A surge in serum mucosal cytokines associated with seroconversion in children at risk for type 1 diabetes.

AIMS/INTRODUCTION: Autoantibodies to pancreatic islet antigens identify young children at high risk of type 1 diabetes. On a background of genetic susceptibility, islet autoimmunity is thought to be driven by environmental factors, of which enteric viruses are prime candidates. We sought evidence for enteric pathology in children genetically at-risk for type 1 diabetes followed from birth who had developed islet autoantibodies ("seroconverted"), by measuring mucosa-associated cytokines in their sera. MATERIALS AND METHODS: Sera were collected 3 monthly from birth from children with a first-degree type 1 diabetes relative, in the Environmental Determinants of Islet Autoimmunity (ENDIA) study. Children who seroconverted were matched for sex, age, and sample availability with seronegative children. Luminex xMap technology was used to measure serum cytokines. RESULTS: Of eight children who seroconverted, for whom serum samples were available at least 6 months before and after seroconversion, the serum concentrations of mucosa-associated cytokines IL-21, IL-22, IL-25, and IL-10, the Th17-related cytokines IL-17F and IL-23, as well as IL-33, IFN-γ, and IL-4, peaked from a low baseline in seven around the time of seroconversion and in one preceding seroconversion. These changes were not detected in eight sex- and age-matched seronegative controls, or in a separate cohort of 11 unmatched seronegative children. CONCLUSIONS: In a cohort of children at risk for type 1 diabetes followed from birth, a transient, systemic increase in mucosa-associated cytokines around the time of seroconversion lends support to the view that mucosal infection, e.g., by an enteric virus, may drive the development of islet autoimmunity.

Cytotoxicity-Related Gene Expression and Chromatin Accessibility Define a Subset of CD4+ T Cells That Mark Progression to Type 1 Diabetes.

Type 1 diabetes in children is heralded by a preclinical phase defined by circulating autoantibodies to pancreatic islet antigens. How islet autoimmunity is initiated and then progresses to clinical diabetes remains poorly understood. Only one study has reported gene expression in specific immune cells of children at risk associated with progression to islet autoimmunity. We analyzed gene expression with RNA sequencing in CD4+ and CD8+ T cells, natural killer (NK) cells, and B cells, and chromatin accessibility by assay for transposase-accessible chromatin sequencing (ATAC-seq) in CD4+ T cells, in five genetically at risk children with islet autoantibodies who progressed to diabetes over a median of 3 years ("progressors") compared with five children matched for sex, age, and HLA-DR who had not progressed ("nonprogressors"). In progressors, differentially expressed genes (DEGs) were largely confined to CD4+ T cells and enriched for cytotoxicity-related genes/pathways. Several top-ranked DEGs were validated in a semi-independent cohort of 13 progressors and 11 nonprogressors. Flow cytometry confirmed that progression was associated with expansion of CD4+ cells with a cytotoxic phenotype. By ATAC-seq, progression was associated with reconfiguration of regulatory chromatin regions in CD4+ cells, some linked to differentially expressed cytotoxicity-related genes. Our findings suggest that cytotoxic CD4+ T cells play a role in promoting progression to type 1 diabetes.

CD52 glycan binds the proinflammatory B box of HMGB1 to engage the Siglec-10 receptor and suppress human T cell function.

CD52, a glycophosphatidylinositol (GPI)-anchored glycoprotein, is released in a soluble form following T cell activation and binds to the Siglec (sialic acid-binding Ig-like lectin)-10 receptor on T cells to suppress their function. We show that binding of CD52-Fc to Siglec-10 and T cell suppression requires the damage-associated molecular pattern (DAMP) protein, high-mobility group box 1 (HMGB1). CD52-Fc bound specifically to the proinflammatory Box B domain of HMGB1, and this in turn promoted binding of the CD52 N-linked glycan, in α-2,3 sialic acid linkage with galactose, to Siglec-10. Suppression of T cell function was blocked by anti-HMGB1 antibody or the antiinflammatory Box A domain of HMGB1. CD52-Fc induced tyrosine phosphorylation of Siglec-10 and was recovered from T cells complexed with HMGB1 and Siglec-10 in association with SHP1 phosphatase and the T cell receptor (TCR). Thus, soluble CD52 exerts a concerted immunosuppressive effect by first sequestering HMGB1 to nullify its proinflammatory Box B, followed by binding to the inhibitory Siglec-10 receptor, triggering recruitment of SHP1 to the intracellular immunoreceptor tyrosine-based inhibitory motif of Siglec-10 and its interaction with the TCR. This mechanism may contribute to immune-inflammatory homeostasis in pathophysiologic states and underscores the potential of soluble CD52 as a therapeutic agent.

Antigen-based vaccination and prevention of type 1 diabetes.

