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We have previously shown that Ag-specific IL-10-producing regulatory T cells (Tr1) participate in the regulation of experimental autoimmune encephalomyelitis and that their specificity undergoes determinant spread in a reciprocal manner to effector T cell specificity. The current study shows that coadministration of plasmid DNA vaccines encoding IL-10 together with a plasmid encoding a myelin basic protein (MBP) encephalitogenic determinant during an ongoing disease rapidly amplifies this Tr1-mediated response, in a disease-specific manner. Thus, coadministration of both plasmids, but not the plasmid DNA encoding MBP alone, rapidly suppresses an ongoing disease. Tolerance included elevation in Ag-specific T cells producing IL-10 and an increase in apoptosis of cells around high endothelial venules in the CNS after successful therapy. Tolerance could be transferred by MBP-specific primary T cells isolated from protected donors and reversed by neutralizing Abs to IL-10 but not to IL-4. Due to the nature of determinant spread in this model, we could bring about evidence implying that rapid and effective induction of Tr1-induced active tolerance is dependent on redirecting the Tr1 response to the epitope to which the effector function dominates the response at a given time. The consequences of these findings to multiple sclerosis, and possibly other inflammatory autoimmune diseases are discussed.

IL-27 is a recently defined family member of the long-chain four-helix bundle cytokines, which consists of EBI3, an IL-12p40-related protein, and p28, an IL-12p35-related polypeptide. The role of IL-27 in the regulation of inflammatory autoimmune diseases has never been studied. The current study uses the DNA vaccination technology, and highly specific Abs to the p28 subunit of IL-27 that were generated by this technology, to delineate its role in the regulation of adjuvant-induced arthritis in Lewis rats. Neutralizing the in vivo function of IL-27 by targeted DNA vaccines and by Abs against IL-27 p28 that were produced in protected donors could rapidly suppress an ongoing disease. Disease suppression was associated with a reduced ex vivo production of inflammatory cytokines. We then used these Abs to investigate the mechanistic basis of disease suppression, showing that IL-27 is not only involved in directing the polarization of naive T cells, but also affects the proliferative response and cytokine production of Ag-specific effector/memory Th1 cells. This may explain, in part, its important role in the regulation of inflammatory autoimmune diseases, and also suggest novel ways of therapy.

T-cell-mediated autoimmune diseases such as multiple sclerosis, rheumatoid arthritis or type 1 diabetes result from an aggressive attack of self-components by autoimmune T-cells. Pro-inflammatory mediators, particularly cytokines and chemokines, direct the homing and effectorfunction of these cells. It has recently been demonstrated that the immune system, which can attack self-components, also generates 'beneficial' autoimmunity against pro-inflammatory mediators. During the course of an autoimmune condition, and to a much lesser extent in response to microbial inflammation, the immune system produces auto-antibodies to pro-inflammatory mediators. This reduces the harm from these diseases. We also discovered that targeted DNA vaccines could effectively amplify these responses to provide protective immunity. The underlying mechanism is partially understood. At the site of immunization, the relevant gene product is produced and then presented by dendritic cells/macrophages, which undergo activation due to an interaction of plasmid CpG with toll-like receptor 9 on the dendritic cell. This then activates CD4+ T-cells, which help the production of T-cell-dependent antibodies against the gene product of the vaccines. These antibodies neutralize their target product and suppress inflammation. This review explores this interesting concept and its therapeutic implications.

Naked DNA encoding TNFalpha was introduced to BALB/c mice with experimental antiphospholipid syndrome (APS) induced by beta2GPI. Administration of naked DNA encoding TNFalpha resulted in the generation of immunological memory to its gene product, associated with elevated circulating anti-TNFalpha antibodies. Enriched IgG fraction of the mouse anti-TNFalpha was biologically active since it prevented endothelial cell activation by TNFalpha e.g., inhibition of monocyte adhesion to activated endothelial cells (HUVEC). Mice immunized with beta2GPI, vaccinated with TNFalpha DNA at an early stage of disease development, showed decreased titres of circulating anti-beta2GPI antibodies as compared to the group of mice vaccinated with a control naked DNA. The reduction of antiphospholipid antibody production was followed by amelioration of the foetal loss, increased platelet count to normal values as well as normalization of the prolonged aPTT. APS mice which were introduced to the TNFalpha DNA vector at a later stage of the disease development, showed less improvement in their clinical manifestations. The current study suggests a way in which a DNA vaccine can be employed for induction of a protective immunity in experimental APS.

