Multiple autoantibodies as predictors of Type 1 diabetes in a general population

Comprehensive Diabetes Autoantibody Laboratory-Based Clinical Service Testing in 6044 Consecutive Patients: Analysis of Age and Sex Effects

Background

In 2017, Mayo Clinic Laboratories commenced offering a comprehensive type 1 diabetes mellitus (T1DM) autoantibody (Ab) evaluation including 4 known Abs targeting glutamic acid decarboxylase (GAD65), protein tyrosine phosphatase-like islet antigen 2 (IA2), insulin (IAA), and zinc transporter 8 protein (ZnT8) antigens.

Methods

The objective of this study was to evaluate real-time data on the frequency and patterns of all 4 Abs stratified by age and sex from 6044 unique consecutive adult and pediatric patients undergoing evaluation for suspected diabetes.

Results

At least one Ab was found in 3370 (56%) of all samples: 67% of children (aged 0–17), 49% of young adults (aged 18–35), and 41% for both middle-aged (aged 36–55) and older (aged >55) adults (P ≤ 0.0001). GAD65-Abs were the most common in all age groups, followed by ZnT8-Ab in those <36 years, or IAA-Ab in those ≥36. Frequencies of IA2- and ZnT8-Abs drop significantly with increasing age. Clusters of 3 or 4 Abs were more frequently encountered in younger patients (41% of children vs 12% in middle- and 13% in older age groups, P ≤ 0.0001).

Conclusions

Children undergoing serological evaluation for T1DM were more commonly positive for autoantibodies than older age groups. The frequency of ZnT8- and IA2-Abs decreases, and IAA-Ab frequency increases with increasing age, and clusters of 2 to 4 autoantibodies are more common in children. In clinical practice, comprehensive testing for diabetes autoantibodies resulted in a switch in diagnosis to T1DM for patients previously classified as type 2 diabetes mellitus.

Pancreas Islet Cell-Specific Antibody Detection by ELISA

Background

Islet cell-specific autoantibodies are useful to classify diabetes. The aim of this study was to evaluate the performance of commercially available ELISAs to detect autoantibodies to glutamic acid decarboxylase 65-kDa isoform (GADA), tyrosine phosphatase-related islet antigen 2 (IA-2A), zinc transporter protein 8 (ZnT8A), and insulin (IAA). The performance of ELISA was compared to the performance of RIA.

Methods

We retrospectively identified 76 newly diagnosed type 1 diabetes mellitus patients (median age 27 years, female/male: 0.65) and 131 disease controls (median age 45 years, female/male: 0.60). The ELISAs were from Medipan. RIAs were in-house methods from the Belgian Diabetes Registry or from Medipan or DIASource.

Results

Sensitivity and specificity of ELISA were, respectively, 97% and 97% for GADA, 61% and 99% for IA-2A, 1% and 96% for IAA, and 70% and 98% for ZnT8A. The likelihood ratio for type 1 diabetes increased with increasing antibody levels for GADA, IA-2A, and ZnT8A measured by ELISA. The positive predictive value of double positivity for either GADA, IA-2A, or ZnT8A was 100%.

Conclusions

The ELISAs to detect GADA, IA-2A, and ZnT8A have good performance characteristics. Combining autoantibody assays and taking into account antibody levels improves the interpretation of autoantibody testing.

Frequencies of CD8 and DN MAIT Cells Among Children Diagnosed With Type 1 Diabetes Are Similar to Age-Matched Controls

