Figure 3.

Cellular response induced by RBD-mFc intranasal immunization. Vaccinated BALB/c mice were euthanized at 2 weeks post-2nd boost immunization. The splenocytes harvested from immunized mice (n=4) were stimulated with RBD protein for 42 hours. Cultured supernatants were harvested and pooled. Cytokine production was measured using an ELISA kit. RBD-immunized mice generated a certain amount of IL-2 (A), IL-10 (C) and IFN-γ (D). IL-4 (B) was detected only in RBD-mFc intramuscularly immunized mice. Data represent the mean of three parallel wells in one experiment. Splenocytes were incubated with SARS-CoV-2 RBD protein. The responding CD4+ (E, F) and CD8+ T (G, H) cells were identified by intracellular staining for effector cytokines. The gating strategies are shown in Supplementary Figure S1 . Data are represented as the mean ± SD. Significant differences were determined by one-way ANOVA with Tukey’s multiple comparisons test. ns, not significant; *p < 0.05; **p < 0.01; ****p < 0.0001.