Non-coding plasmid DNA induces IFN-gamma in vivo and suppresses autoimmune encephalomyelitis

Immunogenic properties of empty pcDNA3 plasmid against zoonotic cutaneous leishmaniasis in mice

Background

Leishmania (L) parasite, the causative agent of zoonotic cutaneous leishmaniasis (ZCL), effectively stimulates the mammalian cells to mount strong humoral responses by enhancing T-helper-2 (Th2)-associated cytokines for its survival. The best strategy to decrease the intensity of infection in the host is induction of cellular immunity.

Methods

We evaluated the effects of the empty bacterial pcDNA3 plasmid on mice infected with L. major and quantified the immune mediators including IFN-γ, IL-4, IL-10, IgG2a, IgG1, arginase activity and nitric oxide (NO) in the mice. Moreover, the footpad lesion size and parasite load were assessed.

Results

We observed that pcDNA3 could modulate the immune responses in favor of host cells and decrease the disease severity. Th2- associated mediators, including arginase, IL-4, and IL-10 are downregulated, while cellular responses are upregulated in line with an increase in the levels of nitric oxide (NO) and interfero-gamma (IFN-γ). Interestingly, pcDNA3 induced specific Th1-associated antibodies, IgG2a isotype; however, it suppressed the production of humoral IgG1. The stimulation of the immune response by the empty pcDNA3 is able to shift the immune function to predominant cellular responses caused by Th1, and it had a positive effect on the treatment of zoonotic cutaneous leishmaniasis (ZCL).

Conclusions

Altogether, we introduced the pcDNA3 as a potential interfering factor in the modulation of the immune system against ZCL. Since this vector has been widely used as a control group in different studies, we suggest that the potential function of the empty vector should be deeply assessed, as it exerts anti-parasitic effects on mice infected with L. major.

Failed, Interrupted, or Inconclusive Trials on Immunomodulatory Treatment Strategies in Multiple Sclerosis: Update 2015-2020

In the past decades, multiple sclerosis (MS) treatment has experienced vast changes resulting from major advances in disease-modifying therapies (DMT). Looking at the overall number of studies, investigations with therapeutic advantages and encouraging results are exceeded by studies of promising compounds that failed due to either negative or inconclusive results or have been interrupted for other reasons. Importantly, these failed clinical trials are informative experiments that can help us to understand the pathophysiological mechanisms underlying MS. In several trials, concepts taken from experimental models were not translatable to humans, although they did not lack a well-considered pathophysiological rationale. The lessons learned from these discrepancies may benefit future studies and reduce the risks for patients. This review summarizes trials on MS since 2015 that have either failed or have been interrupted for various reasons. We identify potential causes of failure or inconclusiveness, looking at the path from basic animal experiments to clinical trials, and discuss the implications for our current view on MS pathogenesis, clinical practice, and future study designs. We focus on anti-inflammatory treatment strategies, without including studies on already approved and effective DMT. Clinical trials addressing neuroprotective and alternative treatment strategies are presented in a separate article.

Targeting innate receptors with MIS416 reshapes Th responses and suppresses CNS disease in a mouse model of multiple sclerosis

Modification of the innate immune cell environment has recently been recognized as a viable treatment strategy for reducing autoimmune disease pathology. MIS416 is a microparticulate immune response modifier that targets myeloid cells, activating cytosolic receptors NOD2 and TLR9, and has completed a phase 1b/2a trial for the treatment of secondary progressive multiple sclerosis. Using a mouse model of multiple sclerosis, we are investigating the pathways by which activation of TLR9 and NOD2 may modify the innate immune environment and the subsequent T cell-mediated autoimmune responses. We have found that MIS416 has profound effects on the Th subset balance by depressing antigen-specific Th1, Th17, and Th2 development. These effects coincided with an expansion of specific myeloid subpopulations and increased levels of MIS416-stimulated IFN-γ by splenocytes. Additionally, systemic IFN-γ serum levels were enhanced and correlated strongly with disease reduction, and the protective effect of MIS416 was abrogated in IFN-γ-deficient animals. Finally, treatment of secondary progressive MS patients with MIS416 similarly elevated the levels of IFN-γ and IFN-γ-associated proteins in the serum. Together, these studies demonstrate that administration of MIS416, which targets innate cells, reshapes autoimmune T cell responses and leads to a significant reduction in CNS inflammation and disease.

