Vaccination with DNA encoding an immunodominant myelin basic protein peptide targeted to Fc of immunoglobulin G suppresses experimental autoimmune encephalomyelitis

Evolving understanding of autoimmune mechanisms and new therapeutic strategies of autoimmune disorders

Autoimmune disorders are characterized by aberrant T cell and B cell reactivity to the body's own components, resulting in tissue destruction and organ dysfunction. Autoimmune diseases affect a wide range of people in many parts of the world and have become one of the major concerns in public health. In recent years, there have been substantial progress in our understanding of the epidemiology, risk factors, pathogenesis and mechanisms of autoimmune diseases. Current approved therapeutic interventions for autoimmune diseases are mainly non-specific immunomodulators and may cause broad immunosuppression that leads to serious adverse effects. To overcome the limitations of immunosuppressive drugs in treating autoimmune diseases, precise and target-specific strategies are urgently needed. To date, significant advances have been made in our understanding of the mechanisms of immune tolerance, offering a new avenue for developing antigen-specific immunotherapies for autoimmune diseases. These antigen-specific approaches have shown great potential in various preclinical animal models and recently been evaluated in clinical trials. This review describes the common epidemiology, clinical manifestation and mechanisms of autoimmune diseases, with a focus on typical autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, and sjögren's syndrome. We discuss the current therapeutics developed in this field, highlight the recent advances in the use of nanomaterials and mRNA vaccine techniques to induce antigen-specific immune tolerance.

Nucleic Acids as Novel Therapeutic Modalities to Address Multiple Sclerosis Onset and Progression

The issue of treating Multiple Sclerosis (MS) begins with disease-modifying treatments (DMTs) which may cause lymphopenia, dyspnea, and many other adverse effects. Consequently, further identification and evaluation of alternative treatments are crucial to monitoring their long-term outcomes and hopefully, moving toward personalized approaches that can be translated into clinical treatments. In this article, we focused on the novel therapeutic modalities that alter the interaction between the cellular constituents contributing to MS onset and progression. Furthermore, the studies that have been performed to evaluate and optimize drugs' efficacy, and particularly, to show their limitations and strengths are also presented. The preclinical trials of novel approaches for multiple sclerosis treatment provide promising prospects to cure the disease with pinpoint precision. Considering the fact that not a single treatment could be effective enough to cover all aspects of MS treatment, additional researches and therapies need to be developed in the future. Since the pathophysiology of MS resembles a jigsaw puzzle, researchers need to put a host of pieces together to create a promising window towards MS treatment. Thus, a combination therapy encompassing all these modules is highly likely to succeed in dealing with the disease. The use of different therapeutic approaches to re-induce self-tolerance in autoreactive cells contributing to MS pathogenesis is presented. A Combination therapy using these tools may help to deal with the clinical disabilities and symptoms of the disease in the future.

Current Advancement of Immunomodulatory Drugs as Potential Pharmacotherapies for Autoimmunity Based Neurological Diseases

Dramatic advancement has been made in recent decades to understand the basis of autoimmunity-mediated neurological diseases. These diseases create a strong influence on the central nervous system (CNS) and the peripheral nervous system (PNS), leading to various clinical manifestations and numerous symptoms. Multiple sclerosis (MS) is the most prevalent autoimmune neurological disease while NMO spectrum disorder (NMOSD) is less common. Furthermore, evidence supports the presence of autoimmune mechanisms contributing to the pathogenesis of amyotrophic lateral sclerosis (ALS), which is a neurodegenerative disorder characterized by the progressive death of motor neurons. Additionally, autoimmunity is believed to be involved in the basis of Alzheimer’s and Parkinson’s diseases. In recent years, the prevalence of autoimmune-based neurological disorders has been elevated and current findings strongly suggest the role of pharmacotherapies in controlling the progression of autoimmune diseases. Therefore, this review focused on the current advancement of immunomodulatory drugs as novel approaches in the management of autoimmune neurological diseases and their future outlook.

The development of biological therapies for neurological diseases: moving on from previous failures

INTRODUCTION

Although years of research have expanded the use of biologics for several clinical conditions, such development has not yet occurred in the treatment of neurological diseases. With the advancement of biologic technologies, there is promise for these therapeutics as novel therapeutic approaches for neurological diseases. Areas covered: In this article, the authors review the therapeutic potential of different types of biologics for the treatment of neurological diseases. Preclinical and clinical studies that investigate the efficacy and safety of biologics in the treatment of neurological diseases, namely Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson disease, multiple sclerosis, and stroke, were reviewed. Moreover, the authors describe the key challenges in the development of therapeutically safe and effective biologics for the treatment of neurological diseases. Expert opinion: Several biologics have shown promise in the treatment of neurological diseases. However, the complexity of the CNS, as well as a limited understanding of disease progression, and restricted access of biologics to the CNS has limited successful development. Therefore, more research needs to be conducted to overcome these hurdles before developing effective and safe biologics for neurological diseases. The emergence of new technologies for the design, production and delivery of biologics will accelerate translating biologics to the clinic.

Emerging immunopharmacological targets in multiple sclerosis

Inflammatory demyelination of the central nervous system (CNS) is the hallmark of multiple sclerosis (MS), a chronic debilitating disease that affects more than 2.5 million individuals worldwide. It has been widely accepted, although not proven, that the major pathogenic mechanism of MS involves myelin-reactive T cell activation in the periphery and migration into the CNS, which subsequently triggers an inflammatory cascade that leads to demyelination and axonal damage. Virtually all MS medications now in use target the immune system and prevent tissue damage by modulating neuroinflammatory processes. Although current therapies such as commonly prescribed disease-modifying medications decrease the relapse rate in relapsing-remitting MS (RRMS), the prevention of long-term accumulation of deficits remains a challenge. Medications used for progressive forms of MS also have limited efficacy. The need for therapies that are effective against disease progression continues to drive the search for novel pharmacological targets. In recent years, due to a better understanding of MS immunopathogenesis, new approaches have been introduced that more specifically target autoreactive immune cells and their products, thus increasing specificity and efficacy, while reducing potential side effects such as global immunosuppression. In this review we describe several immunopharmacological targets that are currently being explored for MS therapy.

Tregitope peptides: the active pharmaceutical ingredient of IVIG?

