FIG 4.

DNP ELISA titers of mice immunized with wild-type and six-Asp mutant rPA conjugated to DNP. Two groups of 20 mice each were immunized with freshly prepared wild-type rPA-DNP (9.5 DNP molecules/rPA molecule) or six-Asp mutant rPA-DNP (10.0 DNP molecules/rPA molecule) Alhydrogel formulations (10 μg of rPA conjugated to DNP/mouse). At 28 days postimmunization, mice were bled, and serum samples were analyzed by ELISA for anti-DNP antibody titers as described in Materials and Methods. The graph shows the anti-DNP antibody titer for each mouse. The horizontal lines represent the geometric mean titer (GMT) with 95% confidence interval (CI) for each group. The GMT for the wild-type rPA-DNP group was 3,475 (95% CI, 1,552 to 7,780); the GMT for the six-Asp mutant rPA-DNP group was 1,069 (95% CI, 601 to 1,896). An unpaired t test was performed to calculate the statistical significance using GraphPad Prism software. The P value is indicated. This figure is a representative of two independent immunization studies.