Murine monoclonal antibodies reactive with a human monoclonal anti-RhD antibody (BRAD-5)

BRAD-3 and BRAD-5 are human monoclonal antibodies that recognize the RhD antigen on red blood cells. Both antibodies are currently in clinical trials for use as a replacement for polyclonal anti-RhD in the prophylactic treatment of haemolytic disease of the newborn. We have produced three murine IgG1 antibodies that cause agglutination of cells sensitized with BRAD-5 and also block binding of BRAD-5 to its target antigen. Using a haemagglutination assay, these antibodies, 1D7, 2E6 and 3B1, have shown specificity for BRAD-5 as they did not bind to other monoclonal anti-RhD antibodies of differing specificity or derived from other donors. This assay has also been used to show a lack of reactivity with anti-RhD antibodies present in 198 human serum samples from 44 anti-RhD immune individuals. The three anti-BRAD-5 antibodies have been shown to recognize different epitopes on the BRAD-5 molecule using a blocking ELISA. These antibodies appear to recognize private idiotopes on BRAD-5 that were not detectable in RhD immune sera, and therefore they will be of use for monitoring BRAD-5 in clinical trials.