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. 2021 Mar 11;12:636768. doi: 10.3389/fimmu.2021.636768

Figure 2.

Figure 2

SARS-CoV-2-specific CD4+ T cells response in unexposed donors and recovered COVID-19 patients. The magnitude of SARS-CoV-2 specific CD4+ T cells was determined in PBMCs collected from unexposed donors (“Unexposed”, n=32) prior to pandemic and in COVID-19 patients (“COVID-19”, n=28) up to 5 months of recovery. The PBMCs were stimulated with the peptide megapool specific to Spike glycoprotein (Spike) or to the remainder of the SARS-CoV-2 polyprotein (Non-spike). DMSO was used as the negative control, and CMV peptide megapool and SEB were used for positive stimulation controls. (A) Representative FACS contour plots of unexposed and COVID-19 patient in stimulation conditions of DMSO, Spike peptide megapool, Non-spike peptide megapool, CMV and SEB. Paired graphs depicting the reactivity of AIM+ (OX40+CD137+) CD4+ T cells between the negative control (DMSO) and antigen-specific stimulation in (B) Unexposed donors (C) COVID-19 patients. (D) Frequency of responders to Spike and Non-spike peptide pools in unexposed and COVID-19 recovered subjects as determined by the Fischer’s exact test. The value on bars denote the number of responders/total number of donors tested. (E) Stimulation index quantitation of the AIM+ (OX40+CD137+) CD4+ T cells in Unexposed versus COVID-19 cases analysed in the same samples as in panel B and (C) Black bars indicate the geometric mean. Dotted line in panels B, C and E represent the limit of detection. Statistical comparisons were performed by (B, C) Wilcoxon paired t-test and (E) two-tail Mann-Whitney test. ns: non-significant.