Potential risk of oral insulin with adjuvant for the prevention of Type I diabetes: a protocol effective in NOD mice may exacerbate disease in BB rats

The pertussis hypothesis: Bordetella pertussis colonization in the etiology of asthma and diseases of allergic sensitization

Decades of peer reviewed evidence demonstrate that: 1)Bordetellapertussisand pertussis toxin are potent adjuvants, inducing asthma and allergic sensitization in animal models of human disease, 2)Bordetella pertussisoften colonizes the human nasopharynx, and is well documented in highly pertussis-vaccinated populations and 3) in children, a history of whooping cough increases the risk of asthma and allergic sensitization disease. We build on these observations with six case studies and offer a pertussis-based explanation for the rapid rise in allergic disease in former East Germany following the fall of the Berlin Wall; the current asthma, peanut allergy, and anaphylaxis epidemics in the United States; the correlation between the risk of asthma and gross national income per capita by country; the lower risk of asthma and allergy in children raised on farms; and the reduced risk of atopy with increased family size and later sibling birth order. To organize the evidence for the pertussis hypothesis, we apply the Bradford Hill criteria to the association between Bordetella pertussisand asthma and allergicsensitization disease. We propose that, contrary to conventional wisdom that nasopharyngealBordetella pertussiscolonizing infections are harmless, subclinicalBordetella pertussiscolonization is an important cause of asthma and diseases of allergic sensitization.

Vaccination with a co-expression DNA plasmid containing GAD65 fragment gene and IL-10 gene induces regulatory CD4(+) T cells that prevent experimental autoimmune diabetes

BACKGROUND

The non-obese diabetic (NOD) mouse is a commonly used animal model for studying type 1 diabetes (T1D). The aims of our study were to explore the diabetes-preventive effect in NOD mice and the potential mechanisms of an optimized co-expression DNA vaccine containing GAD65 fragment gene with the IL-10 gene (SGAD65190-315 /IL-10).

METHODS

Female NOD mice at the age of 3-4 weeks old were randomly divided into two groups and received intra-muscular injection of either blank pBudCE4.l vector (n = 34) or pBudCE4.l carrying the SGAD65190-315 /IL-10 (n = 32). The incidence of diabetes was monitored up to 30 weeks of age. The severity of insulitis, apoptosis rate of β cells and relevant mechanisms were examined.

RESULTS

Administration with SGAD65190-315 /IL-10 blocked the onset of autoimmune diabetes in NOD mice, significantly suppressed islet inflammation, inhibited the apoptosis of islet β cells, induced immune tolerance to autoantigen GAD65 and proinsulin and shifted the Th1/Th2 balance towards Th2. More importantly, the frequencies of CD4(+) CD25(+) Foxp3(+) regulatory T cells (Tregs) in the spleen and pancreatic lymph nodes in vaccine-immunized mice were significantly increased, and these Tregs were GAD65-reactive. In addition, Treg depletion by anti-CD25 mAb administration abolished the protective effects of SGAD65190-315 /IL-10 on diabetes and insulitis. Moreover, depletion of CD4(+) CD25(+) T cells using magnetic-activated cell sorting impaired the protective effect of SGAD65190-315 /IL-10 vaccination on adoptive transfer of diabetes.

CONCLUSIONS

Our data suggested that SGAD65190-315 /IL-10 DNA vaccine had protective effects on T1D by upregulating autoantigen-reactive Tregs. Our findings may provide a novel preventive therapy for T1D. Copyright © 2016 John Wiley & Sons, Ltd.

Clinical potential of antigen-specific therapies in type 1 diabetes

In type 1 diabetes (T1D), pancreatic beta-cells are attacked and destroyed by the immune system, which leads to a loss of endogenous insulin secretion. The desirable outcome of therapeutic intervention in autoimmune diseases is the restoration of immune tolerance to prevent organ damage. Past trials with immune suppressive drugs highlight the fact that T1D is in principle a curable condition. However, the barrier in T1D therapy in terms of drug safety is set particularly high because of the predominantly young population and the good prognosis associated with modern exogenous insulin therapy. Thus, there is a general consensus that chronic immune suppression is associated with unacceptable long-term safety risks. On the other hand, immune-modulatory biologicals have recently failed to confer significant protection in phase 3 clinical trials. However, the concept of antigen-specific tolerization may offer a unique strategy to safely induce long-term protection against T1D. In this review, we analyze the potential reasons for the failure of the different tolerization therapies, and describe how the concept of antigen-specific toleraization may overcome the obstacles associated with clinical therapy in T1D.

Can we vaccinate against Type 1 diabetes?

Vaccination is the administration of antigenic material to stimulate the immune system to develop adaptive immunity to a disease. As the most successful prophylactic in medical history, there is now an emerging interest as to whether vaccination can be applied in autoimmune and inflammatory conditions. These are diseases of failed immune regulation; vaccination in this context aims to exploit the power of antigenic material to stimulate immune homeostasis in the form of active, adaptive, regulatory immune responses. Type 1 diabetes is an autoimmune disease that could benefit from the therapeutic potential of vaccination. The major conditions necessary to make prophylaxis feasible are in place; the self antigens are known, the failure of existing immune regulation has been demonstrated, early studies of vaccine approaches have proved safe, and the preclinical prodrome of the disease can be easily detected by simple blood tests. Challenges for future implementation include finding the best mode of delivery and the best blend of adjunctive therapies that create the favorable conditions required for a vaccine to be effective.