Five years ago, we reported the identification and characterization of several regulatory T-cell epitopes (now called Tregitopes) that were discovered in the heavy and light chains of IgG (De Groot et al. Blood, 2008). When added ex vivo to human PBMCs, these Tregitopes activated regulatory T cells (Tregs), increased expression of the transcription factor FoxP3, and induced IL-10 expression in CD4(+) T cells. We have now shown that coadministration of the Tregitopes in vivo, in a number of different murine models of autoimmune disease, can suppress immune responses to antigen in an antigen-specific manner, and that this response is mediated by Tregs. In addition we have shown that, although these are generally promiscuous epitopes, the activity of individual Tregitope peptides is restricted by HLA. In this brief report, we provide an overview of the effects of Tregitopes in vivo, discuss potential applications, and suggest that Tregitopes may represent one of the "active pharmaceutical ingredients" of IVIg. Tregitope applications may include any of the autoimmune diseases that are currently treated almost exclusively with intravenous immunoglobulin G (IVIG), such as Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) and Multifocal Motor Neuropathy (MMN), as well as gene therapy and allergy where Tregitopes may provide a means of inducing antigen-specific tolerance.

Treg cell resistance to apoptosis in DNA vaccination for experimental autoimmune encephalomyelitis treatment

Background

Regulatory T (Treg) cells can be induced with DNA vaccinations and protect mice from the development of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS). Tacrolimus (FK506) has been shown to have functions on inducing immunosuppression and augmenting apoptosis of pathologic T cells in autoimmune disease. Here we examined the therapeutic effect of DNA vaccine in conjunction with FK506 on EAE.

Methodology/Principal Findings

After EAE induction, C57BL/6 mice were treated with DNA vaccine in conjunction with FK506. Functional Treg cells were induced in treated EAE mice and suppressed Th1 and Th17 cell responses. Infiltrated CD4 T cells were reduced while Treg cells were induced in spinal cords of treated EAE mice. Remarkably, the activated CD4 T cells augmented apoptosis, but the induced Treg cells resisted apoptosis in treated EAE mice, resulting in alleviation of clinical EAE severity.

Conclusions/Significance

DNA vaccine in conjunction with FK506 treatment ameliorates EAE by enhancing apoptosis of CD4 T cells and resisting apoptosis of induced Treg cells. Our findings implicate the potential of tolerogenic DNA vaccines for treating MS.

Experimental autoimmune encephalomyelitis (EAE) as a model for multiple sclerosis (MS)

Experimental autoimmune encephalomyelitis (EAE) is the most commonly used experimental model for the human inflammatory demyelinating disease, multiple sclerosis (MS). EAE is a complex condition in which the interaction between a variety of immunopathological and neuropathological mechanisms leads to an approximation of the key pathological features of MS: inflammation, demyelination, axonal loss and gliosis. The counter-regulatory mechanisms of resolution of inflammation and remyelination also occur in EAE, which, therefore can also serve as a model for these processes. Moreover, EAE is often used as a model of cell-mediated organ-specific autoimmune conditions in general. EAE has a complex neuropharmacology, and many of the drugs that are in current or imminent use in MS have been developed, tested or validated on the basis of EAE studies. There is great heterogeneity in the susceptibility to the induction, the method of induction and the response to various immunological or neuropharmacological interventions, many of which are reviewed here. This makes EAE a very versatile system to use in translational neuro- and immunopharmacology, but the model needs to be tailored to the scientific question being asked. While creating difficulties and underscoring the inherent weaknesses of this model of MS in straightforward translation from EAE to the human disease, this variability also creates an opportunity to explore multiple facets of the immune and neural mechanisms of immune-mediated neuroinflammation and demyelination as well as intrinsic protective mechanisms. This allows the eventual development and preclinical testing of a wide range of potential therapeutic interventions.

Tolerogenic DNA vaccine for prevention of autoimmune ovarian disease

DNA vaccines have been widely used to induce immune responses against molecular targets. In this study, we explored the possibility of using DNA vaccine combined with the immunosuppressant FK506 (tacrolimus) to antigen-specifically suppress unwanted immune responses and prevent autoimmune ovarian disease. To that end, we immunized C57BL/6 mice with a DNA vaccine encoding mouse zona pellucida 3 (ZP3) together with FK506. The immunization induced ZP3-specific CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg), which suppressed the induction of ZP3-specific delayed-type hypersensitivity in the animals. Significantly, the immunization also protected the animals from experimentally induced autoimmune ovarian disease. These results suggest that DNA vaccination in the presence of FK506 may be used to induce Treg cells and prevent AOD.

Inverse vaccination, the opposite of Jenner's concept, for therapy of autoimmunity

DNA-based vaccines to induce antigen-specific inhibition of immune responses in human autoimmune diseases represent the inverse of what Jenner intended when he invented vaccination. Jenner's vaccine induced antigen-specific immunity to small pox. DNA vaccines for autoimmunity have been developed in preclinical settings, and now tested in human trials. The first two clinical trials, one in relapsing remitting multiple sclerosis, and the other in type 1 diabetes indicate that specific inhibition of antigen-specific antibody and T-cell responses is attainable in humans. Further development of this approach is ongoing. This new version of immunization termed 'inverse vaccination' when applied to autoimmune diseases, may allow targeted reduction of unwanted antibody and T-cell responses to autoantigens, while leaving the remainder of the immune system intact. The method of specifically reducing a pathological adaptive autoimmune response is termed inverse vaccination.

FK506 as an adjuvant of tolerogenic DNA vaccination for the prevention of experimental autoimmune encephalomyelitis

BACKGROUND

DNA vaccination is a strategy that has been developed primarily to elicit protective immunity against infection and cancer.

METHODS

DNA vaccine was used, in conjunction with an immunosuppressant, to tolerize harmful autoimmunity.

RESULTS

Immunization of C57BL/6 mice with MOG(35-55), a myelin oligodendrocyte glycoprotein-derived peptide, and FK506 (Tacrolimus) as a tolerogenic adjuvant stimulated regulatory dendritic cells, induced antigen-specific regulatory T cells (Treg), and protected the animals from subsequent induction of experimental autoimmune encephalomyelitis (EAE). After EAE induction, there were fewer lymphocytes, including fewer T helper 17 cells, and more Treg infiltrating the spinal cord in the immunized mice compared to in control mice. Furthermore, at the peak of the EAE manifestation, CD4 T cells in the immunized mice showed decreased expression of interferon-gamma and interleukin (IL)-17, but not IL-4, in treated mice.

CONCLUSIONS

DNA vaccination, when applied with an immunosuppressant as adjuvant, can induce antigen-specific tolerance and prevent autoimmune disease.

