Immunological characterization and therapeutic activity of an altered-peptide ligand, NBI-6024, based on the immunodominant type 1 diabetes autoantigen insulin B-chain (9-23) peptide

An antigen-specific immunotherapeutic, AKS-107, deletes insulin-specific B cells and prevents murine autoimmune diabetes

Introduction

The antigen-presenting cell function of insulin-reactive B cells promotes type 1 diabetes (T1D) in non-obese diabetic (NOD) mice by stimulating pathogenic T cells leading to destruction of insulin-producing β-cells of pancreatic islets.

Methods/Results

To target insulin-reactive B cells, AKS-107, a human IgG1 Fc molecule fused with human insulin A and B chains, was engineered to retain conformational insulin epitopes that bound mouse and human B cell receptors but prevented binding to the insulin metabolic receptor. AKS-107 Fc-mediated deletion of insulin-reactive B cells was demonstrated via ex vivo and in vivo experiments with insulin-reactive B cell receptor transgenic mouse strains, VH125Tg/NOD and Tg125(H+L)/NOD. As an additional immune tolerance feature, the Y16A mutation of the insulin B(9-23) dominant T cell epitope was engineered into AKS-107 to suppress activation of insulin-specific T cells. In mice and non-human primates, AKS-107 was well-tolerated, non-immunogenic, did not cause hypoglycemia even at high doses, and showed an expectedly protracted pharmacokinetic profile. AKS-107 reproducibly prevented spontaneous diabetes from developing in NOD and VH125Tg/NOD mice that persisted for months after cessation of treatment, demonstrating durable immune tolerance.

Discussion

These preclinical outcomes position AKS-107 for clinical development in T1D prevention settings.

A peptide derived from HSP60 reduces proinflammatory cytokines and soluble mediators: a therapeutic approach to inflammation

Cytokines are secretion proteins that mediate and regulate immunity and inflammation. They are crucial in the progress of acute inflammatory diseases and autoimmunity. In fact, the inhibition of proinflammatory cytokines has been widely tested in the treatment of rheumatoid arthritis (RA). Some of these inhibitors have been used in the treatment of COVID-19 patients to improve survival rates. However, controlling the extent of inflammation with cytokine inhibitors is still a challenge because these molecules are redundant and pleiotropic. Here we review a novel therapeutic approach based on the use of the HSP60-derived Altered Peptide Ligand (APL) designed for RA and repositioned for the treatment of COVID-19 patients with hyperinflammation. HSP60 is a molecular chaperone found in all cells. It is involved in a wide diversity of cellular events including protein folding and trafficking. HSP60 concentration increases during cellular stress, for example inflammation. This protein has a dual role in immunity. Some HSP60-derived soluble epitopes induce inflammation, while others are immunoregulatory. Our HSP60-derived APL decreases the concentration of cytokines and induces the increase of FOXP3+ regulatory T cells (Treg) in various experimental systems. Furthermore, it decreases several cytokines and soluble mediators that are raised in RA, as well as decreases the excessive inflammatory response induced by SARS-CoV-2. This approach can be extended to other inflammatory diseases.

Auto-antigen and Immunomodulatory Agent-Based Approaches for Antigen-Specific Tolerance in NOD Mice

PURPOSE OF REVIEW

Type 1 diabetes (T1D) can be managed by insulin replacement, but it is still associated with an increased risk of microvascular/cardiovascular complications. There is considerable interest in antigen-specific approaches for treating T1D due to their potential for a favorable risk-benefit ratio relative to non-specific immune-based treatments. Here we review recent antigen-specific tolerance approaches using auto-antigen and/or immunomodulatory agents in NOD mice and provide insight into seemingly contradictory findings.

RECENT FINDINGS

Although delivery of auto-antigen alone can prevent T1D in NOD mice, this approach may be prone to inconsistent results and has not demonstrated an ability to reverse established T1D. Conversely, several approaches that promote presentation of auto-antigen in a tolerogenic context through cell/tissue targeting, delivery system properties, or the delivery of immunomodulatory agents have had success in reversing recent-onset T1D in NOD mice. While initial auto-antigen based approaches were unable to substantially influence T1D progression clinically, recent antigen-specific approaches have promising potential.

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.

Development of a Bioconjugate Platform for Modifying the Immune Response of Autoreactive Cytotoxic T Lymphocytes Involved in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disorder characterized by autoimmune cell mediated destruction of pancreatic beta cells. Pancreatic beta cells are the only source of insulin in the body. T1D patients then have to depend on insulin injections for their lifetime. Insulin injection can modulate the blood sugar levels, but insulin has little effect on the autoimmune process. Altered peptide ligands (APL) derived from known autoantigens in T1D are able to induce tolerance in autoreactive cells in T1D animal models, but are currently unable to elicit this protection in humans. There is a need to improve immunogenicity of the APLs, as these short peptides can be easily degraded by enzymes in the blood. GAD546-554 is a dominant epitope recognized by autoreactive T cells in the nonobese diabetic (NOD) mouse model that can cause destruction of beta cells. Alanine substitution at the eighth position of GAD546-554 peptide (APL9) induced tolerance in a GAD546-554 specific cytotoxic T lymphocyte clone. To improve the antigen presentation and endosomal escape of APL9, we developed a bioconjugate platform that consists of a liposome containing a bioconjugate of APL9 and toll-like receptor 2 ligand Pam₃CysSK₄ as well as an antibody against macrophage protein F4/80. APL9 bioconjugate liposome with F4/80 antibody was able to induce tolerance in a GAD 546-554 specific clone. Diabetic NOD splenocytes pretreated with APL9 bioconjugate were also not able to transfer diabetes into prediabetic NOD recipient mice. This work is beneficial to prevent T1D as an immunotherapy strategy to render autoreactive immune cells more tolerant of beta cells.

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.