IFN-gamma-inducible protein 10 (IP-10) is a CXC chemokine that is thought to manifest a proinflammatory role because it stimulates the directional migration of activated T cells, particularly Th1 cells. It is an open question whether this chemokine is also directly involved in T cell polarization. We show here that during the course of adjuvant-induced arthritis the immune system mounts a notable Ab titer against self-IP-10. Upon the administration of naked DNA encoding IP-10, this titer rapidly accelerates to provide protective immunity. Self-specific Ab to IP-10 developed in protected animals, as well as neutralizing Ab to IP-10 that we have generated in rabbits, could inhibit leukocyte migration, alter the in vivo and in vitro Th1/Th2 balance toward low IFN-gamma, low TNF-alpha, high IL-4-producing T cells, and adoptively transfer disease suppression. This not only demonstrates the pivotal role of this chemokine in T cell polarization during experimentally induced arthritis but also suggests a practical way to interfere in the regulation of disease to provide protective immunity. From the basic science perspective, this study challenges the paradigm of in vivo redundancy. After all, we did not neutralize the activity of other chemokines that bind CXCR3 (i.e., macrophage-induced gene and IFN-inducible T cell alpha chemoattractant) and yet significantly blocked not only adjuvant-induced arthritis but also the in vivo competence to mount delayed-type hypersensitivity.

IFN-gamma-inducible protein 10 (IP-10) is a CXC chemokine that stimulates the directional migration of activated T cells, particularly Th1 cells. We demonstrate in this work that during activation this chemokine drives naive CD4(+) T cells into Th1 polarization. Administration of plasmid DNA encoding self IP-10 was found capable of breaking down immunological tolerance to IP-10, resulting in the generation of self-specific immunity to the gene product of the vaccine. Despite the CpG motif that drives T cells into Th1, the vaccine redirected the polarization of myelin basic protein-specific T cells into Th2 and conferred the vaccinated recipients a high state of resistance against experimental autoimmune encephalomyelitis, a T cell-mediated autoimmune disease of the CNS. The vaccine also suppressed full-blown ongoing disease in a mouse model of multiple sclerosis. Self-specific Ab to IP-10 developed in protected animals could inhibit leukocyte migration, alter the in vitro Th1/Th2 balance of autoimmune T cells, and adoptively transfer disease suppression. This demonstrates not only the pivotal role of a chemokine in T cell polarization and function but also its potential implications for plasmid DNA gene therapy.

Depending on the mode of immunization, a single administration of CFA may result in the development of a local inflammatory process or chronic poly adjuvant-induced arthritis (AA). Administration of naked DNA encoding TNF-alpha results in the generation of immunological memory to its gene product. Upon induction of AA, this memory effectively inhibited the development of disease. Self-specific Abs developed in DNA-vaccinated animals were neutralizing in vitro and could adoptively transfer the beneficial effect of the vaccine. Administration of CFA to induce a local delayed-type hypersensitivity response rather than AA did not lead to an elicited production of Abs to the gene product of the above vaccine. Thus, elicitation of protective immunity is dependent on the development of an autoimmune condition. Most importantly, the administration of the TNF-alpha DNA construct after the onset of disease led to a rapid, long-lasting remission. This suggests a highly effective way by which a DNA vaccine encoding an autologous proinflammatory cytokine can be used to reprogram the immune system to generate protective immunity to its own potentially harmful activities.

This study used naked DNA vaccination to induce breakdown of tolerance to self and thus elicit immunological memory to native, membrane-bound Fas ligand (FasL). Upon induction of experimental autoimmune encephalomyelitis (EAE), this memory was turned on to provide protective immunity. FasL-specific autoantibodies isolated from protected animals differentially downregulated the in vitro production of TNF-alpha, but not IFN-gamma, by cultured T cells. These autoantibodies were highly protective when they were administered to rats at the onset of EAE. In contrast, administration of these FasL-specific Ab's to EAE rats after the peak of the acute phase of disease prevented spontaneous recovery from disease. This extended illness is partially explained by inhibition of mononuclear cell apoptosis at the target organ, which resulted in increased accumulation of T cells and macrophages at the site of inflammation. Hence, FasL exerts two distinct, stage-specific regulatory functions in the control of this T-cell mediated autoimmune disease of the central nervous system.