Nasal insulin to prevent type 1 diabetes in children with HLA genotypes and autoantibodies conferring increased risk of disease: a double-blind, randomised controlled trial

BACKGROUND

In mouse models of diabetes, prophylactic administration of insulin reduced incidence of the disease. We investigated whether administration of nasal insulin decreased the incidence of type 1 diabetes, in children with HLA genotypes and autoantibodies increasing the risk of the disease.

METHODS

At three university hospitals in Turku, Oulu, and Tampere (Finland), we analysed cord blood samples of 116 720 consecutively born infants, and 3430 of their siblings, for the HLA-DQB1 susceptibility alleles for type 1 diabetes. 17 397 infants and 1613 siblings had increased genetic risk, of whom 11 225 and 1574, respectively, consented to screening of diabetes-associated autoantibodies at every 3-12 months. In a double-blind trial, we randomly assigned 224 infants and 40 siblings positive for two or more autoantibodies, in consecutive samples, to receive short-acting human insulin (1 unit/kg; n=115 and n=22) or placebo (n=109 and n=18) once a day intranasally. We used a restricted randomisation, stratified by site, with permuted blocks of size two. Primary endpoint was diagnosis of diabetes. Analysis was by intention to treat. The study was terminated early because insulin had no beneficial effect. This study is registered with ClinicalTrials.gov, number NCT00223613.

FINDINGS

Median duration of the intervention was 1.8 years (range 0-9.7). Diabetes was diagnosed in 49 index children randomised to receive insulin, and in 47 randomised to placebo (hazard ratio [HR] 1.14; 95% CI 0.73-1.77). 42 and 38 of these children, respectively, continued treatment until diagnosis, with yearly rates of diabetes onset of 16.8% (95% CI 11.7-21.9) and 15.3% (10.5-20.2). Seven siblings were diagnosed with diabetes in the insulin group, versus six in the placebo group (HR 1.93; 0.56-6.77). In all randomised children, diabetes was diagnosed in 56 in the insulin group, and 53 in the placebo group (HR 0.98; 0.67-1.43, p=0.91).

INTERPRETATION

In children with HLA-conferred susceptibility to diabetes, administration of nasal insulin, started soon after detection of autoantibodies, could not be shown to prevent or delay type 1 diabetes.

Update on coeliac disease and type 1 diabetes mellitus in childhood

The increased prevalence of coeliac disease (CD) among children with type 1 diabetes mellitus (DM1) implies that there is more than a simple association. A link between the gut immune system and DM1 has been suggested both in animal models and in humans. We review the literature on the epidemiology and genetic and clinical aspects shared by these two diseases and speculate on the role of gluten on the possible relationship between CD and DM1, on the basis of recent animal and human studies. The data suggest a failure in oral tolerance mechanisms in DM1 other than that in CD. It remains to be understood why only a small proportion of patients with DM1 proceed to the production of coeliac-associated antibodies and to overt enteropathy.

Mycobacterial Hsp65-IgG-expressing tolerogenic B cells confer protection against adjuvant-induced arthritis in Lewis rats

OBJECTIVE

Tolerization of T cells directed against a target autoantigen is a desired goal of experimental approaches for the treatment of autoimmune diseases, and novel and improved methods of tolerance induction are continuously being sought. Because most traditional methods of tolerance induction using soluble antigen are effective in the prevention of autoimmunity but fail to control established disease, this study was carried out to explore an innovative tolerogenic approach for the treatment of ongoing disease, using the rat adjuvant-induced arthritis (AIA) model of human rheumatoid arthritis.

METHODS

Lewis (RT.1(l)) rats were injected subcutaneously with heat-killed Mycobacterium tuberculosis H37Ra to induce AIA. Before or after AIA induction, Lewis rats were treated intraperitoneally (IP) with tolerogenic B cells expressing a fusion construct of mycobacterial 65-kd heat-shock protein (Hsp65) and IgG heavy-chain. For comparison, control rats were treated IP with ovalbumin (OVA)-IgG-expressing B cells or soluble mycobacterial Hsp65, and the effects on AIA were observed. We also tested the immune response to mycobacterial Hsp65 in B cell-tolerized rats.

RESULTS

Administration of tolerogenic mycobacterial Hsp65-expressing B cells as well as soluble mycobacterial Hsp65, but not OVA-expressing B cells, resulted in a significant decrease in the severity of subsequent AIA. However, in rats with established disease, only the B cell regimen of mycobacterial Hsp65, but not the soluble antigen, suppressed ongoing AIA.

CONCLUSION

Mycobacterial Hsp65-IgG-expressing B cells can successfully attenuate the progression of AIA. This study introduces a promising approach for the treatment of arthritis that should be further explored.

Mucosal exposure to antigen: cause or cure of type 1 diabetes?

The human gut offers more than 200 m2 of mucosal surface, where direct interactions between the immune system and foreign antigens take place to eliminate pathogens or induce immune tolerance toward food antigens or normal gut flora. Therefore, mucosally administered antigens can induce tolerance under certain circumstances. In autoimmune diabetes, mucosal vaccination with autoantigens elicits some efficacy in restoring tolerance in mice, but it never succeeded in humans. Furthermore, in some instances autoimmunity can be precipitated upon oral or intranasal autoantigen administration. Therefore, it is difficult to predict the effect of mucosal vaccination on autoimmunity and much effort should be put into establishing better assays to reduce the risk for possible adverse events in humans and enable a rapid and smooth translation.