Therapies to Suppress β Cell Autoimmunity in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is generally considered to be T cell-driven. Accordingly, most strategies of immunotherapy for T1D prevention and treatment in the clinic have targeted the T cell compartment. To date, however, immunotherapy has had only limited clinical success. Although certain immunotherapies have promoted a protective effect, efficacy is often short-term and acquired immunity may be impacted. This has led to the consideration of combining different approaches with the goal of achieving a synergistic therapeutic response. In this review, we will discuss the status of various T1D therapeutic strategies tested in the clinic, as well as possible combinatorial approaches to restore β cell tolerance.

An altered CD8+ T cell epitope of insulin prevents type 1 diabetes in humanized NOD mice

Autoreactive CD8⁺ T cells, which play an indispensable role in β cell destruction, represent an emerging target for the prevention of type 1 diabetes (T1D). Altered peptide ligands (APLs) can efficiently induce antigen-specific T cells anergy, apoptosis or shifts in the immune response. Here, we found that HLA-A*0201-restricted CD8⁺ T cell responses against a primary β-cell autoantigen insulin epitope InsB1_5-14 were present in both NOD.β2m^null.HHD NOD mice and T1D patients. We generated several APL candidates for InsB1_5-14 by residue substitution at the p6 position. Only H6F exhibited an inhibitory effect on mInsB1_5-14-specific CD8⁺ T cell responses in vitro. H6F treatment significantly reduced the T1D incidence, which was accompanied by diminished autoreactive CD8⁺ T cell responses to mInsB1_5-14, inhibited infiltration of CD8⁺ and CD4⁺ T cells in the pancreas and reduced pro-inflammatory cytokine production in pancreatic and splenic T cells in NOD.β2m^null.HHD mice. Mechanistically, H6F treatment significantly augmented a tiny portion of CD8⁺CD25⁺Foxp3⁺ T cells in the spleen and especially in the pancreas. This subset exhibited typical Treg phenotypes and required peptide-specific restimulation to exert immunosuppressive activity. Therefore, this APL H6F may be a promising candidate with potential clinical application value for antigen-specific prevention of T1D.

Recent advances in the development of vaccines for chronic inflammatory autoimmune diseases

Chronic inflammatory autoimmune diseases leading to target tissue destruction and disability are not only causing increase in patients' suffering but also contribute to huge economic burden for the society. General increase in life expectancy and high prevalence of these diseases both in elderly and younger population emphasize the importance of developing safe and effective vaccines. In this review, at first the possible mechanisms and risk factors associated with chronic inflammatory autoimmune diseases, such as rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE) and type 1 diabetes (T1D) are discussed. Current advances in the development of vaccines for such autoimmune diseases, particularly those based on DNA, altered peptide ligands and peptide loaded MHC II complexes are discussed in detail. Finally, strategies for improving the efficacy of potential vaccines are explored.

Analysis of antigen specific T cells in diabetes - Lessons from pre-clinical studies and early clinical trials

Antigen-specific immune tolerance promises to provide safe and effective therapies to prevent type 1 diabetes (T1D). Antigen-specific therapy requires two components: well-defined, clinically relevant autoantigens; and safe approaches to inducing tolerance in T cells specific for these antigens. Proinsulin is a critical autoantigen in both NOD mice, based on knockout mouse studies and induction of immune tolerance to proinsulin preventing disease whereas most antigens cannot, and also in human T1D based on proinsulin-specific T cells being found in the islets of affected individuals and the early appearance of insulin autoantibodies. Effective antigen-specific therapies that prevent T1D in humans have not yet been developed although doubt remains about the best molecular form of the antigen, the dose and the route of administration. Preclinical studies suggest that antigen specific therapy is most useful when administered before onset of autoimmunity but this time-window has not been tested in humans until the recent "pre-point" study. There may be a 'window of opportunity' during the neonatal period when 'vaccine' like administration of proinsulin for a short period may be sufficient to prevent diabetes. After the onset of autoimmunity, naive antigen-specific T cells have differentiated into antigen-experienced memory cells and the immune responses have spread to multiple antigens. Induction of tolerance at this stage becomes more difficult although recent studies have suggested generation of antigen-specific TR1 cells can inhibit memory T cells. Preclinical studies are required to identify additional 'help' that is required to induce tolerance to memory T cells and develop protocols for effective therapy in individuals with established autoimmunity.

Distortion of the Major Histocompatibility Complex Class I Binding Groove to Accommodate an Insulin-derived 10-Mer Peptide

The non-obese diabetic mouse model of type 1 diabetes continues to be an important tool for delineating the role of T-cell-mediated destruction of pancreatic β-cells. However, little is known about the molecular mechanisms that enable this disease pathway. We show that insulin reactivity by a CD8⁺ T-cell clone, known to induce type 1 diabetes, is characterized by weak T-cell antigen receptor binding to a relatively unstable peptide-MHC. The structure of the native 9- and 10-mer insulin epitopes demonstrated that peptide residues 7 and 8 form a prominent solvent-exposed bulge that could potentially be the main focus of T-cell receptor binding. The C terminus of the peptide governed peptide-MHC stability. Unexpectedly, we further demonstrate a novel mode of flexible peptide presentation in which the MHC peptide-binding groove is able to “open the back door” to accommodate extra C-terminal peptide residues.

Taming the TCR: antigen-specific immunotherapeutic agents for autoimmune diseases

Current treatments for autoimmune diseases are typically non-specific anti-inflammatory agents that affect not only the autoreactive cells but also the parts of the immune system that are required to maintain health. There is a need for the development of antigen-specific therapeutic agents that can effectively prevent the autoimmune attack while leaving the rest of the immune system functioning as normal. The simplest way to achieve this is using the autoantigen itself as a tolerizing agent; however, there is some risk involved with administering a potentially pathogenic antigen. In this review, we focus instead on the development and use of modified T cell receptor (TCR) ligands, in which the peptide ligand is modified to change the response by the T cell from a disease inducing to a protective response, and still retain the antigen-specificity necessary to target the autoreactive T cells. We review the use of modified TCR ligands as therapeutic agents in animal models of autoimmunity and in human autoimmune disease, and finally consider how they need to be improved in order to use them effectively in patients with autoimmune disease.

