Figure 6.

Deimmunized PE-III variants induce lower antibody titers but effectively prime CD4+ T cells. A, BALB/c mice were immunized i.v. for 4 weeks, and serum samples were taken 4 days after each immunization. PE-III–specific antibodies were detected by direct ELISA. Each line indicates average titer as logEC₅₀ determined by nonlinear regression. Error bars indicate standard error; asterisks indicate significance by one-way ANOVA (n = 8 per group). Data are representative of three independent experiments. B, BALB/c mice were immunized once intranasally with PE-III and dmLT. Spleens were isolated, and splenocytes were restimulated with peptides spanning the sequence of WT PE-III with mutant peptides substituted as necessary in duplicate. Bars show average spot-forming units (SFU) per 5 × 10⁵ cells. Error bars indicate standard deviation; asterisks indicate significance by the Wilcoxon signed-rank test, and a mean SFU greater than 20. Dashed line indicates an SFU value 2 S.D. over background.