Effects of a vitamin D3 analog on diabetes in the bio breeding (BB) rat

Non-hypercalcemic analogs of vitamin D(3) modulate the immune response through antigen-presenting cells (APCs) and activated T-cells. A large population-base case-control showed that vitamin D(3) intake significantly decreases the risk of type 1 diabetes development. The aim of this study was, therefore, to observe the in vivo effects of a vitamin D(3) analog administered to Bio Breeding (BB) rats. 1,25-Dihydroxy-16,23Z-diene-26,27-hexafluoro-19-nor vitamin D(3) (BXL-219, formerly Ro 26-2198) (BioXell, Milan, Italy) was administered in vivo to BB rats from days 42 to 110 of life at 0.2 microg/Kg BW. Control animals received only vehicle (olive oil, 4.8 microl/100 g BW). The animals of these two groups were subjected to insulin treatment as they became diabetic. Insulin (Humulin, 28.6 UI/day) was administered irrespective of diabetes occurrence to another group of rats for comparison. Blood glucose, insulin levels, glycosuria, degree of islet infiltration, and the expression of some antigens were observed. Results showed that the vitamin D(3) analog reduced diabetes incidence, although limitedly, in BB rats while administration of oral insulin increased diabetes incidence. In addition, the vitamin D(3) analog did not stimulate an enhancement in the expression of CD4 and CD25 in BB rats as it does in NOD mice, which may explain the failure of this as well as other antidiabetic treatments in the BB animal model of type 1 diabetes.

Dietary proteins as environmental modifiers of type 1 diabetes mellitus

Type 1 diabetes is an autoimmune disease in which the patient's immune system destroys the insulin-secreting beta-cells in the pancreatic islets of Langerhans. A majority of cases is thought to occur as a result of gene-environment interactions. The identity of the environmental factors remains unknown mainly because of the difficulty in linking past exposures with later disease development. Overall, the data suggest a model in which individuals develop diabetes by several different pathways, each influenced by numerous genetic and environmental variables. The most investigated environmental factors are diet and viruses. In this review, we examine the evidence that the source of dietary proteins can modify diabetes outcome, describe new approaches to identify candidate diabetes-related dietary agents, examine possible links with gut dysfunction, discuss some of the limitations, and propose a multifactorial model for dietary modification of diabetes. The key to diabetes pathogenesis, its prevention, and the ultimate success of beta-cell replacement therapies lies in understanding how the environment controls disease expression. Dietary proteins could be one of these keys.

Oral tolerance

Multiple mechanisms of tolerance are induced by oral antigen. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral antigen induces T-helper 2 [interleukin (IL)-4/IL-10] and Th3 [transforming growth factor (TGF)-beta] T cells plus CD4+CD25+ regulatory cells and latency-associated peptide+ T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-beta, cholera toxin B subunit, Flt-3 ligand, and anti-CD40 ligand. Oral (and nasal) antigen administration suppresses animal models of autoimmune diseases including experimental autoimmune encephalitis, uveitis, thyroiditis, myasthenia, arthritis, and diabetes in the non-obese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, graft rejection, allergy, colitis, stroke, and models of Alzheimer's disease. Oral tolerance has been tested in human autoimmune diseases including multiple sclerosis (MS), arthritis, uveitis, and diabetes and in allergy, contact sensitivity to dinitrochlorobenzene (DNCB), and nickel allergy. Although positive results have been observed in phase II trials, no effect was observed in phase III trials of CII in rheumatoid arthritis or oral myelin and glatiramer acetate (GA) in MS. Large placebo effects were observed, and new trials of oral GA are underway. Oral insulin has recently been shown to delay onset of diabetes in at-risk populations, and confirmatory trials of oral insulin are being planned. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time, and antigen-specific mechanisms of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy, and early therapy.

Rat models of type 1 diabetes: genetics, environment, and autoimmunity

For many years, the vast amount of data gathered from analysis of nonobese diabetic (NOD) and congenic NOD mice has eclipsed interest in the rat for the study of type 1 diabetes. The study of rat models has continued, however, and recently there has been a reanimation of interest for several reasons. First, genetic analysis of the rat has accelerated. Ian4L1, cblb, and Iddm4 are now known to play major roles in rat autoimmunity. Second, rats are amenable to study the interactions of genetics and environment that may be critical for disease expression in humans. Environmental perturbants that predictably enhance the expression of rat autoimmune diabetes include viral infection, toll-like receptor ligation, and depletion of regulatory T cell populations. Finally, data generated in the rat have correctly predicted the outcome of several human diabetes prevention trials, notably the failure of nicotinamide and low dose parenteral and oral insulin therapies.

Effects of oral insulin in relatives of patients with type 1 diabetes: The Diabetes Prevention Trial--Type 1

OBJECTIVE

This randomized, double-masked, placebo-controlled clinical trial tested whether oral insulin administration could delay or prevent type 1 diabetes in nondiabetic relatives at risk for diabetes.

RESEARCH DESIGN AND METHODS

We screened 103,391 first- and second-degree relatives of patients with type 1 diabetes and analyzed 97,273 samples for islet cell antibodies. A total of 3,483 were antibody positive; 2,523 underwent genetic, immunological, and metabolic staging to quantify risk of developing diabetes; 388 had a 5-year risk projection of 26-50%; and 372 (median age 10.25 years) were randomly assigned to oral insulin (7.5 mg/day) or placebo. Oral glucose tolerance tests were performed every 6 months. The median follow-up was 4.3 years, and the primary end point was diagnosis of diabetes.

