Figure 3.

Non-spike-specific T cells were found in some vaccinated pregnant subjects who were not aware of previous asymptomatic COVID-19 infection. The T cell response to non-spike proteins has been evaluated with two peptide pools: pool 1 = 69 amino acids, recognized by most convalescing from COVID-19, and pool 2 = 215 amino acids. PBMC were primed for 24 h prior to studying T cell activation with the AIM assay. (A) CD4+ and CD8+ T cell response to non-spike peptides; the percentage of CCR6+ T cells is shown. The two peptide pools have been found to be equally immunogenic in this cohort: all the subjects who had previously been infected, except for subject 5, had a CD4+ Th response. Subject 5 was the only subject who developed an appreciable CD8+ CTL response within the cohort who was aware of previous COVID-19 infection. T cells from several subjects were responding to non-spike peptide epitopes, suggesting that they were unaware of previous asymptomatic COVID-19. CCR6 was found in a considerable percentage of CD4+ and CD8+ non-spike-specific T cells. (B) T cell memory phenotypes. Each dot shows the percentage of memory populations: CD4+ Th were mostly T_EM and T_CM, but not T_EMRA; (C) CD8+ CTL were mostly T_EMRA and a few T_EM and T_CM, as previously shown for the spike-specific T cell memory repertoire.