Peptide and major histocompatibility complex-specific breaking of humoral tolerance to native insulin with the B9-23 peptide in diabetes-prone and normal mice

100 Years of Insulin: Lifesaver, immune target, and potential remedy for prevention

In this review, we bring our personal experiences to showcase insulin from its breakthrough discovery as a life-saving drug 100 years ago to its uncovering as the autoantigen and potential cause of type 1 diabetes and eventually as an opportunity to prevent autoimmune diabetes. The work covers the birth of insulin to treat patients, which is now 100 years ago, the development of human insulin, insulin analogues, devices, and the way into automated insulin delivery, the realization that insulin is the primary autoimmune target of type 1 diabetes in children, novel approaches of immunotherapy using insulin for immune tolerance induction, the possible limitations of insulin immunotherapy, and an outlook how modern vaccines could remove the need for another 100 years of insulin therapy.

Arrest in the Progression of Type 1 Diabetes at the Mid-Stage of Insulitic Autoimmunity Using an Autoantigen-Decorated All-trans Retinoic Acid and Transforming Growth Factor Beta-1 Single Microparticle Formulation

Type 1 diabetes (T1D) is a disorder of impaired glucoregulation due to lymphocyte-driven pancreatic autoimmunity. Mobilizing dendritic cells (DC) in vivo to acquire tolerogenic activity is an attractive therapeutic approach as it results in multiple and overlapping immunosuppressive mechanisms. Delivery of agents that can achieve this, in the form of micro/nanoparticles, has successfully prevented a number of autoimmune conditions in vivo. Most of these formulations, however, do not establish multiple layers of immunoregulation. all-trans retinoic acid (RA) together with transforming growth factor beta 1 (TGFβ1), in contrast, has been shown to promote such mechanisms. When delivered in separate nanoparticle vehicles, they successfully prevent the progression of early-onset T1D autoimmunity in vivo. Herein, we show that the approach can be simplified into a single microparticle formulation of RA + TGFβ1 with surface decoration with the T1D-relevant insulin autoantigen. We show that the onset of hyperglycemia is prevented when administered into non-obese diabetic mice that are at the mid-stage of active islet-selective autoimmunity. Unexpectedly, the preventive effects do not seem to be mediated by increased numbers of regulatory T-lymphocytes inside the pancreatic lymph nodes, at least following acute administration of microparticles. Instead, we observed a mild increase in the frequency of regulatory B-lymphocytes inside the mesenteric lymph nodes. These data suggest additional and potentially-novel mechanisms that RA and TGFβ1 could be modulating to prevent progression of mid-stage autoimmunity to overt T1D. Our data further strengthen the rationale to develop RA+TGFβ1-based micro/nanoparticle “vaccines” as possible treatments of pre-symptomatic and new-onset T1D autoimmunity.

How C-terminal additions to insulin B-chain fragments create superagonists for T cells in mouse and human type 1 diabetes

In type 1 diabetes (T1D), proinsulin is a major autoantigen and the insulin B:9-23 peptide contains epitopes for CD4+ T cells in both mice and humans. This peptide requires carboxyl-terminal mutations for uniform binding in the proper position within the mouse IAg7 or human DQ8 major histocompatibility complex (MHC) class II (MHCII) peptide grooves and for strong CD4+ T cell stimulation. Here, we present crystal structures showing how these mutations control CD4+ T cell receptor (TCR) binding to these MHCII-peptide complexes. Our data reveal stricking similarities between mouse and human CD4+ TCRs in their interactions with these ligands. We also show how fusions between fragments of B:9-23 and of proinsulin C-peptide create chimeric peptides with activities as strong or stronger than the mutated insulin peptides. We propose transpeptidation in the lysosome as a mechanism that could accomplish these fusions in vivo, similar to the creation of fused peptide epitopes for MHCI presentation shown to occur by transpeptidation in the proteasome. Were this mechanism limited to the pancreas and absent in the thymus, it could provide an explanation for how diabetogenic T cells escape negative selection during development but find their modified target antigens in the pancreas to cause T1D.

Transgenic substitution with Greater Amberjack Seriola dumerili fish insulin 2 in NOD mice reduces beta cell immunogenicity

Type I diabetes (T1D) is caused by immune-mediated destruction of pancreatic beta cells. This process is triggered, in part, by specific (aa 9–23) epitopes of the insulin Β chain. Previously, fish insulins were used clinically in patients allergic to bovine or porcine insulin. Fish and human insulin differ by two amino acids in the critical immunogenic region (aa 9–23) of the B chain. We hypothesized that β cells synthesizing fish insulin would be less immunogenic in a mouse model of T1D. Transgenic NOD mice in which Greater Amberjack fish (Seriola dumerili) insulin was substituted for the insulin 2 gene were generated (mouse Ins1^−/− mouse Ins2^−/− fish Ins2^+/+). In these mice, pancreatic islets remained free of autoimmune attack. To determine whether such reduction in immunogenicity is sufficient to protect β cells from autoimmunity upon transplantation, we transplanted fish Ins2 transgenic (expressing solely Seriola dumerili Ins2), NOD, or B16:A-dKO islets under the kidney capsules of 5 weeks old female NOD wildtype mice. The B:Y16A Β chain substitution has been previously shown to be protective of T1D in NOD mice. NOD mice receiving Seriola dumerili transgenic islet transplants showed a significant (p = 0.004) prolongation of their euglycemic period (by 6 weeks; up to 18 weeks of age) compared to un-manipulated female NOD (diabetes onset at 12 weeks of age) and those receiving B16:A-dKO islet transplants (diabetes onset at 12 weeks of age). These data support the concept that specific amino acid sequence modifications can reduce insulin immunogenicity. Additionally, our study shows that alteration of a single epitope is not sufficient to halt an ongoing autoimmune response. Which, and how many, T cell epitopes are required and suffice to perpetuate autoimmunity is currently unknown. Such studies may be useful to achieve host tolerance to β cells by inactivating key immunogenic epitopes of stem cell-derived β cells intended for transplantation.

Endogenous Pancreatic β Cell Regeneration: A Potential Strategy for the Recovery of β Cell Deficiency in Diabetes

Endogenous pancreatic β cell regeneration is a potential strategy for β cell expansion or neogenesis to treat diabetes. Regeneration can occur through stimulation of existing β cell replication or conversion of other pancreatic cells into β cells. Recently, various strategies and approaches for stimulation of endogenous β cell regeneration have been evaluated, but they were not suitable for clinical application. In this paper, we comprehensively review these strategies, and further discuss various factors involved in regulation of β cell regeneration under physiological or pathological conditions, such as mediators, transcription factors, signaling pathways, and potential pharmaceutical drugs. Furthermore, we discuss possible reasons for the failure of regenerative medicines in clinical trials, and possible strategies for improving β cell regeneration. As β cell heterogeneity and plasticity determines their function and environmental adaptability, we focus on β cell subtype markers and discuss the importance of research evaluating the characteristics of new β cells. In addition, based on the autoimmunologic features of type 1 diabetes, NOD/Lt-SCID-IL2rg null (NSG) mice grafted with human immune cells and β cells are recommended for use in evaluation of antidiabetic regenerative medicines. This review will further understand current advances in endogenous β cell regeneration, and provide potential new strategies for the treatment of diabetes focused on cell therapy.

