title: Autoantibodies to IA-2 in type 1 diabetes: measurements with a new enzyme-linked immunosorbent assay.
abstract: The tyrosine phosphatase-like protein IA-2 is an important islet autoantigen in type 1 diabetes. Although the radioligand binding assay with in vitro synthesized (35)S-labeled antigen has been used extensively for measuring autoantibodies to IA-2, disadvantages of both assays with respect to synthesis and handling of the radioactive antigen limit their use in routine laboratories. Therefore, we attempted to develop a nonradioactive ELISA for the simple detection of IA-2 autoantibodies. The biotinylated cytoplasmic domain of IA-2 expressed in Escherichia coli was used as an antigen. We evaluated two kinds of ELISA: ELISA with biotin-IA-2 directly captured on streptavidine-coated plates (solid phase) and ELISA with antigen-antibody preincubation in solution in which serum samples were reacted first with biotin-IA-2 and the mixture was transferred to streptavidine-coated plates (liquid phase). We compared their disease sensitivity and specificity with a conventional radioligand binding assay in 52 patients with recent-onset type 1 diabetes and 138 normal individuals. The radioligand binding assay had 61.5% sensitivity and 99.3% specificity. The liquid-phase ELISA showed relatively higher sensitivity (55.8%) and specificity (99.3%) than the solid-phase ELISA (sensitivity 53.8% and specificity 97.1%). Furthermore, the mean SD score in IA-2 autoantibody-positive serum samples measured by liquid-phase ELISA was significantly higher than the SD score obtained by solid-phase ELISA (P < 0.0001). We concluded that this liquid-phase ELISA is suitable for detecting IA-2 autoantibodies in patients with type 1 diabetes with a similar sensitivity and specificity to those of conventional radioligand binding assay.
authors.affiliation: The First Department of Internal Medicine, Nagasaki University School of Medicine, Nagasaki 852-8501, Japan. f1196@cc.nagasaki-u.ac.jp
authors.forename: Eiji
authors.initials: E
authors.lastname: Kawasaki
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hattori
authors.forename: Toru
authors.initials: T
authors.lastname: Egashira
authors.forename: Katsumi
authors.initials: K
authors.lastname: Eguchi
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011869:Radioligand Assay; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; C096322:ICA512 autoantibody