FIG. 1.

Antibody and toxin-neutralizing responses in sera of rabbits immunized with the MAP peptide or with full-length PA. Shown are antibody responses to the immobilized 305-319 peptide (A) or to PA (B) and TNA activity (C) for sera of rabbits immunized five times at 2-week intervals with either the MAP peptide (MR1 to MR3) or PA (PR1 and PR2) as described in Materials and Methods and as depicted graphically in the timeline. Serum responses are from test bleeds obtained 10 days after the fifth immunization. For analysis of peptide reactivity, the immobilized antigen was a recombinant protein displaying two copies of the peptide sequence comprising aa 299 to 327 of PA. Antibody and TNA titers were determined as described in Materials and Methods and are expressed as reciprocals of the EC₅₀ and ED₅₀, respectively. The lower limit of assay detection for the ELISA and TNA is 16, and sample data below this level are indicated with an asterisk (*). Error bars represent standard errors of the means.