Immunotherapy of type 1 diabetes: lessons for other autoimmune diseases

Antiproliferative and Pro-Oxidant Effect of Polyphenols in Aqueous Leaf Extract of Passiflora alata Curtis on Activated T Lymphocytes from Non-Obese Diabetic (NOD SHILT/J) Mice

The antioxidant, anti-inflammatory and antiproliferative properties of Passiflora alata Curtis are due to the presence of polyphenols in its composition. Our previous work showed that non-obese diabetic (NOD) mice undergoing treatment with aqueous leaf extract of P. alata present reduced insulitis in the pancreas, possibly due to its anti-inflammatory properties. However, depending on the concentration and their ability to interact with other molecules, these phenolic compounds may promote oxidation reactions in some cellular components, such as proteins and lipids, thus presenting a pro-oxidant effect. The present work aimed to evaluate the in vitro effects of aqueous leaf extract of P. alata and its polyphenols (vitexin, isoorientin, rutin and catechin) on lymphocyte proliferation and viability, the cell cycle and oxidative stress. Our results showed that T lymphocytes stimulated with concanavalin A mitogen (ConA) and in the presence of IC50 concentrations of P. alata extract and polyphenols undergo cell injury via inhibition of proliferation, with these effects being more pronounced concerning CD4+ T cells (P. alata, 3.54 ± 0.34%; isoorientin, 57.07 ± 6.4%; vitexin, 16.95 ± 1.11%; catechin, 37.9 ± 4.2% and rutin, 40.14 ± 4.5%), compared to the non-treated group (77.17 ± 6.29) (p < 0.0001 for all comparisons). This process includes late apoptosis/necrosis induction (P. alata, 77.5 ± 0.7%; vitexin, 83 ± 3.3%; isoorientin, 83.8 ± 1.4%; catechin, 83 ± 1.9% and rutin, 74.9 ± 3.2, while the control presented 53.6% ± 3.1 (p < 0.0001 for all comparisons)) and mitochondrial depolarization leading to cell-death induction. Furthermore, an in vitro model of a mixed culture of NOD mice T cells with a mouse pancreatic beta-cell line (MIN6) showed increased intracellular nitric oxide and lipid peroxidation in NOD T cells submitted to P. alata extract (46.41 ± 3.08) compared to the untreated control group (33.57 ± 1.99, p = 0.01315). These results suggest that aqueous leaf extract of P. alata and the polyphenols in these leaves represent a target for translational research showing the plant’s benefits for developing new drugs with immunomodulatory properties against inflammatory diseases such as diabetes mellitus.

Aqueous extract of Passiflora alata leaves modulates in vitro the indoleamine 2,3-dioxygenase (IDO) and CD86 expression in bone marrow-derived professional antigen-presenting cells polarizing NOD mice T cells to a Treg profile

Dendritic cells (DCs) and macrophages are professional antigen-presenting cells (pAPCs), numerous in the pancreas of nonobese diabetic (NOD) mice and playing an essential role in the autoimmune response of type 1 diabetes. The expression of the enzyme indoleamine 2,3-dioxygenase (IDO) is a critical factor for the tolerogenic activity of pAPCs, acting in the catabolism of tryptophan, providing metabolites that suppress the T cell effectors and induce T regulatory cells differentiation. Here we investigated the in vitro mechanisms of lyophilized aqueous extract from Passiflora alata leaves (LAEPAL) that modulates bone marrow-derived professional antigen-presenting cells (BM-pAPCs), affecting their ability to polarize T cells. A cell culture model was defined using mixed cultures of BM-pAPCs and T lymphocytes NOD mice with stressed MIN-6 cells as a source of pancreatic β cells antigens. We showed that the treatment with 300 µg/mL of LAEPAL induces a significant decrease in the CD4 and CD8 T effector lymphocytes proliferation from diabetic but not in non-diabetic mice, followed by a reduction of the IL-6 and IFN-γ cytokines release in the cell cultures supernatants. Moreover, we observed an increase of CD4⁺CD25⁺FoxP3⁺ Tregs in the cell cultures from diabetic mice. These results could be partially explained by the LAEPAL modulatory effects in BM-pAPCs, downregulating the CD86 co-stimulatory molecule expression, and increasing IDO-1 expression in F4/80+ BM-pAPCs. These results contribute to a better understanding of the polyphenols' immunomodulatory properties, meaning they could induce tolerogenic antigen-presenting cells, which could polarize T cells to a Treg profile and decrease the activity of CD4+ and CD8+ T effector cells.

