Immunotherapy of spontaneous type 1 diabetes in nonobese diabetic mice by systemic interleukin-4 treatment employing adenovirus vector-mediated gene transfer

Cytokines in type 1 diabetes: mechanisms of action and immunotherapeutic targets

Cytokines play crucial roles in orchestrating complex multicellular interactions between pancreatic β cells and immune cells in the development of type 1 diabetes (T1D) and are thus potential immunotherapeutic targets for this disorder. Cytokines that can induce regulatory functions-for example, IL-10, TGF-β and IL-33-are thought to restore immune tolerance and prevent β-cell damage. By contrast, cytokines such as IL-6, IL-17, IL-21 and TNF, which promote the differentiation and function of diabetogenic immune cells, are thought to lead to T1D onset and progression. However, targeting these dysregulated cytokine networks does not always result in consistent effects because anti-inflammatory or proinflammatory functions of cytokines, responsible for β-cell destruction, are context dependent. In this review, we summarise the current knowledge on the involvement of well-known cytokines in both the initiation and destruction phases of T1D and discuss advances in recently discovered roles of cytokines. Additionally, we emphasise the complexity and implications of cytokine modulation therapy and discuss the ways in which this strategy has been translated into clinical trials.

New Insights into Immunotherapy Strategies for Treating Autoimmune Diabetes

Type 1 diabetes mellitus (T1D) is an autoimmune illness that affects millions of patients worldwide. The main characteristic of this disease is the destruction of pancreatic insulin-producing beta cells that occurs due to the aberrant activation of different immune effector cells. Currently, T1D is treated by lifelong administration of novel versions of insulin that have been developed recently; however, new approaches that could address the underlying mechanisms responsible for beta cell destruction have been extensively investigated. The strategies based on immunotherapies have recently been incorporated into a panel of existing treatments for T1D, in order to block T-cell responses against beta cell antigens that are very common during the onset and development of T1D. However, a complete preservation of beta cell mass as well as insulin independency is still elusive. As a result, there is no existing T1D targeted immunotherapy able to replace standard insulin administration. Presently, a number of novel therapy strategies are pursuing the goals of beta cell protection and normoglycemia. In the present review we explore the current state of immunotherapy in T1D by highlighting the most important studies in this field, and envision novel strategies that could be used to treat T1D in the future.

Current Status on Immunological Therapies for Type 1 Diabetes Mellitus

PURPOSE OF REVIEW

Type 1 diabetes (T1D) occurs when there is destruction of beta cells within the islets of Langerhans in the pancreas due to autoimmunity. It is considered a complex disease, and different complications can surface and worsen the condition if T1D is not managed well. Since it is an incurable disease, numerous treatments and therapies have been postulated in order to control T1D by balancing hyperglycemia control while minimizing hypoglycemic episodes. The purpose of this review is to primarily look into the current state of the available immunological therapies and their advantages for the treatment of T1D.

RECENT FINDINGS

Over the years, immunological therapy has become the center of attraction to treat T1D. Immunomodulatory approaches on non-antigens involving agents such as cyclosporine A, mycophenolate mofetil, anti-CD20, cytotoxic T cells, anti-TNF, anti-CD3, and anti-thymocyte globulin as well as immunomodulative approaches on antigens such as insulin, glutamic acid decarboxylase, and heat shock protein 60 have been studied. Aside from these two approaches, studies and trials have also been conducted on regulatory T cells, dendritic cells, interleukin 2, interleukin 4, M2 macrophages, and rapamycin/interleukin 2 combination therapy to test their effects on patients with T1D. Many of these agents have successfully suppressed T1D in non-obese diabetic (NOD) mice and in human trials. However, some have shown negative results. To date, the insights into the management of the immune system have been increasing rapidly to search for potential therapies and treatments for T1D. Nevertheless, some of the challenges are still inevitable. A lot of work and effort need to be put into the investigation on T1D through immunological therapy, particularly to reduce complications to improve and enhance clinical outcomes.

Peripheral blood mononuclear cells of patients with latent autoimmune diabetes secrete higher levels of pro- & anti-inflammatory cytokines compared to those with type-1 diabetes mellitus following in vitro stimulation with β-cell autoantigens

Background & objectives:

Type-1 diabetes mellitus (T1DM) and latent autoimmune diabetes in adults (LADA) share similar pathological features but differ in age of onset and progression. There is a scarcity of information on differences in CD4+ T-cell responses, particularly, cytokine secretion, between the two forms of autoimmune diabetes. Here proliferative potential and concentration of pro- and anti-inflammatory cytokines secreted by peripheral blood mononuclear cells (PBMCs) of T1DM and LADA patients were compared, after in vitro stimulation with β-cell autoantigens.

Methods:

A total of 19 patients with LADA, 37 with T1DM and 20 healthy controls were compared on the basis of lymphocyte proliferation and secretion of pro- and anti-inflammatory cytokines belonging to different T-helper types after in vitro stimulation of PBMCs with insulin and glutamic acid decarboxylase 65 (GAD65).