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.

Neonatal BCG immunization followed by DNAhsp65 boosters: highly immunogenic but not protective against tuberculosis - a paradoxical effect of the vector?

A new tuberculosis vaccine is urgently needed. Prime-boost strategies are considered very promising and the inclusion of BCG is highly desirable. In this investigation, we tested the protective efficacy of BCG delivered in the neonatal period followed by boosters in the adult phase with a DNA vaccine containing the hsp65 gene from Mycobacterium leprae (pVAXhsp65). Immune responses were characterized by serum anti-hsp65 antibody levels and IFN-gamma and IL-5 production by the spleen. Amounts of these cytokines were also determined in lung homogenates. Protective efficacy was established by the number of colony-forming units (CFU) and histopathological analysis of the lungs after challenge with Mycobacterium tuberculosis. Immunization with BCG alone triggered a significant reduction of CFU in the lungs and also clearly preserved the pulmonary parenchyma. BCG priming also increased the immunogenicity of pVAXhsp65. However, boosters with pVAXhsp65 or the empty vector abolished the protective efficacy of BCG. Also, higher IL-5 levels were produced by spleen and lungs after DNA boosters. These results demonstrated that neonatal BCG immunization followed by DNAhsp65 boosters is highly immunogenic but is not protective against tuberculosis.

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.

Inflammation and the emerging role of the toll-like receptor system in acute brain ischemia

BACKGROUND AND PURPOSE

Systemic administration of cytosine-guanine (CpG) oligodeoxynucleotides provides neuroprotection against subsequent cerebral ischemic injury. We examined the genomic response of leukocytes and brain cells after ischemia in the context of CpG preconditioning.

METHODS

RNA was isolated from circulating leukocytes and ischemic cortex 3 and 24 hours after middle cerebral artery occlusion after CpG or saline pretreatment and subjected to microarray analysis. Genes uniquely upregulated in CpG-pretreated mice were examined for overrepresented transcriptional regulatory elements.

RESULTS

CpG preconditioning induced a novel response to middle cerebral artery occlusion within circulating leukocytes that was dominated by natural killer cell-associated genes and the GATA-3 transcriptional regulatory element. Preconditioning also caused a novel brain response to stroke that was dominated by Type I interferon, interferon-associated genes, and transcriptional regulatory elements.

CONCLUSIONS

CpG preconditioning invokes novel leukocyte and brain responses to stroke. In this, CpG may be a unique preconditioning agent, coordinating peripheral and brain responses to protect against ischemic injury.

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.

TLR ligand suppression or enhancement of Treg cells? A double-edged sword in immunity to tumours

Toll-like receptor (TLR) agonists are potent activators of innate immune responses, activating dendritic cell (DC) maturation and inflammatory cytokine secretion by innate immune cells and as a consequence they promote adaptive immune response when coadministered with foreign antigens. There is also some evidence from mouse models that TLR ligands can help to break tolerance to self-antigens and promote immune responses to tumour antigens. Therefore, they have been exploited as adjuvants for tumour vaccines or as immunotherapeutics against cancer. Clinical evaluation of TLR agonists has resulted in a licensed immunotherapeutic for basal cell carcinoma, but there have also been disappointing results from clinical trials, with one pharmaceutical company recently halting its clinical programme. A major obstacle to the development of any active immunotherapeutic approach to cancer is the immunosuppressive environment of the growing tumour, including the induction of tolerogenic DCs and regulatory T (Treg) cells, which suppress the development of protective effector T-cell responses. This can be compounded by the use of TLR ligands as immunotherapeutics. A problem with TLR agonists that has not been fully appreciated is that they can generate suppressive as well as inflammatory responses in innate immune cells and can promote the induction of regulatory as well as effector T cells. This is part of a normal mechanism for limiting collateral damage during infection or sterile inflammation, but can constrain their ability to induce protective antitumour immunity, especially in the immune suppressed environment of the tumour. Alternatively, manipulating the TLR-activated innate immune responses to selectively blocking immunosuppressive arm, as well as that induced by the tumour, may hold the key to enhancing their efficacy as tumour immunotherapeutics and as adjuvants for cancer vaccines.