RESULTS

Diabetes was diagnosed in 44 oral insulin and 53 placebo subjects. Annualized rate of diabetes was similar in both groups: 6.4% with oral insulin and 8.2% with placebo (hazard ratio 0.764, P = 0.189). In a hypothesis-generating analysis of a subgroup with insulin autoantibody (IAA) levels confirmed (on two occasions) > or =80 nU/ml (n = 263), there was the suggestion of benefit: annualized diabetes rate 6.2% with oral insulin and 10.4% with placebo (0.566, P = 0.015).

CONCLUSIONS

It is possible to identify individuals at high risk for type 1 diabetes and to enroll them in a large, multisite, randomized, controlled clinical trial. However, oral insulin did not delay or prevent type 1 diabetes. Further studies are needed to explore the potential role of oral insulin in delaying diabetes in relatives similar to those in the subgroup with higher IAA levels.

Current issues in the treatment of human diseases by mucosal tolerance

Tolerance has been defined as a lack of response to self but a more appropriate definition of tolerance is "any mechanism by which a potentially injurious immune response is prevented, suppressed, or shifted to a non-injurious class of immune response." Thus, tolerance is related to productive self-recognition, rather than blindness of the immune system to its auto-components. Oral tolerance, in this sense, is of unique immunologic importance, as it is a continuous natural immunologic event driven by exogenous antigen. Because of their privileged access to the internal milieu, antigens that are continuously in contact with the mucosa are a frontier between foreign and self-components. Thus, oral tolerance is an immunological mechanism that evolved to treat external agents that gain access to the body via a natural route as internal components that then become part of self. Given this, it would seem logical that autoimmune diseases caused by an inappropriate response to self-antigens might ultimately be treated by presenting such autoantigens to the mucosal surface where they can be dealt with in a non-injurious (noninflammatory) immunologic environment. Furthermore, mucosal tolerance as a treatment for autoimmune diseases is an attractive concept, as antigen-specific therapy is the most physiologic means to manipulate immune responses, and mucosal antigen is nontoxic and can be given on a chronic basis. The efficacy of mucosal tolerance has been clearly demonstrated in several animal models.

Deficiencies in gut NK cell number and function precede diabetes onset in BB rats

Defects in the intestinal immune system may contribute to the pathogenesis of autoimmune diseases. Intraepithelial lymphocytes represent a substantial fraction of gut-associated lymphocytes, but their function in mucosal immunity is unclear. A newly described population of NK cells that spontaneously secrete IL-4 and IFN-gamma is present in the intraepithelial lymphocyte compartment of the rat. We hypothesized that defects in the number or function of these cells would be present in rats susceptible to autoimmunity. We report that the number of NKR-P1A(+)CD3(-) intraepithelial NK (IENK) cells is deficient before onset of spontaneous autoimmune diabetes in diabetes-prone BB (BBDP) rats. The absolute number of recoverable IENK cells was only approximately 8% of that observed in WF rats. Bone marrow transplantation from histocompatible WF donors reversed the IENK cell deficiency (and prevented diabetes) in these animals, suggesting a hemopoietic origin for their IENK cell defect. Analysis of diabetes-resistant BB rats, which develop autoimmune diabetes only after perturbation of the immune system, revealed IENK cell numbers intermediate between that of BBDP and WF rats. IENK cells were selectively depleted during treatment to induce diabetes. Prediabetic BBDP and diabetes-resistant BB animals also exhibited defective IENK cell function, including decreased NK cell cytotoxicity and reduced secretion of IL-4 and IFN-gamma. IENK functional defects were also observed in LEW and BN rats, which are susceptible to induced autoimmunity, but not in WF, DA, or F344 rats, which are resistant. Defects in IENK cell number and function may contribute to the pathogenesis of autoimmune diseases including type 1 diabetes.

Immunologic activity in the small intestinal mucosa of pediatric patients with type 1 diabetes

Involvement of gut immune system has been implicated in the pathogenesis of type 1 diabetes. However, few studies have been performed on the gut mucosa from patients with type 1 diabetes. Thus, we characterized the stage of immune activation in jejunal biopsy samples from 31 children with type 1 diabetes by immunohistochemistry, in situ hybridization, and RT-PCR. We found enhanced expressions of HLA-DR, HLA-DP, and intercellular adhesion molecule-1 by immunohistochemistry even on structurally normal intestine of patients with type 1 diabetes and no signs of celiac disease. In addition, the densities of IL-1 alpha- and IL-4-positive cells detected by immunohistochemistry and IL-4 mRNA-expressing cells evaluated by in situ hybridization were increased in the lamina propria in patients with type 1 diabetes and normal mucosa. Instead, the densities of IL-2, gamma-interferon (IFN-gamma), and tumor necrosis factor alpha-positive cells, the density of IFN-gamma mRNA positive cells, and the amounts of IFN-gamma mRNA detected by RT-PCR correlated with the degree of celiac disease in patients with type 1 diabetes. Our study supports the hypothesis that a link exists between the gut immune system and type 1 diabetes.

