Prevention of autoimmune diabetes by immunogene therapy using recombinant vaccinia virus expressing glutamic acid decarboxylase

Glutamic acid decarboxylase immunotherapy for type 1 diabetes

PURPOSE OF REVIEW

To describe recent development of an autoantigen (GAD) treatment towards well tolerated and efficacious precision medicine in type 1 diabetes.

RECENT FINDINGS

Although subcutaneous GAD-alum treatment failed to reach primary endpoint in a phase III trial, metanalyses showed a 97% probability of efficacy, and clear efficacy in patients carrying Hyman Leucoycte Antigen (HLA) DR3DQ2. Efforts have been made to improve efficacy by trying combination therapies with vitamin D + Ibuprofen resp vitamin D + Etanercept (TNF-α inhibition), without any breakthrough until the administration of GAD-alum was changed from subcutaneous to intralymphatic. With a very small dose of GAD-alum (4 μg) given into an inguinal lymph three times with 1 month interval, the efficacy in patients with HLADR3DQ2 has been impressive, with significantly better beta cell preservation than patients who got placebo in a double-blind randomized trial, and clinical efficacy with more patients in partial remission (IDAA1c < 9) and larger proportion of patients with CGM-measured blood glucose Time In Range (TIR), significantly correlated to the C-peptide values. The treatment has been easy for patients and healthcare without treatment-related risk or adverse events.

SUMMARY

Intralymphatic GAD-alum treatment in type 1 diabetes patients carrying HLA DR3DQ2 seems to be an attractive immune intervention.

Latent autoimmune diabetes in adults: a focus on β-cell protection and therapy

Latent autoimmune diabetes in adults (LADA) is a heterogeneous disease sharing some phenotypic, genetic, and immunological features with both type 1 and 2 diabetes. Patients with LADA have a relatively slow autoimmune process and more residual islet β-cell function at onset, allowing a time window to protect residual islet β cells and delay or inhibit disease progression. It is crucial to discover various heterogeneous factors affecting islet β-cell function for precise LADA therapy. In this review, we first describe the natural history of LADA. Thereafter, we summarize β-cell function-related heterogeneous factors in LADA, including the age of onset, body mass index, genetic background, and immune, lifestyle, and environmental factors. In parallel, we evaluate the impact of current hypoglycemic agents and immune intervention therapies for islet β-cell protection. Finally, we discuss the opportunities and challenges of LADA treatment from the perspective of islet β-cell function protection.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prevention of autoimmune diabetes by DNA vaccination

DNA vaccination with antigen expression plasmids has been introduced as a simple method of inducing immunity to the antigens of infectious agents or tumors. Although DNA vaccination is generally immunostimulatory, it is possible to design suppressive vaccines that protect against autoimmune diseases such as Type 1 diabetes. In mice prone to diabetes, investigators have delivered a plasmid encoding an islet-cell antigen such as insulin B chain, glutamic acid decarboxylase, or antigen/immunoglobulin G-Fc fusion constructs, with or without co-delivery of another gene encoding a cytokine or other immunoregulatory molecule. This approach has led to protection against disease, related to the generation of regulatory T-cells and increased production of regulatory cytokines. DNA vaccination is a promising approach to autoimmune disease prevention.

Persistent suppression of type 1 diabetes by a multicomponent vaccine containing a cholera toxin B subunit-autoantigen fusion protein and complete Freund's adjuvant

Data presented here demonstrate multifunctional vaccination strategies that harness vaccinia virus mediated delivery of a gene encoding an immunoenhanced diabetes autoantigen in combination with complete Freund's adjuvant (CFA) that can maintain safe and durable immunologic homeostasis in NOD mice. Systemic coinoculation of prediabetic mice with recombinant vaccinia virus rVV-CTB::GAD and undiluted or 10-fold diluted CFA demonstrated a significant decrease in hyperglycemia and pancreatic islet inflammation in comparison with control animals during 17–61 and 17–105 weeks of age, respectively. Synergy in these beneficial effects was observed during 43–61 and 61–105 wks of age, respectively. Inflammatory cytokine and chemokine levels in GAD-stimulated splenocytes isolated from vaccinated mice were generally lower than those detected in unvaccinated mice. The overall health and humoral immune responses of the vaccinated animals remained normal throughout the duration of the experiments.

