Vaccination against self to prevent autoimmune disease: the type 1 diabetes model

Prevention of Type 1 Diabetes in Children: A Worthy Challenge?

Nowadays, the development of new immuno-therapeutic drugs has made it possible to alter the course of many autoimmune diseases. Type 1 diabetes is a chronic disease with a progressive dependence on exogenous insulin administration. The ability to intercept individuals at high risk of developing type 1 diabetes is the first step toward the development of therapies that can delay the process of β-cell destruction, thus permitting a better glycemic control and reducing the incidence of ketoacidosis. The knowledge of the main pathogenetic mechanisms underlying the three stages of the disease may be helpful to identify the best immune therapeutic approach. In this review, we aim to give an overview of the most important clinical trials conducted during the primary, secondary and tertiary phases of prevention.

Vaccine for Diabetes-Where Do We Stand?

Diabetes is an endocrinological disorder with a rapidly increasing number of patients globally. Over the last few years, the alarming status of diabetes has become a pivotal factor pertaining to morbidity and mortality among the youth as well as middle-aged people. Current developments in our understanding related to autoimmune responses leading to diabetes have developed a cause for concern in the prospective usage of immunomodulatory agents to prevent diabetes. The mechanism of action of vaccines varies greatly, such as removing autoreactive T cells and inhibiting the interactions between immune cells. Currently, most developed diabetes vaccines have been tested in animal models, while only a few human trials have been completed with positive outcomes. In this review, we investigate the undergoing clinical trial studies for the development of a prototype diabetes vaccine.

The dark side of insulin: A primary autoantigen and instrument of self-destruction in type 1 diabetes

Background

Since its discovery 100 years ago, insulin, as the ‘cure’ for type 1 diabetes, has rescued the lives of countless individuals. As the century unfolded and the autoimmune nature of type 1 diabetes was recognised, a darker side of insulin emerged. Autoimmunity to insulin was found to be an early marker of risk for type 1 diabetes in young children. In humans, it remains unclear if autoimmunity to insulin is primarily due to a defect in the beta cell itself or to dysregulated immune activation. Conversely, it may be secondary to beta-cell damage from an environmental agent (e.g., virus). Nevertheless, direct, interventional studies in non-obese diabetic (NOD) mouse models of type 1 diabetes point to a critical role for (pro)insulin as a primary autoantigen that drives beta cell pathology.

Scope of review

Modelled on Koch's postulates for the pathogenicity of an infectious agent, evidence for a pathogenic role of (pro)insulin as an autoantigen in type 1 diabetes, particularly applicable to the NOD mouse model, is reviewed. Evidence in humans remains circumstantial. Additionally, as (pro)insulin is a target of autoimmunity in type 1 diabetes, its application as a therapeutic tool to elicit antigen-specific immune tolerance is assessed.

Major conclusions

Paradoxically, insulin is both a ‘cure’ and a potential ‘cause’ of type 1 diabetes, actively participating as an autoantigen to drive autoimmune destruction of beta cells - the instrument of its own destruction.