Gene therapy in autoimmune diseases: challenges and opportunities

Clinical treatment of autoimmune disorders presents a special challenge. For decades, most clinical regimens in autoimmunity has been largely symptomatic and non-disease specific. Although data from vigorous research has lead to accumulating knowledge on the pathogenic and immunological mechanisms of many autoimmune diseases, their direct clinical applications have been sparse. Advances in biotechnology have laid the groundwork for potent and specific molecular targeting therapies by gene therapy, and have just begun to be investigated in the treatment of autoimmune disorders. Such work has been largely based on the availability of well-established animal models of common autoimmune disorders, and the efficacy of strategic approaches initially investigated and validated in these models. Although these preclinical animal model studies have provided the proof-of-concept for multiple potential applications, human clinical trials on gene therapy in autoimmunity are still at its infancy. The recent success of Phase I/II clinical trials of gene therapy in rheumatoid arthritis and multiple sclerosis, development of cutting edge technology in target identification, as well as gene delivery systems have now set the stage for a more thorough and vigorous pace in the near future to advance this exciting field.

DNA vaccines for autoimmune diseases

Autoimmune diseases represent a group of disorders in which there exists a large unmet medical need for effective treatments, but also where there exists a tremendous responsibility among physicians and drug developers to maintain adequate and acceptable patient safety. Several drugs have been approved and many others are about to be approved for the treatment of autoimmune diseases, but in pushing the envelope of therapeutic efficacy, concerns have been raised about the long-term safety of these new therapies. DNA vaccines provide a method of treating autoimmune diseases in a highly specific manner, and could therefore overcome these safety concerns while still maintaining comparable efficacy. The numerous reports of DNA vaccines in animal models of autoimmune diseases and results from three recent human trials of DNA vaccines in autoimmune diseases are reviewed here.

Encephalitogenicity of complete Freund's adjuvant relative to CpG is linked to induction of Th17 cells

For decades, CFA has been the classic adjuvant for the induction of experimental autoimmune encephalomyelitis (EAE). Its encephalitogenic activity has been originally linked to the induction of Th1 responses. CpG, which is also a potent Th1 inducer, has been suggested by some studies to be comparably encephalitogenic. In this study, using the SJL proteolipid protein (PLP) 139-151 peptide EAE model, we show that active immunizations using CFA but not CpG 1826/IFA as an adjuvant induced disease. Passive induction of EAE resulted in severe disease when cells were transferred from PLP in CFA-primed mice but resulted in only a mild, transient disease when cells originated from PLP in CpG 1826/IFA-primed mice. In accordance with these findings, immunizations using CFA but not CpG 1826/IFA as an adjuvant elicited a delayed-type hypersensitivity response. ELISPOT analysis revealed that CFA promoted the differentiation of much higher levels of PLP-specific, IL-17-secreting cells compared with CpG 1826/IFA. Both adjuvants induced comparable frequencies of PLP-specific, IFN-gamma-secreting cells and also induced Ag-specific proliferation to the same extent. The severity of EAE in PLP in CFA-immunized mice was reduced when IL-17 was neutralized in vivo, demonstrating the crucial role of this cytokine in disease induction. The data show that immunizations using the autoantigen in CpG 1826/IFA result in very low frequencies of Ag-specific IL-17 cells, suggesting a lower risk of Th17-mediated pathology when using this adjuvant.

DNA vaccine containing the mycobacterial hsp65 gene prevented insulitis in MLD-STZ diabetes

Background

Our group previously demonstrated that a DNA plasmid encoding the mycobacterial 65-kDa heat shock protein (DNA-HSP65) displayed prophylactic and therapeutic effect in a mice model for tuberculosis. This protection was attributed to induction of a strong cellular immunity against HSP65. As specific immunity to HSP60 family has been detected in arthritis, multiple sclerosis and diabetes, the vaccination procedure with DNA-HSP65 could induce a cross-reactive immune response that could trigger or worsen these autoimmune diseases.

Methods

In this investigation was evaluated the effect of a previous vaccination with DNA-HSP65 on diabetes development induced by Streptozotocin (STZ). C57BL/6 mice received three vaccine doses or the corresponding empty vector and were then injected with multiple low doses of STZ.

Results

DNA-HSP65 vaccination protected mice from STZ induced insulitis and this was associated with higher production of IL-10 in spleen and also in the islets. This protective effect was also concomitant with the appearance of a regulatory cell population in the spleen and a decreased infiltration of the islets by T CD8⁺ lymphocytes. The vector (DNAv) also determined immunomodulation but its protective effect against insulitis was very discrete.

Conclusion

The data presented in this study encourages a further investigation in the regulatory potential of the DNA-HSP65 construct. Our findings have important implications for the development of new immune therapy strategies to combat autoimmune diseases.

Antigen-Specific Therapies in Multiple Sclerosis

During recent years, many new therapies for human autoimmune diseases such as multiple sclerosis (MS) have been considered based on promising in vitro data or animal experiments. A number of them have proceeded to early clinical testing. However, very few finally advanced to approval by the regulatory agencies and are currently available to patients. The main reasons for failure were either lack of efficacy in humans and/or unexpected and untolerable adverse events. Although previous attempts toward antigen-specific immunomodulation have often been disappointing, these difficulties have led to renewed interest in therapies that aim at reestablishing tolerance to autoantigens at the level of either T cell-mediated or antibody-mediated immune responses or both. Such antigen-specific immunotherapies offer the prospect of correcting pathological immune reactivity against autoantigens in a highly specific and effective manner and also achievement of this goal with relatively little side effects. Here we will review the various approaches that are currently being considered for antigen-specific immunotherapies in MS.

A DNA vaccine for multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a disease in which safety is of paramount importance when developing a potential therapeutic. Antigen-specific treatments provide a method for achieving efficacy while maintaining safety. DNA vaccines are one such form of treatment that have been tested in clinical trials

OBJECTIVE

To determine if a DNA vaccine is a viable method of antigen-specific treatment of MS.

RESULTS/CONCLUSION

Phase I and II trials of BHT-3009, a DNA vaccine encoding myelin basic protein, demonstrated that it was safe, well-tolerated, and caused antigen-specific immune tolerance. BHT-3009 showed efficacy in reducing brain lesion activity as well as clinical relapses in patients that were immunologically active at baseline. BHT-3009 is a promising therapy in development for MS, and may prove to be one of the first antigen-specific treatments for this disease.

Novel therapeutic strategies for multiple sclerosis--a multifaceted adversary

Therapeutic strategies for multiple sclerosis have radically changed in the past 15 years. Five regulatory-approved immunomodulatory agents are reasonably effective in the treatment of relapsing-remitting multiple sclerosis, and appear to delay the time to progression to disabling stages. Inhibiting disease progression remains the central challenge for the development of improved therapies. As understanding of the immunopathogenesis of multiple sclerosis has advanced, a number of novel potential therapeutics have been identified, and are discussed here. It has also become apparent that traditional views of multiple sclerosis simply as a CD4+ T-cell-mediated disease of the central nervous system are incomplete. The pathogenic role of other immune components such as the innate immune system, regulatory T cells, T helper 17 cells and B cells is reaching centre stage, opening up exciting avenues and novel potential targets to affect the natural course of multiple sclerosis.

