Distinguishing Persistent Insulin Autoantibodies With Differential Risk

Abstract

A subset of children develops persistent insulin autoantibodies (IAA; almost always as the only islet autoantibody) without evidence of progression to diabetes. The aim of the current study was the development and characterization of the performance of a nonradioactive fluid phase IAA assay in relation to standard IAA radioassay. We developed a nonradioactive IAA assay where bivalent IAA cross-link two insulin moieties in a fluid phase. The serum samples positive for anti-islet autoantibodies from 150 newly diagnosed patients with diabetes (Barbara Davis Center plus Diabetes Autoantibody Standardization Program [DASP] workshop) and 70 prediabetic subjects who were followed to diabetes were studied. In addition, sequential samples from 64 nondiabetic subjects who were persistently IAA+ were analyzed. With 99th percentile of specificity, the new assay with the technology from Meso Scale Discovery Company (MSD-IAA) detects as positive 61% (61 of 100) of new-onset patients and 80% (56 of 70) of prediabetic patients compared with our current fluid phase micro-IAA radioassay (mIAA; 44 and 74%, respectively). In addition, MSD-IAA demonstrated better sensitivity than our mIAA from blinded DASP workshop (68 vs. 56% with the same 99% specificity). Of 64 IAA+ nondiabetic subjects, 25% (8 of 32) who had only IAA and thus the low risk for progression to diabetes were positive with MSD-IAA assay. In contrast, 100% (32 of 32) high-risk children (IAA plus other islet autoantibodies) were positive with MSD-IAA. The IAA detectable by radioassay, but not MSD-IAA, were usually of lower affinity compared with the IAA of the high-risk children. These data suggest that a subset of IAA with current radioassay (not MSD-IAA) represents biologic false positives in terms of autoimmunity leading to diabetes. We hypothesize that factors related to the mechanism of loss of tolerance leading to diabetes determine high affinity and MSD-IAA reactivity.

The Use of Electrochemiluminescence Assays to Predict Autoantibody and Glycemic Progression Toward Type 1 Diabetes in Individuals with Single Autoantibodies

“…The findings are consistent with other reports showing the enhanced prediction accuracy of ECL measurements. [4][5][6][7] The finding in the present report of a greater progression to multiple autoantibodies among those ECL + is similar to the finding from a prior TrialNet study. 6 The numbers included in the present study were smaller, since we excluded those who did not have the requisite OGTTs for the PS6M analysis.…”

“…[4][5][6][7] Briefly, serum samples were mixed with both SULFO-TAG-and biotin-labeled antigen proteins (either proinsulin or GADA) for overnight incubation at 4°C. The antigen-antibody complexes with biotin were captured by a streptavidin-coated plate, and SULFO-TAG gave the signals with ECL.…”

“…[4][5][6][7] Thus, we have studied TrialNet Pathway to Prevention (PTP) participants, all relatives of T1D patients, to determine whether ECL assays can be used to refine risk assessments for T1D among individuals either positive for GADA alone or mIAA alone.…”

Electrochemiluminescence Assays for Insulin and Glutamic Acid Decarboxylase Autoantibodies Improve Prediction of Type 1 Diabetes Risk

“…10 These methods have improved assay specificity, but most are too costly and cumbersome for a large-scale screening or associated with some loss of sensitivity. Recently, we developed new electrochemiluminescence (ECL) IAA 11,12 and GADA 13 assays that discriminated high-affinity, diabetesspecific iAbs from low-affinity, ''low-risk'' iAbs detected by radioassay (RAD).…”

Targeting the Trimolecular Complex: The Pathway Towards Type 1 Diabetes Prevention

“…Recent work from George's laboratory has resulted in the development of nonradioactive islet autoantibody assays that are more sensitive and specific than the previously used radioimmunoassays. 21 George had a particular interest in the insulin molecule, as evidenced by immunotherapy trials using both subcutaneous and oral insulin to prevent diabetes onset. [22][23][24] In a spontaneous mouse model of autoimmune diabetes, the non-obese (NOD) mouse, he and his lab discovered that insulin is a primary autoantigen in the disease process.…”