Protection of rats from adjuvant arthritis by immunization with naked DNA encoding for mycobacterial heat shock protein 65

Heat Shock Proteins Alterations in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory and autoimmune disease characterized by the attack of the immune system on the body's healthy joint lining and degeneration of articular structures. This disease involves an increased release of inflammatory mediators in the affected joint that sensitize sensory neurons and create a positive feedback loop to further enhance their release. Among these mediators, the cytokines and neuropeptides are responsible for the crippling pain and the persistent neurogenic inflammation associated with RA. More importantly, specific proteins released either centrally or peripherally have been shown to play opposing roles in the pathogenesis of this disease: an inflammatory role that mediates and increases the severity of inflammatory response and/or an anti-inflammatory and protective role that modulates the process of inflammation. In this review, we will shed light on the neuroimmune function of different members of the heat shock protein (HSPs) family and the complex manifold actions that they exert during the course of RA. Specifically, we will focus our discussion on the duality in the mechanism of action of Hsp27, Hsp60, Hsp70, and Hsp90.

Heat shock proteins and their immunomodulatory role in inflammatory arthritis

Autoimmune diseases, including inflammatory arthritis, are characterized by a loss of self-tolerance, leading to an excessive immune responses and subsequent ongoing inflammation. Current therapies are focused on dampening this inflammation, but a permanent state of tolerance is seldom achieved. Therefore, novel therapies that restore and maintain tolerance are needed. Tregs could be a potential target to achieve permanent immunotolerance. Activation of Tregs can be accomplished when they recognize and bind their specific antigens. HSPs are proteins present in all cells and are upregulated during inflammation. These proteins are immunogenic and can be recognized by Tregs. Several studies in animal models and in human clinical trials have shown the immunoregulatory effects of HSPs and their protective effects in inflammatory arthritis. In this review, an overview is presented of the immunomodulatory effects of several members of the HSP family in general and in inflammatory arthritis. These effects can be attributed to the activation of Tregs through cellular interactions within the immune system. The effect of HSP-specific therapies in patients with inflammatory arthritis should be explored further, especially with regard to long-term efficacy and safety and their use in combination with current therapeutic approaches.

The association between rheumatoid arthritis and periodontal disease

Chronic, plaque-associated inflammation of the gingiva and the periodontium are among the most common oral diseases. Periodontitis (PD) is characterized by the inflammatory destruction of the periodontal attachment and alveolar bone, and its clinical appearance can be influenced by congenital as well as acquired factors. The existence of a rheumatic or other inflammatory systemic disease may promote PD in both its emergence and progress. However, there is evidence that PD maintains systemic diseases. Nevertheless, many mechanisms in the pathogenesis have not yet been examined sufficiently, so that a final explanatory model is still under discussion, and we hereby present arguments in favor of this. In this review, we also discuss in detail the fact that oral bacterial infections and inflammation seem to be linked directly to the etiopathogenesis of rheumatoid arthritis (RA). There are findings that support the hypothesis that oral infections play a role in RA pathogenesis. Of special importance are the impact of periodontal pathogens, such as Porphyromonas gingivalis on citrullination, and the association of PD in RA patients with seropositivity toward rheumatoid factor and the anti-cyclic citrullinated peptide antibody.

[Pathogenesis of parodontitis in rheumatic diseases]

Inflammatory periodontal disease (PD) is a common disease worldwide that has a primarily bacterial aetiology and is characterized by dysregulation of the host inflammatory response. The degree of inflammation varies among individuals with PD independently of the degree of bacterial infection, suggesting that alteration of the immune function may substantially contribute to its extent. Factors such as smoking, education, and body mass index (BMI) are discussed as potential risk factors for PD. Most PD patients respond to bacterial invaders by mobilizing their defensive cells and releasing cytokines such as interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha, and IL-6, which ultimately causes tissue destruction by stimulating the production of collagenolytic enzymes, such matrix metalloproteinases. Recently, there has been growing evidence suggesting an association between PD and the increased risk of systemic diseases, such ateriosclerosis, diabetes mellitus, stroke, and rheumatoid arthritis (RA). PD and rheumatologic diseases such as RA share many pathological aspects and immunological findings.

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.