The Impact of Biomaterial Cell Contact on the Immunopeptidome

Biomaterials play an increasing role in clinical applications and regenerative medicine. A perfectly designed biomaterial should restore the function of damaged tissue without triggering an undesirable immune response, initiate self-regeneration of the surrounding tissue and gradually degrade after implantation. The immune system is well recognized to play a major role in influencing the biocompatibility of implanted medical devices. To obtain a better understanding of the effects of biomaterials on the immune response, we have developed a highly sensitive novel test system capable of examining changes in the immune system by biomaterial. Here, we evaluated for the first time the immunopeptidome, a highly sensitive system that reflects cancer transformation, virus or drug influences and passes these cellular changes directly to T cells, as a test system to examine the effects of contact with materials. Since monocytes are one of the first immune cells reacting to biomaterials, we have tested the influence of different materials on the immunopeptidome of the monocytic THP-1 cell line. The tested materials included stainless steel, aluminum, zinc, high-density polyethylene, polyurethane films containing zinc diethyldithiocarbamate, copper, and zinc sulfate. The incubation with all material types resulted in significantly modulated peptides in the immunopeptidome, which were material-associated. The magnitude of induced changes in the immunopeptidome after the stimulation appeared comparable to that of bacterial lipopolysaccharides (LPS). The source proteins of many detected peptides are associated with cytotoxicity, fibrosis, autoimmunity, inflammation, and cellular stress. Considering all tested materials, it was found that the LPS-induced cytotoxicity-, inflammation- and cellular stress-associated HLA class I peptides were mainly induced by aluminum, whereas HLA class II peptides were mainly induced by stainless steel. These findings provide the first insights into the effects of biomaterials on the immunopeptidome. A more thorough understanding of these effects may enable the design of more biocompatible implant materials using in vitro models in future. Such efforts will provide a deeper understanding of possible immune responses induced by biomaterials such as fibrosis, inflammation, cytotoxicity, and autoimmune reactions.

A Question of Tolerance-Antigen-Specific Immunotherapy for Type 1 Diabetes

PURPOSE OF REVIEW

Antigen-specific immunotherapy (ASI) is a long sought-after goal for type 1 diabetes (T1D), with the potential of greater long-term safety than non-specific immunotherapy. We review the most recent advances in identification of target islet epitopes, delivery platforms and the ongoing challenges.

RECENT FINDINGS

It is now recognised that human proinsulin contains a hotspot of epitopes targeted in people with T1D. Beta-cell neoantigens are also under investigation as ASI target epitopes. Consideration of the predicted HLA-specificity of the target antigen for subject selection is now being incorporated into trial design. Cell-free ASI approaches delivering antigen with or without additional immunomodulatory agents can induce antigen-specific regulatory T cell responses, including in patients and many novel nanoparticle-based platforms are under development. ASI for T1D is rapidly advancing with a number of modalities currently being trialled in patients and many more under development in preclinical models.

Direct modulation of myelin-autoreactive CD4+ and CD8+ T cells in EAE mice by a tolerogenic nanoparticle co-carrying myelin peptide-loaded major histocompatibility complexes, CD47 and multiple regulatory molecules

Purpose

Numerous nanomaterials have been reported in the treatment of multiple sclerosis or experimental autoimmune encephalomyelitis (EAE). But most of these nanoscale therapeutics deliver myelin antigens together with toxins or cytokines and underlay the cellular uptake and induction of tolerogenic antigen-presenting cells by which they indirectly induce T cell tolerance. This study focuses on the on-target and direct modulation of myelin-autoreactive T cells and combined use of multiple regulatory molecules by generating a tolerogenic nanoparticle.

Materials and methods

Poly(lactic-co-glycolic acid) nanoparticles (PLGA-NPs) were fabricated by co-coupling MOG_40–54/H-2D^b-Ig dimer, MOG_35–55/I-A^b multimer, anti-Fas, PD-L1-Fc and CD47-Fc and encapsulating transforming growth factor-β1. The resulting 217 nm tolerogenic nanoparticles (tNPs) were administered intravenously into MOG_35–55 peptide-induced EAE mice, which was followed by the investigation of therapeutic outcomes and the in vivo mechanism.

Results

Four infusions of the tNPs durably ameliorated EAE with a marked reduction of clinical score, neuroinflammation and demyelination. They were distributed in secondary lymphoid tissues, various organs and brain after intravenous injection, with retention over 36 h, and made contacts with CD4⁺ and CD8⁺ T cells. Two injections of the tNPs markedly decreased the MOG_35–55-reactive Th1 and Th17 cells and MOG_40–55-reactive Tc1 and Tc17 cells, increased regulatory T cells, inhibited T cell proliferation and elevated T cell apoptosis in spleen. Transforming growth factor-β1 and interleukin-10 were upregulated in the homogenates of central nervous system and supernatant of spleen cells.

