Fig. 2. S and/or N DNA vaccines induce antigen-specific polyfunctional T cell responses in K18-hACE2 mice.

a Experimental protocol: On days 0 and 21, K18-hACE2 mice were inoculated with S and/or N DNA vaccines or pVAX control (25 µg, IM), and tissues were harvested at 7 days post-boost. Representation of the experiment timeline was Created with BioRender.com. b–e Splenocytes (b, c) and lung leukocytes (d, e) were stimulated with the indicated SARS-CoV-2 S or N peptides, and polyfunctional (IFN-γ⁺TNF-α⁺ or IFN-γ⁺TNF-α⁺IL-2⁺) or cytotoxic (IFN-γ⁺CD107a⁺) CD4⁺ and CD8⁺ T cells within the population of live CD3⁺ cells were quantified by ICS (representative gating strategy is shown in Figure S1). Data are from 2 independent experiments (n = 7–9 mice/group). Group means were compared using the non-parametric Kruskal-Wallis test. *P < 0.05, **P < 0.01, ***P < 0.001. Circles, individual mice.