C-terminal modification of the insulin B:11-23 peptide creates superagonists in mouse and human type 1 diabetes

Insulin is a target of CD4 T cells in type 1 diabetes in mice and humans. Why the major epitope in the insulin B chain is presented poorly to the diabetogenic CD4 T cells by the disease-associated major histocompatibility class II (MHCII) alleles has been highly debated. Here we present high-resolution mouse and human MHCII structures and T-cell functional data to show that C-terminal modifications of this epitope are required for binding and presentation in the appropriate position in the MHCII binding groove. These results suggest that pancreas-specific posttranslational modifications of this peptide may play a role in the induction of diabetes and explain how the pathogenic T cells escape deletion in the thymus.

A polymorphism at β57 in some major histocompatibility complex class II (MHCII) alleles of rodents and humans is associated with a high risk for developing type 1 diabetes (T1D). However, a highly diabetogenic insulin B chain epitope within the B:9–23 peptide is presented poorly by these alleles to a variety of mouse and human CD4 T cells isolated from either nonobese diabetic (NOD) mice or humans with T1D. We have shown for both species that mutations at the C-terminal end of this epitope dramatically improve presentation to these T cells. Here we present the crystal structures of these mutated peptides bound to mouse IA^g7 and human HLA-DQ8 that show how the mutations function to improve T-cell activation. In both peptide binding grooves, the mutation of B:22R to E in the peptide changes a highly unfavorable side chain for the p9 pocket to an optimal one that is dependent on the β57 polymorphism, accounting for why these peptides bind much better to these MHCIIs. Furthermore, a second mutation of the adjacent B:21 (E to G) removes a side chain from the surface of the complex that is highly unfavorable for a subset of NOD mouse CD4 cells, thereby greatly enhancing their response to the complex. These results point out the similarities between the mouse and human responses to this B chain epitope in T1D and suggest there may be common posttranslational modifications at the C terminus of the peptide in vivo to create the pathogenic epitopes in both species.

Combination therapy with an anti-IL-1β antibody and GAD65 DNA vaccine can reverse recent-onset diabetes in the RIP-GP mouse model

Type 1 diabetes is thought to be an autoimmune condition in which self-reactive T cells attack insulin-secreting pancreatic β-cells. As a proinflammatory cytokine produced by β-cells or macrophages, interleukin-1β (IL-1β) represents a potential therapeutic target in diabetes. We reasoned IL-1β blockade could be combined with islet antigen-specific approaches involving GAD of 65 kDa (GAD65)-expressing plasmids, as previously shown in combination therapies (CTs) with anti-CD3. Thus, we investigated whether anti-IL-1β antibody alone or combined with GAD65 vaccine could reverse diabetes development in a virus-induced mouse model. Given alone, anti-IL-1β had no effect on diabetes, while GAD65 plasmid resulted in 33% disease reversal after a 5-week observation. However, CTs cured 53% of animals and prevented worsening of glycemic control in nonprotected individuals for up to 12 weeks. While the GAD65 vaccine arm of the CT was associated with increased forkhead box p3(+) regulatory T-cell frequency in pancreatic lymph nodes, islet infiltration by CD11b(+/high) cells was less frequent upon CT, and its extent correlated with treatment success or failure. Altogether, our CTs provided prolonged improvement of clinical and immunological features. Despite unsuccessful clinical trials using anti-IL-1β monotherapy, these data hold promise for treatment of type 1 diabetic patients with IL-1β blockade combined with antigen-specific vaccines.

Combination of monoclonal antibodies and DPP-IV inhibitors in the treatment of type 1 diabetes: a plausible treatment modality?

Regulatory T cells (Tregs) are crucial for the maintenance of immunological tolerance. Type 1 diabetes (T1D) occurs when the immune-regulatory mechanism fails. In fact, T1D is reversed by islet transplantation but is associated with hostile effects of persistent immune suppression. T1D is believed to be dependent on the activation of type-1 helper T (Th1) cells. Immune tolerance is liable for the activation of the Th1 cells. The important role of Th1 cells in pathology of T1D entails the depletion of CD4(+) T cells, which initiated the use of monoclonal antibodies (mAbs) against CD4(+) T cells to interfere with induction of T1D. Prevention of autoimmunity is not only a step forward for the treatment of T1D, but could also restore the β-cell mass. Glucagon-like peptide (GLP)-1 stimulates β-cell proliferation and also has anti-apoptotic effects on them. However, the potential use of GLP-1 as a possible method to restore pancreatic β-cells is limited due to rapid degradation by dipeptidyl peptidase (DPP)-IV. We hypothesize that treatment with combination of CD4 mAbs and DPP-IV inhibitors could prevent/reverse T1D. CD4 mAbs have the ability to induce immune tolerance, thereby arresting further progression of T1D; DPP-IV inhibitors have the capability to regenerate the β-cell mass. Consequently, the combination of CD4 mAbs and DPP-IV inhibitor could avoid or at least minimize the constraints of intensive subcutaneous insulin therapy. We presume that if this hypothesis proves correct, it may become one of the plausible therapeutic options for T1D.

Antigen presentation in the autoimmune diabetes of the NOD mouse

This paper reviews the presentation of peptides by major histocompatibility complex (MHC) class II molecules in the autoimmune diabetes of the nonobese diabetic (NOD) mouse. Islets of Langerhans contain antigen-presenting cells that capture the proteins and peptides of the beta cells' secretory granules. Peptides bound to I-A(g7), the unique MHC class II molecule of NOD mice, are presented in islets and in pancreatic lymph nodes. The various beta cell-derived peptides interact with selected CD4 T cells to cause inflammation and beta cell demise. Many autoreactive T cells are found in NOD mice, but not all have a major role in the initiation of the autoimmune process. I emphasize here the evidence pointing to insulin autoreactivity as a seminal component in the diabetogenic process.

Monoclonal antibody blocking the recognition of an insulin peptide-MHC complex modulates type 1 diabetes

The primary autoantigen triggering spontaneous type 1 diabetes mellitus in nonobese diabetic (NOD) mice is insulin. The major T-cell insulin epitope lies within the amino acid 9-23 peptide of the β-chain (B:9-23). This peptide can bind within the peptide binding groove of the NOD MHC class II molecule (MHCII), IA(g7), in multiple positions or "registers." However, the majority of pathogenic CD4 T cells recognize this complex only when the insulin peptide is bound in register 3 (R3). We hypothesized that antibodies reacting specifically with R3 insulin-IA(g7) complexes would inhibit autoimmune diabetes specifically without interfering with recognition of other IA(g7)-presented antigens. To test this hypothesis, we generated a monoclonal antibody (mAb287), which selectively binds to B:9-23 and related variants when presented by IA(g7) in R3, but not other registers. The monoclonal antibody blocks binding of IA(g7)-B:10-23 R3 tetramers to cognate T cells and inhibits T-cell responses to soluble B:9-23 peptides and NOD islets. However, mAb287 has no effect on recognition of other peptides bound to IA(g7) or other MHCII molecules. Intervention with mAb287, but not irrelevant isotype matched antibody, at either early or late stages of disease development, significantly delayed diabetes onset by inhibiting infiltration by not only insulin-specific CD4 T cells, but also by CD4 and CD8 T cells of other specificities. We propose that peptide-MHC-specific monoclonal antibodies can modulate autoimmune disease without the pleiotropic effects of nonselective reagents and, thus, could be applicable to the treatment of multiple T-cell mediated autoimmune disorders.