Disabling an integral CTL epitope allows suppression of autoimmune diabetes by intranasal proinsulin peptide

Insulin is a major target of the autoimmune response associated with destruction of pancreatic beta cells in type 1 diabetes. A peptide that spans the junction of the insulin B chain and the connecting (C) peptide in proinsulin has been reported to stimulate T cells from humans at risk for type 1 diabetes and autoimmune diabetes-prone NOD mice. Here we show that proinsulin B24-C36 peptide binds to I-A(g7), the MHC class II molecule of the NOD mouse, and, after intranasal administration, induces regulatory CD4(+) T cells that, in the absence of CD8(+) T cells, block the adoptive transfer of diabetes. Curiously, however, intranasal B24-C36 did not inhibit development of spontaneous diabetes in treated mice. We then determined that B24-C36, and its core sequence B25-C34, bind to K(d), the NOD mouse MHC class I molecule, and elicit CD8(+) CTLs. When the CD8(+) T lymphocyte epitope was truncated at the C34 valine anchor residue for binding to K(d), the residual CD4(+) T cell epitope, B24-C32/33, significantly inhibited diabetes development after a single intranasal dose. This study identifies a novel CTL epitope in proinsulin and demonstrates that the therapeutic potential of a "tolerogenic" autoantigen peptide can be compromised by the presence of an integral CTL epitope.

Induction of autoimmune diabetes through insulin (but not GAD65) DNA vaccination in nonobese diabetic and in RIP-B7.1 mice

Insulin has been used to modify T-cell autoimmunity in experimental models of type 1 diabetes. In a large clinical trial, the effect of insulin to prevent type 1 diabetes is currently investigated. We here show that insulin can adversely trigger autoimmune diabetes in two mouse models of type 1 diabetes, using intramuscular DNA vaccination for antigen administration. In female nonobese diabetic (NOD) mice, diabetes development was enhanced after preproinsulin (ppIns) DNA treatment, and natural diabetes resistance in male NOD mice was diminished by ppIns DNA vaccination. In contrast, GAD65 DNA conferred partial diabetes protection, and empty DNA plasmid was without effect. In RIP-B7.1 C57BL/6 mice (expressing the T-cell costimulatory molecule B7.1 in pancreatic beta-cells), autoimmune diabetes occurred in 70% of animals after ppIns vaccination, whereas diabetes did not develop spontaneously in RIP-B7.1 mice or after GAD65 or control DNA treatment. Diabetes was characterized by diffuse CD4(+)CD8(+) T-cell infiltration of pancreatic islets and severe insulin deficiency, and ppIns, proinsulin, and insulin DNA were equally effective for disease induction. Our work provides a new model of experimental autoimmune diabetes suitable to study mechanisms and outcomes of insulin-specific T-cell reactivity. In antigen-based prevention of type 1 diabetes, diabetes acceleration should be considered as a potential adverse result.

Mucosal inflammation in a genetic model of spontaneous type I diabetes mellitus

The BioBreeding (BB) rat provides a model of spontaneous type I diabetes mellitus that closely resembles the human disease. Diabetes-prone BB rats demonstrate increased intestinal permeability prior to the development of insulinitis. Studies suggest that alterations in intestinal permeability can lead to increased intestinal inflammatory activity. Diabetes-prone (BBdp) and diabetes-resistant (BBdr) BB rats were examined at 45 days and at >70 days of age following the development of clinical disease (BBd). In separate experiments, tissue was assayed for myeloperoxidase (MPO) or fixed for histological assessment and immunohistochemistry. Blood was obtained for leukocyte MPO measurements and morphological assessment of circulating leukocytes. MPO activity was significantly elevated in the distal small intestine of 45-day-old BBdp rats. In contrast, at >70 days of age, MPO activity was significantly increased throughout the small intestine of BBd and non-diabetic BBdp rats. Subsequently, all measurements were performed in >70-day-old rats. An increase in inflammatory infiltrate was noted in the distal small intestine of BBd rats by light microscopy. Infiltrating cells were identified as bands (a maturing cell type of the neutrophil lineage) and mature neutrophils. The findings suggest diabetes susceptibility is associated with an increase in intestinal inflammatory activity.

Transient blockade of CD40 ligand dissociates pathogenic from protective mucosal immunity

Antigen administration via oral and other mucosal routes can suppress systemic immunity to the antigen and has been used to prevent experimental autoimmune disease. This approach may prove ineffective or even harmful if it leads to a concomitant induction of cytotoxic T lymphocytes (CTLs), and indeed, mucosal administration of the model antigen ovalbumin (OVA) has been shown to elicit CTL activation while simultaneously inducing oral tolerance. Here we show that induction by oral OVA of CTLs in wild-type mice, and of diabetes in mice expressing OVA transgenically in pancreatic beta cells, can be prevented by transiently blocking the CD40 ligand (CD40L). However, CD40L blockade did not diminish oral tolerance, as measured by suppression of systemic OVA-primed T cell proliferation, IFN-gamma secretion, and Ab production. Consistent with these findings, mice lacking CD40 expression could be orally tolerized to OVA. Transient CD40L blockade therefore dissociates pathogenic from protective immunity and should enhance the efficacy and safety of oral tolerance for preventing autoimmune disease.