Conclusion

Our data suggest a novel therapeutic nanoparticle to directly modulate autoreactive T cells by surface presentation of multiple ligands and paracrine release of cytokine in the antigen-specific combination immunotherapy for T cell-mediated autoimmune diseases.

Construction of a novel vaccine by conjugating a B-cell epitope of DPP4 to peptide IA2(5)-P2-1 to significantly control type 1 diabetes in NOD mice

Type 1 diabetes is a chronic organ-specific autoimmune disease in which selective destruction of insulin-producing β cells leads to impaired glucose metabolism and its attendant complications. IA2(5)P2-1, a potent immunogenic carrier which designed by our laboratory, can induce high titer specific antibodies when carry a B cell epitope, such as B cell epitopes of DPP4, xanthine oxidase, and Urate transporter protein. In this report, we describe a novel multi-epitope vaccine composing a peptide of DPP4, an anti-diabetic B epitope of Insulinoma antigen-2(IA-2) and a Th2 epitope (P2:IPALDSLTPANED) of P277 peptide in human heat shock protein 60 (HSP60). Immunization with the multi-epitope vaccine in non-obese diabetic (NOD) mice successfully induced specific anti-DPP4 antibody, inhibited plasma DPP4 activity, and increased serum GLP-1 level. Moreover, this antibody titer was correlated with the dose of immunization (20μg, 100μg). Inoculation of this vaccine in NOD mice significantly control blood glucose level, improved glucose excursion and increased insulin level in vivo. Consistent with a lower diabetic and insulitis incidence, a induced splenic T cells proliferation and tolerance were observed. IFN-γ secretion reduced and IL-10 increased significantly in the D41-IA2(5)-P2-1 treated mice compared to P277 and control group due to the potential immunomodulatory effect of the epitope in the vaccine. Immunohistochemical analysis and cytometry showed a rebalance of Th1/Th2 in NOD mice. Our results demonstrate that this multi-epitope vaccine may serve as a promising therapeutic approach for type 1 diabetes.

An antigen-specific semi-therapeutic treatment with local delivery of tolerogenic factors through a dual-sized microparticle system blocks experimental autoimmune encephalomyelitis

Antigen-specific treatments are highly desirable for autoimmune diseases in contrast to treatments which induce systemic immunosuppression. A novel antigen-specific therapy has been developed which, when administered semi-therapeutically, is highly efficacious in the treatment of the mouse model for multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). The treatment uses dual-sized, polymeric microparticles (dMPs) loaded with specific antigen and tolerizing factors for intra- and extra-cellular delivery, designed to recruit and modulate dendritic cells toward a tolerogenic phenotype without systemic release. This approach demonstrated robust efficacy and provided complete protection against disease. Therapeutic efficacy required encapsulation of the factors in controlled-release microparticles and was antigen-specific. Disease blocking was associated with a reduction of infiltrating CD4⁺ T cells, inflammatory cytokine-producing pathogenic CD4⁺ T cells, and activated macrophages and microglia in the central nervous system. Furthermore, CD4⁺ T cells isolated from dMP-treated mice were anergic in response to disease-specific, antigen-loaded splenocytes. Additionally, the frequency of CD86^hiMHCII^hi dendritic cells in draining lymph nodes of EAE mice treated with Ag-specific dMPs was reduced. Our findings highlight the efficacy of microparticle-based drug delivery platform to mediate antigen-specific tolerance, and suggest that such a multi-factor combinatorial approach can act to block autoimmunity.