Mucosal-associated invariant T (MAIT) cells have been implicated in various forms of autoimmunity, including type 1 diabetes (T1D). Here, we tested the hypothesis that CD8 and double negative (DN) MAIT cell frequencies were altered among diagnosed T1D subjects compared to controls. To do this, we analyzed cryopreserved peripheral blood mononuclear cells (PBMCs) from age-matched T1D and control children using flow cytometry. We observed that CD8 and DN MAIT cell frequencies were similarly abundant between the two groups. We tested for associations between MAIT cell frequency and T1D-associated parameters, which could reveal a pathogenic role for MAIT cells in the absence of changes in frequency. We found no significant associations between CD8 and DN MAIT cell frequency and levels of islet cell autoantibodies (ICA), glutamate decarboxylase 65 (GAD65) autoantibodies, zinc transporter 8 (ZNT8) autoantibodies, and insulinoma antigen 2 (IA-2) autoantibodies. Furthermore, CD8 and DN MAIT cell frequencies were not significantly associated with time since diagnosis, c-peptide levels, HbA1c, and BMI. As we have examined this cohort for multiple soluble factors previously, we tested for associations between relevant factors and MAIT cell frequency. These could help to explain the broad range of MAIT frequencies we observed and/or indicate disease-associated processes. Although we found nothing disease-specific, we observed that levels of IL-7, IL-18, 25 (OH) vitamin D, and the ratio of vitamin D binding protein to 25 (OH) vitamin D were all associated with MAIT cell frequency. Finally, previous cytomegalovirus infection was associated with reduced CD8 and DN MAIT cells. From this evaluation, we found no connections between CD8 and DN MAIT cells and children with T1D. However, we did observe several intrinsic and extrinsic factors that could influence peripheral MAIT cell abundance among all children. These factors may be worth consideration in future experimental design.

Early prediction of autoimmune (type 1) diabetes

Underlying type 1 diabetes is a genetic aetiology dominated by the influence of specific HLA haplotypes involving primarily the class II DR-DQ region. In genetically predisposed children with the DR4-DQ8 haplotype, exogenous factors, yet to be identified, are thought to trigger an autoimmune reaction against insulin, signalled by insulin autoantibodies as the first autoantibody to appear. In children with the DR3-DQ2 haplotype, the triggering reaction is primarily against GAD signalled by GAD autoantibodies (GADA) as the first-appearing autoantibody. The incidence rate of insulin autoantibodies as the first-appearing autoantibody peaks during the first years of life and declines thereafter. The incidence rate of GADA as the first-appearing autoantibody peaks later but does not decline. The first autoantibody may variably be followed, in an apparently non-HLA-associated pathogenesis, by a second, third or fourth autoantibody. Although not all persons with a single type of autoantibody progress to diabetes, the presence of multiple autoantibodies seems invariably to be followed by loss of functional beta cell mass and eventually by dysglycaemia and symptoms. Infiltration of mononuclear cells in and around the islets appears to be a late phenomenon appearing in the multiple-autoantibody-positive with dysglycaemia. As our understanding of the aetiology and pathogenesis of type 1 diabetes advances, the improved capability for early prediction should guide new strategies for the prevention of type 1 diabetes.

Feasibility of screening for T1D and celiac disease in a pediatric clinic setting

OBJECTIVE

Type 1 diabetes (T1D) or celiac disease (CD) develops in at least 2% of the general population. Early detection of disease-specific autoimmunity and subsequent monitoring would be possible if screening tests were more widely available. Currently, screening for islet autoimmunity is available only in a research setting, and CD-specific autoimmunity screening is limited to those in high-risk groups. This study assessed the feasibility of incorporating T1D and CD autoantibody screening into a pediatric practice.

METHODS

Patient engagement strategies, blood collection preference, blood sample volume, rate of autoantibody detection in the general population, and parental satisfaction were assessed. Over 5 weeks, research staff recruited 200 patients, aged 2-6 yr from two pediatric practices in the Denver area to be screened for islet autoantibodies (IAs) and the transglutaminase antibody.

RESULTS

Of the 765 parents approached, 200 (26%) completed the same-day screening. Of the 565 subjects who did not complete the screening, 345 expressed interest, but were unable to make a participation decision. A finger stick, compared with a venous draw, was the preferred method of sample collection. Both methods yielded sufficient blood volume for autoantibody determination. IAs or the transglutaminase antibody were detected in 11 subjects. Parents expressed satisfaction with all aspects of participation.