Treg vaccination in autoimmune type 1 diabetes

Foxp3⁺ regulatory T (Treg) cells are critical contributors to the establishment and maintenance of immunological self-tolerance. Autoimmune type 1 diabetes (T1D) is characterized by the loss of self-tolerance to the insulin-producing β cells in the pancreas and the destruction of β cells, resulting in the development of chronic hyperglycemia at diagnosis. The application of strong agonistic T-cell receptor ligands provided under subimmunogenic conditions functions as a critical means for the efficient de novo conversion of naive CD4⁺ T cells into Foxp3⁺ Treg cells. The specific induction of Treg cells upon supply of strong-agonistic variants of certain self-antigens could therefore function as a critical instrument in order to achieve safe and specific prevention of autoimmunity such as T1D via the restoration of self-tolerance. Such immunotherapeutic strategies are being developed, and in the case of T1D aim to restrict autoimmunity and β-cell destruction. In this review, we discuss the requirements and opportunities for Treg-based tolerance approaches with the goal of interfering with autoimmune T1D.

Antigen-specific therapy against type 1 diabetes: mechanisms and perspectives

Type 1 diabetes (T1D) is an immune-mediated disease that occurs when the insulin-producing β‑cells of the pancreatic islets are destroyed by an inflammatory process perpetuated by cells of the immune system. The logical approach to suppress T1D is to inactivate or eliminate the lymphocytes responsible for inducing inflammation and targeting the β‑cells. Antigen-specific approaches have been devised and were able to target inflammatory lymphocytes and induce apoptosis or block trafficking to pancreatic islets. Lack of costimulation, expansion of Tregs and bystander suppression are likely mechanisms by which antigen-specific treatments modulate pathogenic T cells. This strategy, however, while prevents the onset of T1D, could not overcome overt T1D, perhaps because of collateral damage to the islet vascular network. Recent developments indicate that donor endothelial stem cell precursors can repair the islets' vascular niche and assist antigen-specific therapy against overt T1D.

γδ T cells recognize the insulin B:9-23 peptide antigen when it is dimerized through thiol oxidation

The insulin peptide B:9-23 is a natural antigen in the non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D). In addition to αβ T cells and B cells, γδ T cells recognize the peptide and infiltrate the pancreatic islets where the peptide is produced within β cells. The peptide contains a cysteine in position 19 (Cys19), which is required for the γδ but not the αβ T cell response, and a tyrosine in position 16 (Tyr16), which is required for both. A peptide-specific mAb, tested along with the T cells, required neither of the two amino acids to bind the B:9-23 peptide. We found that γδ T cells require Cys19 because they recognize the peptide antigen in an oxidized state, in which the Cys19 thiols of two peptide molecules form a disulfide bond, creating a soluble homo-dimer. In contrast, αβ T cells recognize the peptide antigen as a reduced monomer, in complex with the MHCII molecule I-A(g7). Unlike the unstructured monomeric B:9-23 peptide, the γδ-stimulatory homo-dimer adopts a distinct secondary structure in solution, which differs from the secondary structure of the corresponding portion of the native insulin molecule. Tyr16 is required for this adopted structure of the dimerized insulin peptide as well as for the γδ response to it. This observation is consistent with the notion that γδ T cell recognition depends on the secondary structure of the dimerized insulin B:9-23 antigen.

MAS-1 adjuvant immunotherapy generates robust Th2 type and regulatory immune responses providing long-term protection from diabetes in late-stage pre-diabetic NOD mice

MAS-1, a nanoparticular, emulsion-based adjuvant, was evaluated for its ability to promote Th2 and regulatory immune responses and prevent type 1 diabetes progression when given alone or as antigen-specific immunotherapy (ASI) using insulin B chain (IBC; MER3101) and its analog B:9-23(19Ala) (MER3102). MAS-1 formulations were administered to NOD mice at age 9 and 13 weeks and followed through 52 weeks. MER3101 and MER3102 provided long-term protection with 60% and 73% of mice remaining diabetes-free at week 35, and 60% and 47% at week 52. MAS-1 adjuvant emulsion by itself also provided protection with 60% and 40% of mice diabetes-free at 35 and 52 weeks, respectively. Higher levels of interleukin (IL)-10 and IL-2 positive T cells were detected among splenocytes by week 15 in MER3101 and MER3102 immunized mice, whereas MAS-1 alone induced higher levels of IL-10-positive T cells. Diabetes-free 52-week-old mice expressed significant levels of antigen-specific IL-10-positive type 1 regulatory T cells and FoxP3-positive T cells when stimulated ex vivo with IBC. Antibodies targeting IBC and B:9-23(19Ala) induced by MER3101 and MER3102 were overwhelmingly Th2 type IgG1 and IgG2b isotypes. Splenocyte cultures from 52 week diabetes-free, MER3101-treated mice secreted significantly increased levels of IL-4 and IL-5 Th2 cytokines. Based on these pre-clinical results and its clinical safety profile, MAS-1 has the requisite qualities to be considered for use in prophylactic or early stage disease settings to augment ASI to prevent disease progression in type 1 diabetes.

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.

Mimicry epitope from Ehrlichia canis for interphotoreceptor retinoid-binding protein 201-216 prevents autoimmune uveoretinitis by acting as altered peptide ligand

We report here identification of novel mimicry epitopes for interphotoreceptor retinoid-binding protein (IRBP) 201-216, a candidate ocular antigen that causes experimental autoimmune uveoretinitis (EAU) in A/J mice. One mimicry epitope from Ehrlichia canis (EHC), designated EHC 44-59, induced cross-reactive T cells for IRBP 201-216 capable of producing T helper (Th)1 and Th17 cytokines, but failed to induce EAU in A/J mice. In addition, animals first primed with suboptimal doses of IRBP 201-216 and subsequently immunized with EHC 44-59 did not develop EAU; rather, the mimicry epitope prevented the disease induced by IRBP 201-216. However, alteration in the composition of EHC 44-59 by substituting alanine with valine at position 49, similar to the composition of IRBP 201-216, enabled the mimicry epitope to acquire uveitogenicity. The data provide new insights as to how microbes containing mimicry sequences for retinal antigens can prevent ocular inflammation by acting as naturally occurring altered peptide ligands.