Results:

Following insulin stimulation, LADA group secreted higher concentration of interleukin-17 (IL-17) (P=0.02) and had higher proportion of interferon gamma (IFN-γ) secretors (P<0.001) than T1DM group. Post-GAD65 stimulation, higher proportion of LADA patients secreted IL-23 than T1DM group (P=0.02). Proportion of responders, as well as levels of secreted IL-10, were significantly higher in LADA than T1DM group, following stimulation with both insulin (P=0.01) and GAD65 (P=0.03). A significant positive correlation was observed between body mass index and IL-17 levels (r=0.41, P=0.04) and fasting plasma C-peptide with IL-10 levels (r=0.37, P=0.04).

Interpretation & conclusions:

There are differences in the portfolio of cytokine secretion in diabetic subjects with varying rates of β-cell destruction as LADA subjects secrete higher levels of both pro- and anti-inflammatory cytokines on exposure to β-cell autoantigens, thus highlighting another distinguishing feature in the pathophysiology of the two forms of autoimmune diabetes.

Emerging role of chemokine CC motif ligand 4 related mechanisms in diabetes mellitus and cardiovascular disease: friends or foes?

Chemokines are critical components in pathology. The roles of chemokine CC motif ligand 4 (CCL4) and its receptor are associated with diabetes mellitus (DM) and atherosclerosis cardiovascular diseases. However, due to the complexity of these diseases, the specific effects of CCL4 remain unclear, although recent reports have suggested that multiple pathways are related to CCL4. In this review, we provide an overview of the role and potential mechanisms of CCL4 and one of its major receptors, fifth CC chemokine receptor (CCR5), in DM and cardiovascular diseases. CCL4-related mechanisms, including CCL4 and CCR5, might provide potential therapeutic targets in DM and/or atherosclerosis cardiovascular diseases.

Cationic nanomicelles for delivery of plasmids encoding interleukin-4 and interleukin-10 for prevention of autoimmune diabetes in mice

PURPOSE

To evaluate the in vivo transfection efficiency of N-acyl derivatives of low-molecular weight chitosan (LMWC) to deliver pVIVO2-mIL4-mIL10 plasmid encoding interleukin-4 (IL-4) and interleukin-10 (IL-10) in multiple, low-dose streptozotocin induced diabetic mouse model.

METHODS

N-acyl LMWC nanomicelles were characterized for size and charge. The pVIVO2-mIL4-mIL10/N-acyl LMWC polyplexes were injected intramuscularly in mice and compared for transfection efficiency with naked DNA and FuGENE® HD. Bicistronic pVIVO2-mIL4-mIL10 plasmid was compared with individual plasmids encoding IL-4 and IL-10 for efficacy. The levels of blood glucose and serum IL-4, IL-10, TNF-α and IFN-γ were monitored. The ability of plasmid administration to protect from insulitis and biocompatibility of N-acyl LMWC were studied.

RESULTS

The N-acyl LMWC led to significantly higher (p < 0.05) expression of IL-4 and IL-10 and reduced the levels of blood glucose, TNF-α and IFN-γ, especially in animals treated with pVIVO2-mIL4-mIL10 plasmid. The pancreas of pDNA/N-acyl LMWC polyplex treated animals exhibited protection from insulitis and the delivery systems were found to be biocompatible.

CONCLUSIONS

N-acyl derivatives of LMWC are efficient and biocompatible gene delivery vectors, and the administration of bicistronic pVIVO2-mIL4-mIL10 plasmid polyplexes can protect the pancreatic islets from insulitis, possibly due to the synergistic effect of IL-4 and IL-10 encoding plasmids.

Genetic vaccination for re-establishing T-cell tolerance in type 1 diabetes

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease resulting in the destruction of the insulin-secreting β cells. Currently, there is no established clinical approach to effectively suppress long-term the diabetogenic response. Genetic-based vaccination offers a general strategy to reestablish β-cell specific tolerance within the T-cell compartment. The transfer of genes encoding β-cell autoantigens, anti-inflammatory cytokines and/or immunomodulatory proteins has proven to be effective at preventing and suppressing the diabetogenic response in animal models of T1D. The current review will discuss genetic approaches to prevent and treat T1D with an emphasis on plasmid DNA- and adeno-associated virus-based vaccines.

