Fig 3.

High neutralizing antibody titers against PlyD1 correlate with reduced lung damage induced by PLY. (A) Immunization of mice with PlyD1 provides dose-dependent protection to mouse lungs following i.n. PLY challenge. Mice were immunized with increasing doses of PlyD1 (0.06 to 10 μg/dose) and challenged with PLY at 5 μg/dose. Lung damage was scored as indicated in Materials and Methods. Circles indicate data points for individual mice. (B) Hemolysis inhibition titers of individual sera taken from the above mice immunized with increasing doses of PlyD1 (0.06 to 10 μg/dose). The HI titers are represented as a ratio between postbleed and prebleed sera. The P value indicates a significant difference between the placebo control group and each test group. Circles indicate data points for individual mice. (C) Correlation between the neutralizing HI titers and protection from lung damage. Using the Spearman correlation coefficient, a significant correlation (r = −0.82) is observed.