Pharmacological approaches to the prevention of autoimmune diabetes

Single-tube test for autoantibodies to glutamic acid decarboxylase and proinsulin as first-line screening for autoimmunity in adult-onset diabetic patients

The aim of this work was develop a new combined radioligand-binding assay (RBA-combi) for the rapid and simultaneous determination of two autoimmunity markers, GADA and PAA, known to be differentially distributed in young and in some adult diabetic patients. The methodology was applied to sera from 85 young type 1 and 98 adult-onset diabetic patients with different marker profiles and insulin requirements, and to 53 normal control sera. Among type 1 diabetes sera used as autoimmunity controls, 100% of those with at least one positive marker by single methods and 17.7% of those with double negative markers were positive by RBA-combi (RBA-combi+). Among sera from adult-onset diabetes, 100% of those PAA+ (GADA+ or GADA-), 92.3% of GADA+/PAA-, and 1.3% of GADA-/PAA- were RBA-combi+. In conclusion, the new RBA-combi allowed the simultaneous detection of GADA and PAA markers with acceptable performance. Moreover, 16 out of 18 (88.9%) of adult patients RBA-combi+ evolved to insulin requirement, suggesting that this test is a valuable tool for assessing autoimmune processes associated to future impairment of insulin secretion.

Prevention strategies for type 1 diabetes mellitus: current status and future directions

Type 1 diabetes mellitus affects about 1 in 300 people in North America and Europe. Epidemiological studies indicate that the incidence and thus prevalence of type 1 diabetes is rising worldwide. Intervention in autoimmune type 1a diabetes could occur at the time of diagnosis or, preferably, prior to clinical presentation during the 'prediabetic' period (e.g. prevention). Prediabetes is best recognised by the detection of islet autoantibodies in the serum. Promising intervention strategies include monoclonal antibody therapies (e.g. anti-CD3, anti-CD25, anti-CD52 or anti-CD20 monoclonal antibodies), immunosuppression (e.g. calcineurin inhibitors, B7 blockade, glucocorticoids, sirolimus (rapamycin), azathioprine or mycophenolate mofetil), immunomodulatory therapies (e.g. plasmapheresis, intravenous immunoglobulin, cytokine administration, adoptive cellular gene therapy) and tolerisation interventions (e.g. autoantigen administration or avoidance, altered peptide ligand or peptide-based therapies). To date, islet and pancreas transplantation have essentially been reserved for patients with long-standing diabetes who have complications and are also in need of a concurrent kidney transplant. None of the therapies attempted to date has produced long-term remissions in new-onset type 1 diabetes patients and no therapies have been shown to prevent the disease. Nevertheless, with advances in our understanding of basic immunology and the cellular and molecular mechanisms of tolerance induction and maintenance, successful intervention therapies will be developed. The balance between safety and efficacy is critical. Higher rates of adverse events might be more tolerable in new-onset type 1 diabetes patients if the therapy is extremely effective at inducing a permanent remission. However, therapies must not harm the beta-cells themselves or any organ system that is a potential target of diabetes complications, such as the nervous system, retina, cardiovascular system or kidney. In the treatment of prediabetes, successful therapies should provide a level of safety similar to that of currently used vaccines and a high level of efficacy.

A radioligand-binding assay for detecting antibodies specific for proinsulin and insulin using 35S-proinsulin

A new radioligand-binding assay (RBA) is described for the detection of insulin/proinsulin-specific antibodies using 35S-labeled proinsulin produced by a cell-free reticulocyte extract. Direct use of the crude expression product in the RBA was not feasible because the protein failed to fold properly (or had incorrectly paired disulphide bridges) and purification was hindered by interfering by-products. A refolding protocol and a chromatographic procedure were devised that readily allowed production of purified and immunochemically competent 35S-labeled proinsulin. The new RBA was compared with the reference test, in which the tracer was standard 125I-insulin. The analysis included sera from 41 diabetic patients and 25 healthy controls. Twenty-six (63.4%) and 29 (70.7%) patients scored positive by RBA using 35S-PI and 125I-insulin, respectively. The methods showed a satisfactory correlation with r(2)=0.77 and a slope not significantly different from unity (m=1.16+/-0.10; 95% confidence interval). Since the nuclide used in the assay is 35S, the procedure is compatible with standard assays for GADA and IA-2A, and thus may permit combined assays for the major early markers of autoimmune diabetes.

Type 1 diabetes islet autoantibody markers

The diagnosis of type 1 diabetes versus other forms of diabetes such as type 2 diabetes is paramount to guiding proper therapy. Several islet autoantibodies have been identified that serve to diagnose immune-mediated, type 1a diabetes in clinically ambiguous cases. These autoantibodies also serve to predict type 1 diabetes in nondiabetic individuals. The most useful islet autoantibodies include islet cell cytoplasmic autoantibodies, insulin autoantibodies, glutamic acid decarboxylase autoantibodies, and insulinoma-associated-2 autoantibodies. Once type 1 diabetes can be safely and reliably prevented, large-scale islet autoantibody screening programs of the general pediatric population may be warranted. It is controversial whether islet autoantibodies influence the course of type 1 diabetes following diagnosis.

Type 1 diabetes and prediabetic state in a monozygotic triplet

Type 1 diabetes mellitus (IDDM) results from a chronic process of autoimmune destruction of beta cells of the Langerhans islets. The presence of autoantibodies (ICA, GADA, anti-IA2, IAA) in serum precedes the clinical onset of the disease. Genetic predisposition for IDDM is connected with HLA, CTLA-4 and insulin gene region. The aim of the study was the genetic and immunological analysis of a triplet. One of them developed Type 1 diabetes mellitus. We analysed HLA class II, CTLA-4 and insulin gene polymorphisms in the whole family. Besides, we investigated immunological status of three brothers. All patients present identical genotype for VNTR loci: D1S80, D17S5 and Apo B, as well as for HLA-DRB1, -DQA1, -DQB1, CTLA-4 gene and all studied insulin gene polymorphisms. That proves their monozigosity. The triplet presents strong genetic predisposition for IDDM. The two patients without overt diabetes have increased levels of ICA, GADA, IA2 and IAA.