Pathogenic CD4⁺ T cells recognizing an unstable peptide of insulin are directly recruited into islets bypassing local lymph nodes

In the nonobese diabetic mouse, a predominant component of the autoreactive CD4(+) T cell repertoire is directed against the B:9-23 segment of the insulin B chain. Previous studies established that the majority of insulin-reactive T cells specifically recognize a weak peptide-MHC binding register within the B:9-23 segment, that to the 12-20 register. These T cells are uniquely stimulated when the B:9-23 peptide, but not the insulin protein, is offered to antigen presenting cells (APCs). Here, we report on a T cell receptor (TCR) transgenic mouse (8F10) that offers important new insights into the biology of these unconventional T cells. Many of the 8F10 CD4(+) T cells escaped negative selection and were highly pathogenic. The T cells were directly recruited into islets of Langerhans, where they established contact with resident intra-islet APCs. Immunogenic insulin had to be presented in order for the T cells to localize and cause disease. These T cells bypassed an initial priming stage in the pancreatic lymph node thought to precede islet T cell entry. 8F10 T cells induced the production of antiinsulin antibodies and islets contained immunoglobulin (IgG) deposited on β cells and along the vessel walls.

Tumor immunotherapy based on tumor-derived heat shock proteins (Review)

Heat shock proteins (HSPs), the most important type of molecular chaperone, are expressed in all eukaryotic cells and have multiple functions, including the folding and unfolding of other proteins and peptides, the transport of proteins and peptides and the support of antigen presentation processes. Due to these important properties, the use of HSPs has been explored as a promising tumor immunotherapy strategy. It has been previously demonstrated that HSP peptide complex (HSP.PC) derived from tumors is the immunogenic entity that elicits powerful antitumor immune responses. Previous animal studies and phase III clinical trials have demonstrated the efficacy, safety and feasibility of HSP-based tumor vaccines. However, the limitations are also apparent and specific alternatives have been developed. The present review focused on the history of HSP-based immunotherapy, the mechanism of its immunogenicity and the previous efforts to promote the efficacy. The current review may be useful for antitumor studies based on the tumor-derived HSPs.

Advancing animal models of human type 1 diabetes by engraftment of functional human tissues in immunodeficient mice

Despite decades of studying rodent models of type 1 diabetes (T1D), no therapy capable of preventing or curing T1D has successfully been translated from rodents to humans. This inability to translate otherwise promising therapies to clinical settings likely resides, to a major degree, from significant species-specific differences between rodent and human immune systems as well as species-related variances in islets in terms of their cellular composition, function, and gene expression. Indeed, taken collectively, these differences underscore the need to define interactions between the human immune system with human β cells. Immunodeficient mice engrafted with human immune systems and human β cells represent an interesting and promising opportunity to study these components in vivo. To meet this need, years of effort have been extended to develop mice depleted of undesirable components while at the same time, allowing the introduction of constituents necessary to recapitulate physiological settings as near as possible to human T1D. With this, these so-called "humanized mice" are currently being used as a preclinical bridge to facilitate identification and translation of novel discoveries to clinical settings.

Short-term subcutaneous insulin treatment delays but does not prevent diabetes in NOD mice

Despite encouraging results in the NOD mouse, type 1 diabetes prevention trials using subcutaneous insulin have been unsuccessful. To explain these discrepancies, 3-week-old NOD mice were treated for 7 weeks with subcutaneous insulin at two different doses: a high dose (0.5 U/mouse) used in previous mouse studies; and a low dose (0.005 U/mouse) equivalent to that used in human trials. Effects on insulitis and diabetes were monitored along with immune and metabolic modifications. Low-dose insulin did not have any effect on disease incidence. High-dose treatment delayed but did not prevent diabetes, with reduced insulitis reappearing once insulin discontinued. This effect was not associated with significant immune changes in islet infiltrates, either in terms of cell composition or frequency and IFN-γ secretion of islet-reactive CD8(+) T cells recognizing the immunodominant epitopes insulin B(15-23) and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)(206-214). Delayed diabetes and insulitis were associated with lower blood glucose and endogenous C-peptide levels, which rapidly returned to normal upon treatment discontinuation. In conclusion, high- but not low-dose prophylactic insulin treatment delays diabetes onset and is associated with metabolic changes suggestive of β-cell "rest" which do not persist beyond treatment. These findings have important implications for designing insulin-based prevention trials.

Antigen-specific blocking of CD4-specific immunological synapse formation using BPI and current therapies for autoimmune diseases

In this review, we discuss T-cell activation, etiology, and the current therapies of autoimmune diseases (i.e., MS, T1D, and RA). T-cells are activated upon interaction with antigen-presenting cells (APC) followed by a "bull's eye"-like formation of the immunological synapse (IS) at the T-cell-APC interface. Although the various disease-modifying therapies developed so far have been shown to modulate the IS and thus help in the management of these diseases, they are also known to present some undesirable side effects. In this study, we describe a novel and selective way to suppress autoimmunity by using a bifunctional peptide inhibitor (BPI). BPI uses an intercellular adhesion molecule-1 (ICAM-1)-binding peptide to target antigenic peptides (e.g., proteolipid peptide, glutamic acid decarboxylase, and type II collagen) to the APC and therefore modulate the immune response. The central hypothesis is that BPI blocks the IS formation by simultaneously binding to major histocompatibility complex-II and ICAM-1 on the APC and selectively alters the activation of T cells from T(H)1 to T(reg) and/or T(H)2 phenotypes, leading to tolerance.

Immunization with an insulin peptide-MHC complex to prevent type 1 diabetes of NOD mice

BACKGROUND

Mutating the insulin B:9-23 peptide prevents diabetes in NOD mice. Thus, the trimolecular complex of I-Ag7-insulin B:9-23 peptide-TCR may be essential for the development of spontaneous diabetes. Pathogenic T cells recognize the B:9-23 peptide presented by I-Ag7 in what is termed register 3, with the B22 basic amino acid (arginine) of the peptide bound in pocket 9 of I-Ag7. Our hypothesis is that immunization with an insulin B:12-22 peptide linked to I-Ag7 in register 3 (I-Ag7-B:RE#3 complex) can induce specific antibodies to the complex, block pathogenic TCRs, and thus prevent diabetes.