Targeting antigen presentation in autoimmunity

Autoimmune diseases are heterogeneous group of disorders that together represent an enormous societal and medical problem. CD4+ T cells have critical roles in the initiation and pathogenesis of autoimmune disease. As such, modulation of T cell activity has proven to have significant therapeutic effects in multiple autoimmune settings. T cell activation is a complex process with multiple potential therapeutic targets, many of which have been successfully utilized to treat human disease. Current pharmacological treatment largely targets T cell intrinsic activities as a means of treating various autoimmune disorders. Here I review extant and potential therapeutic approaches that instead specifically target antigen presentation to CD4+ T cells as a critical checkpoint in autoimmune responses. In addition, the contribution of antigen modulation components in current therapeutic approaches is considered along with the impact of new antigen targeted treatment modalities. Finally, potential challenges are considered in the context of the potential for antigen specific targeting of the antigen presentation process.

Leukotriene B4-mediated sterile inflammation promotes susceptibility to sepsis in a mouse model of type 1 diabetes

Type 1 diabetes mellitus (T1DM) is associated with chronic systemic inflammation and enhanced susceptibility to systemic bacterial infection (sepsis). We hypothesized that low insulin concentrations in T1DM trigger the enzyme 5-lipoxygenase (5-LO) to produce the lipid mediator leukotriene B4 (LTB4), which triggers systemic inflammation that may increase susceptibility to polymicrobial sepsis. Consistent with chronic inflammation, peritoneal macrophages from two mouse models of T1DM had greater abundance of the adaptor MyD88 (myeloid differentiation factor 88) and its direct transcriptional effector STAT-1 (signal transducer and activator of transcription 1) than macrophages from nondiabetic mice. Expression of Alox5, which encodes 5-LO, and the concentration of the proinflammatory cytokine interleukin-1β (IL-1β) were also increased in peritoneal macrophages and serum from T1DM mice. Insulin treatment reduced LTB4 concentrations in the circulation and Myd88 and Stat1 expression in the macrophages from T1DM mice. T1DM mice treated with a 5-LO inhibitor had reduced Myd88 mRNA in macrophages and increased abundance of IL-1 receptor antagonist and reduced production of IL-β in the circulation. T1DM mice lacking 5-LO or the receptor for LTB4 also produced less proinflammatory cytokines. Compared to wild-type or untreated diabetic mice, T1DM mice lacking the receptor for LTB4 or treated with a 5-LO inhibitor survived polymicrobial sepsis, had reduced production of proinflammatory cytokines, and had decreased bacterial counts. These results uncover a role for LTB4 in promoting sterile inflammation in diabetes and the enhanced susceptibility to sepsis in T1DM.

Viruses and Type 1 diabetes: a dynamic labile equilibrium

Type 1 diabetes (T1D) results from the specific immune-mediated destruction of the insulin-producing β-cells of the pancreas. In genetically susceptible individuals, a still undetermined initiating 'hit' triggers a cascade of events that eventually leads to autoreactive CD8 T cells infiltrating the pancreatic islets and, subsequently, destroying them. There is increasing evidence that viruses, especially enteroviruses, are major environmental candidates; however, despite decades of investigation, we still lack certainty with regard to the causation of T1D. Moreover, studies in animal models of diabetes suggest a protective role of certain enteroviral infections upon diabetes contraction, making the quest for viral involvement in T1D even more difficult. Analyzing the foundation and the results of the most current work in the field, this article gives a brief overview of current knowledge, as well as providing an outlook for future directions.

Anti-idiotypic antibody specific to GAD65 autoantibody prevents type 1 diabetes in the NOD mouse

Overt autoantibodies to the smaller isoform of glutamate decarboxylase (GAD65Ab) are a characteristic in patients with Type 1 diabetes (T1D). Anti-idiotypic antibodies (anti-Id) directed to GAD65Ab effectively prevent the binding of GAD65 to GAD65Ab in healthy individuals. Levels of GAD65Ab-specific anti-Id are significantly lower in patients with T1D, leading to overt GAD65Ab in these patients. To determine the possible protective role of GAD65Ab-specific anti-Id in T1D pathogenesis, we developed the monoclonal anti-Id MAb 8E6G4 specifically targeting human monoclonal GAD65Ab b96.11. MAb 8E6G4 was demonstrated as a specific anti-Id directed to the antigen binding site of b96.11. MAb 8E6G4 recognized human antibodies in sera from healthy individuals, T2D patients, and T1D patients as established by ELISA. We confirmed these MAb 8E6G4-bound human antibodies to contain GAD65Ab by testing the eluted antibodies for binding to GAD65 in radioligand binding assays. These findings confirm that GAD65Ab are present in sera of individuals, who test GAD65Ab-negative in conventional detection assays. To test our hypothesis that GAD65Ab-specific anti-Id have an immune modulatory role in T1D, we injected young Non Obese Diabetic (NOD) mice with MAb 8E6G4. The animals were carefully monitored for development of T1D for 40 weeks. Infiltration of pancreatic islets by mononuclear cells (insulitis) was determined to establish the extent of an autoimmune attack on the pancreatic islets. Administration of MAb 8E6G4 significantly reduced the cumulative incidence rate of T1D and delayed the time of onset. Insulitis was significantly less severe in animals that received MAb 8E6G4 as compared to control animals. These results support our hypothesis that anti-Id specific to GAD65Ab have a protective role in T1D.

