Gene delivery GAD500 autoantigen by AAV serotype 1 prevented diabetes in NOD mice: Transduction efficiency do not play important roles

Induction of Antigen-Specific Tolerance in T Cell Mediated Diseases

The development of novel approaches to control unwanted immune responses represents an ambitious goal in the management of a number of clinical conditions, including autoimmunity, autoinflammatory diseases, allergies and replacement therapies, in which the T cell response to self or non-harmful antigens threatens the physiological function of tissues and organs. Current treatments for these conditions rely on the use of non-specific immunosuppressive agents and supportive therapies, which may efficiently dampen inflammation and compensate for organ dysfunction, but they require lifelong treatments not devoid of side effects. These limitations induced researchers to undertake the development of definitive and specific solutions to these disorders: the underlying principle of the novel approaches relies on the idea that empowering the tolerogenic arm of the immune system would restore the immune homeostasis and control the disease. Researchers effort resulted in the development of cell-free strategies, including gene vaccination, protein-based approaches and nanoparticles, and an increasing number of clinical trials tested the ability of adoptive transfer of regulatory cells, including T and myeloid cells. Here we will provide an overview of the most promising approaches currently under development, and we will discuss their potential advantages and limitations. The field is teaching us that the success of these strategies depends primarily on our ability to dampen antigen-specific responses without impairing protective immunity, and to manipulate directly or indirectly the immunomodulatory properties of antigen presenting cells, the ultimate in vivo mediators of tolerance.

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.

Insulin B chain 9-23 gene transfer to hepatocytes protects from type 1 diabetes by inducing Ag-specific FoxP3+ Tregs

Antigen (Ag)-specific tolerance in type 1 diabetes (T1D) in human has not been achieved yet. Targeting lentiviral vector (LV)-mediated gene expression to hepatocytes induces active tolerance toward the encoded Ag. The insulin B chain 9-23 (InsB9-23) is an immunodominant T cell epitope in nonobese diabetic (NOD) mice. To determine whether auto-Ag gene transfer to hepatocytes induces tolerance and control of T1D, NOD mice were treated with integrase-competent LVs (ICLVs) that selectively target the expression of InsB9-23 to hepatocytes. ICLV treatment induced InsB9-23-specific effector T cells but also FoxP3(+) regulatory T cells (Tregs), which halted islet immune cell infiltration, and protected from T1D. Moreover, ICLV treatment combined with a single suboptimal dose of anti-CD3 monoclonal antibody (mAb) is effective in T1D reversal. Splenocytes from LV.InsB9-23-treated mice, but not from LV.OVA (ovalbumin)-treated control mice, stopped diabetes development, demonstrating that protection is Ag-specific. Depletion of CD4(+)CD25(+)FoxP3(+) T cells led to diabetes progression, indicating that Ag-specific FoxP3(+) Tregs mediate protection. Integrase-defective LVs (IDLVs).InsB9-23, which alleviate the concerns for insertional mutagenesis and support transient transgene expression in hepatocytes, were also efficient in protecting from T1D. These data demonstrate that hepatocyte-targeted auto-Ag gene expression prevents and resolves T1D and that stable integration of the transgene is not required for this protection. Gene transfer to hepatocytes can be used to induce Ag-specific tolerance in autoimmune diseases.

Concise Review: Cell-Based Therapies and Other Non-Traditional Approaches for Type 1 Diabetes

The evolution of Type 1 diabetes (T1D) therapy has been marked by consecutive shifts, from insulin replacement to immunosuppressive drugs and targeted biologics (following the understanding that T1D is an autoimmune disease), and to more disease‐specific or patient‐oriented approaches such as antigen‐specific and cell‐based therapies, with a goal to provide efficacy, safety, and long‐term protection. At the same time, another important paradigm shift from treatment of new onset T1D patients to prevention in high‐risk individuals has taken place, based on the hypothesis that therapeutic approaches deemed sufficiently safe may show better efficacy if applied early enough to maintain endogenous β cell function, a concept supported by many preclinical studies. This new strategy has been made possible by capitalizing on a variety of biomarkers that can more reliably estimate the risk and rate of progression of the disease. More advanced (“omic”‐based) biomarkers that also shed light on the underlying contributors of disease for each individual will be helpful to guide the choice of the most appropriate therapies, or combinations thereof. In this review, we present current efforts to stratify patients according to biomarkers and current alternatives to conventional drug‐based therapies for T1D, with a special emphasis on cell‐based therapies, their status in the clinic and potential for treatment and/or prevention. Stem Cells2016;34:809–819

Inducing immune tolerance: a focus on Type 1 diabetes mellitus

Tolerogenic strategies that specifically target diabetogenic immune cells in the absence of complications of immunosuppression are the desired treatment for the prevention or even reversal of Type 1 diabetes (T1D). Antigen (Ag)-based therapies must not only suppress disease-initiating diabetogenic T cells that are already activated, but, more importantly, prevent activation of naive auto-Ag-specific T cells that may become autoreactive through epitope spreading as a result of Ag liberation from damaged islet cells. Therefore, identification of auto-Ags relevant to T1D initiation and progression is critical to the design of effective Ag-specific therapies. Animal models of T1D have been successfully employed to identify potential diabetogenic Ags, and have further facilitated translation of Ag-specific tolerance strategies into human clinical trials. In this review, we highlight important advances using animal models in Ag-specific T1D immunotherapies, and the application of the preclinical findings to human subjects. We provide an up-to-date overview of the strengths and weaknesses of various tolerance-inducing strategies, including infusion of soluble Ags/peptides by various routes of delivery, genetic vaccinations, cell- and inert particle-based tolerogenic approaches, and various other strategies that target distinct tolerance-inducing pathways.

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.

Safety of adeno-associated viral vectors

Vectors based on recombinant adeno-associated viruses (AAVs) are being extensively explored for gene therapy owing to some of their distinguishing characteristicss such as lack of pathogenicity, wide range of infectivity and ability to provide long-term transgene expression. For many of the same reasons, recombinant AAV (rAAV) vectors have also been used as vaccine carriers to elicit immune responses against their transgene products. Extensive studies of rAAV vectors in animal models and in the clinic have revealed some safety concerns relating to their construction and production, adverse events following delivery, potential integration of the vector’s genome into host cell genomes, and the impairment of rAAV-induced CD8+ T-cell responses, which could have dire consequences for rAAV-treated individuals. Further studies to advance our knowledge of the biology of AAV and rAAV vectors are deemed necessary to allow for their more successful application in the clinic.