FIG 3.

Binding activities of anti-PTx antibodies. (A) ELISA was used to assess the binding of the monoclonal antibodies to native PTx and genetically modified PTx (PTg). ELISAs were performed at least twice, with similar results. Error bars represent standard errors for replicate experiments. Due to availability, the murine 1B7 antibody was assessed for binding to PTg, while the rest of the antibodies have a human constant domain. (B) Binding specificities of the isolated anti-PTx antibodies for purified S1 and B subunits, as assessed by ELISA. The gap for A12 indicates no detectable binding to either subunit, suggesting that it binds an epitope spanning the subunit interface. (C) Binding of the antibodies to purified PTx S1 on a Western immunoblot. Assays were performed in parallel, with equal loading of prestained molecular size markers and PTx (500 ng) onto SDS-PAGE gels. After transfer, the strips were separated, probed with the indicated primary antibodies, and then combined for staining with the secondary antibodies, detection, and imaging. The experiment was repeated at least three times with identical results.