Self heat-shock protein 65-mediated regulation of autoimmune arthritis

Heat-shock proteins (Hsps) have been invoked in the pathogenesis of a variety of autoimmune diseases. The mycobacterial heat-shock protein 65 (Bhsp65) has been studied extensively as one of the antigenic triggers of autoimmunity in experimental models of, as well as patients with, rheumatoid arthritis. As Hsps are highly conserved and immunogenic, it is generally anticipated that self Hsps might serve as the endogenous targets of the immune response initiated by the homologous foreign Hsps. Contrary to this expectation, studies in the rat adjuvant arthritis (AA) model have revealed that priming of the self (rat) hsp65 (Rhsp65)-directed T cells in the Lewis rat leads to protection against AA instead of disease induction or aggravation. The arthritis-protective attribute of the self hsp65 is also evident following spontaneous priming of the anti-Rhsp65 T cells during the natural course of AA. Furthermore, immunization of rats with human hsp60, or with Bhsp65 peptides that are crossreactive with the corresponding self hsp65 peptides, leads to protection against AA. Importantly, high levels of T cell reactivity against self hsp60 in patients with juvenile idiopathic arthritis positively correlate with a favorable outcome of the disease. Thus, immune response against self hsp65 in autoimmune arthritis is protective rather than being pathogenic.

Tolerizing DNA vaccines for autoimmune arthritis

Current therapies for rheumatoid arthritis (RA) and other autoimmune diseases non-specifically suppress immune function, and there is great need for fundamental approaches such as antigen-specific tolerizing therapy. In this paper we describe development of antigen-specific tolerizing DNA vaccines to treat collagen-induced arthritis (CIA) in mice, and use of protein microarrays to monitor response to therapy and to identify potential additional autoimmune targets for next generation vaccines. We demonstrate that tolerizing DNA vaccines encoding type II collagen (CII) reduced the incidence and severity of CIA. Atorvastatin, a statin drug found to reduce the severity of autoimmunity, potentiated the effect of DNA vaccines encoding CII. Analysis of cytokines produced by collagen-reactive T cells derived from mice receiving tolerizing DNA encoding CII, as compared to control vaccines, revealed reduced production of the pro-inflammatory cytokines IFN-gamma and TNF-alpha. Arthritis microarray analysis demonstrated reduced spreading of autoantibody responses in mice treated with DNA encoding CII. The development of tolerizing DNA vaccines, and the use of antibody profiling to guide design of and to monitor therapeutic responses to such vaccines, represents a promising approach for the treatment of RA and other autoimmune diseases.

HSP60 as a target of anti-ergotypic regulatory T cells

The 60 kDa heat shock protein (HSP60) has been reported to influence T-cell responses in two ways: as a ligand of toll-like receptor 2 signalling and as an antigen. Here we describe a new mechanism of T-cell immuno-regulation focused on HSP60: HSP60 is up-regulated and presented by activated T cells (HSP60 is an ergotope) to regulatory (anti-ergotypic) T cells. Presentation of HSP60 by activated T cells was found to be MHC-restricted and dependent on accessory molecules - CD28, CD80 and CD86. Anti-ergotypic T cells responded to T-cell HSP60 by proliferation and secreted IFNγ and TGFβ1. In vitro, the anti-ergotypic T cells inhibited IFNγ production by their activated T-cell targets. In vivo, adoptive transfer of an anti-ergotypic HSP60-specific T-cell line led to decreased secretion of IFNγ by arthritogenic T cells and ameliorated adjuvant arthritis (AA). Thus, the presentation of HSP60 by activated T cells turns them into targets for anti-ergotypic regulatory T cells specific for HSP60. However, the direct interaction between the anti-ergotypic T regulators (anti-HSP60) and the activated T cells also down-regulated the regulators. Thus, by functioning as an ergotope, HSP60 can control both the effector T cells and the regulatory HSP60-specific T cells that control them.

Mycobacterial Hsp65-IgG-expressing tolerogenic B cells confer protection against adjuvant-induced arthritis in Lewis rats

OBJECTIVE

Tolerization of T cells directed against a target autoantigen is a desired goal of experimental approaches for the treatment of autoimmune diseases, and novel and improved methods of tolerance induction are continuously being sought. Because most traditional methods of tolerance induction using soluble antigen are effective in the prevention of autoimmunity but fail to control established disease, this study was carried out to explore an innovative tolerogenic approach for the treatment of ongoing disease, using the rat adjuvant-induced arthritis (AIA) model of human rheumatoid arthritis.

