FIG. 3.

Recognition of similar epitopes by anti-OmpA MAbs. Studies of MAb competition for binding to OmpA were carried out by competitive inhibition ELISA. Plates were coated with the homologous antigen (purified Salmonella OmpA or heat-killed whole cells of strain SH5014). Unbiotinylated MAbs were added at various concentrations (2.0 to 0.016 μg/ml) followed by the biotinylated MAbs at a preselected concentration that yielded an absorbance of 0.5 to 1.0 at 420 nm versus the homologous antigen. ELISA was then carried out as described in Materials and Methods. Unrelated IgG2a and IgG2b mouse antibodies were used as negative controls (A), whereas unlabeled homologous MAbs were used as positive controls (A) in the competition experiments (B).