Fig. 5: Caspase-3 expression in T cells during acute SARS-CoV-2 infection.

a Frequency of caspase-3 expression in CD4⁺ and CD8⁺T cells after stimulation with membrane (M), nucleocapsid (N) or spike protein (S) and PMA/Ionomycin, in nonhospitalized (orange, n = 14), mild (blue, n = 20), and severe (pink, n = 12) COVID-19 patients. Data are shown as individual patients and boxes and error bars represent median and interquartile range (IQR). Statistical comparisons were performed using Kruskal–Wallis rank-sum test with Dunn’s multiple comparison test (two-sided): CD4⁺ (M, p < 0.0001 and p < 0.0001; PMA/Io p = 0.036) and CD8⁺ (S, p = 0.007 and p = 0.002). b Correlation between days to hospital discharge since symptoms onset, viral load or baseline interleukin (IL)-6 levels (pg/mL) and the net frequency (background subtracted) of caspase-3 in CD4⁺ and CD8⁺T cells after stimulation with the spike protein or PMA/Ionomycin. c Frequency of caspase-3 expression in CD8⁺ CCR7^hCXCR3^dT cells after stimulation in the same groups as in a. Statistical comparisons were performed using Kruskal–Wallis rank-sum test with Dunn’s multiple comparison test (two-sided): p = 0.026. d Correlations between clinical parameters and the net frequency of caspase-3 expression in CD8⁺ CCR7⁺ T cell subsets after stimulation. e Frequency of caspase-3 expression in IL-10-secreting SARS-CoV-2-specific CD4⁺ and CD8⁺T cells responding to the spike protein, the nucleocapsid protein or to PMA/Ionomycin in the same groups as in a. Statistical comparisons were performed using Kruskal–Wallis rank-sum test with Dunn’s multiple comparison test (two-sided): CD4⁺ (S, p = 0.003; PMA/Io, p = 0.036) and CD8⁺ (N, p = 0.013; PMA/Io, p = 0.004). f Correlation between clinical parameters and IL-10-expressing SARS-CoV-2-specific CD4⁺ or CD8⁺T cells, or after PMA/Ionomycin stimulation. g Correlation between viral load and the frequency of caspase-3 expression in basal CD107a⁺ degranulating CD4⁺T cells and between IL-6 and the net frequency of caspase-3 expression in CD107a-expressing CD4⁺ in response to N peptides. Two-tailed spearman rank correlation (n = 46 for all correlations except for viral load, which corresponds to n = 33).