The humanized NOD/SCID mouse as a preclinical model to study the fate of encapsulated human islets

Despite encouraging results in animal models, the transplantation of microencapsulated islets into humans has not yet reached the therapeutic level. Recent clinical trials using microencapsulated human islets in barium alginate showed the presence of dense fibrotic overgrowth around the microcapsules with no viable islets. The major reason for this is limited understanding of what occurs when encapsulated human islets are allografted. This warrants the need for a suitable small animal model. In this study, we investigated the usefulness of NOD/SCID mice reconstituted with human PBMCs (called humanized NOD/SCID mice) as a preclinical model. In this model, human T cell engraftment could be achieved, and CD45+ cells were observed in the spleen and peripheral blood. Though the engrafted T cells caused a small fibrotic overgrowth around the microencapsulated human islets, this failed to stop the encapsulated islets from functioning in the diabetic recipient mice. The ability of encapsulated islets to survive in this mouse model might partly be attributed to the presence of Th2 cytokines IL-4 and IL-10, which are known to induce graft tolerance. In conclusion, this study showed that the hu-NOD/SCID mouse is not a suitable preclinical model to study the allograft rejection mechanisms of encapsulated human islets. As another result, the maintained viability of transplanted islets on the NOD/SCID background emphasized a critical role of protective mechanisms in autoimmune diabetes transplanted subjects due to specific immunoregulatory effects provided by IL-4 and IL-10.

Human and rodent pancreatic β-cells express IL-4 receptors and IL-4 protects against β-cell apoptosis by activation of the PI3K and JAK/STAT pathways

Secretion of pro-inflammatory cytokines is associated with loss of pancreatic β-cell viability and cell death. IL-4 (interleukin-4) has been reported to mediate a protective effect against the loss of pancreatic β-cells, and IL-4 receptors have been found in rat pancreatic β-cells at both the RNA and the protein level. The aim of the present study was to investigate IL-4 receptor expression in human islet cells and to examine the signalling pathways by which IL-4 exerts its effects using the rat β-cell lines, BRIN-BD11 and INS-1E. By means of immunohistochemistry, it was demonstrated that IL-4 receptors are present on human islet cells. Using a flow cytometric method for evaluating cell death, it was confirmed that incubating β-cells with IL-4 attenuated cell death induced by IL-1β and interferon-γ by approx. 65%. This effect was abrogated by the presence of the PI3K (phosphoinositide 3-kinase) inhibitor, wortmannin, suggesting that activation of the PI3K pathway is involved. In support of this, Western blotting revealed that incubation of cells with IL-4 resulted in increased phosphorylation of Akt (also called protein kinase B), a downstream target of PI3K. Increased tyrosine phosphorylation of STAT6 (signal transducer and activator of transcription 6) also occurred in response to IL-4 and a selective JAK3 (Janus kinase 3) inhibitor reduced the cytoprotective response. Both effects were prevented by overexpression of the tyrosine phosphatase, PTP-BL (protein tyrosine phosphatase-BL). We conclude that IL-4 receptors are functionally competent in pancreatic β-cells and that they signal via PI3K and JAK/STAT pathways. These findings may have implications for future therapeutic strategies for the management of diabetes.

Tissue-targeted therapy of autoimmune diabetes using dendritic cells transduced to express IL-4 in NOD mice

A deficit in IL-4 production has been previously reported in both diabetic human patients and non-obese diabetic (NOD) mice. In addition, re-introducing IL-4 into NOD mice systemically, or as a transgene, led to a beneficial outcome in most studies. Here, we show that prediabetic, 12-week old female NOD mice have a deficit in IL-4 expression in the pancreatic lymph nodes (PLN) compared to age-matched diabetes-resistant NOD.B10 mice. By bioluminescence imaging, we demonstrated that the PLN was preferentially targeted by bone marrow-derived dendritic cells (DCs) following intravenous (IV) administration. Following IV injection of DCs transduced to express IL-4 (DC/IL-4) into 12-week old NOD mice, it was possible to significantly delay or prevent the onset of hyperglycemia. We then focused on the PLN to monitor, by microarray analysis, changes in gene expression induced by DC/IL-4 and observed a rapid normalization of the expression of many genes, that were otherwise under-expressed compared to NOD.B10 PLN. The protective effect of DC/IL-4 required both MHC and IL-4 expression by the DCs. Thus, adoptive cellular therapy, using DCs modified to express IL-4, offers an effective, tissue-targeted cellular therapy to prevent diabetes in NOD mice at an advanced stage of pre-diabetes, and may offer a safe approach to consider for treatment of high risk human pre-diabetic patients.

Pre-incubation with interleukin-4 mediates a direct protective effect against the loss of pancreatic beta-cell viability induced by proinflammatory cytokines

