FIG. 6.

Immune recognition of the OmpA epitope in mice. Competition for binding to the epitope on the C-terminal domain by anti-OmpA MAbs and the immune mouse sera raised against serovar Typhimurium strains WB600 (wild type) (A) and SH5014 (rfa) (B) was measured by competitive ELISA. Plates were coated with the homologous antigen (see Fig. 3), blocked, and filled with serial twofold dilutions of preimmune normal mouse serum (NMS) or immune mouse serum raised against live (LV) or heat-killed (HK) serovar Typhimurium strain WB600 (WB) or SH5014 (SH). A preselected concentration of biotinylated MAb that yielded an absorbance of 0.5 to 1.0 at 420 nm versus the homologous antigen was added to each well, the well contents were mixed, and the plate was incubated overnight at 4°C. The plates were washed and developed with streptavidin-alkaline phosphatase as described in Materials and Methods.