The clinical and immunological significance of GAD-specific autoantibody and T-cell responses in type 1 diabetes

Antigen-specific interventions are desirable approaches in Type 1 Diabetes (T1D) as they can alter islet-specific autoimmunity without systemic side effects. Glutamic acid decarboxylase of 65 kDa (GAD65) is a major autoantigen in type 1 diabetes (T1D) and GAD-specific autoimmunity is a common feature of T1D in humans but also in mouse models of the disease. In humans, administration of the GAD65 protein in an alum formulation has been shown to reduce C-peptide decline in recently diagnosed patients, however, these observations were not confirmed in subsequent phase II/III clinical trials. As GAD-based immune interventions in different formulations have successfully been employed to prevent the establishment of T1D in mouse models of T1D, we sought to analyze the efficacy of GAD-alum treatment and the effects on the GAD-specific immune response in two different mouse models of T1D. Consistent with the latest clinical trials, mice treated with GAD-alum were not protected from diabetes, although GAD-alum induced a GAD-specific Th2-deviated immune response in transgenic rat insulin promoter-glycoprotein (RIP-GP) mice. These observations underline the importance of a thorough, preclinical evaluation of potential drugs before the initiation of clinical trials.

Role of immune system modulation in prevention of type 1 diabetes mellitus

An increased incidence of Type 1 diabetes mellitus (T1DM) is expected worldwide. Eventually, T1DM is fatal unless treated with insulin. The expansion of interventions to prevent diabetes and the use of alternative treatments to insulin is a dream to be fulfilled. The pathophysiology in T1DM is basically a destruction of beta cells in the pancreas, regardless of which risk factors or causative entities have been present. Individual risk factors can have separate patho-physiological processes to, in turn, cause this beta cell destruction. Currently, autoimmunity is considered the major factor in the pathophysiology of T1DM. In a genetically susceptible individual, viral infection may stimulate the production of antibodies against a viral protein that trigger an autoimmune response against antigenically similar beta cell molecules. Many components of the immune system have been implicated in autoimmunity leading to β-cell destruction, including cytotoxic and helper T-cells, B-cells, macrophages, and dendritic cells. The inflammatory process in early diabetes is thought to be initiated and propagated by the effect of Th1-secreted cytokines (e.g. g interferon) and suppressed by Th2-secreted antiinflammatory cytokines (interleukins). Structure and function of β-cell may be modulated by using Th1/Th2-secreted cytokines. Several experimental and clinical trials of applying GAD65, Hsp60, peptide-MHC, pepetide-277 immunization, anti-CD3 infusion, and interleukins to modulate immune response in T1DM were done. Applying such trials in patients with prediabetes, will most likely be the future key in preventing Type 1 autoimmune diabetes.

Efficient down-regulation of glia maturation factor expression in mouse brain and spinal cord

Long-lasting siRNA-based down-regulation of gene of interest can be achieved by lentiviral-based expression vectors driving the production of short hairpin RNA (shRNA). We investigated an attractive therapeutic approach to target the expression of proinflammatory GMF by using lentiviral vector encoding GMF-specific shRNA to reduce GMF levels in the spinal cord and brain of mice. To determine the effect of GMF-shRNA on GMF protein levels, we performed quantitative ELISA analysis in brain and in thoracic, cervical and lumbar regions of spinal cord from mice followed by GMF-shRNA (G-shRNA) or control shRNA (C-shRNA) treatments. Our results show a marked reduction of GMF protein levels in brain and spinal cord of mice treated with GMF-shRNA compared to control shRNA treatment. Consistent with the GMF protein analysis, the immunohistochemical examination of the spinal cord sections of EAE mice treated with GMF-shRNA showed significantly reduced GMF-immunoreactivity. Thus, the down-regulation of GMF by GMF-shRNA was efficient and wide spread in CNS as evident by the significantly reduced levels of GMF protein in the brain and spinal cord of mice.

Construction of Plasmid Insulin Gene Vector Containing Metallothionein IIA (pcDNAMTChIns) and Carbohydrate Response Element (ChoRE), and Its Expression in NIH3T3 Cell Line

BACKGROUND

Type 1 diabetes mellitus is one of the metabolic diseases that cause insulin-producing pancreatic ß cells be destroyed by immune system self-reactive T cells. Recent-ly, new treatment methods have been developed including use of the stem cells, ß islet cells transplantation and gene therapy by viral and non-viral gene constructs.

OBJECTIVES

The aim of this project was preparing the non-viral vector containing the glucose inducible insulin gene and using it in the NIH3T3 cell line.

MATERIALS AND METHODS

Cloning was carried out by standard methods. Total RNA was extracted from pancreatic tissue, RNA was converted to cDNA using RT-PCR reaction and preproinsulin gene was amplified using specific primers. PNMTCH plasmid was extract-ed and digested by NotI, HindIII, and MTIIA and ChoRE genes were purified and cloned into pcDNA3.1 (-) plasmid and named pcDNAMTCh. Finally, the preproinsulin genes were cloned into pcDNA3.1 (-) plasmid and pcDNAMTChIns was built.

RESULTS

The cloned gene constructs were evaluated by restriction enzyme digestion and RT-PCR. The NIH3T3 cells were transfected by plasmid naked DNA containing preproinsu-lin gene and expression was confirmed by Reverse Transcriptase PCR and Western Blot-ting Techniques.