Antiinfective applications of toll-like receptor 9 agonists

The innate immune system detects pathogens by the presence of highly conserved pathogen-expressed molecules, which trigger host immune defenses. Toll-like receptor (TLR) 9 detects unmethylated CpG dinucleotides in bacterial or viral DNA, and can be stimulated for therapeutic applications with synthetic oligodeoxynucleotides containing immune stimulatory "CpG motifs." TLR9 activation induces both innate and adaptive immunity. The TLR9-induced innate immune activation can be applied in the prevention or treatment of infectious diseases, and the adaptive immune-enhancing effects can be harnessed for improving vaccines. This article highlights the current understanding of the mechanism of action of CpG oligodeoxynucleotides, and provides an overview of the preclinical data and early human clinical trial results, applying these TLR9 agonists in the field of infectious diseases.

Induction of immunity to neuroblastoma early after syngeneic hematopoietic stem cell transplantation using a novel mouse tumor vaccine

Autologous HSCT has resulted in improved event-free survival in patients with advanced neuroblastoma, but most of these patients still relapse. We previously reported that transient transfection of mouse neuroblastoma cells with plasmid DNA vectors encoding immune costimulatory molecules generates cell-based vaccines capable of inducing potent antitumor T cell immunity. In this study, we explored the effectiveness of tumor vaccine administration soon after HSCT. Soon after transplantation, only vaccinated mice that had received an adoptive transfer of syngeneic T cells survived tumor challenge. Tumor protective immunity in the transplant recipients was dependent on CD4(+) and CD8(+) T cells, and tumor-reactive T cells in the spleens of vaccinated mice could be detected in IFN-gamma enzyme-linked immunosorbent spot (ELISPOT) assays. Our data indicate that the adoptive transfer of T cells was absolutely required for induction of protective immunity by the tumor vaccine. Adoptive transfer of T cells accelerated T cell reconstitution, but it also resulted in increased percentages of CD4(+)CD25(+)Foxp3(+) cells soon after HSCT. Treatment of HSC transplant recipients with an anti-CD25 mAb before tumor vaccination inhibited antitumor immunity and significantly decreased the number of IFN-gamma-secreting tumor-specific CD4 T cells. However, physical depletion of CD25(+) cells from the adoptively transferred splenocytes appeared to increase the efficacy of tumor vaccination. Collectively, these results demonstrate that anti-neuroblastoma immunity can be induced soon after HSCT using a novel cell-based cancer vaccine. However, sufficient numbers of T cells must be added to the graft to achieve protective antitumor immunity, and depletion of CD25(+) T cells from adoptively transferred T cells might provide some additional benefit. These translational studies will aid in our development of post-HSCT vaccines for neuroblastoma.

Therapeutic potential of Toll-like receptor 9 activation

In the decade since the discovery that mouse B cells respond to certain unmethylated CpG dinucleotides in bacterial DNA, a specific receptor for these 'CpG motifs' has been identified, Toll-like receptor 9 (TLR9), and a new approach to immunotherapy has moved into the clinic based on the use of synthetic oligodeoxynucleotides (ODN) as TLR9 agonists. This review highlights the current understanding of the mechanism of action of these CpG ODN, and provides an overview of the preclinical data and early human clinical trial results using these drugs to improve vaccines and treat cancer, infectious disease and allergy/asthma.