CONCLUSIONS

The results of this study suggest that it is feasible to conduct this type of screening in a pediatric clinic. Such screening could lead to increased disease awareness and the possible benefits that can result from early detection.

Validation of a rapid type 1 diabetes autoantibody screening assay for community-based screening of organ donors to identify subjects at increased risk for the disease

The Network for Pancreatic Organ donors with Diabetes (nPOD) programme was developed in response to an unmet research need for human pancreatic tissue obtained from individuals with type 1 diabetes mellitus and people at increased risk [i.e. autoantibody (AAb)-positive] for the disease. This necessitated the establishment of a type 1 diabetes-specific AAb screening platform for organ procurement organizations (OPOs). Assay protocols for commercially available enzyme-linked immunosorbent assays (elisas) determining AAb against glutamic acid decarboxylase (GADA), insulinoma-associated protein-2 (IA-2A) and zinc transporter-8 (ZnT8A) were modified to identify AAb-positive donors within strict time requirements associated with organ donation programmes. These rapid elisas were evaluated by the international islet AAb standardization programme (IASP) and used by OPO laboratories as an adjunct to routine serological tests evaluating donors for organ transplantation. The rapid elisas performed well in three IASPs (2011, 2013, 2015) with 98-100% specificity for all three assays, including sensitivities of 64-82% (GADA), 60-64% (IA-2A) and 62-68% (ZnT8A). Since 2009, nPOD has screened 4442 organ donors by rapid elisa; 250 (5·6%) were identified as positive for one AAb and 14 (0.3%) for multiple AAb with 20 of these cases received by nPOD for follow-up studies (14 GADA+, two IA-2A(+) , four multiple AAb-positive). Rapid screening for type 1 diabetes-associated AAb in organ donors is feasible, allowing for identification of non-diabetic, high-risk individuals and procurement of valuable tissues for natural history studies of this disease.

Screening of endocrine organ-specific humoral autoimmunity in 47,XXY Klinefelter's syndrome reveals a significant increase in diabetes-specific immunoreactivity in comparison with healthy control men

The aim of this study was to evaluate the frequency of humoral endocrine organ-specific autoimmunity in 47,XXY Klinefelter's syndrome (KS) by investigating the autoantibody profile specific to type 1 diabetes (T1DM), Addison's disease (AD), Hashimoto thyroiditis (HT), and autoimmune chronic atrophic gastritis (AG). Sixty-one adult Caucasian 47,XXY KS patients were tested for autoantibodies specific to T1DM (Insulin Abs, GAD Abs, IA-2 Abs, Znt8 Abs), HT (TPO Abs), AD (21-OH Abs), and AG (APC Abs). Thirty-five of these patients were not undergoing testosterone replacement therapy TRT (Group 1) and the remaining 26 patients started TRT before the beginning of the study (Group 2). KS autoantibody frequencies were compared to those found in 122 control men. Six of 61 KS patients (9.8 %) were positive for at least one endocrine autoantibody, compared to 6.5 % of controls. Interestingly, KS endocrine immunoreactivity was directed primarily against diabetes-specific autoantigens (8.2 %), with a significantly higher frequency than in controls (p = 0.016). Two KS patients (3.3 %) were TPO Ab positive, whereas no patients were positive for AD- and AG-related autoantigens. The autoantibody endocrine profile of untreated and treated KS patients was not significantly different. Our findings demonstrate for the first time that endocrine humoral immunoreactivity is not rare in KS patients and that it is more frequently directed against type 1 diabetes-related autoantigens, thus suggesting the importance of screening for organ-specific autoimmunity in clinical practice. Follow-up studies are needed to establish if autoantibody-positive KS patients will develop clinical T1DM.

