Dynamic changes of GAD65 autoantibody epitope specificities in individuals at risk of developing type 1 diabetes

Diabetologia. 2005 May;48(5):922-30. doi: 10.1007/s00125-005-1719-1. Epub 2005 Apr 16.


Aims/hypothesis: 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/interpretation: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Autoantibodies / blood*
  • Child
  • Diabetes Mellitus, Type 1 / epidemiology*
  • Diabetes Mellitus, Type 1 / immunology*
  • Epitopes / analysis
  • Female
  • Genotype
  • Glutamate Decarboxylase / immunology*
  • HLA Antigens
  • Humans
  • Immunoglobulin Fab Fragments / immunology
  • Isoenzymes / immunology*
  • Major Histocompatibility Complex
  • Male
  • Risk Factors


  • Autoantibodies
  • Epitopes
  • HLA Antigens
  • Immunoglobulin Fab Fragments
  • Isoenzymes
  • Glutamate Decarboxylase
  • glutamate decarboxylase 2