Otelixizumab in the treatment of Type 1 diabetes mellitus

Anti-CD3 antibodies have been demonstrated in both animal and human studies to be able to reverse autoimmune diseases; for example Type 1 diabetes. Not only does treatment with anti-CD3 antibodies result in the removal of pathogenic T cells but evidence suggests that a state of operational tolerance can be induced through the effects on regulatory T cells. The clinical use of anti-CD3 antibodies has been hampered by their safety profile. However, the introduction of humanized, nonmitogenic, aglycosylated anti-CD3 antibodies, such as otelixizumab, and promising results reported in newly-diagnosed patients with Type 1 diabetes, have renewed the interest for these antibodies in the treatment of autoimmune diseases.

The dangerous liaison between iNKT cells and dendritic cells: does it prevent or promote autoimmune diseases?

Invariant natural killer T (iNKT) cells represent an important regulatory T-cell subset that perceives signals of danger and/or cellular distress and modulate the adaptive immune response accordingly. In the presence of pathogens, iNKT cells acquire an adjuvant function that is fundamental to boost anti-microbial and anti-tumor immunity. At the same time, iNKT cells can play a negative regulatory function to maintain peripheral T-cell tolerance toward self-antigens and to prevent autoimmune disease. Both these effects of iNKT cells involve the modulation of the activity of dendritic cells (DCs) through cell-cell interaction. Indeed, iNKT cells can either boost Th1 immunity by enhancing maturation of pro-inflammatory DCs or promote immune tolerance through the maturation of tolerogenic DCs. This dual action of iNKT cells opens questions on the modalities by which a single-cell subset can exert opposite effects on DCs and may even put in question the overall immunosuppressive properties of iNKT cells. This review presents the large body of evidence that shows the ability of iNKT cells to negatively regulate autoimmunity and to prevent autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus. In addition, an update is provided on the mechanisms of iNKT-DCs interactions and how this can result in inflammatory or tolerogenic responses.

Diacerhein downregulate proinflammatory cytokines expression and decrease the autoimmune diabetes frequency in nonobese diabetic (NOD) mice

NOD mice are used as experimental models as they develop type 1 diabetes mellitus (DM-1) spontaneously, with a strong similarity to the human disease. Diabetes mellitus type 1 is characterized by the destruction of the islet, orchestrated by T lymphocytes that induce cytokine release like IL-1beta, promoting an inflammatory process. Diacerhein has antiinflammatory properties, inhibiting IL-1. However, the mechanisms involved in immune modulation are not completely understood. In the present study, serum and pancreatic islets were isolated to investigate the relationship between IL-1beta, IFN-gamma, IL-12 and TNF-alpha expression and diabetes onset, morphological aspects, and diacerhein dose dependence in animals treated with different doses (5, 10 and 50 mg/kg/day) and the control group (saline solution). The results demonstrated upregulation of mRNA islets and downregulation of the serum concentration of IL-1beta, IL-12 and TNF-alpha in the group treated with 5 and 10 mg/kg/day diacerhein, when compared with the saline group, and increased IFN-gamma serum concentration in the group treated with 50 mg/kg/day. These results suggest that diacerhein in NOD mice, decreases, in a dose-dependent manner, the diabetes frequency downregulating proinflammatory cytokines, such as IL-1beta, TNF-alpha, IFN-gamma and IL-12 at posttranscriptional or posttranslational level. Furthermore, using the HPLC method, diacerhein and rhein (active metabolite) were detected in serum and pancreas of treated mice.