Oral exposure to diabetes-promoting food or immunomodulators in neonates alters gut cytokines and diabetes

Disease development in diabetes-prone BB rats is modified by the type of diet fed after weaning. The aim of this investigation was to determine whether exposure during the first week of life to antigens from a known diabetes-promoting diet (NIH-07) could modify diabetes incidence and, if so, to what extent this occurs via alterations in systemic T-cell reactivity, gut cytokines, or islet infiltration. Diabetes-prone BB (BBdp) rats were hand-fed twice daily between age 4 and 7 days with vehicle, a hydrolyzed casein (HC)-based infant formula, Pregestimil (PG), PG + cereal-based NIH-07 diet, PG + lipopolysaccharides (LPS) or PG + LPS + silica. After weaning, they were fed either an NIH-07 diet or a semipurified HC (diabetes-retardant) diet until 150 days. In separate studies, 5-day-old BBdp rat pups were administered the aforementioned treatments, and expression of intestinal mRNA for gamma-interferon (IFN-gamma) or transforming growth factor-beta (TGF-beta) was quantified using reverse transcriptase-polymerase chain reaction. The effect of early oral treatment with NIH-07 or PG on systemic T-cell reactivity was evaluated using footpad swelling delayed-type hypersensitivity (DTH) and the popliteal lymph node assay. Oral exposure of neonates to a complex mixture of antigens from the diabetes-promoting diet delayed onset of diabetes (79 vs. 88 days) and prevented disease in approximately one-third of animals. A similar protective effect was seen for neonatal exposure to wheat gluten in animals subsequently weaned onto a semipurified wheat gluten diet. By contrast, LPS-treated neonates displayed more severe insulitis and developed diabetes at an increased rate, which was significantly suppressed by co-administration of silica particles. The protective effect of early exposure to diabetogenic diets was not associated with significant reduction of islet infiltration, and there was no impact on the DTH response to food antigens. However, whereas diabetes-resistant BBc rats developed systemic tolerance to NIH-07 antigens fed chronically, BBdp rats did not. The lack of effect of the early oral antigen regimen on the DTH reaction in the footpad, a classic Th1-mediated reaction, suggests little effect on systemic T-cell reactivity. However, local effects were observed in the small intestine. Oral exposure to diabetes-promoting food antigens or LPS downregulated the Th1 cytokine IFN-gamma and decreased the IFN-gamma/TGF-beta ratio. Thus, oral exposure to diabetes-promoting food antigens and immune modulators in neonates can modify diabetes expression in association with changes in local cytokine balance in the gut.

Inhaled insulin and insulin antibodies: a new twist to an old debate

The recent development of inhaled insulin for the treatment of diabetes has the potential to significantly improve patient compliance and diabetes control. Preliminary studies have shown inhaled insulin to be effective in lowering blood glucose and HbA(1c) levels. However, inhaled insulin may stimulate insulin antibody production more than is commonly observed with highly purified human insulin administered subcutaneously. The significance of insulin antibodies in patient care has been a topic of frequent debate and has been studied extensively. This review will discuss the potential implications of elevated insulin antibody levels, the role insulin antibodies play in the metabolic control of diabetes and the effect inhaled insulin may have on the immune system.

Immunotherapy of insulin-dependent diabetes mellitus

Immunotherapy of diabetes is now focusing on induction of tolerance to beta cell antigens using either soluble antigens or monoclonal anti-T-cell antibodies. These approaches have reached the clinical arena. At the experimental level, strategies are being developed that use or target cytokines (with gene therapy) or stimulate regulatory T cells.

Tolerance to islet autoantigens in type 1 diabetes

Tolerance to beta cell autoantigens represents a fragile equilibrium. Autoreactive T cells specific to these autoantigens are present in most normal individuals but are kept under control by a number of peripheral tolerance mechanisms, among which CD4(+) CD25(+) CD62L(+) T cell-mediated regulation probably plays a central role. The equilibrium may be disrupted by inappropriate activation of autoantigen-specific T cells, notably following to local inflammation that enhances the expression of the various molecules contributing to antigen recognition by T cells. Even when T cell activation finally overrides regulation, stimulation of regulatory cells by CD3 antibodies may reset the control of autoimmunity. Other procedures may also lead to disease prevention. These procedures are essentially focused on Th2 cytokines, whether used systemically or produced by Th2 cells after specific stimulation by autoantigens. Protection can also be obtained by NK T cell stimulation. Administration of beta cell antigens or CD3 antibodies is now being tested in clinical trials in prediabetics and/or recently diagnosed diabetes.

Translating data from animal models into methods for preventing human autoimmune diabetes mellitus: caveat emptor and primum non nocere

Type 1 diabetes in humans is a serious autoimmune disorder of children that is still poorly understood, unpreventable, and irreversible. Study of its animal models, notably the NOD mouse and BB rat, has generated a wealth of information concerning genetics and immunopathogenesis, but that information has still not altered the way in which we treat children with diabetes. In this review we attempt to identify the most promising avenues of continuing research in these models and the most important issues that must be faced by the designers of human therapies based on the animal dataset.

Mucosal antigen primes diabetogenic cytotoxic T-lymphocytes regardless of dose or delivery route

Administration of antigens via mucosal routes, such as orally or intranasally, can induce specific immunological tolerance and has been used as a rational basis for the treatment of autoimmune diseases, including type 1 diabetes. Recently, however, orally delivered antigens were shown to induce CD8 cytotoxic T-lymphocytes (CTLs) capable of causing autoimmune diabetes. In this report, we have examined several mucosal routes for their ability to induce CTLs and autoimmune diabetes, with the aim of identifying approaches that would maximize tolerance and minimize CTL generation. In normal C57BL/6 mice, ovalbumin (OVA) delivered by either the oral or nasal routes or by aerosol inhalation was able to prime CTL immunity in both high- and low-dose regimens. To address the relevance of these CTLs to autoimmune disease, OVA was given to mice that transgenically expressed this antigen in their pancreatic beta-cells. Irrespective of antigen dose or the route of delivery, mucosal OVA triggered diabetes, particularly after intranasal administration. These findings suggest that CTL immunity is likely to be a consequence of mucosal antigen delivery, regardless of the regimen, and should be considered in the clinical application of mucosal tolerance to autoimmune disease prevention.