Predictors of Progression From the Appearance of Islet Autoantibodies to Early Childhood Diabetes: The Environmental Determinants of Diabetes in the Young (TEDDY)

OBJECTIVE

While it is known that there is progression to diabetes in <10 years in 70% of children with two or more islet autoantibodies, predictors of the progression to diabetes are only partially defined.

RESEARCH DESIGN AND METHODS

The Environmental Determinants of Diabetes in the Young (TEDDY) study has observed 8,503 children who were at increased genetic risk for autoimmune diabetes. Insulin autoantibodies (IAAs), GAD65 autoantibodies (GADAs), and insulinoma-associated protein 2 autoantibodies (IA-2As) were measured every 3 months until 4 years of age and every 6 months thereafter; if results were positive, the autoantibodies were measured every 3 months.

RESULTS

Life table analysis revealed that the cumulative incidence of diabetes by 5 years since the appearance of the first autoantibody differed significantly by the number of positive autoantibodies (47%, 36%, and 11%, respectively, in those with three autoantibodies, two autoantibodies, and one autoantibody, P < 0.001). In time-varying survival models adjusted for first-degree relative status, number of autoantibodies, age at first persistent confirmed autoantibodies, and HLA genotypes, higher mean IAA and IA-2A levels were associated with an increased risk of type 1 diabetes in children who were persistently autoantibody positive (IAAs: hazard ratio [HR] 8.1 [95% CI 4.6-14.2]; IA-2A: HR 7.4 [95% CI 4.3-12.6]; P < 0.0001]). The mean GADA level did not significantly affect the risk of diabetes.

CONCLUSIONS

In the TEDDY study, children who have progressed to diabetes usually expressed two or more autoantibodies. Higher IAA and IA-2A levels, but not GADA levels, increased the risk of diabetes in those children who were persistently autoantibody positive.

Is It Time to Screen the General Population for Type 1 Diabetes?

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by destruction of insulin-producing β cells in the pancreas. The incidence of T1D is increasing dramatically, and the prevalence has doubled in the last 2 decades, further increasing the morbidity and mortality associated with the disease. T1D is now predictable with the measurement of antibodies directed against β cell proteins. Islet autoantibodies (IAs) are detectable from the peripheral blood months to years before clinical diagnosis. With the presence of two or more antibodies, the risk for developing T1D is nearly 100 % given enough time. Targeted screening for T1D risk has been carried out in first-degree relatives and those with a significant genetic risk. However, more than 85 % of individuals who are diagnosed with T1D do not have a family history. In light of the predictability of T1D and recent advances in IA measurement, general population screening is on the horizon. We provide an overview of the history of general population screening and discuss the rationale for and arguments against screening the general population for T1D risk.

The diagnostic role of autoantibodies in the prediction of organ-specific autoimmune diseases

Due to their pathogenetic role, many serum autoantibodies can be detected a long time before the clinical onset and during the course of organ-specific autoimmune diseases. For these reasons, autoantibodies can be used as predictive markers of an ongoing disease (in healthy subjects) and of disease activity and severity (in ill patients). The new multiplex diagnostic technologies introduced recently in laboratory medicine allow the simultaneous detection of several different autoantibodies and can be used for screening purposes in open populations or high-risk groups. This review examines the various autoantibodies of demonstrated predictive role in organ-specific autoimmune diseases and it introduces the state-of-the-art in the detection of multiple autoantibodies with proteomic systems.

Prediction of type 1 diabetes among siblings of affected children and in the general population

AIMS/HYPOTHESIS

To compare the predictive characteristics of autoantibodies to GAD (GADA) and islet antigen 2 (IA-2A) for type 1 diabetes between siblings of affected children and children from the general population.

METHODS

Seven-hundred and fifty-five siblings and 3,475 population-derived children were screened for GADA and IA-2A and observed for type 1 diabetes for 15 years. Sensitivity and cumulative disease risks from GADA, IA-2A and double positivity were compared between the cohorts.