Impaired autoimmune T helper 17 cell responses following DNA vaccination against rat experimental autoimmune encephalomyelitis

Background

We have previously shown that vaccination with DNA encoding the encephalitogenic peptide myelin oligodendrocyte glycoprotein (MOG)_91–108 (pMOG) suppresses MOG_91–108-induced rat Experimental Autoimmune Encephalomyelitis (EAE), a model for human Multiple Sclerosis (MS). The suppressive effect of pMOG is dependent on inclusion of CpG DNA in the plasmid backbone and is associated with early induction of Interferon (IFN)-β.

Principal Findings

In this study we examined the mechanisms underlying pMOG-induced protection. We found that in the DNA vaccinated cohort proinflammatory Interleukin (IL)-17 and IL-21 responses were dramatically reduced compared to in the control group, but that the expression of Foxp3 and Tumor Growth Factor (TGF)-β1, which are associated with regulatory T cells, was not enhanced. Moreover, genes associated with Type I IFNs were upregulated. To delineate the role of IFN-β in the protective mechanism we employed short interfering RNA (siRNA) to IFN-β in the DNA vaccine. SiRNA to IFN-β completely abrogated the protective effects of the vaccine, demonstrating that a local early elaboration of IFN-β is important for EAE protection. IL-17 responses comparable to those in control rats developed in rats injected with the IFN-β-silencing DNA vaccine.

Conclusions

We herein demonstrate that DNA vaccination protects from proinflammatory Th17 cell responses during induction of EAE. The mechanism involves IFN-β as IL-17 responses are rescued by silencing of IFN-β during DNA vaccination.

Vaccines for multiple sclerosis: progress to date

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS, characterized pathologically by a perivascular infiltrate consisting predominantly of T cells and macrophages. Although its aetiology remains unknown, several lines of evidence support the hypothesis that autoimmune mechanisms play a major role in the development of the disease. Several widely used disease-modifying agents are approved for the treatment of MS. However, these agents are only partially effective and their ability to attenuate the more progressive phases of the disease is not clear at this time. Therefore, there is a need to develop improved treatment options for MS. This article reviews the role of several novel, selective vaccine strategies that are currently under investigation, including: (i) T-cell vaccination (TCV); (ii) T-cell receptor (TCR) peptide vaccination; (iii) DNA vaccination; and (iv) altered peptide ligand (APL) vaccination. The administration of attenuated autoreactive T cells induces regulatory networks to specifically suppress pathogenic T cells in MS, a strategy named TCV. The concept of TCV was based on the experience of vaccination against aetiological agents of infectious diseases in which individuals are purposely exposed to an attenuated microbial pathogen, which then instructs the immune system to recognize and neutralize it in its virulent form. In regard to TCV, attenuated, pathogenic T cells are similarly used to instruct the immune system to recognize and neutralize disease-inducing T cells. In experimental allergic encephalomyelitis (EAE), an animal model for MS, pathogenic T cells use a strikingly limited number of variable-region elements (V region) to form TCR specific for defined autoantigens. Thus, vaccination with peptides directed against these TCR structures may induce immunoregulatory mechanisms, thereby preventing EAE. However, unlike EAE, myelin-reactive T cells derived from MS patients utilize a broad range of different V regions, challenging the clinical utility of this approach. Subsequently, the demonstration that injection of plasmid DNA encoding a reporter gene into skeletal muscle results in expression of the encoded proteins, as well as in the induction of immune responses in animal models of autoimmunity, was explored as another strategy to re-establish self-tolerance. This approach has promise for the treatment of MS and, therefore, warrants further investigation. APLs are molecules in which the native encephalitogenic peptides are modified by substitution(s) of one or a few amino acids critical for contact with the TCR. Depending on the substitution(s) at the TCR contact residues of the cognate peptide, an APL can induce immune responses that can protect against or reverse EAE. However, the heterogeneity of the immune response in MS patients requires further study to determine which patients are most likely to benefit from APL therapy. Other potential approaches for vaccines in MS include vaccination against axonal growth inhibitors associated with myelin, use of dendritic cells pulsed with specific antigens, and active vaccination against proinflammatory cytokines. Overall, vaccines for MS represent promising approaches for the treatment of this devastating disease, as well as other autoimmune diseases.

DNA vaccination efficiently induces antibodies to Nogo-A and does not exacerbate experimental autoimmune encephalomyelitis

Antibodies against the neurite outgrowth inhibitor Nogo-A enhance axonal regeneration following spinal cord injury. However, antibodies directed against myelin components can also enhance CNS inflammation. The present study was designed to assess the efficacy of DNA vaccination for generating antibodies against Nogo-A and to study their pathogenic potential in a mouse model for multiple sclerosis. Mice were immunized by a single i.m. injection of a plasmid expression vector encoding either full length membrane-integral Nogo-A equipped with a signal peptide or two versions of its large N-terminal extramembrane region. The presence of serum antibodies to Nogo-A was measured 4 weeks after injection by ELISA, Western blotting and immunohistochemistry. DNA vaccination efficiently induced production of Nogo-A-specific antibodies that recognized recombinant, intracellular Nogo-A in cell culture but also stained native Nogo-A on the oligodendrocyte surface. Experimental autoimmune encephalomyelitis was induced in DNA-vaccinated mice by immunization with proteolipid peptide (a.a. 139-154). In contrast to vaccination with DNA encoding myelin oligodendrocyte glycoprotein that exacerbates this disease, Nogo-A DNA vaccination did not enhance clinical severity of disease. In summary, DNA vaccination is a simple and efficient method for generating an antibody response to Nogo-A. No pathogenicity was observed even during a full-blown inflammatory response of the central nervous system.

Gene vaccination for the induction of immune tolerance

DNA vaccination is a strategy of immunization based on the injection of a gene encoding for a target protein with the goal of eliciting a potentially protective immune response in the host. Compared to traditional immunization procedures, DNA vaccination offers several advantages: increased availability of antigenic peptides because of the endogenous and long-term synthesis of the gene product, improved antigen processing and presentation, possibility of antigen structure modeling through molecular engineering, coexpression of immunologically relevant agents, and low cost of vaccine production. Although the choice of the most appropriate vector for gene transfer may still be controversial, the application of DNA vaccination to the treatment of autoimmune diseases in different experimental animal models has demonstrated the great potential of this procedure for therapeutic purposes. DNA vaccination has been successful in protecting mice from the development of organ-specific autoimmunity (experimental allergic encephalomyelitis (EAE), autoimmune diabetes, experimental arthritis, experimental uveitis) as well as systemic autoimmune disease (systemic lupus erythematosus (SLE), antiphospholipid syndrome). The protection appears to be highly influenced by the capacity of DNA vaccination to modulate immune responses affecting the Th1, Th2 and, importantly, the T cell immunoregulatory arms. We review here the experimental evidence and most recent data supporting the use of DNA vaccination in the induction of immune tolerance.

