Identification of a novel type 1 diabetes-specific epitope by screening phage libraries with sera from pre-diabetic patients.

We used random peptide libraries displayed on phage to search for ligands to insulin dependent diabetes mellitus-related antibodies and were able to identify several candidate disease-related peptides. One of them, clone 92, showed a significant difference in the frequency of reactivity with the sera of patients and normal controls. Human immunoglobulins immunopurified on phage 92 specifically stained the islets on human pancreatic sections. When injected into rabbits, the selected peptide elicited antibodies that also stained human and rat pancreatic sections, with a pattern similar to that observed with immunoglobulins purified from the sera of patients. No reactivity was observed in other tissues. Our results indicate that the peptide identified in this work mimics a novel, diabetes-related self-antigen.

Naked TSH receptor DNA vaccination: A TH1 T cell response in which interferon-gamma production, rather than antibody, dominates the immune response in mice.

Two approaches have been developed to induce TSH receptor antibodies in mice with properties resembling those in Graves' disease, the Shimojo model of injecting live fibroblasts coexpressing the TSH receptor and major histocompatibility complex antigen Class II, and TSH receptor-DNA vaccination. Thyroid-stimulating antibodies appear to occur less commonly after DNA vaccination, but there has been no direct comparison of these models. We performed a three-way comparison of 1) AKR/N and 2) BALB/c mice vaccinated with TSH receptor-DNA and 3) AKR/N mice injected with fibroblasts expressing the TSH receptor and the major histocompatibility complex antigen class II of AKR/N mice. TSH receptor-DNA vaccinated mice had low or undetectable levels of TSH receptor antibodies determined by ELISA or flow cytometry. Nonspecific binding precluded comparisons with sera from Shimojo mice by these assays. TSH binding inhibition and thyroid-stimulating antibody were undetectable in TSH receptor-DNA vaccinated mice. In Shimojo mice, TSH binding inhibition was positive in approximately 60%, and thyroid-stimulating antibodies were positive in hyperthyroid animals. Unlike the negative antibody data, splenocytes from TSH receptor-vaccinated (but not Shimojo) mice proliferated and produced the Th1 cytokine interferon-gamma in response to TSH receptor antigen. In conclusion, DNA vaccination is less effective at inducing TSH receptor antibodies than the Shimojo approach, but it permits the future characterization of TSH receptor-specific T cells generated without adjuvant.

Presence of interleukin 4 or interleukin 10, but not both cytokines, in pancreatic tissue of two patients with recently diagnosed diabetes mellitus type I.

Studies in the NOD mouse model suggest that development of diabetes mellitus type I can be prevented and established disease cured by deviation towards a Th2-type response. To obtain insight into whether this approach may be applicable to human disease, we investigated the Th1/Th2 cytokine balance in pancreatic tissue from two patients with diabetes of recent onset (Case 1, accidental death; Case 2, ketoacidosis). Using the polymerase chain reaction to amplify reverse-transcribed cDNA, signals for actin and CD36 confirmed mRNA integrity and the presence of T cells in pancreatic tissue from both patients and from a control. IFN-gamma cDNA was also amplified from all three tissues. However, IL-4 (but not IL-10) cDNA, was amplified from the pancreas of Case 1. Conversely, IL-10 (but not IL-4) cDNA was amplified from the the pancreas of Case 2. The control pancreas yielded specific signals for both IL-4 and IL-10. Our data extend the limited database on Th1 and Th2 cytokine expression in human pancreatic tissue from recently diagnosed diabetics. Moreover, together with previous observations, our findings raise the possibility that the lack of both IL-4 and IL-10 may be associated with the development of IDDM in humans.

Does the autoantibody immunodominant region on thyroid peroxidase include amino acid residues 742-771?

Identification of the thyroid peroxidase (TPO) amino acid residues that comprise the autoantibody immunodominant region is an important goal that has proven difficult because of the conformational nature of the epitopes involved. Recent data suggest that the immunodominant region has been located. Thus, by autoantibody recognition of tryptic fragments of native TPO, as well as of conformational portions of TPO expressed as cell-free translates, the autoantibody immunodominant region appears to include amino acid residues 742-771, near the C terminus of the ectodomain. To evaluate this deduction, we expressed as cell-free translates the full TPO ectodomain, as well as TPO truncated after residues 741 and 771. The epitopic integrity of these molecules was first confirmed by immunoprecipitation by patient sera containing TPO autoantibodies. However, autoantibody recognition could involve a minority of TPO autoantibodies with the individual sera, not fulfilling the strict criteria for immunodominance. In order to obtain definitive data, we performed immunoprecipitations on these TPO variants with four recombinant human monoclonal autoantibodies that define the immunodominant region. All four monoclonal autoantibodies immunoprecipitated TPO 1-741 to the same extent as they did TPO 1-771 and the full TPO ectodomain, indicating that the immunodominant region comprises (at least in large part) amino acid residues upstream of residue 741.

Effects of exercise and lifestyle modification on fitness, insulin resistance, skeletal muscle oxidative phosphorylation and intramyocellular lipid content in obese children and adolescents.