Modulation of diabetes in NOD mice by GAD65-specific monoclonal antibodies is epitope specific and accompanied by anti-idiotypic antibodies

Type 1 diabetes is caused by the autoimmune destruction of pancreatic beta cells. Here we show that administration of a human monoclonal antibody (b96.11) specific to the 65-kDa isoform of glutamate decarboxylase (GAD65) to prediabetic non-obese diabetic (NOD) mice significantly delays the onset of autoimmune diabetes. We found this effect to be epitope-specific, as only b96.11 showed this therapeutic property, while a GAD65-specific human monoclonal control antibody (b78) derived from the same patient, but specific to a different determinant of GAD65, had no significant effect on the progression of disease. Administration of b96.11 or b78 to NOD mice was accompanied by the generation of anti-idiotypic antibodies. Importantly, the induced anti-idiotypic antibodies were specific for the immunizing antibody and blocked the binding of GAD65 by the respective antibody. These findings suggest a potential role for the internal image of the GAD65 determinant recognized by b96.11 in the anti-idiotypic antibody, supporting an immunomodulatory role for GAD65-specific autoantibodies, as originally postulated by Jerne.

Regulatory T cells in the control of autoimmune diabetes: the case of the NOD mouse

Over the last few years, there has been a revival of the concept of suppressor/regulatory T cells being central players in the control of various immune responses, including autoimmune responses and immune response to transplants, tumors, and infectious agents. It appears that regulatory T cells are diverse in their phenotypes, antigen specificity, and modes of action. Here we summarize studies from various groups, including our own, demonstrating that specialized subsets of regulatory T cells are pivotal in the control of autoimmune diabetes as well shown by the compelling evidence accumulated using the non-obese diabetic (NOD) mouse model. We also provide a discussion of the evidence showing that some biological products (such as CD3-specific monoclonal antibodies) are representatives of a new category of immunotherapeutic agents endowed with unique capacities to promote immunological tolerance (an antigen-specific unresponsiveness in the absence of long-term generalized immunosuppression) through their ability to induce immunoregulatory T cells.

The NOD mouse: a model of immune dysregulation

Autoimmunity is a complex process that likely results from the summation of multiple defective tolerance mechanisms. The NOD mouse strain is an excellent model of autoimmune disease and an important tool for dissecting tolerance mechanisms. The strength of this mouse strain is that it develops spontaneous autoimmune diabetes, which shares many similarities to autoimmune or type 1a diabetes (T1D) in human subjects, including the presence of pancreas-specific autoantibodies, autoreactive CD4+ and CD8+ T cells, and genetic linkage to disease syntenic to that found in humans. During the past ten years, investigators have used a wide variety of tools to study these mice, including immunological reagents and transgenic and knockout strains; these tools have tremendously enhanced the study of the fundamental disease mechanisms. In addition, investigators have recently developed a number of therapeutic interventions in this animal model that have now been translated into human therapies. In this review, we summarize many of the important features of disease development and progression in the NOD strain, emphasizing the role of central and peripheral tolerance mechanisms that affect diabetes in these mice. The information gained from this highly relevant model of human disease will lead to potential therapies that may alter the development of the disease and its progression in patients with T1D.

Design of effective immunotherapy for human autoimmunity

A better understanding of the molecules involved in immune responses has identified many potential targets for the treatment of autoimmune diseases. But although successful therapies have been found for immune disorders in animal studies, few have passed the much harder test of treating human diseases. So far, non-antigen-specific approaches, such as the blocking of tumour-necrosis factor, are achieving some success but the same is not true for antigen-specific approaches. Future therapies will probably include both non-antigen-specific strategies that target cytokines (cell-cell signalling molecules) or block the molecules that stimulate immune responses, and antigen-specific therapies that induce tolerance to self antigens.

1,25-Dihydroxyvitamin D3 modulates expression of chemokines and cytokines in pancreatic islets: implications for prevention of diabetes in nonobese diabetic mice

1,25-Dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) is an immune modulator that prevents experimental autoimmune diseases. Receptors for 1,25-(OH)(2)D(3) are present in pancreatic beta-cells, the target of an autoimmune assault in nonobese diabetic (NOD) mice. The aim of this study was to investigate the in vivo and in vitro effects of 1,25-(OH)(2)D(3) on beta-cell gene expression and death and correlate these findings to in vivo diabetes development in NOD mice. When female NOD mice were treated with 1,25-(OH)(2)D(3) (5 microg/kg per 2 d), there was a decrease in islet cytokine and chemokine expression, which was accompanied by less insulitis. Complementing these findings, we observed that exposure to 1,25-(OH)(2)D(3) in three cell systems INS-1(E) cell line, fluorescence-activated cell sorting purified rat beta-cells, and NOD-severe combined immunodeficient islets) suppressed IP-10 and IL-15 expression in the beta-cell itself but did not prevent cytokine-induced beta-cell death. This 1,25-(OH)(2)D(3)-induced inhibition of chemokine expression in beta-cells was associated with a decreased diabetes incidence in some treatment windows targeting early insulitis. Thus, although a short and early intervention with 1,25-(OH)(2)D(3) (3-14 wk of age) reduced diabetes incidence (35 vs. 58%, P < or = 0.05), a late intervention (from 14 wk of age, when insulitis is present) failed to prevent disease. Of note, only early and long-term treatment (3-28 wk of age) prevented disease to a major extent (more than 30% decrease in diabetes incidence). We conclude that 1,25-(OH)(2)D(3) monotherapy is most effective in preventing diabetes in NOD mice when applied early. This beneficial effect of 1,25-(OH)(2)D(3) is associated with decreased chemokine and cytokine expression by the pancreatic islets.

