+, indicating a sustained T cell response to SARS-CoV-2 virus in recovered pediatric patients.
Fig. 4. Age-dependent differences of SARS-CoV-2-specific S-RBD IgG level and SARS-CoV-2-specific T cell response in recovered children and adolescents . The corresponding reference anti-RBD IgG ratio and T cell response obtained from uninfected control was indicated as a dash line in the figures. (A) Serological analysis in 15 patients who were younger than 12 years and 16 patients who were 12 years or older. Data was adjusted by recovery days and comparisons analyzed by two-sided Student’s t-test *p<0.05. (B) Comparison analysis of the total measured CD4+ T cell responses to (i)mixed peptide pools and (ii) S peptide between younger children and older children. (C) Comparison analysis of the total measured CD8+ T cell responses to (i)mixed peptide pools and (ii)S peptide between younger children and older children. (D) Correlation analysis of anti-RBD IgG level against (i) CD4+ and (ii) CD8+ T cells response in the recovery patients. Data was plotted as age-subgroups with color-labelled dots in the scattered plots. A trendline indicated the correlations direction of the analysis parameters.