FIG. 6.
Antibody recognition of live B. pertussis and B. parapertussis and O-antigen-deficient B. parapertussis by immune serum. C57BL/6 mice were inoculated with 5 × 105 CFU of B. pertussis (Bp) or B. parapertussis (Bpp), and serum was collected 28 days later. Sera from B. pertussis (Bp serum)- or B. parapertussis-infected mice (Bpp serum) or naive sera were examined by ELISA for their ability to bind to live B. pertussis (A) or B. parapertussis (B; white bars) or the O-antigen-deficient B. parapertussis (BppΔO-ag) (B; hatched bars). The dashed line represents the lower limit of detection. Antibody titers are expressed as the end point titers ± standard deviations. **, P < 0.01.