METHODS

Lewis (RT.1(l)) rats were injected subcutaneously with heat-killed Mycobacterium tuberculosis H37Ra to induce AIA. Before or after AIA induction, Lewis rats were treated intraperitoneally (IP) with tolerogenic B cells expressing a fusion construct of mycobacterial 65-kd heat-shock protein (Hsp65) and IgG heavy-chain. For comparison, control rats were treated IP with ovalbumin (OVA)-IgG-expressing B cells or soluble mycobacterial Hsp65, and the effects on AIA were observed. We also tested the immune response to mycobacterial Hsp65 in B cell-tolerized rats.

RESULTS

Administration of tolerogenic mycobacterial Hsp65-expressing B cells as well as soluble mycobacterial Hsp65, but not OVA-expressing B cells, resulted in a significant decrease in the severity of subsequent AIA. However, in rats with established disease, only the B cell regimen of mycobacterial Hsp65, but not the soluble antigen, suppressed ongoing AIA.

CONCLUSION

Mycobacterial Hsp65-IgG-expressing B cells can successfully attenuate the progression of AIA. This study introduces a promising approach for the treatment of arthritis that should be further explored.

Stress, Heat Shock Proteins, and Autoimmunity: How Immune Responses to Heat Shock Proteins Are to Be Used for the Control of Chronic Inflammatory Diseases

Especially since the (re-)discovery of T cell subpopulations with specialized regulatory activities, mechanisms of anti-inflammatory T cell regulation are studied very actively and are expected to lead to the development of novel immunotherapeutic approaches, especially in chronic inflammatory diseases. Heat shock proteins (Hsp) are possible targets for regulatory T cells due to their enhanced expression in inflamed (stressed) tissues and the evidence that Hsp induce anti-inflammatory immunoregulatory T cell responses. Initial evidence for an immunoregulatory role of Hsp in chronic inflammation was obtained through analysis of T cell responses in the rat model of adjuvant arthritis and the findings that Hsp immunizations protected against the induction of various forms of autoimmune arthritis in rat and mouse models. Since then, immune reactivity to Hsp was found to result from inflammation in various disease models and human inflammatory conditions, such as rheumatoid arthritis (RA), type 1 diabetes, and atherosclerosis. Now, also in the light of a growing interest in T cell regulation, it is of interest to further explore the mechanisms through which Hsp can be utilized to trigger immunoregulatory pathways, capable of suppressing such a wide and diversified spectrum of inflammatory diseases.

Novel therapies for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease that causes significant morbidity and mortality. The pathogenesis outlined to date in RA consists of a cascade of pro-inflammatory cytokines and chemokines leading to the recruitment of inflammatory cells and the self perpetuation of inflammation, ultimately leading to cartilage and bone destruction. The dramatic progress in understanding the molecular immunology in RA has led to a transition from conventional treatment with aggressive immune suppression to targeted biological-based therapies that control the inflammatory pathways associated with RA. This article reviews the current biological and small-molecule therapies approved for the treatment of RA and those in development, including antibodies, tolerising agents and vaccines.

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.

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.

Heat-shock proteins induce T-cell regulation of chronic inflammation

Immune responses to certain heat-shock proteins (HSPs) develop in almost all inflammatory diseases; however, the significance of such responses is only now becoming clear. In experimental disease models, HSPs can prevent or arrest inflammatory damage, and in initial clinical trials in patients with chronic inflammatory disease, HSP-derived peptides have been shown to promote the production of anti-inflammatory cytokines, indicating that HSPs have immunoregulatory potential. In this Review, we discuss the unique characteristics of HSPs that endow them with these immunoregulatory qualities.

DNA vaccines coding for heat-shock proteins (HSPs): tools for the activation of HSP-specific regulatory T cells

Heat-shock proteins (HSPs) perform opposing functions in autoimmune arthritis. HSP-specific T cells drive the progression of adjuvant arthritis (AA), an experimental model of autoimmune arthritis. However, HSP-specific T cells can also have a regulatory phenotype, controlling arthritogenic T cells and inhibiting AA progression. This manuscript reviews the use of DNA vaccines coding for HSPs to analyse the role of these proteins in the regulation of arthritis. Recent studies suggest that HSPs participate in the control of pathological autoimmunity. Indeed, DNA vaccines coding for HSPs can be used to activate these HSP-specific built-in regulatory mechanisms. Thus, DNA vaccines coding for HSPs may serve not only as tools for the dissection of immunoregulatory mechanisms, but also as agents for the treatment of autoimmune disorders.