Combinatorial drug delivery approaches for immunomodulation

Immunotherapy has been widely explored for applications to both augment and suppress intrinsic host immunity. Clinical achievements have seen a number of immunotherapeutic drugs displace established strategies like chemotherapy in treating immune-associated diseases. However, single drug approaches modulating an individual arm of the immune system are often incompletely effective. Imperfect mechanistic understanding and heterogeneity within disease pathology have seen monotherapies inadequately equipped to mediate complete disease remission. Recent success in applications of combinatorial immunotherapy has suggested that targeting multiple biological pathways simultaneously may be critical in treating complex immune pathologies. Drug delivery approaches through engineered biomaterials offer the potential to augment desired immune responses while mitigating toxic side-effects by localizing immunotherapy. This review discusses recent advances in immunotherapy and highlights newly explored combinatorial drug delivery approaches. Furthermore, prospective future directions for immunomodulatory drug delivery to exploit are provided.

CoVaccine HT™ adjuvant is superior to Freund's adjuvants in eliciting antibodies against the endogenous alarmin HMGB1

Adjuvants are used to enhance the immune response against specific antigens for the production of antibodies, with the choice of adjuvant most critical for poorly immunogenic and self-antigens. This study quantitatively and qualitatively evaluated CoVaccine HT™ and Freund's adjuvants for eliciting therapeutic ovine polyclonal antibodies targeting the endogenous alarmin, high mobility group box-1 (HMGB1). Sheep were immunised with HMGB1 protein in CoVaccine HT™ or Freund's adjuvants, with injection site reactions and antibody titres periodically assessed. The binding affinity of antibodies for HMGB1 and their neutralisation activity was determined in-vitro, with in vivo activity confirmed using a murine model of endotoxemia. Results indicated that CoVaccine HT™ elicited significantly higher antibody tires with stronger affinity and more functional potency than antibodies induced with Freund's adjuvants. These studies provide evidence that CoVaccine HT™ is superior to Freund's adjuvants for the production of antibodies to antigens with low immunogenicity and supports the use of this alternative adjuvant for clinical and experimental use antibodies.

Primary prevention of beta-cell autoimmunity and type 1 diabetes - The Global Platform for the Prevention of Autoimmune Diabetes (GPPAD) perspectives

OBJECTIVE

Type 1 diabetes can be identified by the presence of beta-cell autoantibodies that often arise in the first few years of life. The purpose of this perspective is to present the case for primary prevention of beta-cell autoimmunity and to provide a study design for its implementation in Europe.

METHODS

We examined and summarized recruitment strategies, enrollment rates, and outcomes in published TRIGR, FINDIA and BABYDIET primary prevention trials, and the TEDDY intensive observational study. A proposal for a recruitment and implementation strategy to perform a phase II/III primary prevention randomized controlled trial in infants with genetic risk for developing beta-cell autoimmunity is outlined.

RESULTS

Infants with a family history of type 1 diabetes (TRIGR, BABYDIET, TEDDY) and infants younger than age 3 months from the general population (FINDIA, TEDDY) were enrolled into these studies. All studies used HLA genotyping as part of their eligibility criteria. Predicted beta-cell autoimmunity risk in the eligible infants ranged from 3% (FINDIA, TEDDY general population) up to 12% (TRIGR, BABYDIET). Amongst eligible infants, participation was between 38% (TEDDY general population) and 97% (FINDIA). Outcomes, defined as multiple beta-cell autoantibodies, were consistent with predicted risks. We subsequently modeled recruitment into a randomized controlled trial (RCT) that could assess the efficacy of oral insulin treatment as adapted from the Pre-POINT pilot trial. The RCT would recruit infants with and without a first-degree family history of type 1 diabetes and be based on general population genetic risk testing. HLA genotyping and, for the general population, genotyping at additional type 1 diabetes susceptibility SNPs would be used to identify children with around 10% risk of beta-cell autoimmunity. The proposed RCT would have 80% power to detect a 50% reduction in multiple beta-cell autoantibodies by age 4 years at a two-tailed alpha of 0.05, and would randomize around 1160 infants to oral insulin or placebo arms in order to fulfill this. It is estimated that recruitment would require testing of between 400,000 and 500,000 newborns or infants.