CONCLUSIONS

Gel electrophoresis of PCR products confirmed that cloning was per-formed correctly. The expression of preproinsulin gene in recombinant plasmid in NI-H3T3 cell line was observed for the first time. The findings in this study can be the basis of further research on diabetes mellitus type 1 gene therapy on animals.

T-cell vaccination leads to suppression of intrapancreatic Th17 cells through Stat3-mediated RORγt inhibition in autoimmune diabetes

Immunization with inactivated autoreactive T cells is an effective therapeutic approach to ameliorating autoimmune diseases, while the underlying mechanisms that regulate autoreactive T cells are not completely understood. This study tested the hypothesis that T-cell vaccination (TCV) inhibits autoimmune diabetes in mice through the suppression of Th17 cells. The results showed that TCV treatment decreased hyperglycemia in type 1 diabetes (T1D) induced by multiple low-dose streptozotocin (MLD-STZ) as compared with the controls, preserved the number of healthy pancreatic islets and increased the production of insulin in the islets. Further study revealed that TCV significantly decreased the production of both interleukin (IL)-17 and IL-23 in intrapancreatic infiltrating lymphocytes (IPL) through marked inhibition of mRNA level of retinoic acid-related orphan receptor γt (RORγt) and signal transducer and activator of transcription 3 (Stat3) phosphorylation. The role of TCV-induced Th17 suppression was further validated in adoptive transfer experiments with polarized Th17 cells in sub-diabetogenic mice, which was similar to the effect of anti-IL-17 antibody treatment. Collectively our study shows that intrapancreatic Th17 cell suppression and healthy islet preservation play an important role in the treatment of T1D by TCV.

GAD-alum immunotherapy in Type 1 diabetes mellitus

Glutamic acid decarboxylase (GAD)-alum (Diamyd®, Diamyd Medical, Stockholm, Sweden) is an adjuvant-formulated vaccine incorporating recombinant human GAD65, the specific isoform of GAD expressed in human pancreatic β-cells and a major antigen targeted by autoreactive T lymphocytes in Type 1 diabetes mellitus. Intermittent vaccination with this protein is theorized to induce immune tolerance to GAD65, thereby potentially interrupting further β-cell destruction. Hence, clinical trials are ongoing to examine the efficacy and safety of GAD-alum immunotherapy in patients with autoimmune-mediated forms of diabetes, including Type 1 diabetes and latent autoimmune diabetes in adults.

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.

Autoantigens plus interleukin-10 suppress diabetes autoimmunity

BACKGROUND

Recombinant vaccinia virus (rVV) strains expressing the immunomodulatory cholera toxin B subunit (CTB) fused to the autoantigen glutamic acid decarboxylase (GAD) or the immunosuppressive cytokine interleukin-10 (IL-10) were independently able to generate only low levels of immune suppression of type 1 diabetes mellitus (T1DM). Here we suggest that a vaccinia virus (VV)-mediated combination of CTB::GAD fusion and IL-10 proteins promises a effective and durable immunotherapeutic strategy for T1DM.

METHODS

To explore this hypothesis, a CTB::GAD fusion gene was co-delivered with a gene encoding IL-10 by rVV infection (rVV-CTB::GAD + rVV-IL10) into 5-7-week-old non-obese diabetic (NOD) mice. The mice were assessed for vaccine protection against development of hyperglycemia from 12 to 64 weeks of age by assessment of pancreatic inflammation (insulitis) and splenocyte-secreted interferon-gamma and IL-10 cytokine levels.

RESULTS

By 36 weeks of age, from 54% to 80% of the mice in the negative control animal groups (either mock-infected or inoculated with unrelated plasmid or VV) had developed hyperglycemia. Similarly, no statistically significant improvement in protection against diabetes onset was achieved by inoculation with VV expressing CTB::GAD or IL-10 independently. Surprisingly, only 20% of mice co-inoculated with rVV-CTB::GAD + rVV-IL10 developed hyperglycemia by 28 weeks of age. Other treatment groups developed hyperglycemia by 32-36 weeks. After 36 weeks, diabetes incidence no longer increased in any groups until the end of experiment at 64 weeks of age. Histological analysis of pancreatic tissues of hyperglycemic mice revealed high levels of intra-islet insulitis. Analysis of insulitis at termination of the experiment showed that euglycemic mice co-inoculated with VV expressing CTB::GAD and IL-10 had more effectively reduced inflammation in comparison with the other groups.

CONCLUSIONS

A combinatorial vaccination strategy based on VV co-delivery of genes encoding the immunoenhanced autoantigen CTB::GAD and the anti-inflammatory cytokine IL-10 can maintain effective and durable euglycemia and immunological homeostasis in NOD mice with prediabetes.