Loss of pancreatic beta-cells in type I diabetes is associated with an increase in T helper 1 (Th1) proinflammatory cytokines in the islet milieu, with a concomitant reduction in Th2 anti-inflammatory cytokines. In animal models, manoeuvres designed to polarize Th1 responses towards Th2, particularly involving interleukin (IL)-4, have been shown to protect against insulitis and diabetes. The aim of this study was to determine whether IL-4 can exert a direct effect on beta-cell viability. The rat pancreatic beta-cell line, BRIN-BD11, was used. IL-4R mRNA expression was assayed by reverse transcription-polymerase chain reaction and DNA sequencing and protein expression measured using anti-IL-4R antibodies and confocal microscopy. Cells were pretreated in vitro with IL-4, incubated with IL-1beta and interferon (IFN)-gamma and DNA fragmentation and nitrite production analysed by flow cytometry and Griess assay, respectively. Expression of type I (IL-4R alpha and common gamma-chain) and type II (IL-4R alpha, IL-13R alpha-1) IL-4R mRNA transcripts, together with cell surface expression of IL-4R, was demonstrated. Pre-incubation with IL-4 reduced significantly cell death induced by IL-1beta alone or by a combination of IL-1beta and IFN-gamma, although this was not accompanied by a reduced production of nitrite. The protective effect of IL-4 was not seen when all three cytokines were added simultaneously. These results demonstrate, for the first time, expression of IL-4 receptor components on rat pancreatic beta-cells and reveal a direct protective effect on the loss of viability mediated by proinflammatory cytokines when beta-cells are pre-incubated with IL-4.

Adenovirus-mediated gene transfer of interleukin-4 into pancreatic stellate cells promotes interleukin-10 expression

Pancreatic stellate cells (PSC) are crucially involved in the development of fibrosis, a hallmark of chronic pancreatitis. Therefore, PSC represent an attractive target for the modulation of cellular functions providing the prerequisite for the establishment of novel therapeutic strategies like transfer of genetic material to the cells. Based on recent studies suggesting that the chronic course of pancreatitis is associated with immune deviation towards a Th1 cytokine profile, we have investigated the applicability of primary PSC to an adenovirus-mediated transfer of the cDNA encoding the Th2 cytokine interleukin (IL) 4 and the autocrine-acting effects of IL 4 on the cells in vitro. The trans-duction of primary PSC with a replication-incompetent adenovirus type 5 vector carrying the cDNA encoding rat IL-4 resulted in a distinct expression of the cytokine on mRNA and protein level for two weeks. Similar to recombinant IL 4, effects of the endogenously synthesized cytokine were mediated by the signal transducer and activator of transcription (STAT)6. Interestingly, beside the increase of PSC proliferation, IL 4 transduction was accompanied by an up-regulation in the endogenous expression of the anti-inflammatory cytokine IL 10. In summary, our data suggest that PSC are suitable targets for gene therapy modulating cellular interactions in the pancreas.

Interleukin-10 plasmid construction and delivery for the prevention of type 1 diabetes

Studies of animals with spontaneous autoimmune diabetes have revealed that autoreactive T cells that mediate islet beta cell destruction can be manipulated by the administration of Th(2) cytokines. In this article, the effect of interleukin-10 (IL-10) gene delivery was evaluated in vitro and in vivo with a novel IL-10 plasmid, pSI-IL-10-NFkappaB. In pSI-IL-10-NFkappaB, the expression of the IL-10 gene was driven by the SV40 promotor/enhancer. The nuclear factor kappaB (NFkappaB) binding sites were also introduced to facilitate nuclear transport of the plasmid in the cell. In vitro transfection assay with pSI-IL-10-NFkappaB showed a similar expression level of IL-10 to the plasmid without NFkappaB binding sites (pSI-IL-10). pSI-IL-10-NFkappaB and pSI-IL-10 were intravenously injected into 5-week-old nonobese diabetic (NOD) mice using polyethylenimine (PEI) as a gene carrier. Both groups had persistent gene expression, longer than 5 weeks, and secreted the similarly high IL-10 serum levels. Interestingly, the degree of insulitis in the pSI-IL-10-NFkappaB group was improved over the pSI-IL-10 group, PEI-only group, and noninjected controls. The serum glucose levels showed that single injection of pSI-IL-10-NFkappaB prevented the development of diabetes in 100% of the pSI-IL-10-NFkappaB-injected animals (5/5), while that of pSI-IL-10 prevented diabetes in 40% of the treated animals (2/5). These results suggest that pSI-IL-10-NFkappaB with PEI can effectively reduce the incidence of insulitis and type 1 diabetes in NOD mice.

Antigen-specific induction of regulatory T cells for type 1 diabetes therapy

Since their discovery decades ago, regulatory T (Treg) cells have prompted many investigations into their potential role in the generation or prevention of autoimmune disorders such as type 1 diabetes (T1D). Initially identified based on their ability to maintain tolerance to self-antigens in peripheral organs, Treg cells have since been efficiently induced therapeutically and shown to prevent the progression of T1D as well as other autoimmune diseases. Beneficial modification of immunity through the induction of Treg cells has been successfully achieved by antigen-based therapy as well as non-antigen-specific (systemic) treatments. In the current article, we review different strategies that have proved effective in preventing autoimmune diabetes and analyze them with respect to translation into clinical applications. Current evidence indicates that antigen-specific induction of potent regulatory mechanisms is influenced by the systemic milieu, suggesting that systemic modulation might be an essential prerequisite for antigen-based therapy and the successful maintenance or reestablishment of tolerance.

