Fig. 3: The prime-boost regimen triggers enhanced memory T-cell responses.

a Scheme of experiments. The immunization schemes were identical to Fig. 2. Lung tissues and spleens were harvested at 8 week post-vaccination. b, c Frequencies of pulmonary CD4+ T cells (b) and CD8+ T cells (c) producing cytokines following re-stimulation with peptide pools for RBD, TCEs, and HA. d, e Frequencies of splenic CD4+ T cells (d) and CD8+ T cells (e) producing cytokines following re-stimulation with peptide pools for RBD, TCEs, and HA. All data are represented as mean ± SEM and analyzed by one-way ANOVA with Tukey correction. *P ≤ 0.05, **P ≤ 0.01.