Innovative Immune-Based Therapeutic Approaches for the Treatment of Type 1 Diabetes Mellitus

Type 1 diabetes mellitus is an autoimmune disease caused by a culmination of noxious processes of autoimmunity composed of various components of the innate and adaptive immune systems. Current treatment of type 1 diabetes focuses on restraining the endocrine disease without affecting the autoimmune process that underlies it. Prevention of this disease requires immune modulation and early intervention. New therapeutic approaches can be classified on the basis of the immunological arm targeted, that is, T-cell immune modulation (using cytokines, anti-CD3 monoclonal antibodies, and peptide MHC class II dimers), innate immune system modulation (using alpha-galactosylceramide or peptide 277), or specific antigen vaccination (glutamic acid decarboxylase and insulin). Here we review the most promising therapies developed based on these targets and emphasize those that have reached human phase clinical investigation.

Therapy with GAD in diabetes

The enzyme glutamic acid decarboxylase (GAD) is of great importance for the neurotransmission in the central nervous system, and therefore of interest for treatment of pain and neurological disease. However, it is also released in pancreas although its role is not quite clear. GAD is a major auto-antigen in the process leading to type 1 diabetes with both a clear cell-mediated immune response to GAD and auto-antibodies to GAD (GADA), which can be used as a predictor of diabetes. Administration of the isoform GAD65 can prevent autoimmune destruction of pancreatic beta cells in non-obese diabetic (NOD) mice and the subsequent need for exogenous insulin replacement. In Phase I and II studies an alum-formulated vaccine (Diamyd) has shown to be safe, and in a dose-finding study in Latent Autoimmune Diabetes in Adults (LADA) patients 20-microg was given subcutaneously one month apart indicating preservation of residual insulin secretion. A double-blind randomized Phase II trial in 70 patients (10-18 years old) with recent-onset type 1 diabetes showed significant preservation of residual insulin secretion and a GAD-specific immune response, both humoral and cell-mediated, but no treatment-related adverse events. With this promising background further studies are on their way, both intervention in newly diagnosed type 1 diabetic patients, and trials to prevent the disease.

The role of immunomodulation therapy in autoimmune diabetes

Type 1 diabetes (T1DM) is characterized by loss of virtually all endogenous insulin secretion. If residual insulin secretion is preserved, this will lead to improved metabolic balance, less acute and late complications, improved quality of life, and, in case of pronounced improvement of residual insulin secretion, complete remission and even cure of the disease. Immune suppression or immune modulation have been demonstrated as a proof of principle to stop/decrease the destructive process and thereby preserve beta-cell function. Several methods to save residual beta-cell function have been tried for more than three decades with little or no evidence of efficacy. Positive effects have been seen mainly in adult patients but have been minimal or absent in children with diabetes. Furthermore, the safety of these immune interventions and/or their benefit to risk relationships have not been found to justify clinical use. More specific immune modulation with anti-CD3 monoclonal antibodies has resulted in more encouraging postponement of C-peptide decline, but with frequent and serious adverse effects. Still more promising are the autoantigen therapies, of which glutamic acid decarboxylase (GAD) vaccination has shown significant preservation of residual insulin secretion in 10-18-year-old type 1 diabetes patients with recent onset. Efficacy was most impressive in the subgroup of patients with diabetes of short duration (<3 months). The treatment was simple, well tolerated, and showed no treatment-related adverse events. If these results can be confirmed, there is a realistic hope that GAD vaccination, perhaps in combination with vaccinations with other autoantigens and/or other therapies, will result in remission for some patients. The prospects of cure and prevention of T1DM will become less remote.

An update on preventive and regenerative therapies in diabetes mellitus

Type 1A (immune-mediated) and type 2 diabetes mellitus are two of the most common severe chronic illnesses, affecting over 230 million people worldwide with an estimated global prevalence of 5.1%. Although type 1 and type 2 diabetes differ greatly in modes of pathogenesis, these illnesses share a common pathology and consequences characterized by loss of functional beta-cell mass and subsequent dysregulation of carbohydrate and lipid metabolism. Since therapy for diabetes and the associated complications poses enormous public health and economic burdens, novel preventive and regenerative therapies have emerged in the past decade with the aim to preserve beta-cell mass and delay the onset of diabetes. The goal of this review is to provide a comprehensive overview of current efforts in the fight against diabetes, and attempts to document all strategies that have emerged in clinical studies within the past 25 years. First, strategies to identify individuals at risk, ranging from whole-genome scans to autoantibody screening, will be discussed. Second, novel approaches to prevent or delay the onset of disease will be covered. Particular focus is given on emerging strategies for individuals at risk for type 1 diabetes that target T-cell regulation and induction of tolerance, while new pharmaceutical concepts in combination with lifestyle interventions are discussed within the scope of type 2 diabetes prevention. Lastly, important efforts to halt disease progression with emphasis on beta-cell regeneration are presented.