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.

Intramuscular immunization with a DNA vaccine encoding a 26-amino acid CETP epitope displayed by HBc protein and containing CpG DNA inhibits atherosclerosis in a rabbit model of atherosclerosis

Rabbits were intramuscularly immunized with the plasmid pCR-X8-HBc-CETP encoding a B-cell epitope of cholesteryl ester transfer protein (CETP) C-terminal fragment (CETPC) displayed by Hepatitis B virus core (HBc) particle. This plasmid also contained immunostimulatory sequences (ISS) which included eight CpG motifs 5'-GACGTT-3', functioning as immunomodulators. After anti-CETP antibodies were successfully produced, rabbits were fed with a high-cholesterol diet for 15 weeks, and then the antiatherogenic effects of this DNA immunization were evaluated. The results showed that the fraction of plasma cholesterol in HDL significantly increased and the fraction of plasma cholesterol in LDL decreased in the pCR-X8-HBc-CETP immunized rabbits compared with those in the saline control group and one group treated with the plasmid pCR-X8-HBc containing ISS but lacking CETP epitope. More importantly, DNA immunization with pCR-X8-HBc-CETP markedly reduced the average percentage of aortic lesions in the entire aorta area by 80.60% compared with the saline control (3.78% versus 19.48%) and the average thickness of hyperplastic coronary artery in this group was also significantly less than in the saline control group (146+/-11 microm versus 248+/-18 microm). Our data also showed that CpG DNA alone could be antiatherogenic in this model because the average percentage of aortic lesions in pCR-X8-HBc immunized rabbits was 16.53% lower than that of the saline control group and the average thickness of hyperplastic coronary artery was also substantially lower than saline control group (155+/-13 microm versus 248+/-18 microm). Thus, plasmid pCR-X8-HBc-CETP could significantly inhibit the progression of atherosclerosis and be potentially developed as a suitable DNA vaccine against atherosclerosis.

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.

Immunomodulation and protection induced by DNA-hsp65 vaccination in an animal model of arthritis

We described a prophylactic and therapeutic effect of a DNA vaccine encoding the Mycobacterium leprae 65-kDa heat shock protein (DNA-hsp65) in experimental murine tuberculosis. However, high homology of the vaccine to the corresponding mammalian hsp60, together with the CpG motifs in the plasmidial vector, could trigger or exacerbate an autoimmune disease. In the present study, we evaluate the potential of DNA-hsp65 vaccination to induce or modulate arthritis in mice genetically selected for acute inflammatory reaction (AIR), either maximal (AIRmax) or minimal (AIRmin). Mice immunized with DNA-hsp65 or injected with the corresponding DNA vector (DNAv) developed no arthritis, whereas pristane injection resulted in arthritis in 62% of AIRmax mice and 7.3% of AIRmin mice. Administered after pristane, DNA-hsp65 downregulated arthritis induction in AIRmax animals. Levels of interleukin (IL)-12 were significantly lower in mice receiving pristane plus DNA-hsp65 or DNAv than in mice receiving pristane alone. However, when mice previously injected with pristane were inoculated with DNA-hsp65 or DNAv, the protective effect was significantly correlated with lower IL-6 and IL-12 levels and higher IL-10 levels. Our results strongly suggest that DNA-hsp65 has no arthritogenic potential and is actually protective against experimentally induced arthritis in mice.