CONCLUSION

It is timely and feasible to establish a platform for primary prevention trials for type 1 diabetes in Europe. This multi-site European infrastructure would perform RCTs, supply data coordination and biorepository, provide cohorts for mechanistic and observational studies, and increase awareness for autoimmune diabetes.

Pathogenic aquaporin-4 reactive T cells are sufficient to induce mouse model of neuromyelitis optica

Introduction

Neuromyelitis Optica (NMO) is an autoimmune disease primarily targeting the spinal cord and optic nerve leading to paralysis and blindness. The discovery of an antibody against the astrocytic water channel, aquaporin-4 (AQP4), in the majority of patients, has led to the presumption that the antibody was necessary for disease pathogenesis. The potential role of T cells in the central nervous system, however, has not been thoroughly examined.

Results

We generated an anti-AQP4 antibody seronegative model of NMO using pathogenic AQP4-reactive T cells in mice by immunizing AQP4 null mice with peptides corresponding to the second extracellular loop of AQP4, loop C. When polarized to a Th17 phenotype and transferred to wild-type mice, these cells caused tail and limb weakness. Histology showed demyelination and T cell infiltration in the spinal cord, optic nerve and brain. Animals receiving cells re-stimulated in culture with non-specific proteins resulted in no behavioral disease, indicating that specific targeting of AQP4 is essential for this phenotype.

Conclusions

In summary, we show that AQP4-reactive T cells are sufficient to trigger an NMO-like disease in mice, independent of antibodies, indicating that pathogenic AQP4-reactive T cells may play a similar role in humans.

Characterization of a novel oil-in-water emulsion adjuvant for swine influenza virus and Mycoplasma hyopneumoniae vaccines

Vaccines consisting of subunit or inactivated bacteria/virus and potent adjuvants are widely used to control and prevent infectious diseases. Because inactivated and subunit antigens are often less antigenic than live microbes, a growing need exists for the development of new and improved vaccine adjuvants that can elicit rapid and long-lasting immunity. Here we describe the development and characterization of a novel oil-in-water emulsion, OW-14. OW-14 contains low-cost plant-based emulsifiers and was added to antigen at a ratio of 1:3 with simple hand mixing. OW-14 was stable for prolonged periods of time at temperatures ranging from 4 to 40°C and could be sterilized by autoclaving. Our results showed that OW-14 adjuvanted inactivated swine influenza viruses (SIV; H3N2 and H1N1) and Mycoplasma hyopneumoniae (M. hyo) vaccines could be safely administered to piglets in two doses, three weeks apart. Injection sites were monitored and no adverse reactions were observed. Vaccinated pigs developed high and prolonged antibody titers to both SIV and M. hyo. Interestingly, antibody titers were either comparable or greater than those produced by commercially available FluSure (SIV) or RespiSure (M. hyo) vaccines. We also found that OW-14 can induce high antibody responses in pigs that were vaccinated with a decreased antigen dose. This study provides direct evidence that we have developed an easy-to-use and low-cost emulsion that can act as a powerful adjuvant in two common types of swine vaccines.

Trials in type 1 diabetes: Antigen-specific therapies

Type 1 diabetes (T1D) results from an aberrant immunological response against the insulin-producing beta cells in the islets of the pancreas. The ideal therapy would restore immune balance in a safe and lasting fashion, stopping the process of beta cell decay. The efficacy of immune suppressive agents such as cyclosporin underscores the notion that T1D can in principle be prevented, albeit at an unacceptable long-term safety risk. Immune modulatory drugs such as monoclonal anti-CD3 antibody, on the other hand, have recently had rather disappointing results in phase 3 trials, possibly due to inadequate dosing or choice of inappropriate endpoints. Therefore, it is argued that striking the right balance between safety and efficacy, together with careful trial design, will be paramount in preventing T1D. Here we outline the concept of antigen-specific tolerization as a strategy to safely induce long-term protection against T1D, focusing on available clinical trial data, key knowledge gaps and potential future directions.

