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IDENTIFICATION OF NEW HLA-A2 EPITOPES SHARED WITH OTHER HLA-A, -B & -C ALLELES.
Andreas C. Papassavas, Ph.D , Delordson Kallon , Colin Brown Ph.D , Sally Brough , Giorgos Gortzolidis MD , Anastasia Scandalis MD, Ph.D , Catherine Stavropoulos-Giokas Director and Cristina Navarrete Head of H&I . Athens Greece, General Hospital
G Gennimatas, 11527, Immunology and National Tissue Typing Center ; London United Kingdom, National Blood Service, Colindale, NW9 5BG, Histocompatibility & Immunogenetics ; London United Kingdom, Royal Free & University College Medical School, University College, Immunology & Molecular Pathology and Athens Greece, General Hospital G Gennimatas, 11527, Hematology .
HLA-A2 is one of the most immunogenic HLA class I antigens and it is represented at a relatively high frequency in most ethnic groups. The aim of the study was to investigate the presence of new HLA-A2 shared epitopes, in order to increase the spectrum of the shared epitopes between HLA class I and II antigens. The amino acid sequence of the HLA-A2 molecule was compared with other known HLA class I and II sequences. In order to examine the reactivity of HLA class I specific antibodies to the newly defined HLA-A2 shared epitopes, 20 sera from onco-hematology patients containing well characterized HLA-A2 and other HLA class I specific antibodies (e.g. HLA-B8) were tested. These sera were assayed by the peptide enzyme immunoassay (EIA). The following six new shared epitopes were defined: 43Q, 63-64ET, 96-97QR, 115-116QY, 156-158LRA, 161-163EGT. The 43Q epitope is shared between the HLA-A and B molecules and all the others are shared between HLA-A, -B and -C loci alleles. The results of the peptide EIA assay showed that, in 12/20 patients with both HLA-A2 and other HLA class I specific antibodies (HLA-A25, -A26, -A29, -B7, -B13, -B51, -B52 and -Cw3), the sera reacted with the peptides which contained the relevant shared epitope. The preliminary results of this study show the existence of new HLA-A2 epitopes shared with other HLA-A, -B and -C alleles. The definition of these new shared HLA-A2 epitopes may increase the probability of identifying HLA matched platelet donors in a restricted pool of HLA typed donors.