A comprehensive review of interventions in the NOD mouse and implications for translation

Type 1 diabetes (T1D) animal models such as the nonobese diabetic (NOD) mouse have improved our understanding of disease pathophysiology, but many candidate therapeutics identified therein have failed to prevent/cure human disease. We have performed a comprehensive evaluation of disease-modifying agents tested in the NOD mouse based on treatment timing, duration, study length, and efficacy. Interestingly, some popular tenets regarding NOD interventions were not confirmed: all treatments do not prevent disease, treatment dose and timing strongly influence efficacy, and several therapies have successfully treated overtly diabetic mice. The analysis provides a unique perspective on NOD interventions and suggests that the response of this model to therapeutic interventions can be a useful predictor of the human response as long as careful consideration is given to treatment dose, timing, and protocols; more thorough investigation of these parameters should improve clinical translation.

Disruption of the Jnk2 (Mapk9) gene reduces destructive insulitis and diabetes in a mouse model of type I diabetes

The c-Jun NH(2)-terminal kinase isoform (JNK) 1 is implicated in type 2 diabetes. However, a potential role for the JNK2 protein kinase in diabetes has not been established. Here, we demonstrate that JNK2 may play an important role in type 1 (insulin-dependent) diabetes that is caused by autoimmune destruction of beta cells. Studies of nonobese diabetic mice demonstrated that disruption of the Mapk9 gene (which encodes the JNK2 protein kinase) decreased destructive insulitis and reduced disease progression to diabetes. CD4(+) T cells from JNK2-deficient nonobese diabetic mice produced less IFN-gamma but significantly increased amounts of IL-4 and IL-5, indicating polarization toward the Th2 phenotype. This role of JNK2 to control the Th1/Th2 balance of the immune response represents a mechanism of protection against autoimmune diabetes. We conclude that JNK protein kinases may have important roles in diabetes, including functions of JNK1 in type 2 diabetes and JNK2 in type 1 diabetes.

Regulatory T-cells in type 1 diabetes

Type 1 diabetes is a T-cell-mediated autoimmune disease, resulting in destruction of the insulin-producing beta cells in the pancreas. Disease progression is thought to involve the action of T-cells, particularly those producing Th1-type cytokines. Given the complexity in understanding the precise etiology of autoimmune diseases, the diversity of autoantigens, and the variability that exists between individual patients, it might be very difficult to eliminate autoaggressive T-cell responses without resorting to generalized means of immunosuppression. However, recent evidence shows that autoimmune processes are composed not only of autoaggressive T-cell responses but also of autoreactive regulatory components. Enhancing regulatory T-cell responses, therefore, has become an area of intense focus as a means of treating autoimmune diseases like type 1 diabetes. This review will concentrate on two different types of regulatory T-cells, the naturally occurring ('professional') CD4+CD25+ T-cells and antigen-induced ('adaptive') CD4+ Th2-like regulatory T-cells.

Hepatic insulin gene therapy in insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease resulting in destruction of the pancreatic beta-cells in the islets of Langerhans. Commonly employed treatment of IDDM requires periodic insulin therapy, which is not ideal because of its inability to prevent chronic complications such as nephropathy, neuropathy and retinopathy. Although pancreas or islet transplantation are effective treatments that can reverse metabolic abnormalities and prevent or minimize many of the chronic complications of IDDM, their usefulness is limited as a result of shortage of donor pancreas organs. Gene therapy as a novel field of medicine holds tremendous therapeutic potential for a variety of human diseases including IDDM. This review focuses on the liver-based gene therapy for generation of surrogate pancreatic beta-cells for insulin replacement because of the innate ability of hepatocytes to sense and metabolically respond to changes in glucose levels and their high capacity to synthesize and secrete proteins. Recent advances in the use of gene therapy to prevent or regenerate beta-cells from autoimmune destruction are also discussed.

Interleukin-4-expressing plasmid DNA inhibits reovirus type-2-triggered autoimmune insulitis in DBA/1 J suckling mice

In this study we have examined the effect of systemic administration of T helper (Th) 2 cytokines on reovirus type-2 (Reo-2)-triggered Th1-mediated autoimmune insulitis with impaired glucose tolerance (IGT) in DBA/1J suckling mice. We have demonstrated clearly that the systemic administration of both interleukin (IL)-4-expressing plasmid DNA (pIL-4) and recombinant IL-4 (rIL-4) inhibited the development of insulitis with IGT in a dose dependent manner as compared to untreated groups in Reo-2-infected DBA/1J suckling mice. The inhibitory effects of IL-4 on the development of insulitis with IGT and the advantages of pIL-4 as compared to rIL-4 in this model are discussed.