Engineering synthetic vaccines using cues from natural immunity

Vaccines aim to protect against or treat diseases through manipulation of the immune response, promoting either immunity or tolerance. In the former case, vaccines generate antibodies and T cells poised to protect against future pathogen encounter or attack diseased cells such as tumours; in the latter case, which is far less developed, vaccines block pathogenic autoreactive T cells and autoantibodies that target self tissue. Enormous challenges remain, however, as a consequence of our incomplete understanding of human immunity. A rapidly growing field of research is the design of vaccines based on synthetic materials to target organs, tissues, cells or intracellular compartments; to co-deliver immunomodulatory signals that control the quality of the immune response; or to act directly as immune regulators. There exists great potential for well-defined materials to further our understanding of immunity. Here we describe recent advances in the design of synthetic materials to direct immune responses, highlighting successes and challenges in prophylactic, therapeutic and tolerance-inducing vaccines.

Non-antigenic and antigenic interventions in type 1 diabetes

Type 1 diabetes (T1D) results from autoimmune destruction of the pancreatic β-cells. Current T1D therapies are exclusively focused on regulating glycemia rather than the underlying immune response. A handful of trials have sought to alter the clinical course of T1D using various broad immune-suppressors, e.g., cyclosporine A and azathioprine.^1–3 The effect on β-cell preservation was significant, however, these therapies were associated with unacceptable side-effects. In contrast, more recent immunomodulators, such as anti-CD3 and antigenic therapies such as DiaPep277, provide a more targeted immunomodulation and have been generally well-tolerated and safe; however, as a monotherapy there appear to be limitations in terms of therapeutic benefit. Therefore, we argue that this new generation of immune-modifying agents will likely work best as part of a combination therapy. This review will summarize current immune-modulating therapies under investigation and discuss how to move the field of immunotherapy in T1D forward.

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 β-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 β-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.

T cell regulation mediated by interaction of soluble CD52 with the inhibitory receptor Siglec-10

Functionally diverse T cell populations interact to maintain homeostasis of the immune system. We found that human and mouse antigen-activated T cells with high expression of the lymphocyte surface marker CD52 suppressed other T cells. CD52(hi)CD4(+) T cells were distinct from CD4(+)CD25(+)Foxp3(+) regulatory T cells. Their suppression was mediated by soluble CD52 released by phospholipase C. Soluble CD52 bound to the inhibitory receptor Siglec-10 and impaired phosphorylation of the T cell receptor-associated kinases Lck and Zap70 and T cell activation. Humans with type 1 diabetes had a lower frequency and diminished function of CD52(hi)CD4(+) T cells responsive to the autoantigen GAD65. In diabetes-prone mice of the nonobese diabetic (NOD) strain, transfer of lymphocyte populations depleted of CD52(hi) cells resulted in a substantially accelerated onset of diabetes. Our studies identify a ligand-receptor mechanism of T cell regulation that may protect humans and mice from autoimmune disease.

Helminth mediated modulation of Type 1 diabetes (T1D)

Type 1 diabetes is increasing dramatically in incidence in the developed world. While there may be several reasons for this, improved sanitation and public health measures have altered our interactions with certain infectious agents such as helminths. There is increasing interest in the use of helminths or their products to alleviate inflammatory or allergic conditions. Using rodent models of diabetes, it has been possible to explore the therapeutic potential of both live infections as well as helminth-derived products on the development of autoimmunity. This review provides an overview of the findings from animal models and additionally explores the potential for translation to the clinic.

