Monoclonal antibody specific to the Di a blood group antigen generated by phage display technology.

Background - Alloanti-Di(a) can be implicated in mild to severe blood transfusion reactions. Given the concomitance of a high, prevalence of the Di(a) antigen and antibody circulating in some populations, an anti-Di(a) typing reagent is required in order to enable safe blood transfusions. Limitations of hybridoma technology to produce such a reagent led to the use of phage display technology to generate an anti-Di(a) monoclonal antibody. Materials and methods - A library of phages displaying murine single-chain variable fragment antibody (scFv-phages) was consecutively adsorbed with different panels of Di(a-b+) red cells to eliminate scFc-phages that potentially bind irrelevant blood group antigens. Thereafter, the subtractive library was specifically selected for the scFv-phages that bound Dia antigen by sequentially biopanning the library with Di(a+b+) cell ghosts and Di(a+b-) intact red cells. A specific interaction between the selected scFv-phages and Di(a) epitope was validated with the Di(a) peptide by a competitive haemagglutination inhibition assay and confirmed with the red cells by flow cytometry. Results - An scFv-phage clone specifically bound the Di(a) epitope, as shown by its binding competition with the human anti-Dia to the Di(a) peptide in a haemagglutination inhibition test. Moreover, it was highly reactive to Di(a+b+) red cells but not to Di(a-b+) red cells, as determined by flow cytometry. Discussion - In this study, a Di(a)-specific scFv-phage antibody was successfully produced. The selection protocol might be a prototypic platform for producing monoclonal antibodies to relevant blood group antigens. The scFv-phage produced in this way warrants further development for use as a reagent for Di(a) red cell typing.