RESULTS

Fifty-six siblings (7.4%) tested positive for GADA, 39 (5.2%) for IA-2A and 29 (3.8%) for both autoantibodies. Thirty-four population derived participants (1.0%) had GADA, 22 (0.6%) had IA-2A and 7 (0.2%) had double positivity. Fifty-one siblings (6.8%) and 15 participants in the population cohort (0.4%) progressed to type 1 diabetes. The predictive sensitivity of GADA was 68% (95% CI 53-81%) among siblings and 50% (95% CI 23-77%) in the general population, while the corresponding values were 58 (95% CI 43-72%) and 43% (95% CI 18-71%) for IA-2A. Double-autoantibody positivity had a sensitivity of 48% (95% CI 34-63%) among siblings and 36% (95% CI 13-65%) in the population cohort. Cumulative disease risks from GADA, IA-2A and double positivity were, respectively, 61% (95% CI 48-74%), 74% (95% CI 61-88%) and 83% (95% CI 69-97%) among siblings compared with those of 24% (95% CI 9-38%), 32% (95% CI 12-51%) and 86% (95% CI 60-100%) in the general population.

CONCLUSIONS/INTERPRETATION

There were no significant differences in the disease-predictive sensitivity of GADA and IA-2A positivity or their combination between siblings and the population cohort, whereas, for each antibody, positivity was associated with a higher cumulative disease risk among siblings. Double-antibody positivity conferred similar cumulative disease risk both among siblings and in the general population.

Lessons on autoimmune diabetes from animal models

T1DM (Type I diabetes mellitus) results from selective destruction of the insulin-producing beta-cells of the pancreas by the immune system, and is characterized by hyperglycaemia and vascular complications arising from suboptimal control of blood glucose levels. The discovery of animal models of T1DM in the late 1970s and early 1980s, particularly the NOD (non-obese diabetic) mouse and the BB (BioBreeding) diabetes-prone rat, had a fundamental impact on our ability to understand the genetics, aetiology and pathogenesis of this disease. NOD and BB diabetes-prone rats spontaneously develop a form of diabetes that closely resembles the human counterpart. Early studies of these animals quickly led to the realization that T1DM is caused by autoreactive T-lymphocytes and revealed that the development of T1DM is controlled by numerous polymorphic genetic elements that are scattered throughout the genome. The development of transgenic and gene-targeting technologies during the 1980s allowed the generation of models of T1DM of reduced genetic and pathogenic complexity, and a more detailed understanding of the immunogenetics of T1DM. In this review, we summarize the contribution of studies in animal models of T1DM to our current understanding of four fundamental aspects of T1DM: (i) the nature of genetic elements affording T1DM susceptibility or resistance; (ii) the mechanisms underlying the development and recruitment of pathogenic autoreactive T-cells; (iii) the identity of islet antigens that contribute to the initiation and/or progression of islet inflammation and beta-cell destruction; and (iv) the design of avenues for therapeutic intervention that are rooted in the knowledge gained from studies of animal models. Development of new animal models will ensure continued progress in these four areas.

Identification and Functional Validation of Novel Autoantigens in Equine Uveitis

The development, progression, and recurrence of autoimmune diseases are frequently driven by a group of participatory autoantigens. We identified and characterized novel autoantigens by analyzing the autoantibody binding pattern from horses affected by spontaneous equine recurrent uveitis to the retinal proteome. Cellular retinaldehyde-binding protein (cRALBP) had not been described previously as autoantigen, but subsequent characterization in equine recurrent uveitis horses revealed B and T cell autoreactivity to this protein and established a link to epitope spreading. We further immunized healthy rats and horses with cRALBP and observed uveitis in both species with typical tissue lesions at cRALBP expression sites. The autoantibody profiling outlined here could be used in various autoimmune diseases to detect autoantigens involved in the dynamic spreading cascade or serve as predictive markers.