METHODS

We immunized young NOD mice with recombinant I-Ag7-B:RE#3 protein, in which two amino acids of the peptide were mutated to fix the peptide in register 3, and investigated the induced antibodies targeted to the peptide in register 3.

RESULTS

Specific antibodies targeting I-Ag7-B:RE#3 but not I-Ag7-HEL were identified in the sera of I-Ag7-B:RE#3 immunized mice. The sera inhibited B:9-23-induced T-cell responses in vitro. I-Ag7-B:RE#3 immunization delayed progression to diabetes (versus PBS, p=0.0005), while immunization with I-Ag7-HEL control complex did not.

CONCLUSIONS

Immunization with I-Ag7-B:RE#3 complex significantly delays the development of insulin autoantibodies and the onset of diabetes in NOD mice, which is associated with the induction of I-Ag7-B:RE#3 antibodies.

Beyond the hormone: insulin as an autoimmune target in type 1 diabetes

Insulin is not only the hormone produced by pancreatic β-cells but also a key target antigen of the autoimmune islet destruction leading to type 1 diabetes. Despite cultural biases between the fields of endocrinology and immunology, these two facets should not be regarded separately, but rather harmonized in a unifying picture of diabetes pathogenesis. There is increasing evidence suggesting that metabolic factors (β-cell dysfunction, insulin resistance) and immunological components (inflammation and β-cell-directed adaptive immune responses) may synergize toward islet destruction, with insulin standing at the crossroad of these pathways. This concept further calls for a revision of the classical dichotomy between type 1 and type 2 diabetes because metabolic and immune mechanisms may both contribute to different extents to the development of different forms of diabetes. After providing a background on the mechanisms of β-cell autoimmunity, we will explain the role of insulin and its precursors as target antigens expressed not only by β-cells but also in the thymus. Available knowledge on the autoimmune antibody and T-cell responses against insulin will be summarized. A unifying scheme will be proposed to show how different aspects of insulin biology may lead to β-cell destruction and may be therapeutically exploited. We will argue about possible reasons why insulin remains the mainstay of metabolic control in type 1 diabetes but has so far failed to prevent or halt β-cell autoimmunity as an immune modulatory reagent.

[Antitumor effects of raddeanin A on S180, H22 and U14 cell xenografts in mice]

BACKGROUND & OBJECTIVE

Raddeanin A, a triterpenoid saponin from Anemone raddeana Regel, has good antitumor activity in vitro. This study was to investigate its antitumor effects on tumor cell xenografts in mice.

METHODS

The inhibitory effects of raddeanin A on the proliferation of human nasopharyngeal carcinoma KB cells and ovarian cancer SKOV3 cells were measured by MTT assay. The inhibitory effects of raddeanin A injection on the growth of sarcoma S180, liver cancer H22 and cervical carcinoma U14 cell xenografts in mice and the effect of raddeanin A lavage on the growth of S180 cell xenografts were measured. The acute toxicity of raddeanin A was also measured.

RESULTS

The 50% inhibition concentration (IC(50)) of raddeanin A was 4.64 microg/mL for KB cells and 1.40 microg/mL for SKOV3 cells. When injected with raddeanin A at a dose of 4.5 mg/kg, the growth inhibition rates of S180, H22 and U14 cell xenografts were 60.5%, 36.2% and 61.8%, respectively. When lavaged with raddeanin A at a dose of 200 mg/kg, the growth inhibition rate of S180 cell xenografts was 64.7%. The median lethal dose (LD50) of raddeanin A lavage was 1.1 g/kg and that of raddeanin A injection was 16.1 mg/kg.

CONCLUSION

Raddeanin A has good antitumor activity both in vitro and in vivo, and would be a potential antitumor medicine.

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.

Insulin: a critical autoantigen and potential therapeutic agent in Type 1 diabetes

Insulin is a polypeptide hormone secreted by pancreatic beta-cells and is critical for glucose homeostasis. Abnormalities in insulin secretion result in various forms of diabetes. Type 1A diabetes is an autoimmune form in which insulin has been identified as a critical autoantigen. Recent studies have identified genetic determinants of insulin-specific autoimmune responses and insulin epitopes targeted by autoreactive T lymphocytes. The study of insulin as an autoantigen has also led to discoveries about basic mechanisms of immunological tolerance and autoimmunity. Experimental and clinical evidence suggests that insulin and insulin-derived peptides may delay and perhaps prevent the development of diabetes. Further clinical trials may identify effective treatment modalities for inhibiting diabetogenic autoimmunity and preventing disease development.

Banting Lecture 2009: An unfinished journey: molecular pathogenesis to prevention of type 1A diabetes

The Banting Medal for Scientific Achievement Award is the American Diabetes Association's highest scientific award and honors an individual who has made significant, long-term contributions to the understanding of diabetes, its treatment, and/or prevention. The award is named after Nobel Prize winner Sir Frederick Banting, who codiscovered insulin treatment for diabetes.

Dr. Eisenbarth received the American Diabetes Association's Banting Medal for Scientific Achievement at the Association's 69th Scientific Sessions, June 5–9, 2009, in New Orleans, Louisiana. He presented the Banting Lecture, An Unfinished Journey—Type 1 Diabetes—Molecular Pathogenesis to Prevention , on Sunday, June 7, 2009.

Unique autoreactive T cells recognize insulin peptides generated within the islets of Langerhans in autoimmune diabetes

In addition to the genetic framework, there are two other critical requirements for the development of tissue-specific autoimmune disease. First, autoreactive T cells need to escape thymic negative selection. Second, they need to find suitable conditions for autoantigen presentation and activation in the target tissue. We show here that these two conditions are fulfilled in diabetic mice of the nonobese diabetic (NOD) strain. A set of autoreactive CD4(+) T cells specific for an insulin peptide, with the noteworthy feature of not recognizing the insulin protein when processed by antigen-presenting cells (APCs), escaped thymic control, participated in diabetes and caused disease. Moreover, APCs in close contact with beta cells in the islets of Langerhans bore vesicles with the antigenic insulin peptides and activated peptide-specific T cells. Our findings may be relevant for other cases of endocrine autoimmunity.

Etiopathogenesis of type 1 diabetes mellitus: prognostic factors for the evolution of residual beta cell function

Type 1A diabetes mellitus (T1ADM) is a progressive autoimmune disease mediated by T lymphocytes with destruction of beta cells. Up to now, we do not have precise methods to assess the beta cell mass, "in vivo" or "ex-vivo". The studies about its genetic susceptibility show strong association with class II antigens of the HLA system (particularly DQ). Others genetics associations are weaker and depend on the population studied. A combination of precipitating events may occur at the beginning of the disease. There is a silent loss of immune-mediated beta cells mass which velocity has an inverse relation with the age, but it is influenced by genetic and metabolic factors. We can predict the development of the disease primarily through the determination of four biochemically islet auto antibodies against antigens like insulin, GAD65, IA2 and Znt8. Beta cell destruction is chronically progressive but at clinical diagnosis of the disease a reserve of these cells still functioning. The goal of secondary disease prevention is halt the autoimmune attack on beta cells by redirecting or dampening the immune system. It is remains one of the foremost therapeutic goals in the T1ADM. Glycemic intensive control and immunotherapeutic agents may preserve beta-cell function in newly diagnosed patients with T1ADM. It may be assessed through C-peptide values, which are important for glycemic stability and for the prevention of chronic complications of this disease. This article will summarize the etiopathogenesis mechanisms of this disease and the factors can influence on residual C-peptide and the strategies to it preservation.