The role of the gut in beta-cell autoimmunity and type 1 diabetes: a hypothesis

The origin of autoimmunity leading to the destruction of insulin-producing beta-cells is not known. Several studies suggest that a link exists between the gut immune system and the islets infiltrating lymphocytes. Inflamed pancreatic islets express the same adhesion molecules involved with the homing of gut-associated lymphocytes. The manifestation of autoimmune diabetes in the animal models can be modified by dietary factors, which cause changes in the cytokine production by islet-infiltrating lymphocytes. Increased risk of type 1 diabetes has been associated with an early introduction of cows' milk formula in infancy, indicating that triggering of the gut immune system in early infancy may contribute to the later development of beta-cell autoimmunity. Enhanced immune reactivity to cow milk (CM) proteins in the patients with type 1 diabetes suggests aberrant regulation of the gut immune system in this disease. In the patients with newly diagnosed type 1 diabetes, anti-glutamate decarboxylase (GAD)-reactivity was found in the subpopulation of lymphocytes expressing gut-associated homing receptor alpha 4 beta 7. Based on these findings, the hypothesis that aberrant function of the gut immune system would lead to the development of beta-cell autoimmunity and type 1 diabetes has recently received a lot of attention. The possibility that regulation of the gut immune system is not normal in subjects at risk of autoimmune diabetes should be considered when treatments interfering with mucosal immunity for the prevention of type 1 diabetes are planned.

Antigen-specific therapy for autoimmune disease

The application of self-antigens as therapeutic tools is validated in inbred animal models of autoimmune disease. Mechanisms of antigen-induced tolerance (apoptosis, anergy, regulatory T cells and immune deviation) are being clarified in relation to the properties of antigens and the modes and routes of their delivery. Mucosa-mediated tolerance remains the predominant mode of antigen-specific therapy but awaits demonstration of clinical efficacy in human autoimmune disease.

Role of tolerogen conformation in induction of oral tolerance in experimental autoimmune myasthenia gravis

We recently demonstrated that oral or nasal administration of recombinant fragments of the acetylcholine receptor (AChR) prevents the induction of experimental autoimmune myasthenia gravis (EAMG) and suppresses ongoing EAMG in rats. We have now studied the role of spatial conformation of these recombinant fragments in determining their tolerogenicity. Two fragments corresponding to the extracellular domain of the human AChR alpha-subunit and differing in conformation were tested: Halpha1-205 expressed with no fusion partner and Halpha1-210 fused to thioredoxin (Trx), and designated Trx-Halpha1-210. The conformational similarity of the fragments to intact AChR was assessed by their reactivity with alpha-bungarotoxin and with anti-AChR mAbs, specific for conformation-dependent epitopes. Oral administration of the more native fragment, Trx-Halpha1-210, at the acute phase of disease led to exacerbation of EAMG, accompanied by an elevation of AChR-specific humoral and cellular reactivity, increased levels of Th1-type cytokines (IL-2, IL-12), decreased levels of Th2 (IL-10)- or Th3 (TGF-beta)-type cytokines, and higher expression of costimulatory factors (CD28, CTLA4, B7-1, B7-2, CD40L, and CD40). On the other hand, oral administration of the less native fragments Halpha1-205 or denatured Trx-Halpha1-210 suppressed ongoing EAMG and led to opposite changes in the immunological parameters. It thus seems that native conformation of AChR-derived fragments renders them immunogenic and immunopathogenic and therefore not suitable for treatment of myasthenia gravis. Conformation of tolerogens should therefore be given careful attention when considering oral tolerance for treatment of autoimmune diseases.

Peptide dose, MHC affinity, and target self-antigen expression are critical for effective immunotherapy of nonobese diabetic mouse prediabetes

Cross-reactive T cells that recognize both Tep69 (dominant nonobese diabetic (NOD) T cell epitope in ICA69 (islet cell autoantigen of 69 kDa)) and ABBOS (dominant NOD T cell epitope in BSA) are routinely generated during human and NOD mouse prediabetes. Here we analyzed how systemic administration of these mimicry peptides affects progressive autoimmunity in adoptively transferred and cyclophosphamide-accelerated NOD mouse diabetes. These models were chosen to approximate mid to late stage prediabetes, the typical status of probands in human intervention trials. Unexpectedly, high dose (100 microg) i.v. ABBOS prevented, while Tep69 exacerbated, disease in both study models. Peptide effects required cognate recognition of endogenous self-Ag, because both treatments were ineffective in ICA69null NOD congenic mice adoptively transferred with wild-type, diabetic splenocytes. The affinity of ABBOS for NOD I-A(g7) was orders of magnitude higher than that of Tep69. This explained 1) the expansion of the mimicry T cell pool following i.v. Tep69, 2) the long-term unresponsiveness of these cells after i.v. ABBOS, and 3) precipitation of the disease after low dose i.v. ABBOS. Disease precipitation and prevention in mid to late stage prediabetes are thus governed by affinity profiles and doses of therapeutic peptides. ABBOS or ABBOS analogues with even higher MHC affinity may be candidates for experimental intervention strategies in human prediabetes, but the dose translation from NOD mice to humans requires caution.

