Relationships between major epitopes of the IA-2 autoantigen in Type 1 diabetes: Implications for determinant spreading

McLaughlin, Kerry A.; Richardson, Carolyn C.; Williams, Stefan Rhys; Bonifacio, Ezio; Morgan, Diana; Feltbower, Richard; Powell, Michael J.; Smith, Bernard Rees; Furmaniak, Jadwiga; Christie, Michael R.

doi:10.1016/j.clim.2015.06.002

Cited by 11 publications

(8 citation statements)

References 35 publications

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“…Although canonical immune responses to IA-2ic are considered to be immunodominant (29–31), we found autoantibody and T-cell responses specifically directed to IA-2ec in individuals with or without antibodies directed to IA-2ic. Our results reinforce the notion that long-lived autoantibody responses in the natural history of autoimmune disorders, such as type 1 diabetes, are generally regarded to be polyclonal and yet not restricted to one portion of a given self-antigen (32–35).…”

Section: Discussionmentioning

confidence: 58%

Identification of Unique Antigenic Determinants in the Amino Terminus of IA-2 (ICA512) in Childhood and Adult Autoimmune Diabetes: New Biomarker Development

et al. 2017

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OBJECTIVEThe characterization of diverse subtypes of diabetes is a dynamic field of clinical research and an active area of discussion. The objective of this study was to identify new antigenic determinants in the neuroendocrine autoantigen IA-2 (ICA512) and assess whether circulating autoantibodies directed to new IA-2 epitopes identify autoimmune diabetes in young and adult populations with diabetes.RESEARCH DESIGN AND METHODSClinically diagnosed patients with type 2 diabetes (n = 258; diabetes duration: 0.01–31 years) were evaluated using a new biomarker detecting autoantibodies directed to the extracellular domain of the neuroendocrine autoantigen IA-2 (IA-2ec). The proportion of IA-2ec autoantibodies was also evaluated in newly diagnosed patients with type 1 diabetes (n = 150; diabetes duration: 0.04–0.49 years). In addition, IA-2 (intracellular domain), GAD65, and zinc transporter 8 autoantibodies were assayed.RESULTSIA-2ec autoantibodies were detected in patients with type 1 diabetes and, surprisingly, in 5% of patients with type 2 diabetes without serologic responses to other IA-2 antigenic epitopes or other islet autoantigens. We also assessed the ability of IA-2ec–derived peptides to elicit CD4+ T-cell responses by stimulating peripheral blood mononuclear cells from patients with type 1 diabetes (n = 18) and HLA-matched healthy subjects (n = 13) with peptides and staining with the peptide/DQ8-specific tetramers, observing disease-associated responses to previously unreported epitopes within IA-2ec.CONCLUSIONSWe developed a new antibody biomarker identifying novel antigenic determinants within the N terminus of IA-2. IA-2ec autoantibodies can be detected in patients with type 1 diabetes and in a subgroup of adult autoimmune patients with type 2 diabetes phenotype negative for conventional islet autoantibody testing. These observations suggest that islet autoimmunity may be more common in clinically diagnosed type 2 diabetes than previously observed.

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Section: Discussionmentioning

confidence: 58%

Identification of Unique Antigenic Determinants in the Amino Terminus of IA-2 (ICA512) in Childhood and Adult Autoimmune Diabetes: New Biomarker Development

et al. 2017

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“…We cannot exclude that the low frequency of islet antigen reactive B cells detected in our study was the consequence of sequence artefacts introduced during the cloning that affected the CDR3-binding region of the B cell receptors (BCRs). Nevertheless, the study produced two antibodies against IA-2, one from a lymph node and one from peripheral blood, both to the PTP region, with binding profiles similar to each other and to other type 1 diabetes-derived autoantibodies [9]. This epitope, therefore, is a common target of autoreactive B cells in type 1 diabetes.…”

Section: Discussionmentioning

confidence: 93%

“…IA-2 epitope mapping of the human antibodies (hAb) was performed using constructs containing cytoplasmic IA-2 (amino acid 605-979), juxtamembrane (JM; 605-693), protein tyrosine phosphatase (PTP; 643-979) or central IA-2 PTP (643-937) regions, and alaninesubstituted mutants of these, using radiobinding assays as previously described [9]. Inhibition by >50% was taken as evidence that amino acid substitution affected binding.…”

