Figure 1.

Comprehensive mapping of CD4⁺ T cell epitopes in SARS-CoV-2 BA.1 spike and nucleocapsid proteins C57BL/6 mice were immunized subcutaneously (s.c.) with BA.1 spike or nucleocapsid proteins plus CFA as adjuvant, and 9-10 days later, CD4⁺ T cells from secondary lymphoid organs (SLO) were assessed for IFNγ production by ELISpot following in vitro restimulation with peptide libraries covering the entire sequence of (A) spike and (B) nucleocapsid. Mean values ± SEM (thin black lines extending above bars) are shown for n=3 independent experiments. Red bars indicate putative epitopes that were subsequently evaluated by peptide:MHCII tetramer staining. (C) Representative images of ELISpot samples stimulated with PBS alone (No peptide, negative control), Concanavalin A (Con A, positive control), or overlapping peptides encompassing the S-26 epitope of spike (Spike 21-25 and Spike 25-39). Numbers at the lower right edges of images indicate the raw number of spot-forming units counted per well.