Identification of peptides from autoantigens GAD65 and IA-2 that bind to HLA class II molecules predisposing to or protecting from type 1 diabetes.
Type 1 diabetes is a T-cell-mediated disease in which presentation of autoantigens to CD4+ T-cells is thought to play a crucial role. Polymorphism of HLA class II genes accounts for 50% of the genetic risk of contracting type 1 diabetes. HLA-DQ and -DR molecules predisposing to or protecting from type 1 diabetes have been identified, but the molecular basis controlling these associations is as yet undefined. Apart from distinct thymic selection of autoreactive T-cells by susceptible and protective HLA molecules, exclusive presentation of autoantigenic peptides by type 1 diabetes-predisposing HLA molecules or, alternatively, induction of regulatory T-cells by protective alleles are potential mechanisms for modification of type 1 diabetes risk by HLA polymorphism. As a first step in exploring the role of HLA molecules in autoantigen-specific cellular responses in type 1 diabetes, we have screened peptides covering the sequence of two major autoantigens targeted by humoral and cellular immune responses, GAD65 and islet associated-2 (IA-2), for binding to class II molecules. We developed a sensitive novel competition binding assay allowing us to measure peptide binding on intact cells to 10 HLA-DR and 4 HLA-DQ molecules. For all tested alleles, multiple peptides binding with high affinity were identified. We report clustering of binding peptides in the COOH-terminal regions of GAD65 and IA-2, as well as highly promiscuous binding patterns of some peptides. Our results demonstrate that most peptides derived from the GAD and IA-2 autoantigens can bind to both type 1 diabetes-predisposing and type 1 diabetes-protective HLA molecules, although some exceptions were observed. The binding inventory presented here for GAD and IA-2 peptides can be useful for mapping natural epitopes and predicting peptide-specific responses induced by preventive immunization.
Harfouch-Hammoud
E
E
Laboratory of Immunology and INSERM U25, Hôpital Necker, Paris, France.
Walk
T
T
Otto
H
H
Jung
G
G
Bach
J F
JF
van Endert
P M
PM
Caillat-Zucman
S
S
D000483:Alleles; D000595:Amino Acid Sequence; D001324:Autoantigens; D001667:Binding, Competitive; D002455:Cell Division; D002460:Cell Line; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D005968:Glutamate Decarboxylase / Q000276:immunology / Q000378:metabolism*; D006683:HLA-DQ Antigens / Q000378:metabolism; D006684:HLA-DR Antigens / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000276:immunology / Q000378:metabolism*; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D013601:T-Lymphocytes / Q000378:metabolism
D001324:Autoantigens; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D008565:Membrane Proteins; C516862:PTPRN protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D005968:Glutamate Decarboxylase