Orally administered lead chloride induces bias of mucosal immunity

The hypothesis that lead disturbs gut immune functions upon oral ingestion was tested. Long-term exposure to oral PbCl(2)for 10 days caused persistent downregulation of TGF-beta mRNA levels in intestinal tissue. PbCl(2) also disturbed oral tolerance induction to the dietary antigen ovalbumin. Upon challenge with an immunizing dose of ovalbumin and rechallenge of draining lymph node cells in vitro, tolerance induction was partially suppressed in animals exposed to oral PbCl(2). This was shown by increased proliferation to antigenic stimulus, increased production of IFN-gamma and decreased secretion of TGF-beta. In conclusion, we show for the first time that oral exposure to PbCl(2)has a significant effect on the gut immune system, demonstrated by a bias of the cytokine pattern towards Th(1)and by disturbed oral tolerance mechanisms.

Oral insulin administration and residual beta-cell function in recent-onset type 1 diabetes: a multicentre randomised controlled trial. Diabète Insuline Orale group

BACKGROUND

Oral administration of autoantigens can slow the progression of beta-cell destruction in non-obese diabetic mice. We investigated whether oral administration of recombinant human insulin could protect residual beta-cell function in recent-onset type 1 diabetes.

METHODS

We enrolled 131 autoantibody-positive diabetic patients aged 7-40 years within 2 weeks of diagnosis (no ketoacidosis at diagnosis, weight loss <10%, polyuria for <6 weeks). They were randomly assigned 2.5 mg or 7.5 mg oral insulin daily or placebo for 1 year, in addition to subcutaneous insulin therapy. Serum C-peptide concentrations were measured in the fasting state and after stimulation, to assess beta-cell function. Autoantibodies to beta-cell antigens were assayed. Analyses were by intention to treat.

FINDINGS

Baseline C-peptide and haemoglobin A1c concentrations were similar in the three groups. During follow-up, there were no differences between the groups assigned 2.5 mg or 7.5 mg oral insulin or placebo in subcutaneous insulin requirements, haemoglobin A1c concentrations, or measurements of fasting (mean at 12 months 0.18 [SD 0.17], 0.17 [0.17], and 0.17 [0.12] nmol/L) or stimulated C-peptide concentrations (glucagon-stimulated 0.39 [0.38], 0.37 [0.39], and 0.33 [0.24] nmol/L; meal-stimulated 0.72 [0.60], 0.49 [0.49], and 0.57 [0.51 nmol/L]. Neither age nor C-peptide concentration at entry influenced treatment effects. No differences were seen in the time-course or titres of antibodies to insulin, glutamic acid decarboxylase, or islet antigen 2.

INTERPRETATION

At the doses used in this trial, oral administration of insulin initiated at clinical onset of type 1 diabetes did not prevent the deterioration of beta-cell function.

Cellular and humoral immunity against cow's milk proteins in type 1 diabetes

Cow's milk beta-casein has been proposed as a candidate trigger of autoimmunity associated with type 1 diabetes. In this study, cellular and humoral immunity against beta-casein was compared to that against other major cow's milk proteins in patients with recent onset type 1 diabetes and control subjects. T cell responses were found against alpha-casein, beta-casein, beta-lactoglobulin and bovine serum albumin in both patients with type 1 diabetes (stimulation index: 0.2-22.8, n=23) and control subjects (stimulation index: 0.1-18.2, n=22), with no significant differences between groups. Twelve (52%) patients and nine (41%) control subjects had stimulation indices >3 to at least one protein, including 9 (39%) patients and 4 (18%) control subjects against beta-casein, all but one of these also having elevated responses to alpha-casein. The highest responses (stimulation index >9) were against alpha- and beta-casein in some patients and control subjects who had the HLA DR3 allele. Antibody levels against alpha-casein, beta-casein and beta-lactoglobulin were low in both patients (n=59) and control subjects (n=52). Nevertheless, significantly higher IgG binding to both alpha-casein in ELISA (P=0.02) and beta-casein using ELISA (P=0.02) and RIA (P=0.04) was observed in patients aged <15 years compared to control subjects of similar age. No relationship was found between cellular and humoral immunity against individual antigens. These data show that immune responses to cow's milk are not limited to patients with diabetes and not solely against beta-casein.

The gut cytokine balance as a target of lead toxicity

The impact of exposure to lead on gut cytokine gene expression and oral tolerance was analyzed. Oral tolerization with ovalbumin (OVA) increased levels of IL-10 and TGF-beta in gut tissue while IFN-gamma mRNA levels remained unchanged in both autoimmune diabetes prone NOD and normal C57BL/6 mice. This shift towards Th2/Th3 type cytokine gene expression was completely abolished by concomitant treatment with PbCl2 (6 x 0.5 mg/kg) in NOD mice while the cytokine balance in C57BL/6 mice was unaffected. Suppression of Th2/Th3 type cytokine expression was associated with a dampened oral tolerance response to OVA as determined by T cell proliferation assays. We conclude that in autoimmunity prone NOD mice environmental toxicants may disturb immune homeostasis by targeting the gut immune system.