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

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

Suppression of hyperglycemia in NOD mice after inoculation with recombinant vaccinia viruses

In autoimmune (type 1) diabetes, autoreactive lymphocytes destroy pancreatic beta-cells responsible for insulin synthesis. To assess the feasibility of gene therapy for type 1 diabetes, recombinant vaccinia virus (rVV) vectors were constructed expressing pancreatic islet autoantigens proinsulin (INS) and a 55-kDa immunogenic peptide from glutamic acid decarboxylase (GAD), and the immunomodulatory cytokine interleukin (IL)-10. To augment the beneficial effects of recombinant virus therapy, the INS and GAD genes were fused to the C terminus of the cholera toxin B subunit (CTB). Five-week-old non-obese diabetic (NOD) mice were injected once with rVV. Humoral antibody immune responses and hyperglycemia in the infected mice were analyzed. Only 20% of the mice inoculated with rVV expressing the CTB::INS fusion protein developed hyperglycemia, in comparison to 70% of the mice in the uninoculated animal group. Islets from pancreatic tissues isolated from euglycemic mice from this animal group showed no sign of inflammatory lymphocyte invasion. Inoculation with rVV producing CTB::GAD or IL-10 was somewhat less effective in reducing diabetes. Humoral antibody isotypes of hyperglycemic and euglycemic mice from all treated groups possessed similar IgG1/IgG2c antibody titer ratios from 19 to 32 wk after virus inoculation. In comparison with uninoculated mice, 11-wk-old NOD mice injected with virus expressing CTB::INS were delayed in diabetes onset by more than 4 wk. The experimental results demonstrate the feasibility of using rVV expressing CTB::INS fusion protein to generate significant protection and therapy against type 1 diabetes onset and progression.

GAD65 autoantibody epitopes in adult patients with latent autoimmune diabetes following GAD65 vaccination

AIMS

Subcutaneous injection of recombinant human GAD65 (rhGAD65) in patients with latent autoimmune diabetes in adults (LADA) correlates with an increase in C-peptide levels. In this study we analysed the effect of rhGAD65 administration on the GAD65-specific autoimmune response.

METHODS

Longitudinal serum samples obtained from LADA patients (n = 47) who received 4, 20, 100 or 500 microg alum-formulated rhGAD65 or placebo by subcutaneous injection twice (4 weeks apart) were analysed for their epitope recognition using GAD65-specific recombinant Fab and GAD65/67 fusion proteins.

RESULTS

Overall, minor changes in the epitope pattern were observed using either approach. Only in the 500-microg dosage group was an increase in GAD65Ab level associated with a significant increase in the binding to a conformational epitope located at the middle part of GAD65.

CONCLUSIONS

Our data suggest that the apparent beneficial effects of 20 microg alum-formulated recombinant human GAD65 is not explained by changes in the GAD65Ab epitope pattern.

Plasmid-based gene therapy of diabetes mellitus

Type I diabetes mellitus (T1D) is due to a loss of immune tolerance to islet antigen and thus, there is intense interest in developing therapies that can re-establish it. Tolerance is maintained by complex mechanisms that include inhibitory molecules and several types of regulatory T cells (Tr). A major historical question is whether gene therapy can be employed to generate Tr cells. This review shows that gene transfer of immunoregulatory molecules can prevent T1D and other autoimmune diseases. In our studies, non-viral gene transfer is enhanced by in vivo electroporation (EP). This technique can be used to perform DNA vaccination against islet cell antigens and when combined with appropriate immune ligands results in the generation of Tr cells and protection against T1D. In vivo EP can also be applied for non-immune therapy of diabetes. It can be used to deliver protein drugs such as glucagon-like peptide 1 (GLP-1), leptin or transforming growth factor beta (TGF-beta). These act in T1D or type II diabetes (T2D) by restoring glucose homeostasis, promoting islet cell survival and growth or improving wound healing and other complications. Furthermore, we show that in large animals EP can deliver peptide hormones, such as growth hormone releasing hormone (GHRH). We conclude that the non-viral gene therapy and EP represent a safe and efficacious approach with clinical potential.