A heterologous DNA priming-Mycobacterium bovis BCG boosting immunization strategy using mycobacterial Hsp70, Hsp65, and Apa antigens improves protection against tuberculosis in mice

Tuberculosis is responsible for >2 million deaths a year, and the number of new cases is rising worldwide. DNA vaccination combined with Mycobacterium bovis bacillus Calmette Guerin (BCG) represents a potential strategy for prevention of this disease. Here, we used a heterologous prime-boost immunization approach using a combination of DNA plasmids and BCG in order to improve the efficacy of vaccination against Mycobacterium tuberculosis infection in mice. As model antigens, we selected the M. tuberculosis Apa (for alanine-proline-rich antigen) and the immunodominant Hsp65 and Hsp70 mycobacterial antigens combined with BCG. We demonstrated that animals injected with a combination of DNA vectors expressing these antigens, when boosted with BCG, showed increased specific antimycobacterial immune responses compared to animals vaccinated with BCG alone. More importantly, the protection achieved with this regimen was also significantly better than with BCG alone.

Inhibition of adjuvant-induced arthritis by DNA vaccination with the 70-kd or the 90-kd human heat-shock protein: immune cross-regulation with the 60-kd heat-shock protein

OBJECTIVE

Adjuvant arthritis can be induced in Lewis rats by immunization with Mycobacterium tuberculosis (Mt). The mycobacterial 65-kd heat-shock protein (Hsp65) is targeted by arthritogenic T cells. However, Hsp65 and the mycobacterial 71-kd heat-shock protein are also recognized by T cells that can down-regulate adjuvant-induced arthritis (AIA). We have recently demonstrated that vaccination with human Hsp60 DNA inhibits AIA. The present study was undertaken to analyze the role of the T cell responses to self HSP molecules other than Hsp60 in the control of AIA.

METHODS

Lewis rats were immunized with DNA vaccines coding for human Hsp70 or Hsp90 (Hsp70 plasmid [pHsp70] or pHsp90), and AIA was induced. The T cell response to Mt, Hsp60, Hsp70, and Hsp90 (proliferation and cytokine release) was studied, and the T cell response to Hsp60 was mapped with overlapping peptides.

RESULTS

The Hsp70 or Hsp90 DNA vaccines shifted the arthritogenic T cell response from a Th1 to a Th2/3 phenotype and inhibited AIA. We detected immune crosstalk between Hsp70/90 and Hsp60: both the Hsp70 and Hsp90 DNA vaccines induced Hsp60-specific T cell responses. Similarly, DNA vaccination with Hsp60 induced Hsp70-specific T cell immunity. Epitope mapping studies revealed that Hsp60-specific T cells induced by pHsp70 vaccination reacted with known regulatory Hsp60 epitopes.

CONCLUSION

T cell immunity to Hsp70 and to Hsp90, like Hsp60-specific immunity, can modulate the arthritogenic response in AIA. In addition, our results suggest that the regulatory mechanisms induced by Hsp60, Hsp70, and Hsp90 are reinforced by an immune network that connects their reactivities.

Effect of Mycobacterium tuberculosis chaperonins on bronchial eosinophilia and hyper-responsiveness in a murine model of allergic inflammation

BACKGROUND

Epidemiological evidence suggests that infection with Mycobacterium tuberculosis protects children against asthma. Several laboratories have shown that, in mouse models of allergic inflammation, administration of the whole live tuberculosis vaccine, Mycobacterium bovis bacillus Calmette-Guerin (BCG), prevents ovalbumin (OVA)-induced pulmonary eosinophilia.

OBJECTIVE

The aim of this study was to characterize specific M. tuberculosis molecules that are known to modulate immune responses to see if they affected pulmonary eosinophilia and bronchial hyper-responsiveness.

METHODS

C57Bl/6 mice were sensitized to OVA on days 0 and 7 and subsequently challenged with OVA on day 14 over a 3-day period. Pulmonary eosinophilia and bronchial hyper-responsiveness were measured 24 h following the last antigen challenge. In some groups, mice were pre-treated with M. tuberculosis or M. tuberculosis chaperonins (Cpns)60.1, 60.2 and 10, and the effect of this treatment on the allergic inflammatory response to aerosolized OVA was established.

