Sequence and Specificity Analysis of Recombinant Human Fab Anti–Rh D Isolated by Phage Display

Abstract

Background and Objectives: Hyperimmune anti–Rh D serum is worldwide in short supply. As a first step to develop an alternative source of Rh D antibodies, we describe in this study the isolation and characterization of recombinant anti–Rh D Fab fragments. Materials and Methods: Peripheral blood mononuclear cells harvested from a hyperimmunized donor were used to construct two combinatorial Fab libraries. Phages expressing these Fab fragments were selected on whole red blood cells followed by testing of positive clones in an indirect hemagglutination assay. Results: Individual Fab clones are of high affinity and competitively inhibit the binding of a registered anti–D immunoglobulin. The Fab clones are also specific against the partial D phenotypes, Rh33, D^III, D^IVa, D^IVb, D^Va, and D^VII. The 13 different but highly homologous clones express preferentially VH3 segments. Conclusion: These Fab fragments show potential for the development of a new generation of therapeutic anti–Rh D reagents.