Proteomic strategies in multiple sclerosis and its animal models

The early and precise diagnosis, the prognosis, and the clinical management of multiple sclerosis, remain a considerable challenge. In recent years, the development of novel and powerful proteomic techniques prompted the use of these approaches for the search of unique biomarkers in the cerebrospinal fluid of multiple sclerosis patients. A few studies have also utilized proteomics to delineate the profile of differentially expressed proteins in animal models of the human disease in order to gain global insights into affected pathways. The identification of differentially expressed proteins may be an initial step in the discovery of novel targets and mechanisms that play critical roles in the pathology of multiple sclerosis. Based on these findings, future investigations may elucidate the events leading to demyelination, axonal damage, and neurodegeneration, providing better insights into mechanisms governing the onset and progression of the disease. Although these proteomic studies provide valuable information, they are also faced with a number of challenges. The present review discusses some of the strengths and limitations of proteomic investigations as applied to multiple sclerosis.

Hydrodynamic vaccination with DNA encoding an immunologically privileged retinal antigen protects from autoimmunity through induction of regulatory T cells

The eye is an immunologically privileged organ whose Ags serve as targets for experimental autoimmune uveitis (EAU), a model for human uveitis. We used a hydrodynamic i.v. injection of naked DNA to express the uveitogenic retinal Ag interphotoreceptor retinoid-binding protein (IRBP) in the periphery, thus revoking its immune-privileged status. IRBP was expressed in the liver within hours of administration of as little as 10 microg of IRBP-DNA. Vaccinated mice were highly protected from EAU induced by immunization with IRBP for at least 10 wk after vaccination. Protection was partial in a reversal protocol. Mechanistic studies revealed specific hyporesponsiveness to IRBP without immune deviation, no evidence for apoptosis either by the Fas- or Bcl-2-regulated (mitochondrial) pathway and apparent lack of dependence on CD8(+) cells, IL-10, or TGF-beta. In contrast, depletion of CD25(+) cells after vaccination and before challenge markedly abrogated protection. IRBP-specific CD4(+)CD25(high) T cells could be cultured from vaccinated mice and transferred protection to unvaccinated, EAU-challenged recipients. In vitro characterization of these cells revealed that they are Ag specific, anergic, express FoxP3, CTLA-4, and glucocorticoid-induced TNFR, and suppress by contact. Thus, expression of IRBP in the periphery by DNA vaccination results in tolerance that acts at least in part through induction of IRBP-specific, FoxP3(+)CD4(+)CD25(+) regulatory T cells. DNA vaccination may offer a new approach to Ag-specific therapy of uveitis.

Protective DNA vaccination against myelin oligodendrocyte glycoprotein is overcome by C3d in experimental autoimmune encephalomyelitis

Complement receptor 2 (CR2) and its physiological ligand, C3d, known for its molecular adjuvant property on the immune response, exhibit opposite effects with regard to autoimmunity. Although CR2 has been implicated in maintaining self-tolerance, recent studies reported a role for C3d signaling to CR2 in tolerance breakdown to self-antigens and the initiation of inflammatory autoimmune pathologies. In the present study, we have investigated the effect of C3d in a model of tolerogenic DNA vaccination encoding the myelin oligodendrocyte glycoprotein (MOG-DNA) which protected mice from the induction of an experimental autoimmune encephalomyelitis (EAE). We show that fusing two or three copies of C3d to MOG overcomes the protective effect of DNA vaccination. Multimeric C3d was able to revert the unresponsiveness state of specific T cells induced by MOG-DNA, independently of a modification in the Th1/Th2 cytokine pattern. Interestingly, the adjuvant effect of C3d was not sufficient to boost the anti-MOG antibody response after DNA vaccination. These findings suggest that C3d might be involved in self-tolerance breakdown and could contribute to the pathogenesis of central nervous system autoimmune disorders.

Nonviral Abeta DNA vaccine therapy against Alzheimer's disease: long-term effects and safety

It was recently demonstrated that amyloid beta (Abeta) peptide vaccination was effective in reducing the Abeta burden in Alzheimer model mice. However, the clinical trial was halted because of the development of meningoencephalitis in some patients. To overcome this problem, anti-Abeta antibody therapy and other types of vaccination are now in trial. In this study, we have developed safe and effective nonviral Abeta DNA vaccines against Alzheimer's disease. We administered these vaccines to model (APP23) mice and evaluated Abeta burden reduction. Prophylactic treatments started before Abeta deposition reduced Abeta burden to 15.5% and 38.5% of that found in untreated mice at 7 and 18 months of age, respectively. Therapeutic treatment started after Abeta deposition reduced Abeta burden to approximately 50% at the age of 18 months. Importantly, this therapy induced neither neuroinflammation nor T cell responses to Abeta peptide in both APP23 and wild-type B6 mice, even after long-term vaccination. Although it is reported that other anti-Abeta therapies have pharmacological and/or technical difficulties, nonviral DNA vaccines are highly secure and easily controllable and are promising for the treatment of Alzheimer's disease.

Antigen-specific therapies in multiple sclerosis: going beyond proteins and peptides

Multiple sclerosis (MS) is a complex immune-mediated disease resulting largely from an autoimmune attack against components of central nervous system myelin, including several proteins and lipids. Knowledge about the details of this anomalous immune response has come mostly from studies in the animal model experimental autoimmune encephalomyelitis (EAE). In this model, it has been possible to prevent and effectively treat established disease through several antigen-specific therapeutic strategies, which have included administration of whole myelin or myelin proteins by various routes, random copolymers consisting of the main major histocompatability complex (MHC) and T-cell receptor (TCR) contact amino acid residues, altered peptide ligands of dominant myelin epitopes in which one or more residues are selectively substituted, and lately DNA vaccination encoding self-myelin antigens. However, there have been difficulties in making successful transitions from animal models to human clinical trials, due either to lack of efficacy or unforeseen complications. Despite these problems, antigen-specific therapies have retained their attraction for clinicians and scientists alike, and hopefully the upcoming generation of agents--including altered peptide ligands and DNA vaccines--will benefit from the increasing knowledge about this disease and surmount existing difficulties to make an impact in the treatment of multiple sclerosis.