Prevention of autoantibody-mediated Graves'-like hyperthyroidism in mice with IL-4, a Th2 cytokine

Graves' hyperthyroidism has long been considered to be a Th2-type autoimmune disease because it is directly mediated by autoantibodies against the thyrotropin receptor (TSHR). However, several lines of evidence have recently challenged this concept. The present study evaluated the Th1/Th2 paradigm in Graves' disease using a recently established murine model involving injection of adenovirus expressing the TSHR (AdCMVTSHR). Coinjection with adenovirus expressing IL-4 (AdRGDCMVIL-4) decreased the ratio of Th1/Th2-type anti-TSHR Ab subclasses (IgG2a/IgG1) and suppressed the production of IFN-gamma by splenocytes in response to TSHR Ag. Importantly, immune deviation toward Th2 was accompanied by significant inhibition of thyroid-stimulating Ab production and reduction in hyperthyroidism. However, in a therapeutic setting, injection of AdRGDCMVIL-4 alone or in combination with AdCMVTSHR into hyperthyroid mice had no beneficial effect. In contrast, coinjection of adenoviruses expressing IL-12 and the TSHR promoted the differentiation of Th1-type anti-TSHR immune responses as demonstrated by augmented Ag-specific IFN-gamma secretion from splenocytes without changing disease incidence. Coinjection of adenoviral vectors expressing IL-4 or IL-12 had no effect on the titers of anti-TSHR Abs determined by ELISA or thyroid-stimulating hormone-binding inhibiting Ig assays, suggesting that Ab quality, not quantity, is responsible for disease induction. Our observations demonstrate the critical role of Th1 immune responses in a murine model of Graves' hyperthyroidism. These data may raise a cautionary note for therapeutic strategies aimed at reversing Th2-mediated autoimmune responses in Graves' disease in humans.

Prevention of autoimmune insulitis by delivery of a chimeric plasmid encoding interleukin-4 and interleukin-10

The combined administration of interleukin-4 (IL-4) and interleukin-10 (IL-10) expression plasmids has demonstrated synergistic effects on the prevention of autoimmune diabetes. To this end, we constructed a co-expression 'chimeric' plasmid, pCMV-IL4-IL10, in which the expression of IL-4 and IL-10 was driven by two separate CMV immediate early promoters by using the biodegradable polymer, poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA) as a gene carrier to optimize gene delivery. In vitro transfection assays of the chimeric plasmid in 293T cells showed higher expression levels as well as dose dependence than the single gene expression plasmids. To evaluate the in vivo efficacy of the chimeric plasmid, the pCMV-IL4-IL10/PAGA complex was intravenously injected into 4-week-old non-obese diabetic (NOD) mice and compared to the co-administration group. While both groups had persistent gene expression longer than 5 weeks, the IL-4 and IL-10 serum levels of the chimeric group were higher than those in the co-administration group. Furthermore, the degree of insulitis in the chimeric group was improved over both the co-administration and non-injected control groups. These results suggest that the chimeric IL-4 and IL-10 expression plasmid can effectively reduce the incidence of autoimmune insulitis.

Gene and cell therapies for diabetes mellitus: strategies and clinical potential

The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.

Dendritic cells transduced to express interleukin-4 prevent diabetes in nonobese diabetic mice with advanced insulitis

Our previous studies demonstrated that adoptive transfer of dendritic cells (DC) prevents diabetes in young nonobese diabetic (NOD) mice by inducing regulatory T(H)2 cells. In this report, as a means of treating NOD mice with more advanced insulitis, we infected DC with adenoviral vectors expressing interleukin (IL)-4 (Ad.IL-4), eGFP (Ad.eGFP), or empty vector (Ad psi 5). DC infected with any of the Ad vectors expressed higher levels of CD40, CD80, and CD86 molecules than uninfected DC and Ad.IL-4 DC produced IL-4 after lipopolysaccharide (LPS) and interferon (IFN)-gamma stimulation. Ad-infected DC efficiently stimulated allogeneic T cells, and cultures of T cells with Ad.IL-4 DC produced lower levels of IFN-gamma and marginally higher levels of IL-4. In vivo studies demonstrated that the Ad.eGFP DC trafficked to the pancreatic lymph nodes within 24 hr of intravenous administration, and could be visualized in the T cell areas of the spleen. The intrapancreatic IFN-gamma:IL-4 or IFN-gamma:IL-10 cytokine ratios were lower in 10-week-old mice treated with Ad.IL-4 DC, and these mice were significantly protected from disease. These results demonstrate, for the first time, that genetically modified DC can prevent diabetes in the context of advanced insulitis.

