Schlosser M, Banga J P, Madec A M, Binder K A, Strebelow M, Rjasanowski I, Wassmuth R, Gilliam L K, Luo D, Hampe C S
Institute of Pathophysiology, Ernst Moritz Arndt University of Greifswald, Karlsburg, Germany.
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).
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.
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.
目的/假设：1型糖尿病的进展与分子内表位扩展至位于谷氨酸脱羧酶65（GAD65）中间区域的疾病特异性抗体表位有关。
在22名高危个体和38名低危个体中测试了GAD65特异性自身抗体的分子内表位扩展与发生1型糖尿病风险之间的关系。在这项纵向研究中，我们通过使用四种GAD65特异性单克隆抗体的重组Fab进行竞争实验来确定构象表位。
临床前期高危儿童的血清识别位于GAD65中间和C末端的GAD65抗体表位的特定组合。疾病进展的高风险与N末端和中间区域构象表位特异性抗体的出现有关。与位于中间和N末端的已确定抗体表位的结合增加，并且与赋予糖尿病发病风险的HLA有显著关系（p = 0.005）。
结论/解读：在1型糖尿病中，GAD65抗体最初是针对GAD65的中间和C末端区域产生的。在遗传易感性个体中，自身免疫反应随后可能经历分子内表位扩展，朝向N末端的表位以及位于中间的其他表位。这些发现清楚地表明，1型糖尿病临床前期的GAD65自身抗体反应是动态的，并且与赋予糖尿病风险的HLA基因型有关。GAD65特异性Fab应有助于预测从胰岛自身免疫到1型糖尿病临床发病的进展。