Widespread and stable pancreatic gene transfer by adeno-associated virus vectors via different routes

Diabetes is a disease of epidemic proportions and is on the rise worldwide. Gene therapy has been actively pursued but limited by technical hurdles and profound inefficiency of direct gene transfer to the pancreas in vivo. Here, we show that, for the first time, appropriate serotypes of adeno-associated virus (AAV), coupled with a double-stranded vector DNA cassette, enable extensive and long-term in vivo gene transfer in the adult mouse pancreas by three different delivery methods. Intraperitoneal and intravenous delivery of AAV8 effectively transduced exocrine acinar cells as well as endocrine beta-cells, while local pancreatic intraductal delivery of AAV6 showed the best efficiency in the beta-cells among all AAV serotypes tested in this study. Nearly the entire islet population showed gene transfer but with distinct gene transfer efficiency and patterns when different delivery methods and vectors were used. Importantly, localized gene delivery coupled with an insulin promoter allowed extensive yet specific gene expression in the beta-cells. These effective new methods should provide useful tools to study diabetes pathogenesis and gene therapy.

Nicotinamide Reduces High Secretion of IFN-γ in High-Risk Relatives Even Though It Does Not Prevent Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease suggested to be of a T helper (Th)1-like origin. This study aimed to investigate the Th1-like and Th2-like profile in high-risk individuals during the prediabetic phase and the immunologic effect of treatment with nicotinamide. High-risk first-degree relatives of T1D patients participating in the European Nicotinamide Diabetes Intervention Trial (ENDIT) were treated with either nicotinamide or placebo. Peripheral blood mononuclear cells (PBMC) were obtained during the prediabetic phase and close to the onset of manifest T1D and from nondiabetic high-risk individuals. Using the sensitive enzyme-linked immunospot (ELISPOT) technique to distinguish Th1-like from Th2-like lymphocytes, secretion of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) was analyzed from PBMCs spontaneously and after in vitro stimulation with the diabetes-associated autoantigens, glutamic acid decarboxylase 65 (GAD65, protein and peptide, aa 247-279), recombinant tyrosine phosphatase (IA-2), and heat shock protein (HSP, aa 437-460). High-risk individuals showed high spontaneous as well as autoantigen-induced IFN-gamma secretion. Secretion of IFN-gamma and the IFN-gamma/IL-4 ratio, induced by autoantigens, decreased in individuals developing T1D (p < 0.05), whereas nondiabetic individuals showed an increased IL-4 response (p < 0.05). Thus, a Th1-dominated cytokine profile observed in high-risk individuals inclined toward a diagnosis of diabetes. Nicotinamide caused decreased spontaneous (p = 0.05) and in vitro autoantigen-induced IFN-gamma secretion (p < 0.05) and may play a role in immune regulation, even though it has not been shown to prevent T1D.

IL-23 leads to diabetes induction after subdiabetogenic treatment with multiple low doses of streptozotocin

IL-23, a proximal regulator of IL-17, may be a major driving force in the induction of autoimmune inflammation. We have used a model of subdiabetogenic treatment with multiple low doses of streptozotocin (MLD-STZ; 4 x 40 mg/kg body weight) in male C57BL/6 mice to study the effect of IL-23 on immune-mediated beta cell damage and the development of diabetes, as evaluated by blood glucose, quantitative histology, immunohistochemistry and expression of relevant cytokines in the islets. Ten daily injections of 400 ng IL-23, starting on the first day of MLD-STZ administration led to significant and sustained hyperglycemia along with weight loss compared with controls (no IL-23), and a significant increase in the number of infiltrating cells, a lower insulin content, enhanced apoptosis, expression of IFN-gamma and IL-17 (not seen in the controls) and a significant increase in the expression of TNF-alpha and IL-18 in the pancreatic islets. IL-23 treatment started 5 days prior to MLD-STZ administration had no effect on diabetogenesis or cytokines expression in the pancreatic islets. We provide the first evidence in an animal model that IL-23 is involved in the development of type-1 diabetes, by inducing IL-17 and possibly IFN-gamma production in the target tissue.

Protection of NOD mice from type 1 diabetes after oral inoculation with vaccinia viruses expressing adjuvanted islet autoantigens

Oral administration of autoantigens and allergens can delay or suppress clinical disease in experimental autoimmune and allergic disorders. However, repeated feeding of large amounts of the tolerogens is required over long periods and is only partially effective in animals systemically sensitized to the ingested antigen. Enhanced suppression of type 1 autoimmune diabetes insulitis and hyperglycemia was demonstrated in both naive and immune animals following oral inoculation with plant-based antigens coupled to the cholera toxin B subunit (CTB). Thus, plant-synthesized antigens linked to the CTB adjuvant, can enhance suppression of inflammatory TH1 lymphocyte-mediated autoreactivity in both naive and immune animals. To stimulate adjuvant-autoantigen fusion protein biosynthesis in the gut mucosae, the authors evaluated oral inoculation of juvenile non-obese diabetic (NOD) mice with recombinant vaccinia virus (rVV) expressing fusion genes encoding CTB linked to the pancreatic islet autoantigens proinsulin (INS) and a 55-kDa C-terminal peptide from glutamate decarboxylase (GAD55). Hyperglycemia in both rVV-CTB:: INS and rVV-CTB:: GAD inoculated mice was substantially reduced in comparison with the uninoculated mouse control. Oral inoculation with rVV carrying the CTB::INS fusion gene generated a significant reduction in insulitis. An increase in IgG1 in comparison with IgG2c antibody isotype titers in rVV-CTB::INS infected mice suggested possible activation of autoantigen specific Th2 lymphocytes. The experimental results demonstrate feasibility of using vaccinia virus oral delivery of adjuvanted autoantigens to the mucosae of prediabetic mice for suppression and therapy of type 1 autoimmune diabetes.