RESULTS

We show that M. tuberculosis Cpns inhibit allergen-induced pulmonary eosinophilia in the mouse. Of the three Cpns produced by M. tuberculosis, Cpn60.1, Cpn10 and Cpn60.2, the first two are effective in preventing eosinophilia when administered by the intra-tracheal route. Furthermore, the increase in airways sensitivity to inhaled methacholine following OVA challenge of immunized mice was suppressed following treatment with Cpn60.1. The allergic inflammatory response was also characterized by an increase in Th2 cytokines IL-4 and IL-5 in bronchoalveolar lavage fluid, which was also suppressed following treatment with Cpn60.1.

CONCLUSION

These data show that bacterial Cpns can suppress eosinophil recruitment and bronchial hyper-responsiveness in a murine model of allergic inflammation.

The T cells specific for the carboxyl-terminal determinants of self (rat) heat-shock protein 65 escape tolerance induction and are involved in regulation of autoimmune arthritis

Immunization of Lewis rats with heat-killed Mycobacterium tuberculosis H37Ra leads to development of polyarthritis (adjuvant-induced arthritis; AA) that shares several features with human rheumatoid arthritis (RA). Immune response to the 65-kDa mycobacterial heat-shock protein (Bhsp65) is believed to be involved in induction of AA as well as in experimental modulation of this disease. However, the understanding of several critical aspects of the pathogenesis of AA in the Lewis rat has severely been hampered by the lack of information both regarding the level as well as epitope specificity of tolerance to the mammalian self (rat) homologue of Bhsp65, 65-kDa rat heat-shock protein (Rhsp65), and about the functional attributes of the T cell repertoire specific for this self protein. In this study, we established that tolerance to Rhsp65 in the Lewis rat is incomplete, and that the residual T cells primed upon challenge with this self hsp65 are disease regulating in nature. We also have defined the T cell epitopes in the C-terminal region within Rhsp65 that contribute predominantly to the immune reactivity as well as the AA-protective effect of this self protein. Furthermore, the T cells primed by peptides comprising these C-terminal determinants can be efficiently restimulated by the naturally generated epitopes from endogenous Rhsp65, suggesting that self hsp65 might also be involved in natural remission from acute AA. These novel first experimental insights into the self hsp65-directed regulatory T cell repertoire in AA would help develop better immunotherapeutic approaches for autoimmune arthritis.

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.

DNA fragments of the human 60-kDa heat shock protein (HSP60) vaccinate against adjuvant arthritis: identification of a regulatory HSP60 peptide

Adjuvant arthritis (AA) is induced by immunizing Lewis rats with Mycobacterium tuberculosis suspended in adjuvant. The mycobacterial 65-kDa heat shock protein (HSP65) contains at least one epitope associated with the pathogenesis of AA: T cell clones that recognize an epitope formed by aa 180-188 of HSP65 react with self-cartilage and can adoptively transfer AA. Nevertheless, vaccination with HSP65 or some of its T cell epitopes can prevent AA by a mechanism that seems to involve cross-reactivity with the self-60-kDa HSP60. We recently demonstrated that DNA vaccination with the human hsp60 gene can inhibit AA. In the present work, we searched for regulatory epitopes using DNA vaccination with HSP60 gene fragments. We now report that specific HSP60 DNA fragments can serve as effective vaccines. Using overlapping HSP60 peptides, we identified a regulatory peptide (Hu3) that was specifically recognized by the T cells of DNA-vaccinated rats. Vaccination with Hu3, or transfer of splenocytes from Hu3-vaccinated rats, inhibited the development of AA. Vaccination with the mycobacterial homologue of Hu3 had no effect. Effective DNA or peptide vaccination was associated with enhanced T cell proliferation to a variety of disease-associated Ags, along with a Th2/3-like shift (down-regulation of IFN-gamma secretion and enhanced secretion of IL-10 and/or tumor growth factor beta1) in response to peptide Mt176-190 (the 180-188 epitope of HSP65). The regulatory response to HSP60 or its Hu3 epitope included both Th1 (IFN-gamma) and Th2/3 (IL-10/tumor growth factor beta1) secretors. These results show that regulatory mechanisms can be activated by immunization with relevant self-HSP60 epitopes.