Characterization of relapsing autoimmune encephalomyelitis and its treatment with decoy chemokine receptor genes

To elucidate the pathomechanisms of relapses of autoimmune disorders and to develop immunotherapy against relapses, we induced acute monophasic and chronic relapsing (CR) experimental autoimmune encephalomyelitis (EAE) in DA rats. Immunopathological and cytokine-chemokine analyses demonstrated that the number of infiltrating macrophages was significantly elevated in the CR-EAE than in acute EAE lesions and that IFN-gamma and IP-10 in the spinal cord were significantly upregulated during the first attack and relapse of CR-EAE, respectively, than at the peak of acute EAE. In vivo administration of decoy chemokine receptor plasmid DNAs encoding the binding sites of CXCR3 and CCR2 suppressed the development of relapse of CR-EAE. Importantly, multiple injections of DNAs did not elicit the antibody production against chemokine receptors. Taken together, these findings demonstrated that neutralization therapy with decoy chemokine receptor DNAs is effective to control autoimmune diseases.

DNA vaccination with CD25 protects rats from adjuvant arthritis and induces an antiergotypic response

Ab's to the alpha-chain of the IL-2 receptor (anti-CD25) are used clinically to achieve immunosuppression. Here we investigated the effects of DNA vaccination with the whole CD25 gene on the induction of rat adjuvant arthritis. The DNA vaccine protected the rats and led to a shift in the cytokine profile of T cells responding to disease target antigens from Th1 to Th2. The mechanism of protection was found to involve the induction of an antiergotypic response, rather than the induction of anti-CD25 Ab's. Antiergotypic T cells respond to activation molecules, ergotopes, expressed on syngeneic activated, but not resting, T cells. CD25-derived peptides function as ergotopes that can be recognized by the antiergotypic T cells. Antiergotypic T cells taken from control sick rats did not proliferate against activated T cells and secreted mainly IFN-gamma. In contrast, antiergotypic cells from CD25-DNA-protected rats proliferated against activated T cells and secreted mainly IL-10. Protective antiergotypic T cells were found in both the CD4+ and CD8+ populations and expressed alpha/beta or gamma/delta T cell receptors. Antiergotypic alpha/beta T cells were MHC restricted, while gamma/delta T cells were MHC independent. Thus, CD25 DNA vaccination may induce protection from autoimmunity by inducing a cytokine shift in both the antiergotypic response and the response to the antigens targeted in the disease.

DNA vaccination with CD25 protects rats from adjuvant arthritis and induces an antiergotypic response

Ab's to the alpha-chain of the IL-2 receptor (anti-CD25) are used clinically to achieve immunosuppression. Here we investigated the effects of DNA vaccination with the whole CD25 gene on the induction of rat adjuvant arthritis. The DNA vaccine protected the rats and led to a shift in the cytokine profile of T cells responding to disease target antigens from Th1 to Th2. The mechanism of protection was found to involve the induction of an antiergotypic response, rather than the induction of anti-CD25 Ab's. Antiergotypic T cells respond to activation molecules, ergotopes, expressed on syngeneic activated, but not resting, T cells. CD25-derived peptides function as ergotopes that can be recognized by the antiergotypic T cells. Antiergotypic T cells taken from control sick rats did not proliferate against activated T cells and secreted mainly IFN-gamma. In contrast, antiergotypic cells from CD25-DNA-protected rats proliferated against activated T cells and secreted mainly IL-10. Protective antiergotypic T cells were found in both the CD4+ and CD8+ populations and expressed alpha/beta or gamma/delta T cell receptors. Antiergotypic alpha/beta T cells were MHC restricted, while gamma/delta T cells were MHC independent. Thus, CD25 DNA vaccination may induce protection from autoimmunity by inducing a cytokine shift in both the antiergotypic response and the response to the antigens targeted in the disease.

Safety of CpG oligodeoxynucleotides in veterinary species

Bacterial DNA and synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in particular sequence contexts (CpG ODN) are recognized as a danger signal by the innate immune system of vertebrates. For this reason, CpG ODNs have a potential application as both an adjuvant and nonspecific immune modulator and are currently being evaluated in a number of human and veterinary clinical trials. Given their potent immunostimulatory activity, CpG ODNs could possibly induce adverse reactions. As all adjuvants and immune modulators must be nontoxic to meet safety requirements, it was essential to address the safety aspects of CpG ODNs. The current review summarizes experiments carried out to date to establish the safety of CpG ODNs in animals.

