FIG. 4.

Recognition of B. pertussis and B. parapertussis by antibodies from convalescent-phase serum. C57BL/6 mice were inoculated with 5 × 10⁵ CFU of B. pertussis (Bp) or B. parapertussis (Bpp), and serum was collected from these mice 28 days later. ELISA was performed on serum from naive (NS), B. pertussis-infected (Bp IS), and B. parapertussis-infected (Bpp IS) mice to quantify titers of antibodies specific for B. pertussis (A) or B. parapertussis (B). The dashed line represents the lower limit of detection. Antibody titers from the ELISA are quantified as the log₁₀ means of the end point titers ± standard deviations. *, P < 0.05; **, P < 0.01. Western blots of pooled B. pertussis-induced (C) and pooled B. parapertussis-induced (D) serum were used to determine if serum raised against one species recognized specific antigens of B. pertussis, B. parapertussis, or the B. parapertussis Δwbm strain (BppΔO-ag).