Helminth infection and type 1 diabetes

The increasing incidence of type 1 diabetes (T1D) and autoimmune diseases in industrialized countries cannot be exclusively explained by genetic factors. Human epidemiological studies and animal experimental data provide accumulating evidence for the role of environmental factors, such as infections, in the regulation of allergy and autoimmune diseases. The hygiene hypothesis has formally provided a rationale for these observations, suggesting that our co-evolution with pathogens has contributed to the shaping of the present-day human immune system. Therefore, improved sanitation, together with infection control, has removed immunoregulatory mechanisms on which our immune system may depend. Helminths are multicellular organisms that have developed a wide range of strategies to manipulate the host immune system to survive and complete their reproductive cycles successfully. Immunity to helminths involves profound changes in both the innate and adaptive immune compartments, which can have a protective effect in inflammation and autoimmunity. Recently, helminth-derived antigens and molecules have been tested in vitro and in vivo to explore possible applications in the treatment of inflammatory and autoimmune diseases, including T1D. This exciting approach presents numerous challenges that will need to be addressed before it can reach safe clinical application. This review outlines basic insight into the ability of helminths to modulate the onset and progression of T1D, and frames some of the challenges that helminth-derived therapies may face in the context of clinical translation.

Revisiting regulatory T cells in type 1 diabetes

PURPOSE OF REVIEW

Regulatory T cells (Treg) maintain immune homeostasis and prevent autoimmune disease. This review summarizes the recent advances in Treg knowledge relevant to type 1 diabetes, focusing on Treg signature, antigen specificity and development and function in the face of inflammation.

RECENT FINDINGS

Thymus-derived natural regulatory T cells (nTreg) programmed by the transcription factor forkhead box P3 (FOXP3) and peripheral-induced regulatory T cells (iTreg) have largely nonoverlapping T-cell receptor repertoires to self-antigens and jointly contribute to immune homeostasis. Initial reports that CD4CD25 (FOXP3) Treg were impaired in frequency or function in type 1 diabetes have not been confirmed. The Treg-specific demethylated region in the FOXP3 locus in nTreg is, in contrast, methylated in iTreg and conventional T cells (Tconv) and is the only feature that reliably distinguishes activated human nTreg and Tconv. Inflammatory cytokines regulate extrathymic differentiation of nTreg but can also reprogram nTreg into Th17 or Th1 effectors and prevent the differentiation of iTreg.

SUMMARY

The methylation status of the FOXP3 locus provides a means to re-examine Treg in autoimmune disease. nTreg and iTreg recognize different self-antigens. Shaping of Treg by the cytokine milieu has implications for the application of Treg cell-based immune therapies.

Making progress: preserving beta cells in type 1 diabetes

The clinical care of patients with type 1 diabetes (T1D) has greatly improved over the past few decades; however, it remains impossible to completely normalize blood sugar utilizing currently available tools. Research is underway with a goal to improve the care and, ultimately, to cure T1D by preserving beta cells. This review will outline the progress that has been made in trials aimed at preserving insulin secretion in T1D by modifying the immune assault on the pancreatic beta cell. Although not yet ready for clinical use, successful trials have been conducted in new-onset T1D that demonstrated utility of three experimental agents with disparate modes of action (anti-T cell, anti-B cell, and costimulation blockade) to preserve insulin secretion. In contrast, prevention studies have so far failed to produce positive results but have shown that such studies are feasible and have identified new promising agents for study.

Generation and expansion of regulatory human CD4(+) T-cell clones specific for pancreatic islet autoantigens