Depending on the method of immunization, a single administration of CFA may result in the development of a local inflammatory process or chronic polyadjuvant-induced arthritis (AA). We administered naked DNA vaccines encoding MIP-1 alpha, MCP-1, MIP-1 beta, and RANTES to Lewis rats and confirmed that each of these vaccines induced immunological memory to the corresponding gene product. Upon induction of disease, this memory effectively inhibited the development of the autoimmune condition. Self-specific Ab's developed in DNA-vaccinated animals were neutralizing in vitro and could adoptively transfer the beneficial effect of each vaccine. Repeated administration of the constructs encoding MCP-1, MIP-1 alpha, or RANTES inhibited the development and progression of AA, even when each vaccine was administered only after the onset of disease. This suggests a highly effective way by which the immune system could be re-educated to generate protective immunity against its own harmful activities.

We recently used a modification of gene therapy (naked DNA vaccination) to induce immunological memory against self-pro-inflammatory chemokines such as macrophage inflammatory protein-1 alpha or monocyte chemoattractant protein-1, and against the pro-inflammatory cytokine tumor necrosis factor-alpha. First, DNA constructs encoding each of the different pro-inflammatory mediators together with a repeated immunostimulatory sequence were prepared. Then, experiment animals were subjected to a repeated administration of each construct. Under these conditions, tolerance to the product of each insert was broken, and immunological memory established. Upon induction of experimental autoimmune encephalomyelitis, a T cell-mediated autoimmune disease of the central nervous system that serves as a model for multiple sclerosis or adjuvant induced arthritis, this memory was "turned on" to provide DNA-vaccinated animals a high state of disease resistance. Antibodies to the product of each inserted gene were isolated form these animals. Each antibody was found capable of neutralizing in vitro the chemoattractive properties of each relevant chemokine, thereby transferring disease resistance. Interestingly, the level of their production was dependent on disease severity, that is, each titer was accelerated in accordance with disease progression. Thus, by using a simple gene therapy technique the immune system could be "re-educated" to restrain its own harmful activities.

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the central nervous system (CNS). RT-PCR verified by Southern blotting and sequencing of PCR products of two C-C chemokines, MIP-1alpha and MCP-1, was performed on brain samples from EAE rats to evaluate mRNA transcription of these chemokines at different stages of disease. mRNA transcription in of each chemokine peaked after the onset of disease and declined during its remission. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1alpha or MCP-1 DNA vaccines prevented EAE. Immunization of CFA without the encephalitogenic epitope did not elicit an anti-C-C chemokine regulatory response in DNA- vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease., (Copyright 1999 Academic Press.)

TNF-alpha is thought to be a key pro-inflammatory cytokine in T cell-mediated autoimmune diseases, particularly in rheumatoid arthritis (RA) and multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE) serves as an animal model for MS. The current study observes a notable TNF-alpha-specific antibody titer generated during the course of EAE, apparently not sufficient to prevent the development of disease. Administration of TNF-alpha-naked DNA vaccine enhanced the production of TNF-alpha-specific antibody titer and conferred EAE resistance. These antibodies were found to be neutralizing in vitro and capable of inhibiting the development of disease when transferred to other EAE rats. Thus, modulation of EAE with TNF-alpha DNA vaccines enhances the regulation of natural immunity to a self pro-inflammatory cytokine and provides a tool by which the immune system is encouraged to elicit anti-self protective immunity to restrain its own harmful reactivity when such a response is needed.

DNA vaccination represents a novel means of expressing Ag in vivo for the generation of both humoral and cellular immune responses. The current study uses this technology to elicit protective immunity against experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease of the central nervous system that serves as an experimental model for multiple sclerosis. RT-PCR verified by Southern blotting and sequencing of PCR products of four different C-C chemokines, macrophage-inflammatory protein-1alpha (MIP-1alpha), monocyte-chemotactic protein-1 (MCP-1), MIP-1beta, and RANTES, were performed on brain samples from EAE rats to evaluate mRNA transcription at different stages of disease. Each PCR product was then used as a construct for naked DNA vaccination. The subsequent in vivo immune response to MIP-1alpha or MCP-1 DNA vaccines prevented EAE, even if disease was induced 2 mo after administration of naked DNA vaccines. In contrast, administration of the MIP-1beta naked DNA significantly aggravated the disease. Generation of in vivo immune response to RANTES naked DNA had no notable effect on EAE. MIP-1alpha, MCP-1, and MIP-1beta mRNA transcription in EAE brains peaked at the onset of disease and declined during its remission, whereas RANTES transcription increased in EAE brains only following recovery. Immunization of CFA without the encephalitogenic epitope did not elicit the anti-C-C chemokine regulatory response in DNA-vaccinated rats. Thus, modulation of EAE with C-C chemokine DNA vaccines is dependent on targeting chemokines that are highly transcribed at the site of inflammation at the onset of disease.