Coxsackievirus B4 and type 1 diabetes pathogenesis: contribution of animal models

The role of enteroviruses, in particular type B coxsackieviruses (CV-B), in type 1 diabetes (T1D) pathogenesis is supported by epidemiological, clinical and experimental observations.The investigation of T1D pathogenesis benefits from the contribution of animal models called spontaneously diabetic. Among these animals the non-obese diabetic (NOD) mouse and the bio-breeding diabetes-prone (BBDP) rat present a genetic susceptibility manifested by the expression of an autoimmune diabetes similar to the pathology observed in human beings. Other models whose genetic predisposition is less known are of considerable contribution as well. Numerous major observations relative to several aspects of T1D pathogenesis in the context of CV-B infections, such as susceptibility, diabetogenicity, pancreatotropism, mechanisms of beta cells destruction and others, have been deduced thanks to investigations with animal models. Despite their limits, these models are necessary in improving our knowledge of the role of enteroviruses, like CV-B4, in the pathogenesis of T1D, and the recent advances ensuing from their contribution may have important therapeutic and preventive spin-offs.

Thymus-specific deletion of insulin induces autoimmune diabetes

Insulin expression in the thymus has been implicated in regulating the negative selection of autoreactive T cells and in mediating the central immune tolerance towards pancreatic beta-cells. To further explore the function of this ectopic insulin expression, we knocked out the mouse Ins2 gene specifically in the Aire-expressing medullary thymic epithelial cells (mTECs), without affecting its expression in the beta-cells. When further crossed to the Ins1 knockout background, both male and female pups (designated as ID-TEC mice for insulin-deleted mTEC) developed diabetes spontaneously around 3 weeks after birth. beta-cell-specific autoimmune destruction was observed, as well as islet-specific T cell infiltration. The presence of insulin-specific effector T cells was shown using ELISPOT assays and adoptive T cell transfer experiments. Results from thymus transplantation experiments proved further that depletion of Ins2 expression in mTECs was sufficient to break central tolerance and induce anti-insulin autoimmunity. Our observations may explain the rare cases of type 1 diabetes onset in very young children carrying diabetes-resistant HLA class II alleles. ID-TEC mice could serve as a new model for studying this pathology.

[Antigen specific treatment for the inhibition and remission of type 1 diabetes]

Treatment with anti-CD3 antibodies appears promising to preserve residual beta-cell function in recent onset type 1 diabetes although many patients had therapy related adverse events. Insulin is an important islet antigen and autoimmunity to insulin may be central to disease pathogenesis of type 1 diabetes in man and NOD mouse. Evidence is strongest for the NOD mouse model, where blocking immune responses to insulin by amino acid substitution at positions B: 16, prevents diabetes. Insulin can be used to immunologically prevent diabetes of NOD mice, however, insulin-based preventive immunoregulation of diabetes in man is not yet possible. Treatment of NOD mice with insulin B-chain peptide and poly I: C, a Toll-like receptor 3 ligand, induces the pathogenic T cells as well as regulatory T cells and recruits them into the islets. Intranasal treatment with insulin B-chain analogue peptide with amino acid substitutions at positions B: 16 and 19 prevented the progression to diabetes and induced remission from hyperglycemia when co-administered with a mucosal adjuvant cholera toxin. Thus, an antigenic peptide vaccination with an alternative adjuvant or route might induce antigen-specific regulatory cell populations rather than pathogenic T cells. We believe that such an improved antigen specific therapy could provide more efficient and safer disease suppression and remission for human type 1 diabetes.

Analysis of T cell receptor beta chains that combine with dominant conserved TRAV5D-4*04 anti-insulin B:9-23 alpha chains

OBJECTIVE

The objective of this study was to define the spectrum of TCR beta chains permissive for T cells with alpha chains containing the conserved TRAV5D-4*04 sequence to target the insulin B:9-23 peptide, a major epitope for initiation of diabetes in the NOD mouse.

MATERIALS AND METHODS

We produced T cell hybridomas from mice with single T cell receptors (BDC12-4.1 TCR alpha(+)beta(+) double transgenic mice and BDC12-4.4 TCR alpha(+)beta(+) double retrogenic mice) or from mice with only the corresponding alpha chains transgene or retrogene and multiple endogenous TCR beta chains.

RESULTS

Hybridomas with the complete BDC12-4.1 and BDC12-4.4 T cell receptors, despite having markedly different TCR beta chains, responded to similar B:9-23 peptides. Approximately 1% of the hybridomas from mice with the fixed TRAV5D-4*04 alpha chains and multiple endogenous beta chains responded to B:9-23 peptides while the majority of hybridomas with different beta chains did not respond. There was no apparent conservation of TCR beta chain sequences in the responding hybridomas.

CONCLUSIONS

Approximately 1% of hybridomas utilizing different TCR beta chains paired with the conserved TRAV5D-4*04 containing alpha chains respond to insulin peptide B:9-23. Therefore, TCR beta chain sequences make an important contribution to insulin B:9-23 peptide recognition but multiple beta chain sequences are permissive for recognition.

Conserved T cell receptor alpha-chain induces insulin autoantibodies

A fundamental question is what are the molecular determinants that lead to spontaneous preferential targeting of specific autoantigens in autoimmune diseases, such as the insulin B:9-23 peptide sequence in type 1 diabetes. Anti-insulin B:9-23 T cell clones isolated from prediabetic NOD islets have a conserved Valpha-segment/Jalpha-segment, but no conservation of the alpha-chain N region and no conservation of the Vbeta-chain. Here, we show that the conserved T cell receptor alpha-chain generates insulin autoantibodies when transgenically or retrogenically introduced into mice without its corresponding Vbeta. We suggest that a major part of the mystery as to why islet autoimmunity develops relates to recognition of a primary insulin peptide by a conserved alpha chain T cell receptor.

