title: Detection of Antibodies Directed to the N-Terminal Region of GAD Is Dependent on Assay Format and Contributes to Differences in the Specificity of GAD Autoantibody Assays for Type 1 Diabetes.
abstract: GAD autoantibodies (GADAs) are sensitive markers of islet autoimmunity and type 1 diabetes. They form the basis of robust prediction models and are widely used for the recruitment of subjects at high risk of type 1 diabetes to prevention trials. However, GADAs are also found in many individuals at low risk of diabetes progression. To identify the sources of diabetes-irrelevant GADA reactivity, we analyzed data from the 2009 and 2010 Diabetes Autoantibody Standardization Program GADA workshop and found that binding of healthy control sera varied according to assay type. The characterization of control sera found positive by radiobinding assay (RBA), but negative by ELISA, showed that many of these sera reacted to epitopes in the N-terminal region of the molecule. This finding prompted development of an N-terminally truncated GAD65 radiolabel, (35)S-GAD65(96-585), which improved the performance of most GADA RBAs participating in an Islet Autoantibody Standardization Program GADA substudy. These detailed workshop comparisons have identified a source of disease-irrelevant signals in GADA RBAs and suggest that N-terminally truncated GAD labels will enable more specific measurement of GADAs in type 1 diabetes.
authors.affiliation: School of Clinical Sciences, University of Bristol, Bristol, U.K. a.j.k.williams@bristol.ac.uk.
authors.forename: Alistair J K
authors.initials: AJ
authors.lastname: Williams
authors.affiliation: Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Lampasona
authors.affiliation: Department of Medical Biochemistry and Molecular Biology and Institute of Pathophysiology, University Medical Center of Greifswald, Karlsburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schlosser
authors.affiliation: Molecular Risk Assessment Laboratory, Centers for Disease Control and Prevention, Atlanta, GA.
authors.forename: Patricia W
authors.initials: PW
authors.lastname: Mueller
authors.affiliation: Department of Pathology, University of Florida, Gainesville, FL.
authors.forename: David L
authors.initials: DL
authors.lastname: Pittman
authors.affiliation: Department of Pathology, University of Florida, Gainesville, FL.
authors.forename: William E
authors.initials: WE
authors.lastname: Winter
authors.affiliation: Division of Diabetes, Endocrinology, and Metabolic Diseases, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD.
authors.forename: Beena
authors.initials: B
authors.lastname: Akolkar
authors.affiliation: School of Clinical Sciences, University of Bristol, Bristol, U.K.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Wyatt
authors.affiliation: Diabetes Research Institute, San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Brigatti
authors.affiliation: Institute of Diabetes Research, Helmholtz Zentrum München, and Forschergruppe Diabetes, Klinikum rechts der Isar, Technische Universität München, Neuherberg, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Krause
authors.affiliation: Institute of Diabetes Research, Helmholtz Zentrum München, and Forschergruppe Diabetes, Klinikum rechts der Isar, Technische Universität München, Neuherberg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Achenbach
mesh_terms: D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000032:analysis*; D016022:Case-Control Studies; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011869:Radioligand Assay; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D005968:Glutamate Decarboxylase