The effects of intradermal vaccination with DNA encoding for the T-cell receptor on the induction of experimental autoimmune encephalomyelitis in B10.PL mice

Intradermal gene administration was found to induce a more profound immune response than direct intramuscular gene injection. We performed intradermal vaccination of B10.PL mice with DNA encoding for the V 8.2 region of the T-cell receptors (TCR). Three weeks later, these mice were immunized with rat myelin basic protein (MBP). Daily mean clinical scores and mortality rate were lower in this group compared with controls. The proliferative responses of lymph node cells to rat MBP were slightly less in the vaccination groups than in the control groups (p < 0.05). However, we detected no differences between the two groups with regard to the production of MBP-specific IgG, IgG1, & IgG2a antibodies. The levels of cytokine mRNA expression in the vaccination groups were observed higher than in the control groups without antigen-specific stimulation, but all of cytokine expressions between the vaccination and control groups after antigen-specific stimulation were identical. These results demonstrate that intradermal DNA vaccines encoding for TCR might prove to be useful in the control of autoimmune disease.

A suppressive oligodeoxynucleotide enhances the efficacy of myelin cocktail/IL-4-tolerizing DNA vaccination and treats autoimmune disease

Targeting pathogenic T cells with Ag-specific tolerizing DNA vaccines encoding autoantigens is a powerful and feasible therapeutic strategy for Th1-mediated autoimmune diseases. However, plasmid DNA contains abundant unmethylated CpG motifs, which induce a strong Th1 immune response. We describe here a novel approach to counteract this undesired side effect of plasmid DNA used for vaccination in Th1-mediated autoimmune diseases. In chronic relapsing experimental autoimmune encephalomyelitis (EAE), combining a myelin cocktail plus IL-4-tolerizing DNA vaccine with a suppressive GpG oligodeoxynucleotide (GpG-ODN) induced a shift of the autoreactive T cell response toward a protective Th2 cytokine pattern. Myelin microarrays demonstrate that tolerizing DNA vaccination plus GpG-ODN further decreased anti-myelin autoantibody epitope spreading and shifted the autoreactive B cell response to a protective IgG1 isotype. Moreover, the addition of GpG-ODN to tolerizing DNA vaccination therapy effectively reduced overall mean disease severity in both the chronic relapsing EAE and chronic progressive EAE mouse models. In conclusion, suppressive GpG-ODN effectively counteracted the undesired CpG-induced inflammatory effect of a tolerizing DNA vaccine in a Th1-mediated autoimmune disease by skewing both the autoaggressive T cell and B cell responses toward a protective Th2 phenotype. These results demonstrate that suppressive GpG-ODN is a simple and highly effective novel therapeutic adjuvant that will boost the efficacy of Ag-specific tolerizing DNA vaccines used for treating Th1-mediated autoimmune diseases.

Autoimmune concepts of multiple sclerosis as a basis for selective immunotherapy: from pipe dreams to (therapeutic) pipelines

Autoimmune T and B cell responses to CNS antigen(s) are thought to drive the pathogenesis of multiple sclerosis (MS), and thus are logical targets for therapy. Indeed, several immunomodulatory agents, including IFN-beta 1b, IFN-beta 1a, glatiramer acetate, and mitoxantrone, have had beneficial clinical effects in different forms of MS. However, because the available treatments are only partially effective, MS therapy needs to be further improved. Selective (antigen-specific) immunotherapies are especially appealing because in theory they combine maximal efficacy with minimal side effects. Indeed, several innovative immunotherapies have been successfully applied in experimental autoimmune encephalomyelitis. For example, autoreactive T cells can be selectively targeted by means of antigen, T cell receptor, or activation markers. However, experimental autoimmune encephalomyelitis is far from being a perfect approximation of MS because MS is more heterogeneous and the target antigen(s) is (are) not known. Further advances in MS therapy will depend on our growing understanding of the pathogenesis of this still incurable disease.

Differential prevention of experimental autoimmune encephalomyelitis with antigen-specific DNA vaccination

We compared the potential therapeutic effect of vaccination with DNA constructs encoding two encephalitogenic proteins, PLP and MOG, on the outcome of subsequent sensitization of EAE induced in SJL/J and C57/B6 mice. Early sensitization for EAE (4 weeks after DNA vaccination) caused recipient animals to develop enhanced disease with DNA-encoding PLP but not with DNA-encoding MOG. Late sensitization (more than 10 weeks) resulted in an amelioration of EAE in animals vaccinated with both PLP and MOG DNA constructs. These results, confirming the DNA-mediated ameliorating effect on EAE, also indicate significant differences in the kinetics of development of EAE tolerance in response to vaccination with different DNA-encoding myelin antigens. Since PLP and MOG require different MHC presentation and induce different EAE models, the results point to potential differences in immune system requirements for efficient DNA-induced amelioration of the autoimmune response.

An immunomodulatory GpG oligonucleotide for the treatment of autoimmunity via the innate and adaptive immune systems

Bacterial DNA and immunostimulatory CpG oligodeoxynucleotides (ODNs) activate the innate immune system to produce proinflammatory cytokines. Shown to be potent Th1-like adjuvants, stimulatory CpG motifs are currently used as effective therapeutic vaccines for various animal models of infectious diseases, tumors, allergies, and autoimmune diseases. In this study, we show that the application of an immunomodulatory GpG ODN, with a single base switch from CpG to GpG, can effectively inhibit the activation of Th1 T cells associated with autoimmune disease. Moreover, this immunomodulatory GpG ODN suppresses the severity of experimental autoimmune encephalomyelitis in mice, a prototypic Th1-mediated animal disease model for multiple sclerosis.

More stringent conditions of plasmid DNA vaccination are required to protect grafted versus endogenous islets in nonobese diabetic mice

Recurrent autoimmune destruction of the insulin-producing beta cells is a key factor limiting successful islet graft transplantation in type I diabetic patients. In this study, we investigated the feasibility of using an Ag-specific plasmid DNA (pDNA)-based strategy to protect pro-islets that had developed from a neonatal pancreas implanted under the kidney capsule of nonobese diabetic (NOD) mice. NOD recipient mice immunized with pDNA encoding a glutamic acid decarboxylase 65 (GAD65)-IgFc fusion protein (JwGAD65), IL-4 (JwIL4), and IL-10 (pIL10) exhibited an increased number of intact pro-islets expressing high levels of insulin 15 wk posttransplant, relative to NOD recipient mice immunized with pDNA encoding a hen egg lysozyme (HEL)-IgFc fusion protein (JwHEL)+JwIL4 and pIL10 or left untreated. Notably, the majority of grafted pro-islets detected in JwGAD65+JwIL4- plus pIL10-treated recipients was free of insulitis. In addition, administration of JwGAD65+JwIL4+pIL10 provided optimal protection for engrafted islets compared with recipient NOD mice treated with JwGAD65+JwIL4 or JwGAD65+pIL10, despite effective protection of endogenous islets mediated by the respective pDNA treatments. Efficient protection of pro-islet grafts correlated with a marked reduction in GAD65-specific IFN-gamma reactivity and an increase in IL-10-secreting T cells. These results demonstrate that pDNA vaccination can be an effective strategy to mediate long-term protection of pro-islet grafts in an Ag-specific manner and that conditions are more stringent to suppress autoimmune destruction of grafted vs endogenous islets.