Changing faces, unmasking the beta-cell: post-translational modification of antigens in type 1 diabetes

PURPOSE OF REVIEW

Description on post-translational modification of islet-autoantigens in type 1 diabetes (T1D).

RECENT FINDINGS

T1D is an autoimmune disease characterized by progressive destruction of the insulin-producing beta-cells. It is a complex disease process that results from the loss of tolerance to beta-cell autoantigens. This loss of tolerance can be caused by modification of beta-cell autoantigens, generating 'neo-autoantigens', and inducing T-cell responses. Post-translational modifications (PTMs) within the endoplasmic reticulum of stressed beta-cells might impact on the autoantigen T-cell epitope repertoire and on T1D pathogenesis progression. This review summarizes the processes involved in beta-cell stress and PTM of beta-cell autoantigens in T1D.

SUMMARY

PTMs of beta-cell autoantigens provide a novel hypothesis to understand how autoreactive T-cells can escape immune tolerance and cause destruction of beta-cells ('beta-cell homicide'). Additionally, aberrant proteins produced by stressed beta-cells can cause their own destruction ('beta-cell suicide'). Upon endoplasmic reticulum-stress, proteins are misfolded or modified changing the protein structure. In T1D, this may generate new beta-cell (neo)autoantigens. PTM of islet-autoantigens provides a mechanism by which pathogenic T-cells can escape thymic deletion. This amplifies the immune response when encountering a modified beta-cell neo-autoantigen bound to T1D predisposing human leucocyte antigen molecules in the periphery.

Antigen-specific therapeutic approaches in Type 1 diabetes

Development of strategies capable of specifically curbing pathogenic autoimmune responses in a disease- and organ-specific manner without impairing foreign or tumor antigen-specific immune responses represents a long sought-after goal in autoimmune disease research. Unfortunately, our current understanding of the intricate details of the different autoimmune diseases that affect mankind, including type 1 diabetes, is rudimentary. As a result, progress in the development of the so-called "antigen-specific" therapies for autoimmunity has been slow and fraught with limitations that interfere with bench-to-bedside translation. Absent or incomplete understanding of mechanisms of action and lack of adequate immunological biomarkers, for example, preclude the rational design of effective drug development programs. Here, we provide an overview of antigen-specific approaches that have been tested in preclinical models of T1D and, in some cases, human subjects. The evidence suggests that effective translation of these approaches through clinical trials and into patients will continue to meet with failure unless detailed mechanisms of action at the level of the organism are defined.

Insulin and type 1 diabetes: immune connections

Insulin is the hormone produced by pancreatic β-cells, with a central role in carbohydrate and fat metabolism. Together with its precursors preproinsulin and proinsulin, insulin is also a key target antigen (Ag) of the autoimmune islet destruction leading to type 1 diabetes. Being recognized by both autoantibodies (aAbs) and autoreactive T cells, insulin plays a triggering role, at least in rodent models, in diabetes pathogenesis. It is expressed not only by β-cells but also in the thymus, where it plays a major role in central tolerance mechanisms. We will summarize current knowledge concerning insulin, its role in β-cell autoimmunity as initial target Ag, its recognition by aAbs and autoreactive T cells, and the detection of these immune responses to provide biomarkers for clinical trials employing insulin as an immune modulatory agent.

Treg vaccination with a strong-agonistic insulin mimetope

Foxp3(+) regulatory T (Treg) cells serve as a vital mechanism of negative regulation to maintain immunological self-tolerance thereby suppressing immune-mediated inflammation. The identification of the transcription factor Foxp3 as the specification factor for the Treg cell lineage facilitated our understanding in the biology of Treg generation and function. In the past, we carefully studied the extrathymic conversion of naive CD4(+) T cells into Foxp3(+) expressing Treg cells and found that this process is most efficient upon subimmunogenic supply of strong-agonistic T cell receptor (TCR) ligands avoiding activation of antigen-presenting and T cells. In contrast, weak-agonistic antigens fail to efficiently induce stable Foxp3(+) Treg cells irrespective of the applied dose. Here, we discuss the specific requirements for the establishment of Treg vaccination protocols to interfere with autoimmunity such as Type 1 diabetes.

Superior molecularly altered influenza virus hemagglutinin peptide 308-317 inhibits collagen-induced arthritis by inducing CD4+ Treg cell expansion

OBJECTIVE

To investigate the inhibitory effect and possible mechanism of a novel influenza virus hemagglutinin 308-317 peptide (altered HA308-317 peptide) in collagen-induced arthritis (CIA).

METHODS

CIA was induced in DBA/1 mice by immunization with type II collagen (CII). Altered HA308-317 peptide, wild HA308-317 peptide, wild CII263-272 peptide, and irrelevant peptide were administered intranasally beginning at arthritis onset. Clinical and histologic scores were assessed, and cytokine levels were determined in the serum or in supernatants from splenocytes. Characteristics of T cell subsets in response to different peptides were analyzed both in vivo and in vitro.

RESULTS

Intranasal administration of wild CII263-272 peptide, wild HA308-317 peptide, or altered HA308-317 peptide could significantly ameliorate CIA, but altered HA308-317 peptide showed greater therapeutic effects than wild CII263-272 peptide and wild HA308-317 peptide. The effect of altered HA308-317 peptide was associated with a substantial decrease in production of interleukin-17 (IL-17) and interferon-γ (IFNγ) and with a marked increase in production of IL-10 and transforming growth factor β, both in serum and in supernatants from splenocytes treated with altered HA308-317 peptide. Both the number and function of CD4+ Treg cells were significantly up-regulated by altered HA308-317 peptide, with a decreased induction of Th1 cells (CD4+IFNγ+) and Th17 cells (CD4+IL-17+). Adoptive transfer of CD4+CD25+ T cells from altered HA308-317 peptide-treated mice resulted in greater suppressive capacity in ameliorating CIA severity than did adoptive transfer of CD4+CD25+ T cells from wild HA308-317 peptide-treated, wild CII263-272 peptide-treated, or irrelevant peptide-treated mice.