Costimulation controls diabetes by altering the balance of pathogenic and regulatory T cells

The development of autoimmune diabetes in the nonobese diabetic (NOD) mouse results from a breakdown in tolerance to pancreatic islet antigens. CD28-B7 and CD40 ligand-CD40 (CD40L-CD40) costimulatory pathways affect the development of disease and are promising therapeutic targets. Indeed, it was shown previously that diabetes fails to develop in NOD-B7-2-/- and NOD-CD40L-/- mice. In this study, we examined the relative role of these 2 costimulatory pathways in the balance of autoimmunity versus regulation in NOD mice. We demonstrate that initiation but not effector function of autoreactive T cells was defective in NOD-B7-2-/- mice. Moreover, the residual proliferation of the autoreactive cells was effectively controlled by CD28-dependent CD4+CD25+ regulatory T cells (Treg's), as depletion of Treg's partially restored proliferation of autoreactive T cells and resulted in diabetes in an adoptive-transfer model. Similarly, disruption of the CD28-B7 pathway and subsequent Treg deletion restored autoimmunity in NOD-CD40L-/- mice. These results demonstrate that development of diabetes is dependent on a balance of pathogenic and regulatory T cells that is controlled by costimulatory signals. Thus, elimination of Treg's results in diabetes even in the absence of costimulation, which suggests a need for alternative strategies for immunotherapeutic approaches.

Different approaches to understanding autoimmune rheumatic diseases: the neuroimmunoendocrine system

Rheumatic autoimmune diseases are characterized by dysregulation of the immune response that leads to inflammation, pain, disease and stiffness and have been shown to have differences in disease pattern, depending on the gender and age of an individual. The majority of these conditions predominantly affect females of all species and also show increased severity of disease in female animal models. In addition to the gender differences in disease development, persons are often more susceptible at specific stages of life. This review will discuss some of the data indicating age and gender differences in development of these diseases and will review hormonal and other factors that may contribute to disease expression and severity.

Neuroendocrine Immuno-ontogeny of the Pathogenesis of Autoimmune Diabetes in the Nonobese Diabetic (NOD) Mouse

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease in which insulin-producing beta cells of the pancreatic islets of Langerhans are destroyed. The nonobese diabetic (NOD) mouse is one of the rare spontaneous models that enable the study of prediabetic pancreatic events. The etiology of the autoimmune attack in human and animal T1D is still unknown, but genetic and environmental factors are involved in both cases. Although several autoantigens have been identified and defective immune-system regulation is implicated, this information does not satisfactorily explain the generally accepted beta-cell specificity of the disease or how so many and diverse environmental factors intervene in its pathogenesis. Based on data obtained from evaluating glucose homeostasis in a variety of situations, particularly stress and cytokine administration, in young prediabetic NOD mice, the author hypothesizes that the islet of Langerhans is a major actor, and its altered regulation through environmentally induced insulin resistance might reveal latent T1D. It is also postulated that T1D pathogenesis might be linked to abnormal pancreas development, probably due to disturbances of glutamic acid decarboxylase (GAD)+ innervation phagocytosis by defective macrophages during the early postnatal period. Also discussed is the role of defective presentation of pancreatic hormones and GAD in the thymus, and its potential repercussion on T-cell tolerance. Observations have demonstrated that the diabetogenic process in the NOD mouse is extremely complex, involving neuroendocrine immune interaction from fetal life onward.

[Prevent and cure insulin-dependent diabetes]

Insulin-dependent mellitus diabetes is an autoimmune disease resulting from the destruction of the beta cells of the islets of Langerhans by autoreactive T cells. Various approaches are being investigated in order to slow down the progression of diabetes using immunotherapy. The most promising results are based on the induction of specific tolerance following the administration of soluble autoantigens or monoclonal anti-CD3 antibodies. These strategies, initially developed in the NOD mouse, have been proven to be efficacious in recently diagnosed diabetics.