Antigen-based immune modulation: DNA vectors and beyond

The ultimate goal for autoimmune immunotherapy is to achieve a specific downregulation or modification of autoaggressive immune responses while leaving in place the normal repertoire, capable of mediating antimicrobial responses. A multitude of preclinical studies, particularly during the last 15 years, raised hopes that self-antigens could be used to achieve the goal of specific immune modulation. Difficulties associated with the translation of this concept to the clinic revealed inherent limitations of antigen-based immune modulation. To increase the efficiency of antigen-dependent immune modulation, researchers started to investigate novel vectors for antigen delivery. Plasmid vectors, as opposed to protein antigens or peptides, have the ability to trigger prolonged production of limited amounts of antigen in the periphery. However, one complicating factor may be the inherent "danger" signal stimulated by the nature of the unmethylated CpG motifs on bacterial plasmid. Currently, various approaches are being explored to improve the efficacy of response while ameliorating the safety concerns of plasmids as immunotherapeutic tools. This manuscript offers a perspective on such efforts and outlines how the knowledge accumulated in the process will help scientists advance to the next generation of immunotherapeutics.

Prevention of autoimmune insulitis by delivery of interleukin-4 plasmid using a soluble and biodegradable polymeric carrier

PURPOSE

We delivered interleukin-4 (IL-4) plasmid (pCAGGS-IL-4) using the biodegradable polymer, poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA), to prevent autoimmune insulitis in NOD mice.

METHODS

The pCAGGS-IL-4/PAGA complex was transfected to 293T cells. The expression level of IL-4 was measured by ELISA. The pCAGGS IL-4/PAGA complex was injected once to NOD mice intravenously at the age of 4 weeks. RT-PCR was performed to evaluate the level of the IL-4 mRNA in the liver. At 6 weeks after the injection, the grade of insulitis of the mice was evaluated by double blind methods.

RESULTS

In vitro transfecton assays showed that PAGA enhanced the expression of IL-4 in 293T cells. RT-PCR of the liver showed that IL-4 was expressed highest in the complex injected group. In the plasmid/PAGA complex injected group, the prevalence of severe insulitis in NOD mice was markedly improved, suggesting that PAGA enhanced the delivery of IL-4 plasmid.

CONCLUSION

The pCAGGS-IL-4/PAGA complex is an effective system to prevent autoimmune insulitis in NOD mice and applicable for the prevention of autoimmune diabetes.

Cytokines in immunotherapy of experimental uveitis

A better understanding of the basic mechanisms of uveitis and of the role of cytokines in experimental ocular inflammation autoimmune diseases should allow us to define new approaches for therapy. Modulation of the cytokine network by either blocking cytokine activity or administration of regulatory Th2 cytokines has shown its efficacy in several experimental autoimmune diseases including uveitis. However, cytokines present pleiotropic activities and thus may exert different effects depending on the autoimmune diseases, making interventions on their production complex. Anti-cytokine therapy or a combination of anti-cytokine drugs, antibodies, and cytokine gene therapy to synergize the therapeutical effects of other treatments appear to be of interest. Improvements in drug delivery and in biotechnology will also allow us to elaborate new and safe immunomodulatory strategies.

Immunotherapy of type 1 diabetes: lessons for other autoimmune diseases

The nonobese diabetic (NOD) mouse is a well-recognised animal model of spontaneous autoimmune insulin-dependent diabetes mellitus. The disease is T-cell mediated, involving both CD4 and CD8 cells. Its progress is controlled by a variety of regulatory T cells. An unprecedented number of immunological treatments have been assessed in this mouse strain. This chapter systematically reviews most of these therapeutic manoeuvres, discussing them in the context of their significance with regard to the underlying mechanisms and the potential clinical applications. The contrast between the surprisingly high rate of success found for a multitude of treatments (more than 160) administered early in the natural history of the disease and the few treatments active at a late stage is discussed in depth. Most of the concepts and strategies derived from this model apply to other autoimmune diseases, for which no such diversified data are available.

Combined administration of plasmids encoding IL-4 and IL-10 prevents the development of autoimmune diabetes in nonobese diabetic mice

Studies of animals with spontaneous autoimmune diabetes have revealed that autoreactive T cells that mediate islet beta-cell destruction belong to the Th1 subset (producing IL-2 and IFN-gamma), whereas regulatory T cells are Th2 type (producing IL-4 and IL-10). Here, we evaluate the effect of combined delivery of plasmid DNA encoding IL-4 and IL-10 using a degradable, cationic polymeric carrier, poly[gamma-(4-aminobutyl)-L-glycolic acid] (PAGA), in nonobese diabetic (NOD) mice. In the liver of NOD mice, we detected mouse Il4 and Il10 mRNA 5 days after intravenous injection of both PAGA-Il4 and PAGA-Il10 plasmid complexes. We found that 6 weeks after injection, 75% of observed islets were intact compared with less than 3% in the control group. Furthermore, in the treatment group, only 5% of the islets were severely infiltrated by the lymphocytes compared with over 30% in the control group. We measured glucose levels weekly up to the age of 32 weeks, revealing that co-injection of PAGA-Il4 and PAGA-Il10 plasmids prevented the development of diabetes in 75% of the treated animals. Thus, combined administration of mouse Il4 and Il10 plasmids prevents the development of autoimmune diabetes in NOD mice.