T-cell reactivity to insulin peptide A1-12 in children with recently diagnosed type 1 diabetes or multiple beta-cell autoantibodies

Insulin-specific immune responses appear early in preclinical type 1 diabetes (T1D), and bovine insulin in cow's milk-based infant formulas has been suggested to be of importance in induction of the primary response to insulin in humans. To characterize insulin-specific T-cell reactivity we studied T-cell responses to 10 insulin peptides derived from bovine (BI) and human insulin (HI) in 42 children with recently diagnosed T1D, 47 children with multiple autoantibodies and 111 autoantibody-negative control children with risk-associated HLA alleles. Proliferation responses detected in antigen-stimulated peripheral blood mononuclear cells did not differ between the three groups when the comparison was performed without considering HLA genotypes. However, significant differences were observed, when children with the high-risk genotype HLA (DRB1*03)-DQA1*05-DQB1*02/DRB1*0401-DQA1*03-DQB1*0302 were analyzed separately. The responses to the peptides including amino acids A1-12 derived from B1 and H1 were significantly higher in children with T1D (P=0.008, P=0.004, for B1 and H1, respectively) and in children with diabetes-associated autoantibodies (P=0.002 and P=0.001, respectively) than in control children. Positive responses (stimulation indices SI> or =3) were seen more frequently in T1D children than in controls (4/7 vs 2/19; P=0.03 and 4/7 vs 1/19; P=0.01 for B1 and H1, respectively). T-cell response to the insulin peptide A1-12 is enhanced in clinical and preclinical T1D associated with the high-risk HLA-genotype emphasizing the importance of this epitope.

Combined insulin B:9-23 self-peptide and polyinosinic-polycytidylic acid accelerate insulitis but inhibit development of diabetes by increasing the proportion of CD4+Foxp3+ regulatory T cells in the islets in non-obese diabetic mice

Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes. Combined treatment with B:9-23 peptide and polyinosinic-polycytidylic acid (poly I:C), but neither alone, induce insulitis in normal BALB/c mice. In contrast, the combined treatment accelerated insulitis, but prevented diabetes in NOD mice. Our immunofluorescence study with anti-CD4/anti-Foxp3 revealed that the proportion of Foxp3 positive CD4(+)CD25(+) regulatory T cells (Tregs) was elevated in the islets of NOD mice treated with B:9-23 peptide and poly I:C, as compared to non-treated mice. Depletion of Tregs by anti-CD25 antibody hastened spontaneous development of diabetes in non-treated NOD mice, and abolished the protective effect of the combined treatment and conversely accelerated the onset of diabetes in the treated mice. These results indicate that poly I:C combined with B:9-23 peptide promotes infiltration of both pathogenic T cells and predominantly Tregs into the islets, thereby inhibiting progression from insulitis to overt diabetes in NOD mice.

Priming and effector dependence on insulin B:9-23 peptide in NOD islet autoimmunity

NOD mice with knockout of both native insulin genes and a mutated proinsulin transgene, alanine at position B16 in preproinsulin (B16:A-dKO mice), do not develop diabetes. Transplantation of NOD islets, but not bone marrow, expressing native insulin sequences (tyrosine at position B16) into B16:A-dKO mice rapidly restored development of insulin autoantibodies (IAAs) and insulitis, despite the recipients' pancreatic islets lacking native insulin sequences. Splenocytes from B16:A-dKO mice that received native insulin-positive islets induced diabetes when transferred into wild-type NOD/SCID or B16:A-dKO NOD/SCID mice. Splenocytes from mice immunized with native insulin B chain amino acids 9-23 (insulin B:9-23) peptide in CFA induced rapid diabetes upon transfer only in recipients expressing the native insulin B:9-23 sequence in their pancreata. Additionally, CD4(+) T cells from B16:A-dKO mice immunized with native insulin B:9-23 peptide promoted IAAs in NOD/SCID mice. These results indicate that the provision of native insulin B:9-23 sequences is sufficient to prime anti-insulin autoimmunity and that subsequent transfer of diabetes following peptide immunization requires native insulin B:9-23 expression in islets. Our findings demonstrate dependence on B16 alanine versus tyrosine of insulin B:9-23 for both the initial priming and the effector phase of NOD anti-islet autoimmunity.

Deleting islet autoimmunity

Even though there are numerous autoantigens for type 1 diabetes, current evidence suggests that a single autoantigen, namely insulin, is responsible for the key initiating event in autoimmunity. If a single autoantigen is necessary for triggering the autoimmune process, then antigen-specific therapy to block or delete the immune response against that autoantigen before epitope spreading occurs, may become a larger focus of future immunotherapeutic strategies. In this article, we review current literature regarding insulin as an autoantigen and potential approaches to deleting insulin-reactive T cells through the use of peptide vaccines and targeted T cell receptor immunizations.

Altered B:9–23 Insulin, When Administered Intranasally with Cholera Toxin Adjuvant, Suppresses the Expression of Insulin Autoantibodies and Prevents Diabetes

Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes that contains two distinct CD4 epitopes (B:9-16 and B:13-23). One of the two epitopes, B:13-23, overlaps with a CTL epitope (B:15-23). In this study, we report that the elimination of the CTL epitope from the B:9-23 peptide by amino acid substitution (with alanine) at positions B:16 and 19 (A16,19 altered peptide ligand) or truncation of the C-terminal amino acids from the peptide (B:9-21), neither of which stimulated the proliferation of insulin B:15-23 reactive CD8 T cells, provided significant intranasally induced suppression of diabetes when coadministered with a potent mucosal adjuvant cholera toxin (CT). Intranasal treatment with A16,19 resulted in the elimination of spontaneous insulin autoantibodies, significant inhibition of insulitis and remission from hyperglycemia, and prevented the progression to diabetes. Intranasal administration of native B:9-23/CT or B:11-23/CT resulted in a significant enhancement of insulin autoantibody expression and severity of insulitis and failed to prevent diabetes. Our present study indicates that elimination of the CTL epitope from the B:9-23 peptide was critically important for mucosally induced diabetes prevention. The A16,19 altered peptide ligand, but not other native insulin peptides, suppresses insulin autoantibodies associated with protection from and remission of diabetes.

Transfusion of apoptotic beta-cells induces immune tolerance to beta-cell antigens and prevents type 1 diabetes in NOD mice

In vivo induction of beta-cell apoptosis has been demonstrated to be effective in preventing type 1 diabetes in NOD mice. Based on the notion that steady-state cell apoptosis is associated with self-tolerance and the need for developing a more practical approach using apoptotic beta-cells to prevent type 1 diabetes, the current study was designed to investigate apoptotic beta-cells induced ex vivo in preventing type 1 diabetes. The NIT-1 cell line serves as a source of beta-cells. Apoptotic NIT-1 cells were prepared by ultraviolet B (UVB) irradiation. Three weekly transfusions of UVB-irradiated NIT-1 cells (1 x 10(5)/mouse) or PBS were used to determine whether transfusions of UVB-irradiated NIT-1 cells induce immune tolerance to beta-cell antigens in vivo and prevent type 1 diabetes. The suppression of anti-beta-cell antibodies, polarization of T-helper (Th) cells, and induction of regulatory T-cells by UVB-irradiated NIT-1 cell treatment were investigated. The transfusions of apoptotic NIT-1 cells suppress anti-beta-cell antibody development and induce Th2 responses and interleukin-10-producing regulatory type 1 cells. Importantly, this treatment significantly delays and prevents the onset of diabetes when 10-week-old NOD mice are treated. Adoptive transfer of splenocytes from UVB-irradiated NIT-1 cell-treated mice prevents diabetes caused by simultaneously injected diabetogenic splenocytes in NOD-Rag(-/-) mice. Moreover, the proliferation of adoptively transferred carboxyfluorescein diacetate succinimidyl ester-labeled beta-cell antigen-specific T-cell receptor-transgenic T-cells in UVB-irradiated NIT-1-cell treated mice is markedly suppressed. The transfusion of apoptotic beta-cells effectively protects against type 1 diabetes in NOD mice by inducing immune tolerance to beta-cell antigens. This approach has great potential for immune intervention for human type 1 diabetes.