Immune modulation for prevention of type 1 diabetes mellitus

Prevention of type 1 diabetes mellitus requires early intervention in the autoimmune process directed against beta cells of the pancreatic islets of Langerhans. This autoimmune inflammatory process is thought to be caused by the effect of Th1 cells and their secreted cytokines (e.g. interferon) and to be suppressed by Th2-secreted anti-inflammatory cytokines (e.g. IL-4, IL-10). Various methods aimed specifically at halting or modulating this response have been attempted. An alternative method is the re-induction of tolerance towards the putative self antigen that causes the disease. Proposed antigens such as insulin, glutamic acid decarboxilase (GAD) and the heat shock protein 60 (Hsp60)-derived peptide 277 have been used successfully in murine diabetes models and in initial clinical trials in early diabetes patients. Here, we review the results of these trials.

Active Tolerance Induction and Prevention of Autoimmune Diabetes by Immunogene Therapy Using Recombinant Adenoassociated Virus Expressing Glutamic Acid Decarboxylase 65 Peptide GAD500–585

Tolerance induction of autoreactive T cells against pancreatic beta cell-specific autoantigens such as glutamic acid decarboxylase 65 (GAD65) and insulin has been attempted as a method to prevent autoimmune diabetes. In this study, we investigate whether adenoassociated virus (AAV) gene delivery of multiple immunodominant epitopes expressing GAD(500-585) could induce potent immune tolerance and persistently suppress autoimmune diabetes in NOD mice. A single muscle injection of 7-wk-old female NOD mice with rAAV/GAD(500-585) (3 x 10(11) IU/mouse) quantitatively reduced pancreatic insulitis and efficiently prevented the development of overt type I diabetes. This prevention was marked by the inactivation of GAD(500-585)-responsive T lymphocytes, the enhanced GAD(500-585)-specific Th2 response (characterized by increased IL-4, IL-10 production, and decreased IFN-gamma production; especially elevated anti-GAD(500-585) IgG1 titer; and relatively unchanged anti-GAD(500-585) IgG2b titer), the increased secretion of TGF-beta, and the production of protective regulatory cells. Our studies also revealed that peptides 509-528, 570-585, and 554-546 in the region of GAD(500-585) played important roles in rAAV/GAD(500-585) immunization-induced immune tolerance. These data indicate that using AAV, a vector with advantage for therapeutic gene delivery, to transfer autoantigen peptide GAD(500-585), can induce immunological tolerance through active suppression of effector T cells and prevent type I diabetes in NOD mice.

Induction of tolerance to self-antigens using genetically modified bone marrow cells

The challenge of finding a lasting cure for autoimmune disease(s) has not been met. Although the use of systemic anti-inflammatory agents still dominates the treatment of these diseases, there is a push towards developing novel and more specific strategies. In addressing autoimmunity, there is the intrinsic need to understand the mechanisms that lead to the development and maintenance of immunological tolerance to self-antigens. Experimental evidence has shown that directed antigen expression in the thymus can induce immunological tolerance to that antigen. This forms the cornerstone of one strategy directed towards the cure of autoimmunity. In this strategy, individuals with autoimmune disease are transplanted with bone marrow stem cells that have been genetically modified and in this way allow expression of the self-antigen in the thymus.

Presence of diabetes-inhibiting, glutamic acid decarboxylase-specific, IL-10-dependent, regulatory T cells in naive nonobese diabetic mice

Immunization of NOD mice with autoantigens such as glutamic acid decarboxylase (GAD) 221-235 peptide (p221) can induce Ag-specific CD4(+) T regulatory (Tr) cells. However, it is unclear whether these Tr cells acquire their regulatory capacity due to immunization or whether they are constitutively harbored in unimmunized naive mice. To address this question, we used an I-Ag7 tetramer to isolate p221-specific T cells from naive NOD mice (N221(+) cells) after peptide-specific in vitro expansion. The N221(+) T cells produced IFN-gamma and IL-10, but very little IL-4, in response to p221 stimulation. These T cells could function as regulatory cells and inhibit in vitro proliferation of diabetogenic BDC2.5 cells. This suppressive activity was cell contact-independent and was abrogated by Abs to IL-10 or IL-10R. Interestingly, IL-2 produced by other T cells present in the cell culture induced unactivated N221(+) T cells to exhibit regulatory activities involving production of IL-10. In vivo, N221(+) cells inhibited diabetes development when cotransferred with NOD splenocytes into NOD/scid recipients. Together, these results demonstrate that p221-specific IL-10-dependent Tr cells, including Tr type 1 cells, are present in naive NOD mice. The use of spontaneously arising populations of GAD peptide-specific Tr cells may represent a promising immunotherapeutic approach for preventing type 1 diabetes.

