Fig. 2.

Frequencies of H1N1 specific CD4 T cells strongly correlated with the SARS-CoV-2 specific CD4 T cells in COVID+ and seronegative participants: Thawed PBMC from COVID19+ (n = 21) and seronegative (n = 33) were stimulated with H1N1 antigen, SARS-CoV-2 specific CD4 non-spike (CD4 R) and spike (CD4 S) peptides for 24 hours and frequencies of antigen specific activation induced markers (AIM) were measured by flow-cytometry. Correlation between H1N1 specific CD4 T cells and SARS-CoV-2 specific CD4 T cells for A), OX40+ CD137+ total S + R responses; B), OX40+ CD137+ R response; C), OX40+ CD137+ S response; D), OX40+ CD69+ R response total S + R responses; E), OX40+ CD69+ R response; F), OX40+ CD69+ S response. For correlation analyses, non-parametric spearman correlation was used. A p value of < 0.05 was considered as significant.