Antigen-based immune modulation: DNA vectors and beyond

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

Inhibition of adjuvant arthritis by a DNA vaccine encoding human heat shock protein 60

Adjuvant arthritis (AA) is an autoimmune disease inducible in rats involving T cell reactivity to the mycobacterial 65-kDa heat shock protein (HSP65). HSP65-specific T cells cross-reactive with the mammalian 60-kDa heat shock protein (HSP60) are thought to participate in the modulation of AA. In this work we studied the effects on AA of DNA vaccination using constructs coding for HSP65 (pHSP65) or human HSP60 (pHSP60). We found that both constructs could inhibit AA, but that pHSP60 was more effective than pHSP65. The immune effects associated with specific DNA-induced suppression of AA were complex and included enhanced T cell proliferation to a variety of disease-associated Ags. Effective vaccination with HSP60 or HSP65 DNA led paradoxically to up-regulation of IFN-gamma secretion to HSP60 and, concomitantly, to down-regulation of IFN-gamma secretion to the P180-188 epitope of HSP65. There were also variable changes in the profiles of IL-10 secretion to different Ags. However, vaccination with pHSP60 or pHSP65 enhanced the production of TGFbeta1 to both HSP60 and HSP65 epitopes. Our results support a regulatory role for HSP60 autoreactivity in AA and demonstrate that this control mechanism can be activated by DNA vaccination with both HSP60 or HSP65.

Cytotoxic T cells and mycobacteria

How the immune system kills Mycobacterium tuberculosis is still a puzzle. The classical picture of killing due to phagocytosis by activated macrophages may be only partly correct. Based on recent evidence, we express here the view that cytotoxic T lymphocytes also make an important contribution and suggest that DNA vaccines might be a good way to enhance this.

Arthritis protective regulatory potential of self-heat shock protein cross-reactive T cells

Immunization with heat shock proteins has protective effects in models of induced arthritis. Analysis has shown a reduced synovial inflammation in such protected animals. Adoptive transfer and immunization with selected T cell epitopes (synthetic peptides) have indicated the protection to be mediated by T cells directed to conserved hsp epitopes. This was shown first for mycobacterial hsp60 and later for mycobacterial hsp70. Fine specificity analysis showed that such T cells were cross-reactive with the homologous self hsp. Therefore protection by microbial hsp reactive T cells can be by cross-recognition of self hsp overexpressed in the inflamed tissue. Preimmunization with hsp leads to a relative expansion of such self hsp cross-responsive T cells. The regulatory nature of such T cells may originate from mucosal tolerance maintained by commensal flora derived hsp or from partial activation through recognition of self hsp as a partial agonist (Altered Peptide Ligand) or in the absence of proper costimulation. Recently, we reported the selective upregulation of B7.2 on microbial hsp600 specific T cells in response to self hsp60. Through a preferred interaction with CTLA-4 on proinflammatory T cells this may constitute an effector mechanism of regulation. Also, regulatory T cells produced IL10.

Induction of antigen specific CD4+ T cell responses by invariant chain based DNA vaccines

In this report, the use of DNA vaccination to induce class II restricted antigen specific proliferative responses was studied. To this end, a construct encoding the invariant chain (Ii) was engineered in which the Class II associated invariant chain peptide (CLIP) sequence was replaced by an immunogenic epitope derived form Heat Shock Protein 60, HSP60 178-186. Transfection studies in vitro showed that this construct can be used to efficiently load MHC class II molecules and present epitopes to MHC class II restricted antigen specific T cells. In addition, we showed that intradermal immunisation of Lewis rats with these constructs induced antigen specific T cells in vivo. Therefore, our Ii-gene constructs can be used to immunise for defined CD4+ T cell epitope sequences.

Arthritis protective regulatory potential of self-heat shock protein cross-reactive T cells

Immunization with heat shock proteins has protective effects in models of induced arthritis. Analysis has shown a reduced synovial inflammation in such protected animals. Adoptive transfer and immunization with selected T cell epitopes (synthetic peptides) have indicated the protection to be mediated by T cells directed to conserved hsp epitopes. This was shown first for mycobacterial hsp60 and later for mycobacterial hsp70. Fine specificity analysis showed that such T cells were cross-reactive with the homologous self hsp. Therefore protection by microbial hsp reactive T cells can be by cross-recognition of self hsp overexpressed in the inflamed tissue. Preimmunization with hsp leads to a relative expansion of such self hsp cross-responsive T cells. The regulatory nature of such T cells may originate from mucosal tolerance maintained by commensal flora derived hsp or from partial activation through recognition of self hsp as a partial agonist (Altered Peptide Ligand) or in the absence of proper costimulation. Recently, we reported the selective upregulation of B7.2 on microbial hsp600 specific T cells in response to self hsp60. Through a preferred interaction with CTLA-4 on proinflammatory T cells this may constitute an effector mechanism of regulation. Also, regulatory T cells produced IL10.

