Figures & data
Figure 1. PCP-I enhances antibody responses against PA. Groups of mice (BALB/c, n = 6) were immunized three times i.m. at two-week intervals with 0.5 μg of PA unadjuvanted or adjuvanted with PCP-I (200 μg). The mice of the control group were injected with PBS. Mice were bled 14 days following their last immunization for measurement of anti-PA antibodies (a), antibody avidity (b), and IgG subclass titers (c) by ELISA. The toxin-neutralizing antibody titers were measured by TNA (d). Results are presented as the mean ± SD (*p < .05, ***p < .001).
Figure 2. PCP-I enhances immune memory against PA. Groups of mice (BALB/c, n = 6) were immunized three times i.m. at two-week intervals with 5 μg of PA unadjuvanted or adjuvanted with PCP-I (200 μg). The control group of mice was injected with PBS. Spleens were collected 14 days after the last immunization to measure the frequency of PA-specific memory B cells by ELISPOT (a). PA-specific splenocyte proliferation was assessed by CCK8 (b). The number of PA-specific cytokine IL-4-secreting cells (c) and IFN-γ-secreting cells (d) was quantified by ELISPOT. PA-specific cytokine expression in the culture supernatant as assessed via MILLIPLEX Multiplex Assays (e). The results are presented as the mean ± SD (*p < .05; **p < .01; ***p < .001).
Figure 3. PCP-I enhances the activation of PA-specific DCs in vitro. Bone marrow-derived DCs were stimulated with 50 μg/mL PA +PCP-I 2 mg/mL, 50 μg/ml PA, 2 μg/mL LPS, or PBS for 24 h in vitro. The cells were stained and the expression of CD11c/MHCII (a), CD11c/CD86 (b) on DCs was analyzed by FACS. Results are representative of two separate experiments (***p < .001).
Figure 4. PCP-I combined with CpG further enhances antibody responses against PA. Groups of mice (BALB/c, n = 8) were immunized three times i.m. at two-week intervals with 0.5 μg of PA unadjuvanted or adjuvanted with PCP-I (200 μg) or PCP-I (200 μg) + CpG (25 μg) or CpG (25 μg). The mice of the control group were injected with PBS. Mice were bled 14 days following their last immunization to measure anti-PA antibodies (a), antibody avidity (c), IgG subclass titers (d (a)), or IgG1/IgG2a ratio (d (b)) by ELISA. The toxin-neutralizing antibody titers were measured by TNA (b). Results are presented as the mean ± SD (*p < .05; **p < .01; ***p < .001).
Figure 5. Protection against anthrax toxin challenge. Four weeks after the last immunization, the mice were challenged with lethal toxin (25 μg of LF + 50 μg of PA in 0.1 mL saline). Survival was monitored every 8 h for seven days following challenge (**p < .01).
