title: Unique epitopes of glutamic acid decarboxylase autoantibodies in slowly progressive type 1 diabetes.
abstract: Disease-specific epitope profiles of glutamic acid decarboxylase (GAD)65 autoantibodies (GAD65Ab) were studied in slowly progressive type 1 (insulin-dependent) diabetes mellitus (SPIDDM) and acute onset type 1 (insulin-dependent) diabetes mellitus (AIDDM) using seven kinds of GAD65/67 chimeric molecules. Sera obtained from Japanese SPIDDM (n = 17) and AIDDM (n = 46) patients followed prospectively were analyzed by immunoprecipitation, ELISA, and Western blotting. GAD65Ab in all SPIDDM samples reacted specifically with an N-terminal linear epitope located on the membrane anchoring domain between amino acids 17-51 and C-terminal conformational epitope between amino acids 443-585 of GAD65. The binding of GAD65Ab with N-terminal 83 residues in SPIDDM inversely correlated with the period in which insulin was not required. GAD65Ab in AIDDM did not react with N-terminal epitope located between amino acids 1-83, irrespective of the titer of GAD65Ab. A novel epitope of GAD65Ab in AIDDM residing between amino acids 244-360 was identified in 17% (8 of 46) of patients whose age of onset was younger than other AIDDM patients. In conclusion, GADAb in SPIDDM has unique N-terminal linear epitopes that are located on the anchoring domain of GAD65 molecules. Association is suggested between GAD65Ab targeted to this region and slowly progressive beta-cell failure in SPIDDM.
authors.affiliation: Third Department of Internal Medicine, Yamanashi Medical University, Tamaho, Yamanashi 409-3898, Japan. tetsurou@yamanashi.ac.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tanaka
authors.forename: Minoru
authors.initials: M
authors.lastname: Okubo
authors.forename: Koji
authors.initials: K
authors.lastname: Nakanishi
authors.forename: Toshio
authors.initials: T
authors.lastname: Murase
authors.forename: Ake
authors.initials: A
authors.lastname: Lernmark
mesh_terms: D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001665:Binding Sites; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology*; D005968:Glutamate Decarboxylase / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D006683:HLA-DQ Antigens / Q000235:genetics; D059848:HLA-DQ alpha-Chains; D059866:HLA-DQ beta-Chains; D006239:Haplotypes; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D007328:Insulin / Q000627:therapeutic use; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008137:Longitudinal Studies; D017434:Protein Structure, Tertiary; D011732:Pyridoxal Phosphate / Q000378:metabolism; D011993:Recombinant Fusion Proteins
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D006683:HLA-DQ Antigens; D059848:HLA-DQ alpha-Chains; D059866:HLA-DQ beta-Chains; C069050:HLA-DQA1 antigen; C069051:HLA-DQB1 antigen; D007004:Hypoglycemic Agents; D007328:Insulin; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D011732:Pyridoxal Phosphate; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; C401141:glutamate decarboxylase 2