Gene therapy for autoimmune disorders

Although many autoimmune disorders do not have a strong genetic basis, their treatment may nevertheless be improved by gene therapies. Most strategies seek to transfer genes encoding immunomodulatory products that will alter host immune responses in a beneficial manner. Used in this fashion, genes serve as biological delivery vehicles for the products they encode. By this means gene therapy overcomes obstacles to the targeted delivery of proteins and RNA, and improves their efficacy while providing a longer duration of effect, and, potentially, greater safety. Additional genetic strategies include DNA vaccination and the ablation of selected tissues and cell populations. There is considerable evidence from animal studies that gene therapies work: examples include the treatment of experimental models of rheumatoid arthritis, multiple sclerosis, diabetes, and lupus. Pre-clinical success in treating animal models of rheumatoid arthritis has led to the first clinical trial of gene therapy for an autoimmune disease. In this Phase I study, a cDNA encoding the interleukin-1 receptor antagonist was transferred to the knuckle joints of patients with advanced rheumatoid arthritis. Two additional clinical trials are in progress. It is likely that gene therapy will provide effective new treatments for a wide range of autoimmune disorders.

Sodium phosphate enhances plasmid DNA expression in vivo

Intramuscular injection of plasmid DNA results in myofiber cell expression of proteins encoded by the DNA. The preferred vehicle for plasmid DNA injections has been saline (154 mM sodium chloride) or PBS (154 mM NaCl plus 10 mM sodium phosphate). Here, it is shown that injection of luciferase or beta-galactosidase encoding plasmid DNA in a 150 mM sodium phosphate vehicle into murine muscle resulted in a two- to seven-fold increase in transgene expression compared with DNA injected in saline or PBS. When the DNA encoded secreted alkaline phosphatase, preproinsulin or interferon, sodium phosphate vehicle increased their serum levels by two- to four-fold. When the DNA encoded mouse erythropoietin, sodium phosphate vehicle increased hematocrits by two-fold compared with DNA injected in saline. When the DNA encoded influenza nucleoprotein, sodium phosphate increased anti-nucleoprotein antibody titers by two-fold. The expression of luciferase from plasmid DNA instilled into lung was increased five-fold compared with that in vehicle without sodium phosphate. Incubation of plasmid DNA with muscle extract or serum showed that sodium phosphate protected the DNA from degradation. Thus, a change from sodium chloride to sodium phosphate vehicle can enhance the expression of plasmid DNA in a tissue, possibly by inhibiting DNA degradation. Gene Therapy (2000) 7, 1171-1182.

A conserved mycobacterial heat shock protein (hsp) 70 sequence prevents adjuvant arthritis upon nasal administration and induces IL-10-producing T cells that cross-react with the mammalian self-hsp70 homologue

Immunization with Mycobacterium tuberculosis heat shock protein (hsp) 60 has been shown to protect rats from experimental arthritis. Previously, the protection-inducing capacity was shown to reside in the evolutionary conserved parts of the molecule. Now we have studied the nature of the arthritis suppressive capacity of a distinct, antigenically unrelated protein, M. tuberculosis hsp70. Again, a conserved mycobacterial hsp70 sequence was found to be immunogenic and to induce T cells that cross-reacted with the rat homologue sequence. However, in this case parenteral immunization with the peptide containing the critical cross-reactive T cell epitope did not suppress disease. Upon analysis of cytokines produced by these peptide-specific T cells, high IL-10 production was found, as was the case with T cells responsive to whole hsp70 protein. Nasal administration of this peptide was found to lead to inhibition of subsequent adjuvant arthritis induction. The data presented here shows the intrinsic capacity of conserved bacterial hsp to trigger self-hsp cross-reactive T cells with the potential to down-regulate arthritis via IL-10.

