Fig. 3: A booster dose of mRNA BNT162b2 elicits robust T cell responses that cross-recognize SARS-CoV-2 Omicron in aged mice.

SARS-CoV-2 spike specific T cell responses were analyzed at week 36 as indicated in Fig. 1. Splenocytes were restimulated with overlapping spike peptides from Omicron (a–e) and wildtype (e) SARS-CoV-2, and expression of intracellular interferon-γ (IFNγ), IL-2, and TNF among CD4⁺ and CD8⁺ T cells were determined by flow cytometry. N = 6–7 per group, except for 21 M Distant vax and Booster groups (N = 4). a, b Frequencies of IFNγ and IL-2 positive T cells among CD4⁺ (a) and CD8⁺ (b) T cells are shown. c, d Frequency of mono-, double-, and triple- cytokine positive cells among CD4⁺ (c) and CD8⁺ (d) T cells are summarized. Lines represent mean ± SEM. Data were analyzed by one-way ANOVA corrected for multiple comparisons. # indicates for comparisons against naïve groups in the same age group. *^/#P < 0.05, **^/##P < 0.01, ***^/###P < 0.001, ****^/####P < 0.0001. e Frequency of cytokine positive (expressing any of IFNγ, IL-2, and/or TNF) CD4⁺ and CD8⁺ T cells against wildtype or Omicron spike peptide pools were assessed. Each symbol represents one mouse. Omicron/wildtype fold change (FC) values were calculated, and the geometric mean of FC values are listed at the top of each graph.