CONCLUSION

Intranasal administration of altered HA308-317 peptide potently suppressed the severity of CIA by increasing the number and function of CD4+ Treg cells, suggesting that altered HA308-317 peptide might be a promising candidate for treatment of rheumatoid arthritis.

Clinical immunologic interventions for the treatment of type 1 diabetes

Type 1 diabetes is an autoimmune disease, hence the rationale for immunotherapy to halt disease progression. Based on knowledge gained from other autoimmune diseases and from transplantation, the first immunointervention trials used immunosuppressive drugs, e.g., cyclosporin, in patients with recently diagnosed type 1 diabetes. Although remarkable, the effect vanished following drug withdrawal. Efforts were then devoted to devise strategies to induce/restore self-tolerance and avoid chronic immunosuppression. Various approaches were identified from work in spontaneous models of autoimmune diabetes, including the use of β-cell autoantigens and monoclonal antibodies directed at relevant immune molecules such as costimulatory ligands, T-cell receptor molecules such as CD3, and B cells. Phase II and phase III trials were launched, results of which are now available. Although the endeavor is challenging, the experience gained indicates that immunotherapy appears as the real hope of inducing long-term remission of the disease provided the treatment is started early and that protocols are adapted based on lessons from the past.

Therapeutic effect of an altered peptide ligand derived from heat-shock protein 60 by suppressing of inflammatory cytokines secretion in two animal models of rheumatoid arthritis

Rheumatoid arthritis is a systemic autoimmune disease mediated by T cells. Productive engagement of T cell receptors by major histocompatibility complex-peptide leads to proliferation, differentiation and the definition of effector functions. Altered peptide ligands (APL) generated by amino acid substitutions in the antigenic peptide have diverse effects on T cell response. We predicted a novel T cell epitope from human heat-shock protein 60, an autoantigen involved in the pathogenesis of rheumatoid arthritis. Three APLs were designed from this epitope and it was demonstrated that these peptides induce the activation of T cells through their ability to modify cell cycle phase's distribution of CD4+T cells from RA patients. Also, IL-17, TNF-α and IL-10 levels were determined in PBMC from these patients. Unlike the wild-type peptide and the other two APLs, APL2 increased the IL-10 level and suppressed IL-17 secretion in these assays. Therapeutic effect of this APL in adjuvant arthritis (AA) and collagen-induced arthritis (CIA) models was also evaluated. Clinical score, histopathology, inflammatory and regulatory cytokine concentration were monitored in the animals. APL2 efficiently inhibited the progression of AA and CIA with a significant reduction of the clinical and histopathologic score. Therapeutic effect of APL2 on CIA was similar to that obtained with MTX; the standard treatment for RA. This effect was associated with a decrease of TNF-α and IL-17 levels. These results suggest that the therapeutic effect of APL2 is mediated in part by down-regulation of inflammatory cytokines and support the potential use of APL2 as a therapeutic drug in RA patients.

Peptide-based approaches to treat lupus and other autoimmune diseases

After a long period where the potential of therapeutic peptides was let into oblivion and even dismissed, there is a revival of interest in peptides as potential drug candidates. Novel strategies for limiting metabolism and improve their bioavailability, and alternative routes of administration have emerged. This resulted in a large number of peptide-based drugs that are now being marketed in different indications. Regarding autoimmunity, successful data have been reported in numerous mouse models of autoimmune inflammation, yet relatively few clinical trials based on synthetic peptides are currently underway. This review reports on peptides that show much promises in appropriate mouse models of autoimmunity and describes in more detail clinical trials based on peptides for treating autoimmune patients. A particular emphasis is given to the 21-mer peptide P140/Lupuzor that has completed successfully phase I, phase IIa and phase IIb clinical trials for systemic lupus erythematosus.

Immunology of Diabetes Society T-Cell Workshop: HLA class II tetramer-directed epitope validation initiative

BACKGROUND

Islet-antigen-specific CD4+ T cells are known to promote auto-immune destruction in T1D. Measuring T-cell number and function provides an important biomarker. In response to this need, we evaluated responses to proinsulin and GAD epitopes in a multicentre study.

METHODS

A tetramer-based assay was used in five participating centres to measure T-cell reactivities to DR0401-restricted epitopes. Three participating centres concurrently performed ELISPOT or immunoblot assays. Each centre used blind-coded, centrally distributed peptide and tetramer reagents.

RESULTS

All participating centres detected responses to auto-antigens and the positive control antigen, and in some cases cloned the corresponding T cells. However, response rates varied among centres. In total, 74% of patients were positive for at least one islet epitope. The most commonly recognized epitope was GAD270-285. Only a minority of the patients tested by tetramer and ELISPOT were concordant for both assays.

CONCLUSIONS

This study successfully detected GAD and proinsulin responses using centrally distributed blind-coded reagents. Centres with little previous experience using class II tetramer reagents implemented the assay. The variability in response rates observed for different centres suggests technical difficulties and/or heterogeneity within the local patient populations tested. Dual analysis by tetramer and ELISPOT or immunoblot assays was frequently discordant, suggesting that these assays detect distinct cell populations. Future efforts should investigate shared blood samples to evaluate assay reproducibility and longitudinal samples to identify changes in T-cell phenotype that correlate with changes in disease course.

Insulin as a key autoantigen in the development of type 1 diabetes

Type 1 diabetes is a T-cell-mediated autoimmune disease against pancreatic beta cells. T cells target various antigens such as insulin, chromogranin A, glutamic acid decarboxylase and islet-specific glucose-6-phosphatase catalytic subunit-related protein. Elimination of insulin dramatically prevents diabetes in the non-obese diabetic (NOD) mouse model and response to insulin occurs prior to that to other antigens. These findings suggest that insulin is a target antigen at the early stage of the disease and is likely to be essential to cause anti-islet autoimmunity in NOD mice. In this review, we discuss whether insulin is truly essential and is only the single essential autoantigen for NOD mice and potentially for man. Although the ultimate principle is still being addressed, it is certain that T-cell response to insulin is a major check point to develop type 1 diabetes in NOD mice. Given multiple similarities between diabetes of NOD mice and man, targeting insulin and insulin-reactive T cells may provide opportunities to develop robust immunotherapies.

