Sequence and specificity analysis of recombinant human Fab anti-Rh D isolated by phage display

Background and Objectives: Hyperimmune anti-Rh D serum is worldwide in shor t supply. As a first step to develop an alternative source of Rh D antibodi es, we describe in this study the isolation and characterization of recombi nant anti-Rh D Fab fragments. Materials and Methods: Peripheral blood monon uclear cells harvested from a hyperimmunized donor were used to construct t wo 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 phen otypes, Rh33, D-III, D-IVa, D-IVb, D-Va, and D-VII. The 13 different but hi ghly homologous clones express preferentially VH3 segments. Conclusion: The se Fab fragments show potential for the development of a new generation of therapeutic anti-Rh D reagents.