Fig. 2

COVID-19 convalescent children can generate SARS-CoV-2 reactive CD4 + and CD8 + T cells with a broad cross-recognition potential. Characterization of SARSCoV-2 Spike-reactive T cells in pediatric subjects. Blood samples of 32 children were stimulated with one of the following SARS-CoV-2 proteins: the pool of B1.617.2 (delta, D) Spike mutant peptides, their reference pool of peptides (Dref), the pool of B.1.1529 (omicron, O) Spike mutant peptides, their reference pool of peptides (Oref) or the complete sequence of WT S-protein and analyzed by flow cytometry. (A) Frequencies of WT-, delta- and omicron-reactive CD4 + T cells. (B) Frequencies of WT-, delta- and omicron-reactive CD8 + T cells. (C) Avidity of SARS-CoV-2 Spike-reactive T cells as defined by determining the CD3_low + cells among CD4 + CD154 + CD137 + and (D) CD8 + CD137 + cells. Frequencies of WT-, delta- and omicron-reactive CD4 + CD3_low + T cells are depicted. SARS-CoV-2 Spike-reactive CD4 + and CD8 + T cells are defined as CD4 + CD154 + CD137 + and CD8 + CD137 + cells, respectively. Antigen-reactive responses were considered positive after the non-reactive background was subtracted, and more than 0.01% were detectable. Scatterplots show line at median. Unpaired data were compared with Mann-Whitney-test. P < 0.05 was considered significant, only significant p values are documented in the figures