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.

DiaPep277 peptide therapy in the context of other immune intervention trials in type 1 diabetes

INTRODUCTION

Type 1 diabetes (T1D) is characterized by the autoimmune destruction of pancreatic β-cells. The aim of immune intervention is to arrest this autoimmune attack. DiaPep277, a major T-cell epitope of heat shock protein 60 (hsp60), has been shown to be effective in the modulation of the immune response in recent onset T1D and is the main focus of this review in the context of other ongoing trials using different approaches.

AREAS COVERED

The authors performed a literature search of Pubmed listed publications (from the last 10 years) and a website search of the company licensing DiaPep277. DiaPep277 has been investigated in Phase I - III trials in humans. Phase II trials showed a significant preservation of β-cell function in adult T1D patients (but not children) with an absence of adverse effects and not accompanied by lower glycosylated haemoglobin (HbA1c) levels or reduced daily insulin requirement compared with placebo-treated patients.

EXPERT OPINION

Administration of DiaPep277 is safe and represents a promising therapeutic strategy in patients with recent-onset T1D. The results of two large Phase III trials will tell us whether this therapy may change our current approach to treating T1D patients at diagnosis.

Extra-thymically induced regulatory T cells: do they have potential in disease prevention?

Fopx3(+) Treg safeguard against autoimmune diseases and immune pathology. The extrathymic conversion of naïve T cells into Foxp3(+) regulatory T cells can be achieved in vivo by the delivery of strong-agonist ligands under subimmunogenic conditions. Tolerogenic vaccination with strong-agonist mimetopes of self-antigen to promote self-antigen specific tolerance may represent the most specific and safest means of preventing autoimmunity. This review discusses the requirements for induction of dominant tolerance exerted by Foxp3(+) Tregs in autoimmunity with special emphasis on their impact to interfere with T1D. The future goals are the understanding of self-non-self discrimination at the cellular and molecular level, which should then enable investigators to develop clinical vaccination protocols that specifically interfere with unwanted immune responses.

Prevention of type 1 diabetes in mice by tolerogenic vaccination with a strong agonist insulin mimetope

Subimmunogenic vaccination with an agonist mimetope of insulin converts naive T cells into regulatory T cells and prevents type 1 diabetes in NOD mice.

Type 1 diabetes (T1D) results from the destruction of insulin-secreting pancreatic β cells by autoreactive T cells. Insulin is an essential target of the autoimmune attack. Insulin epitopes recognized by diabetogenic T cell clones bind poorly to the class II I-A^g7 molecules of nonobese diabetic (NOD) mice, which results in weak agonistic activity of the peptide MHC complex. Here, we describe a strongly agonistic insulin mimetope that effectively converts naive T cells into Foxp3⁺ regulatory T cells in vivo, thereby completely preventing T1D in NOD mice. In contrast, natural insulin epitopes are ineffective. Subimmunogenic vaccination with strongly agonistic insulin mimetopes might represent a novel strategy to prevent T1D in humans at risk for the disease.

Antigen-based immune therapeutics for type 1 diabetes: magic bullets or ordinary blanks?

The ideal drug of modern medicine is the one that achieves its therapeutic target with minimal adverse effects. Immune therapy of Type 1 diabetes (T1D) is no exception, and knowledge of the antigens targeted by pathogenic T cells offers a unique opportunity towards this goal. Different antigen formulations are being considered, such as proteins or peptides, either in their native form or modified ad hoc, DNA plasmids, and cell-based agents. Translation from mouse to human should take into account important differences, particularly in the time scale of autoimmune progression, and intervention. Critical parameters such as administration route, dosing and interval remain largely empirical and need to be further dissected. T1D staging through immune surrogate markers before and after treatment will be key in understanding therapeutic actions and to finally turn ordinary blanks into magic bullets.

An altered peptide ligand corresponding to a novel epitope from heat-shock protein 60 induces regulatory T cells and suppresses pathogenic response in an animal model of adjuvant-induced arthritis

Induction of immune tolerance as therapeutic approach for autoimmune diseases constitutes a current research focal point. In this sense, we aimed to evaluate an altered peptide ligand (APL) for induction of peripheral tolerance in patients with rheumatoid arthritis (RA). A novel T-cell epitope from human heat-shock protein 60 (Hsp60), an autoantigen involved in the pathogenesis of RA, was identified by bioinformatics tools and an APL was design starting from this epitope. We investigated the ability of this APL for inducing regulatory T cells (Treg cells) in mice and evaluated the therapeutic effect of this peptide in an adjuvant-induced arthritis (AA) rat model. Clinical score, TNFα levels and histopathology were monitored, as well as the capacity of this APL for inducing Treg cells. Finally, the potentialities of the APL for inducing Treg cells were evaluated in ex vivo assays using mononuclear cells isolated from peripheral blood (PBMC). The APL induced an increase of the proportions of Treg cells in the draining lymph nodes of the injected site in mice. The APL efficiently inhibited the course of AA, with significant reduction of the clinical and histopathology score. This effect was associated with an increase of the proportions of Treg cells and a decrease of TNFα levels in spleen. Finally, stimulation of PBMCs from RA patients by the APL increases the proportions of the CD4(+)CD25(high)FoxP3(+) Treg cells. These results indicate a therapeutic potentiality of APL and support further investigation of this candidate drug for treatment of RA.

