FIG 4.

Antibody responses to the PH fusion antigen in immunized mice and antibody opsonophagocytic killing capacity. BALB/c mice were immunized with either PBS-Alhydrogel, 10 μg of PH-Alhydrogel, 50 μg of OMV-NA, or 50 μg of OMV-PH by i.m. administration and were then boosted on day 21 after prime immunization. Blood was collected on days 14, 28, and 42, and antigen-specific antibodies were determined by ELISA. Data represent 5 mice per group. (A) Total anti-PH IgG titers at days 14, 28, and 42 in differently immunized mice. (B) IgG2a/IgG1 ratios in response to the PH fusion antigen at days 14, 28, and 42. (C) Total anti-PCL IgG titers at days 14, 28, and 42 in differently immunized mice. (D) IgG2a/IgG1 ratios in response to a PCL at days 14, 28, and 42. (E) Comparative analysis of opsonophagocytic killing activity against PA103 using antisera from differently immunized mice. (F) Assay of antibody inhibition of PA103 cytotoxicity to HeLa cells. Sera collected from different immunized mice were used for this assay (see Materials and Methods). Data are shown as means ± SD. The statistical significance of differences among groups was analyzed by two-way multivariant ANOVA with a Tukey post hoc test (ns, no significance; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001). (F) Inhibition of PA103 cytotoxicity by sera from immunized mice.