Figure 1.

Gating strategy and specific memory T-cell responses to SARS-CoV-2-derived peptide pools in 35 convalescent patients.

(a) Gating strategies to define SARS-CoV-2-specific CD4+ T-cells. Representative examples of flow cytometry plots of SARS-CoV-2-specific CD4+ T-cells after 6 h stimulation with Spike (Pep-S). PBMCs were isolated and stimulated by SARS-CoV-2-derived peptide pools (Pep-S, Pep-M, and Pep-N), with CMV-derived peptides (Pep-CMV), or with CytoStim. CD3, CD4 and CD8 expression was detected by surface labeling and IL-17A, TNF-α, IL-4, IL-2 and IFN-γ expression was detected intracellularly by flow cytometry. (b) Frequencies of IFN-γ-producing CD4+ T-cells. N=35. (c) Frequencies of TNF-α-producing CD4+ T-cells. N=35. Each symbol corresponds to an individual (N=35). One-way ANOVA with multiple-comparison Kruskal–Wallis tests were used. *p < 0.05. (d) Stacked bars comparing the frequency of individuals with a specific T-cell response when cells were stimulated by Pep-S, Pep-M, or Pep-N in CD4+ T cells. Individuals with SIs greater than 2 were considered responding individuals, and those with SIs lower than 2, as non-responding individuals. The response was observed as the intracellular IFN-γ or TNF-α production in CD4+ cells. N= 35. (e) Stacked bars comparing the frequencies of individuals responding and not responding to the SARS-CoV-2-derived peptides in CD8+ T-cells. N=35.