Human Monoclonal Fab Fragments Recovered from a Combinatorial Library Bind Specifically to the Platelet HPA-1a Alloantigen on Glycoprotein IIb—IIIa

• Published in: Vox sanguinis 1997-01, Vol.72 (1), p.52-60
• Main Authors: Proulx, Chantal, Chartrand, Pierre, Roy, Valérie, Goldman, Mindy, Décary, Francine, Rinfret, Aline
• Format: Article
• Language: English
• Subjects: Original Paper
• ISSN: 0042-9007; 1423-0410
• DOI: 10.1159/000461958

Background and objectives: Certain clinical conditions are related to the presence of platelet-specific alloantibodies in the patient’s serum. We studied the molecular diversity of HPA-1a antibodies to analyze some peculiarities of this antibody response. Materials and methods: Human antibody Fab fragments that bind to the platelet alloantigen HPA-la on glycoprotein Ilb-IIIa (GPIIbllla) were generated by using a recombinant phage display system. We established an immunoglobulin Gl, kappa combinatorial library from the peripheral blood lymphocytes of a person undergoing a severe posttransfusion purpura. Results: Characterization of Fab clones selected from the fifth round of antigen-specific panning of this library demonstrates a highly specific reactivity to the HPA-1a alloantigen. The nucleotide sequence analysis of representative HPA-1a-specific clones reveals at least 3 distinct VL and 3 V(H) gene segments that present an extensive degree of mutation as demonstrated by comparison of gene usage and homologies to the nearest germline genes. Conclusions: These human HPA-laspecific Fab reagents should allow us to better understand the molecular mechanism involved in HPA-1a alloimmunization.