BACKGROUND: Obesity is associated with poor fitness and adverse metabolic consequences in children. OBJECTIVE: To investigate how exercise and lifestyle modification may improve fitness and insulin sensitivity in this population. DESIGN AND SUBJECTS: Randomized controlled trial, 21 obese (body mass index ≥ 95% percentile) subjects, ages 10 to 17 years. METHODS: Subjects were given standardized healthful lifestyle advice for 8 weeks. In addition, they were randomized to an in-home supervised exercise intervention (n = 10) or control group (n = 11). MEASUREMENTS: Fasting laboratory studies (insulin, glucose, lipid profile) and assessments of fitness, body composition, skeletal muscle oxidative phosphorylation and intramyocellular lipid content (IMCL), were performed at baseline and study completion. RESULTS: Subjects were 13.0 ± 1.9 (standard deviation) years old, 72% female and 44% non-white. Exercise improved fitness (P = 0.03) and power (P = 0.01), and increased IMCL (P = 0.02). HOMA-IR decreased among all subjects in response to lifestyle modification advice (P = 0.01), regardless of exercise training assignment. In univariate analysis in all subjects, change in cardiovascular fitness was associated with change in HOMA-IR. In exploratory analyses, increased IMCL was associated with greater resting energy expenditure (r = 0.78, P = 0.005) and a decrease in fasting respiratory quotient (r = -0.70, P = 0.02) (n = 11). CONCLUSIONS: Change in fitness was found to be related to change in insulin resistance in response to lifestyle modification and exercise in obese children. IMCL increased with exercise in these obese children, which may reflect greater muscle lipid oxidative capacity.

Gangliosides and autoimmune diabetes.

Gangliosides are sialic acid-containing glycolipids which are formed by a hydrophobic portion, the ceramide, and a hydrophilic part, i.e. the oligosaccharide chain. First described in neural tissue, several studies have shown that gangliosides are almost ubiquitous molecules expressed in all vertebrate tissues. Within cells, gangliosides are usually associated with plasma membranes, where they can act as receptors for a variety of molecules and have been shown to take part in cell-to-cell interaction and in signal transduction. In addition, gangliosides are expressed in cytosol membranes like those of secretory granules of some endocrine cells (adrenal medulla, pancreatic islets). As far as the role of gangliosides in diseases is concerned, there are some cases in which an aberrant ganglioside expression plays a crucial role in the disease pathogenetic process. These diseases include two major forms of ganglioside storage, namely GM2-gangliosidosis (Tay-Sachs and its beta-hexosaminidase deficiency) and GM1-gangliosidosis (beta-galactosidase deficiency), where the most prominent pathological characteristic is the lysosomal ganglioside accumulation in neurons. Other inflammatory or degenerative diseases both within and outside the nervous system have been shown to be associated with an altered pattern of ganglioside expression in the target organ. Since monoclonal antibodies have been discovered and used in immunology, a large variety of ganglioside antigens has been described both as blood group antigens and as tumour-related antigens. Several studies have also indicated that gangliosides can act not only as antigens, but also as autoantigens. As a matter of fact, auto-antibodies to gangliosides, detected by immunostaining methods performed directly on TLC plates or by ELISA, have been described in several autoimmune disorders such as Guillain-Barré syndrome, multiple sclerosis, lupus erythematosus, Hashimoto's thyroiditis and, last but not least, insulin-dependent (type 1) diabetes mellitus. This last disease is caused by the autoimmune destruction of insulin-producing pancreatic islet cells in genetically predisposed individuals. Autoantibodies and T lymphocytes directed towards multiple islet autoantigens have been detected in the circulation, well before the clinical onset of the disease, in a prodromal phase during which pancreatic islet beta-cells are presumably destroyed. Among the target autoantigens, some are of protein nature but others are acidic glycolipids such as sulphatides158 and the gangliosides GT3, GD3 and especially GM2-1. This last component is specifically expressed in pancreatic islets and has been shown to represent a target of IgG autoantibodies highly associated with diabetes development in first-degree relatives of type 1 diabetic individuals. In addition, the GM2-1 ganglioside appears to be one of the antigens recognized by cytoplasmic ICA, a heterogeneous group of antibodies which specifically react with islets on pancreatic frozen sections. In conclusion, studies performed in the last decade have clearly indicated that gangliosides represent a heterogeneous class of molecules that are involved in several cellular processes that are of crucial importance in physiological as well as in pathological conditions. Interestingly, these molecules, despite their small size, have been shown to represent not only important antigens in tumour immunology but are also able to elicit a specific autoimmune response, thus representing important autoantigens in some autoimmune disorders. It is of interest that, in addition to neurological autoimmune disorders where autoimmunity to gangliosides is frequent and usually of considerable magnitude, an autoimmune response to this class of molecules has been observed in autoimmune diabetes. (ABSTRACT TRUNCATED)

Selection of phage-displayed peptides mimicking type 1 diabetes-specific epitopes.

Phage display technology represents a powerful tool for the identification of peptides reacting with disease-related antibodies present in human sera. The application of this technology to type 1 diabetes could provide a set of novel reagents for diabetes prediction and could also lead to the identification of novel autoantigens or even of environmental factors possibly causing the disease. In the present study, sera of prediabetic and high risk individuals were used to select candidate peptides from phage-displayed random peptide libraries. Diabetes specific phage clones were then identified from these through screening and counter screening, using sera from diabetic and non-diabetic individuals. The results presented in this paper demonstrate the feasibility of this methodology to identify peptides reacting preferentially with antibodies present in the serum of diabetic patients.