Extrathymic generation of regulatory T cells--chances and challenges for prevention of autoimmune disease

Fopx3(+) expressing regulatory T cells (Tregs) function as an indispensable cellular constituent of the immune system by establishing and maintaining immunological self-tolerance. T cell receptor (TCR) ligands of high agonist activity, when applied in vivo under subimmunogenic conditions, convert naive but not activated T cells into stable Tregs expressing Foxp3. Tolerogenic vaccination with strong-agonist mimetopes of self-antigens may function as a safe and highly specific instrument in the prevention of autoimmune disease by promoting self-antigen-specific tolerance. In this review, we address the requirements for generation of dominant tolerance exerted by Foxp3(+) Tregs in autoimmune disease with special focus on type 1 diabetes (T1D). Further understanding of differentiation of T cells into Tregs at the cellular and molecular level will facilitate development of additional tolerogenic vaccination strategies that can be used in prevention as well as therapeutically to combat unwanted immunity.

Virtual optimization of nasal insulin therapy predicts immunization frequency to be crucial for diabetes protection

OBJECTIVE

Development of antigen-specific strategies to treat or prevent type 1 diabetes has been slow and difficult because of the lack of experimental tools and defined biomarkers that account for the underlying therapeutic mechanisms.

RESEARCH DESIGN AND METHODS

The type 1 diabetes PhysioLab platform, a large-scale mathematical model of disease pathogenesis in the nonobese diabetic (NOD) mouse, was used to investigate the possible mechanisms underlying the efficacy of nasal insulin B:9-23 peptide therapy. The experimental aim was to evaluate the impact of dose, frequency of administration, and age at treatment on Treg induction and optimal therapeutic outcome.

RESULTS

In virtual NOD mice, treatment efficacy was predicted to depend primarily on the immunization frequency and stage of the disease and to a lesser extent on the dose. Whereas low-frequency immunization protected from diabetes atrributed to Treg and interleukin (IL)-10 induction in the pancreas 1-2 weeks after treatment, high-frequency immunization failed. These predictions were confirmed with wet-lab approaches, where only low-frequency immunization started at an early disease stage in the NOD mouse resulted in significant protection from diabetes by inducing IL-10 and Treg.

CONCLUSIONS

Here, the advantage of applying computer modeling in optimizing the therapeutic efficacy of nasal insulin immunotherapy was confirmed. In silico modeling was able to streamline the experimental design and to identify the particular time frame at which biomarkers associated with protection in live NODs were induced. These results support the development and application of humanized platforms for the design of clinical trials (i.e., for the ongoing nasal insulin prevention studies).

T-cell autoantigens in the non-obese diabetic mouse model of autoimmune diabetes

The non-obese diabetic (NOD) mouse model of autoimmune (type 1) diabetes has contributed greatly to our understanding of disease pathogenesis and has facilitated the development and testing of therapeutic strategies to combat the disease. Although the model is a valuable immunological tool in its own right, it reaches its fullest potential in areas where its findings translate to the human disease. Perhaps the foremost example of this is the field of T-cell antigen discovery, from which diverse benefits can be derived, including the development of antigen-specific disease interventions. The majority of NOD T-cell antigens are also targets of T-cell autoimmunity in patients with type 1 diabetes, and several of these are currently being evaluated in clinical trials. Here we review the journeys of these antigens from bench to bedside. We also discuss several recently identified NOD T-cell autoantigens whose translational potential warrants further investigation.

[Antitumor effects of raddeanin A on S180, H22 and U14 cell xenografts in mice]. Curr Opin Immunol. 2008;27:910-913. [PMID: 18799026 DOI: 10.1016/j.coi.2007.11.005]

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.

Autoantigen-specific regulatory T cells induced in patients with type 1 diabetes mellitus by insulin B-chain immunotherapy. J Autoimmun. 2010;34:408-415. [PMID: 19931408 DOI: 10.1016/j.jaut.2009.10.005]

There is a growing body of evidence to suggest that the autoimmunity observed in type 1 diabetes mellitus (T1DM) is the result of an imbalance between autoaggressive and regulatory cell subsets. Therapeutics that supplement or enhance the existing regulatory subset are therefore a much sought after goal in this indication. Here, we report the results of a double blind, placebo controlled, phase I clinical trial of a novel antigen-specific therapeutic in 12 subjects with recently diagnosed T1DM. Our primary objective was to test its safety. The study drug, human insulin B-chain in incomplete Freund's adjuvant (IFA) was administered as a single intramuscular injection, with subjects followed for 2 years. All subjects completed therapy and all follow-up visits. The therapy was generally safe and well-tolerated. Mixed meal stimulated C-peptide responses, measured every 6 months, showed no statistical differences between arms. All patients vaccinated with the autoantigen, but none who received placebo, developed robust insulin-specific humoral and T cell responses. Up to two years following the single injection, in peripheral blood from subjects in the experimental arm, but not the control arm, insulin B-chain-specific CD4+ T cells could be isolated and cloned that showed phenotypic and functional characteristics of regulatory T cells. The induction of a lasting, robust immune response generating autoantigen-specific regulatory T cells provides strong justification for further testing of this therapy in type 1 diabetes. (clinicaltrials.gov identifier NCT00057499).

Autoantibodies against aminoacyl-tRNA synthetase: novel diagnostic marker for type 1 diabetes mellitus

OBJECTIVES

To investigate whether or not antiaminoacyl-tRNA synthetase (aaRS) autoantibodies could be detected in patients with type 1 diabetes mellitus (DM) and be used as a diagnostic marker for type 1 DM, autoantibodies against aaRSs were measured in the plasma of normal subjects, patients with type 1 DM and patients with type 2 DM.

METHODS

An enzyme-linked immunosorbent assay was performed to detect anti-aaRS autoantibodies in the plasma of normal subjects, and patients with type 1 DM, and patients with type 2 DM.

RESULTS

From the 65 (normal), 58 (type 1 DM) and 57 (type 2 DM) subjects, anti-aaRS autoantibodies were found in 37.9% of patients with type 1 DM compared with 1.54% of the non-diabetic controls, and 5.26% of the patients with type 2 DM (p <0.0001). In addition, anti-aaRS autoantibodies were identified in 30% of patients with type 1 DM without classical type 1 DM autoantibodies.

CONCLUSION

Anti-aaRS autoantibodies were identified in 37.9% of patients with type 1 DM. The results of this study demonstrate for the first time that autoantibodies against aaRSs are specifically associated with type 1 DM.

