title: ICA512(IA-2) epitope specific assays distinguish transient from diabetes associated autoantibodies.
abstract: ICA512/IA-2, a tyrosine phosphatase-like protein, is one of the major autoantigens in type 1 diabetes. Following phage display characterization of ICA512 autoantigenic epitopes, we developed fluid phase autoantibody radioimmunoassays for a series of ICA512 fragments (F1 [amino acids (aa): 761-964], F2A [aa 256-760], F2B [aa 761-928], and F2C [aa 929-979]). With the hypothesis that 'non-diabetes associated' ICA512 autoantibodies would differ from diabetes associated ICA512 autoantibodies in terms of epitopes recognized, we analyzed ten such serum samples (two from normal control individuals, one from a general population subject with transient ICA512 autoantibodies and seven from relatives of patients with type 1 diabetes who had single transient ICA512 positivity). All but one of the 'non-diabetes associated' ICA512 positive samples (9/10) did not react with Fragment 1 which contains the major antigenic epitopes of the molecule that were recognized by almost all (51/52) ICA512 positive new onset patient samples and pre-diabetic relatives (P< 10(-6)). The great majority of samples (44/52) from the new onset patients and pre-diabetic relatives reacted with at least two fragments and 60% (31/52) with three or more fragments. In contrast, only one sample of the ICA512 'non-diabetes associated' sera reacted with multiple fragments (P< 10(-4)). Our findings suggest that diabetes associated anti-ICA512 autoantibodies react with multiple ICA512 epitopes while non-diabetes associated ICA512 autoantibodies may usually represent reactivity of antibodies with determinants of ICA512 unrelated to type 1 diabetes. The ability to distinguish diabetes associated from non-diabetes associated anti-ICA512 autoantibodies should provide prognostic information and more importantly suggests that even with highly specific radioassays positivity may occur unrelated to type 1 diabetes.
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado, Denver 80262, USA.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Miao
authors.forename: Liping
authors.initials: L
authors.lastname: Yu
authors.forename: Claudio
authors.initials: C
authors.lastname: Tiberti
authors.forename: David D
authors.initials: DD
authors.lastname: Cuthbertson
authors.forename: Marian
authors.initials: M
authors.lastname: Rewers
authors.forename: Umberto
authors.initials: U
authors.lastname: di Mario
authors.forename: George S
authors.initials: GS
authors.lastname: Eisenbarth
authors.forename: Francesco
authors.initials: F
authors.lastname: Dotta
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000737:chemistry / Q000235:genetics; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D000939:Epitopes / Q000737:chemistry / Q000235:genetics; D006801:Humans; D007515:Islets of Langerhans / Q000276:immunology; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D018448:Models, Immunological; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; C096322:ICA512 autoantibody; D008565:Membrane Proteins; D010446:Peptide Fragments; C516862:PTPRN protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8