Fig. 2: The prime-boost regimen induces superior humoral immune responses.
a Scheme of experiments. Mice (n = 10 per group) were immunized intranasally with 5 × 107 IFU of AdC68-HATRBD in prime-only or prime-boost regimen. The control group received a placebo (PBS). Serum and BALF were harvested at 8 week post-vaccination. b Binding antibody titers of the serum IgG (left), BAFL IgG (middle), and BAFL IgA (right) to RBD or HA, expressed in log10. c Serum pseudovirus neutralizing antibody against SARS-CoV-2 and VOCs. d Serum live virus neutralizing antibody against WT and Delta. e Spearman correlations of pVNT50 titer and FRNT50 titer against WT (left) and Delta (right). f Antibody titers against pH1N1 by the hemagglutination inhibition assay (left) and neutralization assay (right). g Serum neutralizing antibody against AdC68 vector. Each dot represents data from two mice. The red dashed line representing the lower limit of detection and geometric mean titer (GMT) values are displayed in (c), (d), (f), and (g). In (c) and (d), the numbers after the up arrow indicate the median fold increase in antibody titer induced by prime-boost regimen compared with prime-only regimen. Data are represented as mean ± SEM (b) or GMT ± SD (c, d, f, and g). Significance was assessed by one-way ANOVA with Tukey correction. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001.