Insulin-dependent or type 1 diabetes (T1D) is a paradigm for prevention of autoimmune disease: Pancreatic ß-cell autoantigens are defined, at-risk individuals can be identified before the onset of symptoms, and autoimmune diabetes is preventable in rodent models. Intervention in asymptomatic individuals before or after the onset of subclinical islet autoimmunity places a premium on safety, a requirement met only by lifestyle-dietary approaches or autoantigen-based vaccination to induce protective immune tolerance. Insulin is the key driver of autoimmune ß-cell destruction in the nonobese diabetic (NOD) mouse model of T1D and is an early autoimmune target in children at risk for T1D. In the NOD mouse, mucosal administration of insulin induces regulatory T cells that protect against diabetes. The promise of autoantigen-specific vaccination in humans has yet to be realized, but recent trials of oral and nasal insulin vaccination in at-risk humans provide grounds for cautious optimism.

Evidence for molecular mimicry between human T cell epitopes in rotavirus and pancreatic islet autoantigens.

In type 1 diabetes, insulin-producing beta cells in the islets of the pancreas are destroyed by autoreactive T cells. Rotavirus (RV) has been implicated in the pathogenesis of type 1 diabetes. Peptides in VP7, a major immunogenic protein of RV, have high sequence similarity to T cell epitope peptides in the islet autoantigens tyrosine phosphatase-like insulinoma Ag 2 (IA2) and glutamic acid decarboxylase 65 (GAD65). We aimed to educe evidence for the hypothesis that molecular mimicry with RV promotes autoimmunity to islet autoantigens. Peptides in RV and their sequence-similar counterparts in IA2 and GAD65 were assayed for binding to HLA molecules associated with type 1 diabetes and for the ability to elicit T cell proliferative responses in HLA-typed individuals. T cells expanded or cloned to epitopes in IA2 or RV were then tested for cross-reactivity with these epitopes. Peptides in RV-VP7, similar to T cell epitopes in IA2 and GAD65, bound strongly to HLA-DRB1*04 molecules that confer susceptibility to type 1 diabetes and were also T cell epitopes in humans at risk for type 1 diabetes. The proliferative responses of T cells to the similar peptides in RV and islet autoantigens were significantly correlated. T cells expanded to the IA2 epitope could be restimulated to express IFN-gamma by the similar peptide in RV-VP7, and T cell clones generated to this RV-VP7 peptide cross-reacted with the IA2 epitope. Our findings are consistent with the hypothesis that molecular mimicry with RV could promote autoimmunity to islet Ags.

Pancreatic beta-cell function and immune responses to insulin after administration of intranasal insulin to humans at risk for type 1 diabetes.

OBJECTIVE: Mucosal administration of insulin retards development of autoimmune diabetes in the nonobese diabetic mouse model. We conducted a double-blind crossover study in humans at risk for type 1 diabetes to determine if intranasal insulin was safe, in particular did not accelerate beta-cell destruction, and could induce immune effects consistent with mucosal tolerance. RESEARCH DESIGN AND METHODS: A total of 38 individuals, median age 10.8 years, with antibodies to one or more pancreatic islet antigens (insulin, GAD65, or tyrosine phosphatase-like insulinoma antigen 2) were randomized to treatment with intranasal insulin (1.6 mg) or a carrier solution, daily for 10 days and then 2 days a week for 6 months, before crossover. The primary outcome was beta-cell function measured as first-phase insulin response (FPIR) to intravenous glucose at 0, 6, and 12 months and then yearly; the secondary outcome was immunity to islet antigens, measured monthly for 12 months. RESULTS: No local or systemic adverse effects were observed. Diabetes developed in 12 participants with negligible beta-cell function at entry after a median of 1.1 year. Of the remaining 26, the majority had antibodies to two or three islet antigens and FPIR greater than the first percentile at entry, as well as beta-cell function that generally remained stable over a median follow-up of 3.0 years. Intranasal insulin was associated with an increase in antibody and a decrease in T-cell responses to insulin. CONCLUSIONS: Results from this pilot study suggest that intranasal insulin does not accelerate loss of beta-cell function in individuals at risk for type 1 diabetes and induces immune changes consistent with mucosal tolerance to insulin. These findings justify a formal trial to determine if intranasal insulin is immunotherapeutic and retards progression to clinical diabetes.

CD4+ T cell proliferation in response to GAD and proinsulin in healthy, pre-diabetic, and diabetic donors.

The ability to measure proliferation of autoantigen-specific T cells is critical for the evaluation of cellular immune function. Using a novel, sensitive, CFSE-based assay, we were able to directly quantitate autoantigen-specific CD4(+) T cell proliferation. However, peripheral blood cells from healthy, pre-diabetic and diabetic donors exhibited overlap in responses to glutamic acid decarboxylase (GAD65) and proinsulin (PI). This indicates that autoantigen-induced CD4(+) T cell proliferation in a functionally complex cell population may not discriminate disease in the general population. Clear discrimination was found between diabetic and healthy sibs, suggesting the need to standardize the genetic and environmental background. In addition, the ability of the CFSE assay to allow analysis of the phenotype and function of autoantigen-responsive T cells may improve discrimination.