Suppressive DNA vaccination in myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis involves a T1-biased immune response

Vaccination with DNA encoding a myelin basic protein peptide suppresses Lewis rat experimental autoimmune encephalomyelitis (EAE) induced with the same peptide. Additional myelin proteins, such as myelin oligodendrocyte glycoprotein (MOG), may be important in multiple sclerosis. Here we demonstrate that DNA vaccination also suppresses MOG peptide-induced EAE. MOG(91-108) is encephalitogenic in DA rats and MHC-congenic LEW.1AV1 (RT1(av1)) and LEW.1N (RT1(n)) rats. We examined the effects of DNA vaccines encoding MOG(91-108) in tandem, with or without targeting of the hybrid gene product to IgG. In all investigated rat strains DNA vaccination suppressed clinical signs of EAE. There was no requirement for targeting the gene product to IgG, but T1-promoting CpG DNA motifs in the plasmid backbone of the construct were necessary for efficient DNA vaccination, similar to the case in DNA vaccination in myelin basic protein-induced EAE. We failed to detect any effects on ex vivo MOG-peptide-induced IFN-gamma, TNF-alpha, IL-6, IL-4, IL-10, and brain-derived neurotropic factor expression in splenocytes or CNS-derived lymphocytes. In CNS-derived lymphocytes, Fas ligand expression was down-regulated in DNA-vaccinated rats compared with controls. However, MOG-specific IgG2b responses were enhanced after DNA vaccination. The enhanced IgG2b responses together with the requirement for CpG DNA motifs in the vaccine suggest a protective mechanism involving induction of a T1-biased immune response.

Insights into the immunopathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Significant progress has been made in our understanding of the etiology of MS. MS is widely believed to be an autoimmune disease that results from aberrant immune responses to CNS antigens. T cells are considered to be crucial in orchestrating an immunopathological cascade that results in damage to the myelin sheath. This review summarizes the currently available data supporting the idea that myelin reactive T cells are actively involved in the immunopathogenesis of MS. Some of the therapeutic strategies for MS are discussed with a focus on immunotherapies that aim to specifically target the myelin reactive T cells.

CpG motifs in bacterial DNA and their immune effects

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.

Fusion of C3d molecule with bovine rotavirus VP7 or bovine herpesvirus type 1 glycoprotein D inhibits immune responses following DNA immunization

The binding of the complement C3d molecule with receptors on B cells and/or follicular dendritic cells (FDCs) influences the induction of humoral immune responses. For example, C3d fused to an antigen has been shown to have a strong adjuvant effect on antibody production. We investigated the possibility that co-expression of antigen and C3d as a fusion protein could enhance antigen-specific immune responses, following plasmid immunization. One or two copies of murine C3d-cDNA, C3d or (C3d)(2), respectively, were cloned together with bovine rotavirus (BRV) VP7 or bovine herpesvirus type 1 (BHV-1) glycoprotein D (gD) genes. All constructs contained a signal peptide that resulted in the secretion of the expressed proteins. In vitro, the characterization of the chimeric proteins indicated that both VP7 and gD retained their antigenicity and the C3d remained biologically active. However, immunization with plasmids encoding VP7-C3d chimeras did not enhance rotavirus-specific antibody responses and the frequency of BRV-specific IFN-gamma secreting cells in the spleens were significantly lower in mice immunized with pVP7-(C3d)(2) when compared with mice immunized with plasmid encoding VP7. The same pattern of immune responses was observed for plasmids encoding gD-C3d. Both gD-specific antibody responses and the frequency of gD-specific IFN-gamma secreting cells were significantly lower in mice immunized with plasmid expressing gD-C3d chimeras when compared with mice immunized with plasmid encoding gD alone. These results indicate that co-expression of C3d with an antigen actually inhibit both humoral and cell-mediated antigen-specific immune responses.

Specific treatment of autoimmunity with recombinant invariant chains in which CLIP is replaced by self-epitopes

The invariant chain (Ii) binds to newly synthesized MHC class II molecules with the CLIP region of Ii occupying the peptide-binding groove. Here we demonstrate that recombinant Ii proteins with the CLIP region replaced by antigenic self-epitopes are highly efficient in activating and silencing specific T cells in vitro and in vivo. The Ii proteins require endogenous processing by antigen-presenting cells for efficient T cell activation. An Ii protein encompassing the epitope myelin basic protein amino acids 84-96 (Ii-MBP84-96) induced the model autoimmune disease experimental allergic encephalomyelitis (EAE) with a higher severity and earlier onset than the peptide. When applied in a tolerogenic manner, Ii-MBP84-96 abolished antigen-specific T cell proliferation and suppressed peptide-induced EAE more effectively than peptide alone. Importantly, i.v. administration of Ii proteins after EAE induction completely abrogated the disease, whereas peptides only marginally suppressed disease symptoms. Ii fusion proteins are thus more efficient than peptide in modulating CD4(+) T cell-mediated autoimmunity, documenting their superior qualities for therapeutic antigen delivery in vivo.

Combination of gene delivery and DNA vaccination to protect from and reverse Th1 autoimmune disease via deviation to the Th2 pathway

Using a combination of local gene delivery and tolerizing DNA vaccination, we demonstrate that codelivery of the interleukin-4 (IL-4) gene and a DNA vaccine encoding the self-peptide proteolipid protein 139-151 (PLP139-151) provides protective immunity against experimental autoimmune encephalomyelitis (EAE). We provide evidence for a mechanism whereby IL-4 expressed from the naked DNA is secreted and acts locally on autoreactive T cells via activation of STAT6 to shift their cytokine profile to T helper 2. We also show that DNA vaccines can be used to reverse established EAE by covaccination with the genes for myelin oligodendrocyte glycoprotein and IL-4. This treatment strategy combines the antigen-specific effects of DNA vaccination and the beneficial effects of local gene delivery.