Section: Antibody Screeningmentioning

confidence: 99%

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Isolation of human monoclonal autoantibodies derived from pancreatic lymph node and peripheral blood B cells of islet autoantibody-positive patients

et al. 2015

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Aims/hypothesis Autoantibodies against pancreatic islets and infections by enteroviruses are associated with type 1 diabetes, but the specificity of immune responses within the type 1 diabetic pancreas is poorly characterised. We investigated whether pancreatic lymph nodes could provide a source of antigen-specific B cells for analysis of immune responses within the (pre)diabetic pancreas. Methods Human IgG antibodies were cloned from single B lymphocytes sorted from pancreatic lymph node cells of three organ donors positive for islet autoantibodies, and from the peripheral blood of a patient with type 1 diabetes. Antibodies to insulinoma-associated antigen 2 (IA-2), GAD65, zinc transporter 8 (ZnT8) and Coxsackie B virus proteins were assayed by immunoprecipitation and by immunofluorescence on pancreatic sections. Results Human IgG antibodies (863) were successfully cloned and produced from 4,092 single B cells from lymph nodes and peripheral blood. Reactivity to the protein tyrosine phosphatase domain of the IA-2 autoantigen was detected in two cloned antibodies: one derived from a pancreatic lymph node and one from peripheral blood. Epitopes for these two antibodies were similar to each other and to those for circulating antibodies in type 1 diabetes. The remaining 861 antibodies were negative for reactivity to IA-2, GAD65 or ZnT8 by both assays tested. Reactivity to a Coxsackie viral protein 2 was detected in one antibody derived from a peripheral blood B cell, but not from lymph nodes. Conclusions/interpretation We show evidence for the infrequent presence of autoantigen-specific IgG + B lymphocytes in the pancreatic-draining lymph nodes of islet autoantibodypositive individuals.

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“…This finding suggests either that alanine substitution of the lysine at residue 609 disturbs the conformation of the 625–627 region, for example by disrupting ionic interactions, or that the JM region is folded such that residue 609 is brought in close proximity to the 625–627 region and participates directly in antibody binding. Mouse monoclonal antibodies to the IA-2 JM domain having similar binding characteristics to those seen in human type 1 diabetes [ 14 , 15 ], also displayed sensitivity to amino acid substitutions within noncontiguous regions of the JM domain [ 16 ]. Thus, four different mouse monoclonal antibodies to the IA-2 JM domain were all inhibited by alanine substitutions in the cluster 4 amino acids 615, 635 and 636, with each antibody being also affected by different amino acid substitutions elsewhere in the JM domain, similar to the observations with the patient sera.…”

Section: Discussionmentioning

confidence: 99%

Influence of HLA-DR and -DQ alleles on autoantibody recognition of distinct epitopes within the juxtamembrane domain of the IA-2 autoantigen in type 1 diabetes

et al. 2015

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Aims/hypothesisInsulinoma-associated protein 2 (IA-2) is a major target of autoimmunity in type 1 diabetes. When first detected, IA-2-autoantibodies commonly bind epitopes in the juxtamembrane (JM) domain of IA-2 and antibody responses subsequently spread to the tyrosine phosphatase domain. Definition of structures of epitopes in the JM domain, and genetic requirements for autoimmunity to these epitopes, is important for our understanding of initiation and progression of autoimmunity. The aims of this study were to investigate the contribution of individual amino acids in the IA-2 JM domain to antibody binding to these epitopes and the role of HLA genotypes in determining epitope specificity.MethodsRegions of the JM domain recognised by autoantibodies were identified by peptide competition and inhibitory effects of alanine substitutions of residues within the JM region. Antibody binding was determined by radioligand binding assays using sera from patients genotyped for HLA-DRB1 and -DQB1 alleles.ResultsPatients were categorised into two distinct groups of JM antibody reactivity according to peptide inhibition. Inhibition by substitutions of individual amino acids within the JM domain differed between patients, indicating heterogeneity in epitope recognition. Cluster analysis defined six groups of residues having similar inhibitory effects on antibody binding, with three clusters showing differences in patients affected or unaffected by peptide. One cluster demonstrated significant differences in antibody binding between HLA-DRB1*04 and HLA-DRB1*07 patients and within DRB1*04 individuals; antibody recognition of a second cluster depended on expression of HLA-DQB1*0302.Conclusions/interpretationThe results identify amino acids contributing to distinct epitopes on IA-2, with both HLA-DR and HLA-DQ alleles influencing epitope specificity.

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Relationships between major epitopes of the IA-2 autoantigen in Type 1 diabetes: Implications for determinant spreading

Cited by 11 publications

References 35 publications

Identification of Unique Antigenic Determinants in the Amino Terminus of IA-2 (ICA512) in Childhood and Adult Autoimmune Diabetes: New Biomarker Development

Identification of Unique Antigenic Determinants in the Amino Terminus of IA-2 (ICA512) in Childhood and Adult Autoimmune Diabetes: New Biomarker Development

Isolation of human monoclonal autoantibodies derived from pancreatic lymph node and peripheral blood B cells of islet autoantibody-positive patients

Influence of HLA-DR and -DQ alleles on autoantibody recognition of distinct epitopes within the juxtamembrane domain of the IA-2 autoantigen in type 1 diabetes

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