Transgenic insulin (B:9-23) T-cell receptor mice develop autoimmune diabetes dependent upon RAG genotype, H-2g7 homozygosity, and insulin 2 gene knockout

A series of recent studies in humans and the NOD mouse model have highlighted the central role that autoimmunity directed against insulin, in particular the insulin B chain 9-23 peptide, may play in the pathogenesis of type 1 diabetes. Both pathogenic and protective T-cell clones recognizing the B:9-23 peptide have been produced. This report describes the successful creation of BDC12-4.1 T-cell receptor (TCR) transgenic mice with spontaneous insulitis in F1 mice (FVB x NOD) and spontaneous diabetes in NOD.RAG(-/-) (backcross 1 generation). Disease progression is heterogeneous and is modified by a series of genetic factors including heterozygosity (H-2(g7)/H-2(q)) versus homozygosity for H-2(g7), the presence of additional T-/B-cell receptor-rearranged genes (RAG(+) versus RAG(-/-)), and the insulin 2 gene knockout (the insulin gene expressed in the NOD thymus). Despite lymphopenia, 40% of H-2(g7/g7) BDC12-4.1 TCR(+) RAG(-/-) Ins2(-/-) mice are diabetic by 10 weeks of age. As few as 13,500 transgenic T-cells from a diabetic TCR(+) RAG(-/-) mouse can transfer diabetes to an NOD.scid mouse. The current study demonstrates that the BDC12-4.1 TCR is sufficient to cause diabetes at NOD backcross 1, bypassing polygenic inhibition of insulitis and diabetogenesis.

Immunotherapeutic approaches to prevent, ameliorate, and cure type 1 diabetes

Type 1A diabetes (T1D) is caused by autoimmune islet beta cell destruction precipitated by environmental triggers in genetically predisposed individuals. Islet beta cells produce insulin and are the primary target of this autoimmune disorder. Insulin, glutamic acid decarboxylase, and insulinoma associated-2 autoantibodies (IAA, GAD65, and IA-2) are the autoantibodies that have been associated most clearly with the development of T1D. Despite our current ability to predict T1D using genetic markers and detecting islet autoantibodies, we have yet to find a safe way to prevent the disease. However, there are more than 100 different therapies that prevent T1D in the nonobese diabetic (NOD) mouse model or the BioBreeding (BB) rats. This paper reviews a few select therapeutic approaches that have been or are being evaluated as possibilities for the prevention, amelioration, or cure of T1D.

Interferon-alpha as a mediator of polyinosinic:polycytidylic acid-induced type 1 diabetes

A number of studies and clinical case reports have implicated interferon (IFN)-alpha as a potential mediator of type 1 diabetes pathogenesis. Administration of polyinosinic:polycytidylic acid (poly I:C), a mimic of viral double-stranded RNA, induces diabetes in C57BL/6 mice expressing the B7.1 costimulatory molecule in islets. We investigated the potential role of IFN-alpha in this disease model. The quantitative correlation between IFN-alpha levels and time to diabetes, diabetes prevention with anti-IFN-alpha antibody, and ability of IFN-alpha itself to induce diabetes are consistent with the hypothesis that poly I:C in this model acts by induction of IFN-alpha in a genetically susceptible host. Numerous recent studies highlight the importance of the innate immune system and toll receptors in determining adaptive immune responses, and we speculate that for type 1 diabetes, viral and other environmental factors may act through induction of IFNs.

The stages of type 1A diabetes: 2005

Type 1A diabetes is a chronic autoimmune disease usually preceded by a long prodrome during which autoantibodies to islet autoantigens are present. These antibodies are directed to a variety of antigens, but the best characterized are glutamic acid decarboxylase-65, insulinoma-associated antigen-2, and insulin. We hypothesize that the natural history of type 1A diabetes can be represented by several stages, starting from genetic susceptibility and ending in complete beta-cell destruction and overt diabetes. Type 1A diabetes probably results from a balance between genetic susceptibility and environmental influences. In both humans and animal models, the major determinants of the disease are genes within the major histocompatibility complex. The next best-characterized susceptibility locus is the insulin gene, the variable nucleotide tandem repeat locus. This gene affects the expression of insulin in the thymus and thus may play a role in the modulation of tolerance to this molecule. In a subset of genetically susceptible individuals, the activation of autoimmunity may be triggered by environmental factors such as viruses and/or diet. However, no conclusive association has been established between type 1A diabetes and specific environmental triggers. In this review, we provide evidence that insulin has a fundamental role in anti-islet autoimmunity.

Genetic differentiation of poly I:C from B:9-23 peptide induced experimental autoimmune diabetes

Type 1 diabetes is an immune-mediated disease, in which T cells of the adaptive immune system mediate beta cell destruction. Recently the innate immune system has been linked to etiopathogenesis of several autoimmune diseases including type 1 diabetes, as innate effector cells (e.g. dendritic cells, monocytes/macrophages and NK cells) can prime and promote or regulate (auto)immune responses. We have previously developed an experimental autoimmune diabetes (EAD) model with insulin peptide B:9-23 immunization in transgenic H-2(d)mice expressing the costimulatory molecule B7.1 in their islets (under the Rat Insulin Promotor, RIP). We compared the induction of diabetes with polyinosinic-polycytidylic acid (Poly I:C), a mimic of double stranded viral RNA versus insulin B:9-23 peptide in mice following backcrossing of the B7.1 transgene on to BALB/c mice from original B7.1 C57Bl/6 mice. We find that diabetes induction by Poly I:C is C57Bl/6 associated, whereas B:9-23 peptide induced diabetes and induction of insulin autoantibodies (IAA) are dependent on BALB/c genes. This B:9-23 peptide induced diabetes is consistent with MHC class II H-2(d)being necessary for the response to this peptide. Of note Poly I:C induction of diabetes was lost while B:9-23 induction was retained with backcrossing to BALB/c mice. Interaction of genes and environment (antigenic epitope and viral mimic) can be important in the pathogenesis of immune mediated diabetes and activation of the innate immune system (e.g. Poly I:C) may be one key determinant.

Differential Immune Induction with Subcutaneous versus Oral Administration of a Diabetogenic Insulin Peptide in the NOD Mouse

The B chain insulin peptide 9 to 23 (B:9-23) is a dominant T cell epitope of the NOD mouse. Given in oral form with multiple different vehicles, it did not alter expression of insulin autoantibodies in contrast to subcutaneous administration.

