title: Dynamic changes of GAD65 autoantibody epitope specificities in individuals at risk of developing type 1 diabetes.
abstract: OBJECTIVE
  Progression to type 1 diabetes is associated with intramolecular epitope spreading to disease-specific antibody epitopes located in the middle region of glutamic acid decarboxylase 65 (GAD65).
  
  
  METHODS
  The relationship between intramolecular epitope spreading of autoantibodies specific to GAD65 in relation to the risk of developing type 1 diabetes was tested in 22 high-risk individuals and 38 low-risk individuals. We determined the conformational epitopes in this longitudinal study by means of competition experiments using recombinant Fab of four GAD65-specific monoclonal antibodies.
  
  
  RESULTS
  Sera from high-risk children in the preclinical stage recognise a specific combination of GAD65 antibody epitopes located in the middle and the C-terminus of GAD65. High risk of progressing to disease is associated with the emergence of antibodies specific for conformational epitopes at the N-terminus and the middle region. Binding to already established antibody epitopes located in the middle and at the N-terminus increases and shows a significant relation (p=0.005) with HLA, which confers risk of developing diabetes.
  
  
  CONCLUSIONS
  In type 1 diabetes, GAD65 antibodies are initially generated against the middle and C-terminal regions of GAD65. In genetically predisposed subjects the autoimmune response may then undergo intramolecular epitope spreading towards epitopes on the N-terminus and further epitopes located in the middle. These findings clearly demonstrate that the GAD65 autoantibody response in the preclinical stage of type 1 diabetes is dynamic and related to the HLA genotypes that confer risk of diabetes. GAD65-specific Fab should prove useful in predicting progression from islet autoimmunity to clinical onset of type 1 diabetes.
authors.affiliation: Institute of Pathophysiology, Ernst Moritz Arndt University of Greifswald, Karlsburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schlosser
authors.forename: J P
authors.initials: JP
authors.lastname: Banga
authors.forename: A M
authors.initials: AM
authors.lastname: Madec
authors.forename: K A
authors.initials: KA
authors.lastname: Binder
authors.forename: M
authors.initials: M
authors.lastname: Strebelow
authors.forename: I
authors.initials: I
authors.lastname: Rjasanowski
authors.forename: R
authors.initials: R
authors.lastname: Wassmuth
authors.forename: L K
authors.initials: LK
authors.lastname: Gilliam
authors.forename: D
authors.initials: D
authors.lastname: Luo
authors.forename: C S
authors.initials: CS
authors.lastname: Hampe
mesh_terms: D000293:Adolescent; D001323:Autoantibodies / Q000097:blood*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology* / Q000276:immunology*; D000939:Epitopes / Q000032:analysis; D005260:Female; D005838:Genotype; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006680:HLA Antigens; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007527:Isoenzymes / Q000276:immunology*; D008285:Major Histocompatibility Complex; D008297:Male; D012307:Risk Factors
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D006680:HLA Antigens; D007140:Immunoglobulin Fab Fragments; D007527:Isoenzymes; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2