Poster Presentation The 13th International Congress of the Immunology of Diabetes Society 2013

Peptide elution to identify preproinsulin epitopes from T1D risk-associated MHC class I variants (#149)

Martin Eichmann 1 , Deborah Kronenberg-Versteeg 1 , Arnoud H de Ru 2 , Peter A van Veelen 2 , Mark Peakman 1
  1. Peter Gorer Department of Immunobiology, King's College London, London, United Kingdom
  2. Department of Immunohematology and Blood Transfusion, Leiden University Medical Centre, Leiden, The Netherlands
Type 1 diabetes (T1D) results from CD8 T cell–mediated β-cell destruction. Major risk-determining factors include possession of HLA class I alleles and variants in the gene encoding insulin (INS), one of the major autoantigens in the disease. We set out to test the hypothesis that genetic susceptibility to T1D is determined in part by preferential presentation of preproinsulin (PPI) peptide epitopes by class I HLA susceptibility molecules, a feature that could facilitate recruitment of cytotoxic CD8 T cells and targeting of β-cells. We generated a modified HLA-negative cell line K562, transfected to express HLA class I molecules of interest and secreting proinsulin, as a surrogate β-cell line and examined the peptide ligandome by immunoaffinity purification and mass spectrometry to identify naturally processed and presented peptides. We studied HLA-A*02:01 (susceptible), -A*11:01 (protective), and -B*18:01 (susceptible) molecules. Using a novel, unbiased search-approach we identified the previously described epitope PPI15-24 (ALWGPDPAAA) from HLA-A*02:01, thereby validating our approach. No other HLA-A*02:01 restricted PPI peptide was identified, highlighting the dominance of PPI15-24 presentation in this model. We were unable to identify a PPI peptide for the risk-associated HLA-B*18:01 allele, but identified a PPI peptide originating from the proinsulin C-peptide region for A*11:01. The current study indicates that T1D susceptibility defined by HLA class I variants may not solely be explained by the presentation of PPI epitopes and CD8 T cell-mediated destruction. Potentially, other β-cell autoantigens could be important, or non-CD8 T cell mediated MHC class I-dependent mechanisms are factors that determine risk.