Differential immune response to B:9-23 insulin 1 and insulin 2 peptides in animal models of type 1 diabetes

Mice have two insulin genes that differ in the insulin sequence by two amino acids, including the B9 position. Given prior studies of the B:9-23 insulin peptide in NOD mice, a fundamental question is whether the immune response to the B:9-23 peptide of the two insulins is identical. We investigate responses to the immunization with B:9-23 insulin 1 and 2 peptides in NOD and RIP-B7.1 Balb/c mice. NOD and F1 (Balb/c x C57/Bl6) B7.1 transgenic mice were given either B:9-23 insulin 1, B:9-23 insulin 2 or tetanus toxoid (TT) control peptide. Insulin autoantibodies (IAA), and anti-B:9-23 antibodies (IgG1 and IgG2c) were measured. Subcutaneous injection of the insulin 2 but not the insulin 1 peptide significantly protected NOD mice from diabetes. Conceptually similar, insulin 1 peptide immunization accelerated diabetes in the B7.1 mice compared with insulin 2 peptide. Insulin 1 and 2 peptides induced similar levels of IAA in the NOD mice except at week 26, where insulin 2 induced higher levels of IAA. Anti-IgG1 B:9-23 peptide antibodies were higher in the insulin 2 immunized group of NOD mice, while IgG2c anti-B:9-23 peptide antibodies were higher in the insulin 1 group. Adoptive transfer of splenocytes from insulin 1 immunized mice to NOD.scid mice demonstrated accelerated diabetogenicity. The protection afforded by insulin 2 peptide but not insulin 1 peptide in the NOD mouse is reflected by its predominant Th2 humoral response. This may relate to the protection conferred by the insulin 1 knockout when bred onto NOD mice in contrast to acceleration of disease with an insulin 2 knockout.

Endocrine autoantibodies

The autoantibody assays that exist and that are being refined are of increasing importance to a broad spectrum of endocrine disorders. This is particularly true for type IA diabetes, which is one of the best-studied organ-specific autoimmune diseases. Autoantibodies are used as valuable markers in prediction and prevention studies of type IA diabetes. Autoantibodies related to other endocrine organs are also important because multiple related autoimmune endocrine and non-endocrine disorders are increased in frequency in patients and their families with autoimmunity. The availability of highly sensitive and specific autoantibody assays for the various endocrine disorders can allow physicians to better diagnose and promptly treat these conditions.

Insulin autoimmunity: immunogenetics/immunopathogenesis of type 1A diabetes

We can now predict the development of type 1A diabetes in humans and prevent the disorder in animal models, but we cannot at present safely prevent type 1A diabetes in humans, although a series of clinical trials are under way and planned. A major lack in our current trial design is the inability to measure T lymphocytes directly responsible for beta cell destruction. Given the immunogenetics of type 1A diabetes and increasing knowledge of pathogenesis in the NOD mouse, we believe the disorder results from immune reactivity to a limited set of islet peptides, with reactivity to insulin a major determinant of disease. Insulin autoantibodies precede the development of diabetes in both humans and the NOD mouse. T lymphocytes isolated from the islets of the NOD mouse that recognize insulin peptide B:9-23 can transfer diabetes. Insulin expression within the thymus is correlated with genetic susceptibility, and insulin peptides can be used to induce diabetes and as an immunologic vaccine to prevent the disorder. Nevertheless, at present, routine measurement of anti-insulin T lymphocytes is not standardized. Better assays to monitor such autoreactivity are likely to be essential for the development and evaluation of preventive therapies.

Absence of the T-bet gene coding for the Th1-related transcription factor does not affect diabetes-associated phenotypes in Balb/c mice

The T-box expressed in T cells gene (T-bet) is a member of the T-box family of transcription factors. T-bet-deficient mice show normal lymphoid development, but exhibit profound defects in their Th1-mediated immune responses. As the balance between Th1- and Th2-mediated immune responses plays a role in autoimmune-prone diseases, we have investigated the diabetes-related insulin autoantibody (IAA) and cellular immune responses (insulitis), in the absence of Th1 lineage commitment, in T-bet KO Balb/c mice, after immunization with the B9-23 insulin peptide. We have therefore investigated whether absence of the T-bet gene influences diabetes-related phenotypes in Balb/c T-bet KO mice.

In vivo expression of B:9-23 peptide/I-A(g7) complex may abrogate the inhibition of diabetes induced by RGD-fiber-mutant adenovirus in NOD mice

Insulin B chain peptide B:9-23 given to NOD mice decreases the development of diabetes, and phase II trials of an altered peptide ligand of B:9-23 are under way in humans. We have created a gene for the NOD MHC class II beta chain, covalently linked to the B:9-23 peptide. B lymphoma cells transfected with the gene stimulated NOD islet-derived B:9-23 reactive T cell clones in vitro. In this study, we generated an RGD-fiber-mutant adenovirus vector encoding the covalent B:9-23 peptide/I-A(g7) gene (Ad-RGD-B:9-23) to test whether in vivo expression of the gene could protect NOD mice from diabetes. NOD female mice were injected intramuscularly with 5 x 10(8) PFU of Ad-RGD-B:9-23 and empty RGD-adenovirus vector. A single administration of the empty vector did not alter the expression of insulin autoantibodies, but delayed the onset of diabetes in NOD mice. In contrast, Ad-RGD-B:9-23 immunization induced an early expression of insulin autoantibodies, but did not change the disease occurrence compared to control NOD mice. Our results suggest that adenovirus infection could confer protection from diabetes in NOD mice. The in vivo expression of covalent B:9-23 peptide/class II complex by adenovirus gene transfer might activate anti-insulin autoimmunity, resulting in abrogation of the inhibition of diabetes induced by an RGD-fiber-mutant adenovirus vector.

Nondepleting anti-CD4 monoclonal antibody prevents diabetes and blocks induction of insulin autoantibodies following insulin peptide B:9-23 immunization in the NOD mouse

INTRODUCTION

Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes that induces insulin autoantibodies and prevents diabetes in the NOD. However, immunization with peptide without adjuvant may be insufficient to reverse disease or induce long-term tolerance. Furthermore, recent experience has demonstrated the potential dangers of disease exacerbation or anaphylaxis with peptide immunotherapy.

METHODS

Combination therapy of B:9-23 with a nondepleting anti-CD4 monoclonal antibody (YTS 177.9) was studied in female NOD mice from 4 through 6 weeks of age. Injections of either B:9-23 in saline, YTS 177.9 antibody, or both peptide and antibody were given to mice.

RESULTS

By 52 weeks follow-up, 40% of B:9-23-treated, 100% of YTS177.9-treated, and 70% of B:9-23 and YTS177.9 combination-treated mice remained diabetes-free. IAA, both spontaneous and induced by B:9-23, was almost completely suppressed in mice receiving YTS 177.9. In addition to suppression of IAA expression, anti-B:9-23 peptide antibodies are also suppressed in mice receiving B:9-23 with YTS 177.9, compared to B:9-23 alone.

CONCLUSION

A brief course of the nondepleting anti-CD4 monoclonal antibody (YTS 177.9) in NOD mice confers long-term protection from diabetes and insulitis and profoundly blocks spontaneous and B:9-23 peptide-induced insulin autoantibodies.