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.

Gene therapy in autoimmune, demyelinating disease of the central nervous system

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system (CNS), where suspected autoimmune attack causes nerve demyelination and progressive neurodegeneration and should benefit from both anti-inflammatory and neuroprotective strategies. Although neuroprotection strategies are relatively unexplored in MS, systemic delivery of anti-inflammatory agents to people with MS has so far been relatively disappointing. This is most probably because of the limited capacity of these molecules to enter the target tissue, because of exclusion by the blood-brain barrier. The complex natural history of MS also means that any therapeutic agents will have to be administered long-term. Gene therapy offers the possibility of site-directed, long-term expression, and is currently being preclinically investigated in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. While some immune effects may be targeted in the periphery using DNA vaccination, strategies both viral and nonviral are being developed to target agents into the CNS either via direct delivery or using the trafficking properties of cell-carrier systems. Targeting of leucocyte activation, cytokines and nerve growth factors have shown some promising benefit in animal EAE systems, the challenge will be their application in clinical use.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

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.

From bugs to drugs: therapeutic immunomodulation with oligodeoxynucleotides containing CpG sequences from bacterial DNA

Several types of immune cells possess pattern recognition receptors (PRR) that can distinguish prokaryotic DNA from vertebrate DNA by detecting unmethylated CpG dinucleotides in particular base contexts (CpG motifs). Bacterial DNA or synthetic oligodeoxynucleotides containing these CpG motifs activate both innate and acquired immune responses that have evolved to protect against intracellular infections. These T helper 1 (Th1)-like immune responses include activation of B cells, dendritic cells, macrophages, and natural killer (NK) cells. CpG DNA-induced immune activation can protect against infection either alone or in combination with a vaccine and is effective in the immunotherapy of allergic diseases and cancer. Human clinical trials using such CpG DNA are currently underway.

Delivery to the central nervous system of a nonreplicative herpes simplex type 1 vector engineered with the interleukin 4 gene protects rhesus monkeys from hyperacute autoimmune encephalomyelitis

Systemic administration of antiinflammatory molecules to patients affected by immune-mediated inflammatory demyelinating diseases of the central nervous system (CNS) has limited therapeutic efficacy due to the presence of the blood-brain barrier (BBB). We found that three of five rhesus monkeys injected intrathecally with a replication-defective herpes simplex virus (HSV) type 1-derived vector engineered with the human interleukin 4 (IL-4) gene were protected from an hyperacute and lethal form of experimental autoimmune encephalomyelitis induced by whole myelin. The intrathecally injected vector consistently diffused within the CNS via the cerebrospinal fluid and infected ependymal cells, which in turn sustained in situ production of IL-4 without overt immunological or toxic side effects. In EAE-protected monkeys, IL-4-gene therapy significantly decreased the number of brain as well as spinal cord inflammatory perivenular infiltrates and the extent of demyelination, necrosis, and axonal loss. The protective effect was associated with in situ downregulation of inflammatory mediators such as tumor necrosis factor alpha (TNF-alpha) and monocyte chemoattractant protein 1 (MCP-1), upregulation of transforming growth factor beta (TGF-beta), and preservation of BBB integrity. Our results indicate that intrathecal delivery of HSV-1-derived vectors containing antiinflammatory cytokine genes may play a major role in the future therapeutic armamentarium of inflammatory CNS-confined demyelinating diseases and, in particular, in the most fulminant forms where conventional therapeutic approaches have, so far, failed to achieve a satisfactory control of the disease evolution.

