Figure 3.

Specific humoral and cellular immune response of C57BL/6 and BALB/c mice to prime-boost immunization with Sad23L-nCoV-S and Ad49L-nCoV-S vaccines. (A) C57BL/6 and BALB/c mice (n = 5/group) were prime immunized with a dose of 10⁹ PFU Sad23L-nCoV-S vaccine and boosted with a dose of 10⁹ PFU Ad49L-nCoV-S vaccine at 4 week interval. Sera and splenocytes were collected from vaccinated or control mice for measurement of antibody and T-cell responses 4 weeks after both prime only and boosting immunizations. (B–C) Anti-S-BAb and RBD-BAb titers determined by ELISA. (D–E) NAb titers measured by sVNT and pVNT. (F) IFN-γ secreting T-cell response (SFCs/million cells) to S peptides, S or RBD protein measured by ELISpot. (G) Frequency of IFN-γ or TNF-α expressing CD4⁺ and CD8⁺ T-cell response to S peptides determined by ICS. Data are shown as a mean ± SEM. P values are analysed with one-way ANOVA and two-tailed t test. Statistically significant differences are shown with asterisks (*, P < 0.05; **, P < 0.01 and ***, P < 0.001).