Autoantigen-specific regulatory T cells (Treg) are a potential cell therapy for human autoimmune disease, provided they could be generated in adequate numbers and with stable function. To this end, we determined the feasibility of cloning and expanding human CD4(+) Treg specific for the type 1 diabetes autoantigens, GAD65 and proinsulin. Blood CD4(+) cells stimulated to divide in response to GAD65 (in three healthy individuals) or proinsulin (in one type 1 diabetic) were flow sorted into single cells and cultured on feeder cells in the presence of anti-CD3 monoclonal antibody, IL-2 and IL-4. Clones were expanded over 4-6 weeks and screened for autoantigen-dependent suppression of tetanus toxoid-specific T-cell proliferation. Suppression by Treg clones was then confirmed against autoantigen-specific non-Treg clones. Of a total of 447 clones generated, 98 (21.9%) had autoantigen-dependent suppressor function. Treg clones were anergic but proliferated to autoantigen after addition of IL-2 or in co-culture with stimulated bulk T cells, without loss of suppressor function. Treg clones were stored over liquid N(2), thawed and further expanded over 12 days, whereupon they exhibited decreased suppressor function. Expansion of Treg clones overall was in the order 10⁷-10⁸-fold. Treg clones were not distinguished by markers of conventional CD4(+)CD25(+) Treg and suppressed independently of cell-cell contact but not via known soluble suppressor factors. This study demonstrates that autoantigen-specific CD4(+) Treg clones with potential application as a cell therapy for autoimmune disease can be generated and expanded from human blood.

Insulin auto-immunity: implications for the prevention of Type 1 diabetes mellitus

Mounting evidence suggests insulin is an important and potentially initiating antigen in the pathogenesis of Type 1 diabetes. High-affinity insulin antibodies are found early in disease development and appear to predict progression. Insulin is the only Type 1 diabetes auto-antigen with exclusive pancreatic expression and the only one whose gene maps to a major susceptibility locus. Preclinical studies in rodent models of immune-mediated diabetes show great promise for the possibility of preventing disease by peripheral tolerization. Translation of this evidence to clinical trials of oral, intranasal and parenteral insulin to invoke immune tolerance and prevent diabetes has not proven successful to date, but promising results in a small subset of highest-risk individuals have maintained enthusiasm for this promising prevention strategy. Currently, studies of oral and intranasal insulin are ongoing to determine the optimal dose, timing and target population for Type 1 diabetes prevention.

In vivo delivery of a microRNA-regulated transgene induces antigen-specific regulatory T cells and promotes immunologic tolerance

We previously showed that incorporating target sequences for the hematopoietic-specific microRNA miR-142 into an antigen-encoding transgene prevents antigen expression in antigen-presenting cells (APCs). To determine whether this approach induces immunologic tolerance, we treated mice with a miR-142-regulated lentiviral vector encoding green fluorescent protein (GFP), and subsequently vaccinated the mice against GFP. In contrast to control mice, no anti-GFP response was observed, indicating that robust tolerance to the transgene-encoded antigen was achieved. Furthermore, injection of the miR-142-regulated vector induced a population of GFP-specific regulatory T cells. Interestingly, an anti-GFP response was observed when microRNA miR-122a was inserted into the vector and antigen expression was detargeted from hepatocytes as well as APCs. This demonstrates that, in the context of lentiviral vector-mediated gene transfer, detargeting antigen expression from professional APCs, coupled with expression in hepatocytes, can induce antigen-specific immunologic tolerance.

Type 1 diabetes: lessons for other autoimmune diseases?

Type 1 diabetes (T1D) satisfies many of the criteria for an autoimmune disease. The impact of the environment to promote the development of T1D and the ability to identify individuals at risk for T1D years before clinical presentation afford lessons for other autoimmune diseases, in regard to gene-environment interactions and the potential for rational approaches to pre-clinical diagnosis and prevention. Public health measures aimed at the modern pro-inflammatory environment are required to stem the rising tide not only of T1D but other autoimmune and chronic inflammatory disorders. In the non-obese diabetic (NOD) model of spontaneous autoimmune diabetes, compelling evidence indicates that adaptive autoimmunity to the pancreatic beta cell is initially targeted against proinsulin. Proof-of-principle studies in the NOD mouse, which established that insulin and proinsulin peptides could be applied as tools to induce immune tolerance and protect against diabetes development, await successful translation to at-risk humans. Initial trials of insulin-specific immunotherapy in humans show promise and reveal ways of optimising this approach that are also applicable to other autoimmune diseases.