Vaccination with empty plasmid DNA or CpG oligonucleotide inhibits diabetes in nonobese diabetic mice: modulation of spontaneous 60-kDa heat shock protein autoimmunity

Nonobese diabetic (NOD) mice develop insulitis and diabetes through a process involving autoimmunity to the 60-kDa heat shock protein (HSP60). Treatment of NOD mice with HSP60 or with peptides derived from HSP60 inhibits this diabetogenic process. We now report that NOD diabetes can be inhibited by vaccination with a DNA construct encoding human HSP60, with the pcDNA3 empty vector, or with an oligonucleotide containing the CpG motif. Prevention of diabetes was associated with a decrease in the degree of insulitis and with down-regulation of spontaneous proliferative T cell responses to HSP60 and its peptide p277. Moreover, both the pcDNA3 vector and the CpG oligonucleotide induced specific Abs, primarily of the IgG2b isotype, to HSP60 and p277, and not to other islet Ags (glutamic acid decarboxylase or insulin) or to an unrelated recombinant Ag expressed in bacteria (GST). The IgG2b isotype of the specific Abs together with the decrease in T cell proliferative responses indicate a shift of the autoimmune process to a Th2 type in treated mice. These results suggest that immunostimulation by bacterial DNA motifs can modulate spontaneous HSP60 autoimmunity and inhibit NOD diabetes.

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.

Gene therapy in experimental autoimmune encephalomyelitis

Gene therapy traditionally has been associated with "gene replacement." where exogenous recombinant DNA is introduced ex vivo into somatic cells that are then introduced back into the patient as a way to correct an inherited genetic defect. However, several novel gene therapy strategies for treating autoimmune diseases recently have emerged. Strategies involving the use of several types of DNA vaccines, the application of various viral vectors, and the use of diverse cellular vectors have shown promise in inhibiting autoimmune-mediated inflammation and repairing tissue damaged as a result of autoimmune attack. In the current review, we examine and discuss the development and proposed use of emerging gene therapy strategies for the treatment of autoimmune disease with specific emphasis on experimental autoimmune encephalomyelitis (EAE), an animal model widely used in multiple sclerosis (MS) research.

Cytokine gene therapy of autoimmune demyelination revisited using herpes simplex virus type-1-derived vectors

The peripheral delivery of drugs in patients affected by central nervous system (CNS)-confined diseases is therapeutically ineffective due to the presence of the blood-brain barrier which forms an inaccessible wall to the majority of CNS targeting molecules. When molecules with an anti-inflammatory profile have been systemically administered to patients affected by a chronic inflammatory demyelinating disease of the CNS, such as multiple sclerosis (MS), results have been disappointing. A successful therapeutic approach in MS should therefore consider the delivery of anti-inflammatory molecules directly into the CNS in order to inhibit blood-borne CNS-confined mononuclear cells which act as ultimate effector cells directly destroying oligodendrocytes and/or releasing myelinotoxic substances. Biological and physical vectors engineered with heterologous genes coding for immunomodulatory cytokines with an anti-inflammatory profile might represent the appropriate tool to deliver therapeutic genes into the CNS of patients with MS. So far, cytokine gene therapy has never been attempted in MS, but encouraging results have been obtained in the animal model of MS, experimental autoimmune encephalomyelitis (EAE), using viral vectors or plasmids engineered with cytokine genes and then injected systemically, either in the blood stream or circulating encephalitogenic T cells, or into the CNS. Here, we critically discuss the various attempts made in EAE using gene therapy protocols based on the delivery of immunomodulatory cytokine genes. Special emphasis is put on the use of non-replicative herpes simplex type-1 (HSV)-derived vectors engineered with the gene of the immunomodulatory cytokine interleukin (IL)-4.