Immunotherapy of insulin-dependent diabetes mellitus

Immunotherapy of diabetes is now focusing on induction of tolerance to beta cell antigens using either soluble antigens or monoclonal anti-T-cell antibodies. These approaches have reached the clinical arena. At the experimental level, strategies are being developed that use or target cytokines (with gene therapy) or stimulate regulatory T cells.

Prospects for predicting and stopping the development of type 1 of diabetes

The prevention of diabetes and its devastating complications is the prime goal of diabetes care. In immune-mediated type 1 diabetes, beta cell destruction can be predicted with increasing confidence both before and after diagnosis, thus allowing the development of preventative strategies. Multicentre clinical trials with the natural products insulin and nicotinamide have been launched, but the results will only be available in a few years time. Meanwhile, observational studies in large representative risk groups can help to refine the selection of subjects with a more homogenous risk for beta cell destruction, thereby reducing the need for large sample sizes. The comparison between biological markers and disease progression will help to define surrogate disease end-points that can be monitored before the hard clinical end-points of hyperglycaemia or remission. These advances will facilitate the start of new pilot trials to identify relatively safe candidate interventions adapted to disease stage.

Cell type specific and glucose responsive expression of interleukin-4 by using insulin promoter and water soluble lipopolymer

For gene therapy, tissue targeting of gene delivery systems is required for the maximum efficiency. In this study, we constructed pRIP-IL4 in which the expression of interleukin-4 (IL-4) was driven by the rat insulin promoter. WSLP-pRIP-IL4 complex was characterized by pancreas beta-cell specific and glucose responsive expression of IL-4. pRIP-IL4 was completely retarded at a 6:1 or higher N/P (nitrogen atom of WSLP/phosphate of plasmid) ratio in 1% agarose gel. In addition, WSLP protected plasmid DNA from DNase I for more than 1 h. In cytotoxicity assay, WSLP showed less cytotoxicity than PEI (25000 Da) to mouse insulinoma (MIN6) cells. ELISA showed that pRIP-IL4 expressed much higher levels of IL-4 in MIN6 cells than in NIH3T3 cells. The expression level of IL-4 by pRIP-IL4 increased with increasing concentration of glucose. Also, IL-4 was expressed in a dose-dependent manner. This WSLP-pRIP-IL4 system will be useful in the development of a pancreas specific expression system for the prevention of diabetes without systemic side effects.

Anticytokine gene therapy of autoimmune diseases

Viral and nonviral gene therapy vectors have been successfully employed to deliver inflammatory cytokine inhibitors (anticytokines), or anti-inflammatory cytokines, such as transforming growth factor beta-1 (TGF-beta 1), which protect against experimental autoimmune diseases. These vectors carry the relevant genes into a variety of tissues, for either localised or systemic release of the encoded protein. Administration of cDNA encoding soluble IFN-gamma receptor (IFN-gamma R)/IgG-Fc fusion proteins, soluble TNF-alpha receptors, or IL-1 receptor antagonist (IL-1ra), protects against either lupus, various forms of arthritis, autoimmune diabetes, or other autoimmune diseases. These inhibitors, unlike many cytokines, have little or no toxic potential. Similarly, TGF-beta 1 gene therapy protects against numerous forms of autoimmunity, though its administration entails more risk than anticytokine therapy. We have relied on the injection of naked plasmid DNA into skeletal muscle, with or without enhancement of gene transfer by in vivo electroporation. Expression plasmids offer interesting advantages over viral vectors, since they are simple to produce, non-immunogenic and nonpathogenic. They can be repeatedly administered and after each treatment the encoded proteins are produced for relatively long periods, ranging from weeks to months. Moreover, soluble receptors which block cytokine action, encoded by gene therapy vectors, can be constructed from non-immunogenic self elements that are unlikely to be neutralised by the host immune response (unlike monoclonal antibodies [mAbs]), allowing long-term gene therapy of chronic inflammatory disorders.

Diabetes vaccines: a future to be realized

Immune-mediated (type 1) diabetes mellitus (IMD) is an autoimmune disease resulting from the chronic destruction of pancreatic islet cells by autoreactive T lymphocytes. Although there has been much advancement in diabetes management, targeting the precise etiology of the disease process has remained elusive. Recent progress in the understanding of the immunopathogenesis of IMD, however, has led to new intervention strategies, especially antigen-based therapies given as altered peptide ligands (APLs) or as vaccines. Instead of using immunosuppressive agents to suppress an already dysfunctional immune system, antigen specific vaccines or even non-antigen specific immunostimulants present a unique opportunity to boost regulatory function and thereby regain tolerance to self. We discuss here the pathogenesis of IMD as it relates to therapeutic possibilities, review various intervention strategies that have been successful in rodent models, and then present recent progress in human trials of diabetes intervention and prevention through vaccine prototypes.