Plasmid DNAs encoding insulin and glutamic acid decarboxylase 65 have distinct effects on the progression of autoimmune diabetes in nonobese diabetic mice

We previously demonstrated that administration of plasmid DNAs (pDNAs) encoding IL-4 and a fragment of glutamic acid decarboxylase 65 (GAD65) fused to IgGFc induces GAD65-specific Th2 cells and prevents insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice. To assess the general applicability of pDNA vaccination to mediate Ag-specific immune deviation, we examined the immunotherapeutic efficacy of recombinants encoding murine insulin A and B chains fused to IgGFc. Insulin was chosen based on studies demonstrating that administration of insulin or insulin B chain by a variety of strategies prevents IDDM in NOD mice. Surprisingly, young NOD mice receiving i.m. injections of pDNA encoding insulin B chain-IgGFc with or without IL-4 exhibited an accelerated progression of insulitis and developed early diabetes. Exacerbation of IDDM correlated with an increased frequency of IFN-gamma-secreting CD4(+) and CD8(+) T cells in response to insulin B chain-specific peptides compared with untreated mice. In contrast, treatment with pDNAs encoding insulin A chain-IgGFc and IL-4 elicited a low frequency of IL-4-secreting Th cells and had no effect on the progression of IDDM. Vaccination with pDNAs encoding GAD65-IgGFc and IL-4, however, prevented IDDM. These results demonstrate that insulin- and GAD65-specific T cell reactivity induced by pDNA vaccination has distinct effects on the progression of IDDM.

Vaccination with glutamic acid decarboxylase plasmid DNA protects mice from spontaneous autoimmune diabetes and B7/CD28 costimulation circumvents that protection

The nonobese diabetic (NOD) mouse develops spontaneous T-cell-dependent autoimmune diabetes. We tested here whether vaccination of NOD mice with a plasmid DNA encoding glutamic acid decarboxylase (GAD), an initial target islet antigen of autoimmune T cell repertoire, would modulate their diabetes. Our results showed that vaccination of young or old female NOD mice with the GAD-plasmid DNA, but not control-plasmid DNA, effectively prevented their diabetes, demonstrating that GAD-plasmid DNA vaccination is quite effective in abrogating diabetes even after the development of insulitis. The prevention of diabetes did not follow the induction of immunoregulatory Th2 cells but was dependent upon CD28/B7 costimulation. Our results suggest a potential for treating spontaneous autoimmune diabetes via DNA vaccination with plasmids encoding self-Ag.

Codelivery of DNA coding for the soluble form of CD86 results in the down-regulation of the immune response to DNA vaccines

The costimulatory pathway that includes CD80, CD86, CD28, and CTLA-4 plays a key role in regulating T cell activation and tolerance and is a promising therapeutic target. We have studied the possibility of down-regulating the immune response to DNA vaccine by codelivery of a plasmid coding for the extracellular domains of CD86 (pDelta86). We found that DeltaCD86 was able to inhibit the engagement of FcCTLA-4 but not of FcCD28 to CD80 and CD86 expressed on COS cells. Coadministration of plasmid pDelta86 encoding for the extracellular domains of CD86 along with a plasmid encoding for the glycoprotein D (pgD) of herpes simplex virus-2 (a membrane-bound protein) by the im route in mice resulted in a strong inhibition of the cell-mediated immune response in the spleen and in draining lymph nodes. In addition, when pDelta86 was coadministered together with a plasmid encoding for the ovalbumin (pOVA) (a soluble protein), a strong inhibition of the cell-mediated immune response was observed in draining lymph nodes and only a partial inhibition was found in the spleen. Furthermore, only a partial down-regulation of the humoral immune response was observed. The mechanism involved could be a preferential engagement of DeltaCD86 to CTLA-4 leading to the transmission of a negative signal to T lymphocytes.

Antigen-specific mediated suppression of beta cell autoimmunity by plasmid DNA vaccination

In this study, we have investigated the use of plasmid DNA (pDNA) vaccination to elicit Th2 effector cell function in an Ag-specific manner and in turn prevent insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice. pDNA recombinants were engineered encoding a secreted fusion protein consisting of a fragment of glutamic acid decarboxylase 65 (GAD65) linked to IgGFc, and IL-4. Intramuscular injection of pDNA encoding GAD65-IgGFc and IL-4 effectively prevented diabetes in NOD mice treated at early or late preclinical stages of IDDM. This protection was GAD65-specific since NOD mice immunized with pDNA encoding hen egg lysozyme-IgGFc and IL-4 continued to develop diabetes. Furthermore, disease prevention correlated with suppression of insulitis and induction of GAD65-specific regulatory Th2 cells. Importantly, GAD65-specific immune deviation was dependent on pDNA-encoded IL-4. In fact, GAD65-specific Th1 cell reactivity was significantly enhanced in animals immunized with pDNA encoding only GAD65-IgGFc. Finally, NOD.IL4(null) mice treated with pDNA encoding GAD65-IgGFc and IL-4 continued to develop diabetes, indicating that endogenous IL-4 was also required for disease prevention. These results demonstrate that pDNA vaccination is an effective strategy to elicit beta cell-specific Th2 regulatory cell function for the purpose of preventing IDDM even at a late stage of disease development.

Myelin oligodendrocyte glycoprotein-DNA vaccination induces antibody-mediated autoaggression in experimental autoimmune encephalomyelitis

One strategy to reestablish self tolerance in autoimmune diseases is based on the use of DNA vaccination to induce ectopic expression of the target autoantigen. We assessed the potential of vaccination with a DNA construct encoding the myelin oligodendrocyte glycoprotein (MOG), an important candidate autoantigen in multiple sclerosis, to induce tolerance and protect against experimental autoimmune encephalomyelitis (EAE). Unexpectedly, mice vaccinated with MOG-DNA developed an exacerbated form of EAE when challenged with either MOG or an unrelated encephalitogen, myelin proteolipid protein. We demonstrate that this is due to the inability of DNA vaccination to tolerize the MOG-specific T cell response and to the concomitant induction of a cytopathic MOG-specific autoantibody response, which is pathogenic, enhancing demyelination, inflammation and disease severity. Our data suggest that tolerogenic strategies for autoimmune diseases based on DNA vaccination should be approached with caution, as the outcome is unpredictable.

Gene therapy of chronic inflammatory disease

Immune mediated inflammation that culminates in severe tissue necrosis is the hallmark of diseases that result from an inappropriate response to antigen. The inflammatory response becomes chronic when antigen is non-limiting and persists until the reactive tissue is destroyed, or the environment is changed and exposure to antigen is eliminated. The purpose of this review is to: (1) briefly outline common features of immune related inflammatory diseases such as rheumatoid arthritis (RA), multiple sclerosis (MS), inflammatory bowel disease (IBD), and allergic asthma; (2) provide a rationale for the development of gene based drugs for these indications; and (3) describe current experimental results that support the usefulness of this approach for creating novel DNA based therapeutics.