Tetramer analysis of human autoreactive CD4-positive T cells

Self-reactivity is an intrinsic property of the human immune system. Autoreactive T cells derive directly from the developmental requirement for TCR engagement by self-antigens during lymphocyte maturation. The fundamental questions implicating these autoreactive cells in human autoimmunity then, are not "Where do they come from?", but rather "Why do they persist?", "How do they become activated?", and "How are they regulated or deleted?". New technologies, in which peptide-MHC (pMHC) ligands used for T-cell recognition are utilized as soluble fluorescent multimers, now permit the direct visualization of antigen-specific autoreactive T-lymphocytes. By using multimer technology to study self-reactive cells present in autoimmune patients and control individuals, a very broad range of autoreactive potential has been identified.

Gene Therapy Progress and Prospects: Gene therapy for diabetes mellitus

Diabetes mellitus has long been targeted, as yet unsuccessfully, as being curable with gene therapy. The main hurdles have not only been vector-related toxicity but also the lack of physiological regulation of the expressed insulin. Recent advances in understanding the developmental biology of beta-cells and the transcriptional cascade that drives it have enabled both in vivo and ex vivo gene therapy combined with cell therapy to be used in animal models of diabetes with success. The associated developments in the stem cell biology and immunology have opened up further opportunities for gene therapy to be applied to target autoimmune diabetes.

Cytokine profile and insulin antibody IgG subclasses in patients with recent onset type 1 diabetes treated with oral insulin

AIMS/HYPOTHESIS

Tolerance to orally administered antigens may be generated through the induction of T helper cell type 2 and 3 (Th2/Th3) regulatory cells. We previously reported that treatment of recent onset type 1 diabetes with oral insulin had no effect on residual beta cell function. The aim of this study was to evaluate whether this treatment produces a deviation in the immune response, with polarisation of the cytokine pattern and the induction of a Th2-like antibody response.

METHODS

Mononuclear cells were collected from a total of 20 patients with type 1 diabetes before and after 12 months of treatment with oral insulin (n=11) or placebo (n=9). Following stimulation of the cells with insulin or phytohaemagglutinin, levels of Th2 and Th3 cytokines (including TGF-beta, IFN-gamma, IL-4 and IL-5) in the culture supernatants were assessed by ELISA. In addition, levels of total and specific insulin antibody IgG subclasses were measured by radioimmunoassay in serum samples drawn from 33 patients with type 1 diabetes before and after 3, 6 and 12 months of therapy with oral insulin (n=18) or placebo (n=15).

RESULTS

After 12 months of treatment, the release of TGF-beta was significantly higher in patients who received oral insulin compared with those who received placebo (p=0.025 and p=0.006 for lymphocytes challenged with insulin and phytohaemagglutinin respectively). The two groups had similar levels of IL-4 and IL-5 both at baseline and after 12 months of treatment. The release of IFN-gamma was markedly reduced in patients treated with oral insulin compared with those who received placebo at the 12-month follow-up. Circulating levels of IgG1 and IgG3 subclasses directed against insulin were significantly lower in the oral insulin group than in the placebo group after 12 months of treatment (p=0.05 for IgG1 and p=0.014 for IgG3).

CONCLUSIONS/INTERPRETATION

The increased TGF-beta release observed in patients treated with oral insulin suggests that a regulatory response can be induced in vivo by this treatment. The lower levels of insulin antibody IgG1 and IgG3 subclasses present in patients exposed to oral insulin are consistent with a Th2 deviation of the immune response. The failure of oral insulin treatment to provide any measurable clinical benefit may be due to the timing of treatment initiation.

Recombinant autoantigens for diagnosis and therapy of autoimmune diseases

The characteristic of autoimmune diseases resides in the existence of T- and B-cell autoreactivity when directed against self-proteins. Thus autoantibodies are considered to be of diagnostic relevance. The advent of recombinant protein expression technology has made it possible to produce economically high-quality autoantigens for use in immunoassays for detecting autoantibodies in patients' sera. The intention of this short review is to give the reader a brief description of autoantigen production methodologies with their advantages, disadvantages and the limitations of these techniques in the diagnostics of autoimmune diseases. Further possible usage of recombinant autoantigens as tools in investigation and therapy of autoimmune diseases is discussed.