Fig. 1. Long-term immune responses in immunized C57BL/6 mice.
a Schedule of chimpanzee adenoviral vaccine immunization and bleeding strategies in female C57BL/6 mice (6–8-week-old). Eight groups (n = 5) of C57BL/6 mice were i.m. injected with 2 × 1010 vp viruses. Serum samples were then collected at different time points. b Kinetics of spike-specific total IgG reciprocal endpoint titers (log10) were measured within 27 weeks of initial vaccination. Total IgG immune responses were measured using ELISA. c Kinetics of SARS-CoV-2 pseudovirus neutralizing antibody NT50 titers (log10) were measured within 27 weeks after the first vaccination. d Measurement of live SARS-CoV-2 virus neutralizing antibody NT50 titers of sera collected at week 24. e Neutralization of variant B.1.1.7 SARS-CoV-2 pseudovirus in serum samples obtained at week 27 post initial immunization. Unpaired t-test was used for analysis. f Neutralization of variant B.1.351 SARS-CoV-2 pseudovirus in serum samples collected at week 27 after the first vaccination (unpaired t-test, P = 0.041). g Endpoint titer ratios of IgG2a to IgG1 were calculated. Mouse sera were collected at week 8, and subtypes IgGs were assessed by ELISA. Sera of mice immunized with AdC6-empty and AdC68-empty were not calculated, as the endpoint titer did not reach the lower limit of detection (LLOD). h, i Intracellular cytokine staining was performed in mouse spleen to assess memory T cells at week 27, and cytokines IFN-γ and TNF-α were detected. All data were shown as means ± SEM. P-values were analyzed with one-way ANOVA (nsP ≥ 0.05; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001).