Intra-pinna anti-tumor vaccination with self-replicating infectious RNA or with DNA encoding a model tumor antigen and a cytokine

To optimize polynucleotide vaccinations for protective antitumor immunity we used a self-replicating RNA vaccine in which Semliki Forest virus replicase drives RNA expression of the lacZ gene coding for beta-galactosidase as model tumor-associated antigen (TAA). This was compared with replicase-deficient control RNA and with lacZ DNA plasmids with respect to gene expression in vitro and in vivo and for vaccination using the mouse ear pinna as an optimal immunization site. In vitro, the highest expression was observed with self-replicating RNA. Gene expression following pinna inoculation of either non-replicating DNA plasmids or self-replicating RNA was similar, lasting for 2-3 weeks. Higher antibody responses were obtained with RNA than with DNA. beta-Gal peptide specific CTL memory responses to lacZ DNA or RNA lasted for more than 6 weeks while respective responses induced by lacZ-transfected tumor cells lasted for only 2 weeks. To achieve a protective response against lacZ tumor cells with self-replicating RNA about a 100-fold lower dose of polynucleotide was sufficient in comparison to DNA. The extent of protective antitumor immunity not only depended on the gene dose used for vaccination, but also on the aggressiveness of the lacZ-transfected tumor line used for challenge. In comparison to lacZ-transfected tumor cells as vaccines, polynucleotide vaccination also demonstrated superiority with regard to cross-protection. Protective antitumor immunity could be strongly increased upon co-inoculation of lacZ DNA with IL-2 DNA or IL-12 RNA. IL-2 DNA, but not IL-12 RNA, also augmented the CTL response while IL-12 RNA, but not IL-2 DNA, reduced the antibody response. These results demonstrate efficient protective antitumor immunity after intra-pinna lacZ TAA polynucleotide vaccination and show additional immunomodulatory effects by co-administration of cytokine polynucleotides.

The role of CpG motifs in innate immunity

Pattern recognition receptors of the innate immune system are able to distinguish certain prokaryotic DNAs from vertebrate DNAs by detecting unmethylated CpG dinucleotides in particular base contexts ('CpG motifs'). Recent studies have begun to define the molecular mechanisms of actions of CpG motifs and have demonstrated their stimulatory effects on leukocytes from humans and vertebrates other than mice. Oligodeoxynucleotides containing CpG motifs are highly effective Th1-like vaccine adjuvants through multiple routes of immunization and show promise as immunotherapeutic agents for cancer and allergic diseases.

Presence of CpG DNA and the Local Cytokine Milieu Determine the Efficacy of Suppressive DNA Vaccination in Experimental Autoimmune Encephalomyelitis

We here study the adjuvant properties of immunostimulatory DNA sequences (ISS) and coinjected cytokine-coding cDNA in suppressive vaccination with DNA encoding an autoantigenic peptide, myelin basic protein peptide 68–85, against Lewis rat experimental autoimmune encephalomyelitis (EAE). EAE is an autoaggressive, T1-mediated disease of the CNS. ISS are unmethylated CpG motifs found in bacterial DNA, which can induce production of type 1 cytokines in vertebrates through the innate immune system. Because ISS in the plasmid backbone are necessary for efficient DNA vaccination, we studied the effect of one such ISS, the 5′-AACGTT-3′ motif, in our system. Treatment with a DNA vaccine encoding myelin basic protein peptide 68–85 and containing three ISS of 5′-AACGTT-3′ sequence suppressed clinical signs of EAE, while a corresponding DNA vaccine without such ISS had no effect. We further observed reduced proliferative T cell responses in rats treated with the ISS-containing DNA vaccine, compared with controls. We also studied the possible impact of coinjection of plasmid DNA encoding rat cytokines IL-4, IL-10, GM-CSF, and TNF-α with the ISS-containing DNA vaccine. Coinjection of IL-4-, IL-10-, or TNF-α-coding cDNA inhibited the suppressive effect of the DNA vaccine on EAE, whereas GM-CSF-coding cDNA had no effect. Coinjection of cytokine-coding cDNA with the ISS-deficient DNA vaccine failed to alter clinical signs of EAE. We conclude that the presence of ISS and induction of a local T1 cytokine milieu is decisive for specific protective DNA vaccination in EAE.