The anti-insulin trimolecular complex in type 1 diabetes

PURPOSE OF REVIEW

Description of the immunologic components needed for autoimmune diabetes.

RECENT FINDINGS

The major histocompatability complex (MHC) class II molecules are the primary susceptibility genes for many autoimmune diseases, including type 1 diabetes. Understanding of the structural interaction between MHC molecules, antigenic peptides, and T-cell receptors (the three components of the trimolecular complex) has increased greatly over the past several years. The components of the anti-insulin trimolecular complex and findings that insulin is a key autoantigen in type 1 diabetes are reviewed.

SUMMARY

The anti-insulin trimolecular complex is well defined in the nonobese diabetic mouse model. Insulin and specifically, the amino acid sequence 9 to 23 of the insulin B chain, represents a primary antigenic target for islet autoimmunity in the nonobese diabetic mouse model of type 1 diabetes with a specific mutation of this peptide preventing all diabetes. Initial studies suggest the human homologs of the anti-insulin trimolecular complex may be relevant in human disease.

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.

Processing and presentation of (pro)-insulin in the MHC class II pathway: the generation of antigen-based immunomodulators in the context of type 1 diabetes mellitus

Both CD4(+) and CD8(+) T lymphocytes play a crucial role in the autoimmune process leading to T1D. Dendritic cells take up foreign antigens and autoantigens; within their endocytic compartments, proteases degrade exogenous antigens for subsequent presentation to CD4(+) T cells via MHC class II molecules. A detailed understanding of autoantigen processing and the identification of autoantigenic T cell epitopes are crucial for the development of antigen-based specific immunomodulators. APL are peptide analogues of auto-immunodominant T cell epitopes that bind to MHC class II molecules and can mediate T cell activation. However, APL can be rapidly degraded by proteases occurring in the extracellular space and inside cells, substantially weakening their efficiency. By contrast, protease-resistant APL function as specific immunomodulators and can be used at low doses to examine the functional plasticity of T cells and to potentially interfere with autoimmune responses. Here, we review the latest achievements in (pro)-insulin processing in the MHC class II pathway and the generation of APL to mitigate autoreactive T cells and to activate Treg cells.

Nucleic acid-associated autoantigens: pathogenic involvement and therapeutic potential

Autoimmunity to ubiquitously expressed macromolecular nucleic acid-protein complexes such as the nucleosome or the spliceosome is a characteristic feature of systemic autoimmune diseases. Disease-specificity and/or association with clinical features of some of these autoimmune responses suggest pathogenic involvement which, however, has been proven in only a few cases so far. Although the mechanisms leading to autoimmunity against nucleic acid-containing complexes are still far from being fully understood, there is increasing experimental evidence that the nucleic acid component may act as a co-stimulator or adjuvans via activation of nucleic acid-binding receptor systems such as Toll-like receptors in antigen-presenting cells. Dysregulated apoptosis and inappropriate stimulation of nucleic acid-sensing receptors may lead to loss of tolerance against the protein components of such complexes, activation of autoreactive T cells and formation of autoantibodies. This has been demonstrated to occur in systemic lupus erythematosus and seems to represent a general mechanism that may be crucial for the development of systemic autoimmune diseases. This review provides a comprehensive overview of the most thoroughly-characterized nucleic acid-associated autoantigens, describing their structure and biological function, as well as the nature and pathogenic importance of the reactivities directed against them. Furthermore, recent advances in immunotherapy such as antigen-specific approaches targeted at nucleic acid-binding antigens are discussed.

No effect of the altered peptide ligand NBI-6024 on beta-cell residual function and insulin needs in new-onset type 1 diabetes

OBJECTIVE

This randomized, four-arm, placebo-controlled, dose-ranging phase 2 trial was conducted to determine whether repeated subcutaneous injections of the altered peptide ligand, NBI-6024, designed to inhibit autoreactive T-cells, improves beta-cell function in patients with recently diagnosed type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 188 patients, aged 10-35 years, with recently diagnosed type 1 diabetes were randomly assigned for a treatment consisting of the subcutaneous administration of placebo or 1, 0.5, or 0.1 mg NBI-6024 at baseline, weeks 2 and 4, and then monthly until month 24. Fasting, peak, and area under the curve (AUC) C-peptide concentrations during a 2-h mixed-meal tolerance test were measured at 3-month intervals during treatment. Immune function parameters (islet antibodies and CD4 and CD8 T-cells) were also studied.

RESULTS

The mean peak C-peptide concentration at 24 months after study entry showed no significant difference between the groups treated with 0.1 mg (0.59 pmol/ml), 0.5 mg (0.57 pmol/ml), and 1.0 mg NBI-6024 (0.48 pmol/ml) and the placebo group (0.54 pmol/ml). Fasting, stimulated peak, and AUC C-peptide concentrations declined linearly in all groups by approximately 60% over the 24-month treatment period. The average daily insulin needs at month 24 were also comparable between the four groups. No treatment-related changes in islet antibodies and T cell numbers were observed.

CONCLUSIONS

Treatment with altered peptide ligand NBI-6024 at repeated doses of 0.1, 0.5, or 1.0 mg did not improve or maintain beta-cell function.

Immunotherapy for the Prevention and Treatment of Type 1 Diabetes

A major effort has been on-going to develop immunotherapies to prevent and/or treat type 1 diabetes (T1D). This autoimmune disease is characterized by the selective loss of the insulin-producing beta cells via the cumulative effects of autoantigen-specific CD4(+) and CD8(+) T cells, autoantibodies, and activated antigen-presenting cells. To be applicable in a clinical setting, immunotherapies must suppress established beta-cell autoimmunity. Preclinical studies and recent clinical findings suggest that antigen-specific and systemic-based strategies can be effective in this regard. However, either approach alone may not be sufficient to block the diabetogenic response and establish long-term protection in the clinic. In this review, we will discuss the importance of both strategies and how a combinatorial approach to treat T1D is appealing.