Nucleic acid immunization: concepts and techniques associated with third generation vaccines

A radical change in vaccine methodology arrived nine years ago with the advent of nucleic acid immunization. Aspects such as plasmid design, gene selection, the use of immunostimulatory complexes and clinical trials are discussed in this review. Furthermore, concepts and protocols involved in the construction, evaluation and immunization of a DNA vaccine have been examined as new strategies to enhance this technology continues to grow.

The potential use of heat-shock proteins to vaccinate against mycobacterial infections

Over the last few years, some of our experiments in which mycobacterial heat-shock protein (HSP) antigens were presented to the immune system as if they were viral antigens have had a significant impact on our understanding of protective immunity against tuberculosis. They have also markedly enhanced the prospects for new vaccines. We now know that the mycobacterial HSP65 antigen can confer protection equal to that from live BCG vaccine in mice.

DNA vaccines: technology and application as anti-parasite and anti-microbial agents

DNA vaccines have been termed The Third Generation of Vaccines. The recent successful immunization of experimental animals against a range of infectious agents and several tumour models of disease with plasmid DNA testifies to the powerful nature of this revolutionary approach in vaccinology. Among numerous advantages, a major attraction of DNA vaccines over conventional vaccines is that they are able to induce protective cytotoxic T-cell responses as well as helper T-cell and humoral immunity. Here we review the current state of nucleic acid vaccines and cover a wide range of topics including delivery mechanisms, uptake and expression of plasmid DNA, and the types of immune responses generated. Further, we discuss safety issues, and document the use of nucleic acid vaccines against viral, bacterial and parasitic diseases, and cancer. The early potential promise of DNA vaccination has been fully substantiated with recent, exciting developments including the movement from testing DNA vaccines in laboratory models to non-human primates and initial human clinical trials. These advances and the emerging voluminous literature on DNA vaccines highlight the rapid progress that has been made in the DNA immunization field. It will be of considerable interest to see whether the progress and optimism currently prevailing can be maintained, and whether the approach can indeed fulfil the medical and commerical promise anticipated.

DNA immunization confers systemic, but not mucosal, protection against enteroinvasive bacteria

Naked plasmid DNA (pRc/Y-hsp60) with a cytomegalovirus promoter and a sequence encoding Yersinia enterocolitica 60-kDa heat shock protein (Y-HSP60) was used for vaccination. After intramuscular injection of pRc/Y-hsp60, Y-hsp60 mRNA could be detected by reverse transcription-PCR in muscle, liver and spleen. A single immunization with pRc/Y-hsp60 induced significant Y-HSP60-specific T cell responses after 1 week. IFN-gamma production by spleen cells upon stimulation with Y-HSP60 was strictly dependent on the presence of CD4+ T cells, indicating the generation of a Th1 response upon DNA immunization. DNA immunization in addition induced strong Y-HSP60-specific IgG2a, weak IgG1, but not IgA antibodies. Immunization of BALB/c and C57BL/6 mice with pRc/Y-hsp60 conferred protection against disseminated Y. enterocolitica infection in spleen, but not at the site of mucosal entry, the Peyer's patches. Furthermore, pRc/Y-hsp60 vaccination did not induce cross-protection against related pathogens. Vaccination of beta2-microglobulin- and H2-I-Abeta-deficient mice was not protective, suggesting that both CD4+ and CD8+ T cells are required for protective immunity induced by DNA vaccination.

Role of heat shock proteins in protection from and pathogenesis of infectious diseases

Increased synthesis of heat shock proteins (hsp) occurs in prokaryotic and eukaryotic cells when they are exposed to stress. By increasing their hsp content, cells protect themselves from lethal assaults, primarily because hsp interfere with the uncontrolled protein unfolding that occurs under stress. However, hsp are not produced only by stressed cells; some hsp are synthesized constitutively and perform important housekeeping functions. Accordingly, hsp are involved in the assembly of molecules which play important roles in the immune system. It is not surprising that due to their wide distribution and their homology among different species, hsp represent target antigens of the immune response. Frequent confrontation of the immune system with conserved regions of hsp which are shared by various microbial pathogens can potentiate antimicrobial immunity. However, long-term confrontation of the immune system with hsp antigens which are similar in the host and invaders may convert the immune response against these host antigens and promote autoimmune disease. This review provides an overview of the role of hsp in immunity with a focus on infectious and autoimmune diseases.

Heat shock proteins as potential targets in the therapy of inflammatory arthritis

Whether heat shock proteins (hsp) will be therapeutic targets in arthritis depends on their role in pathogenesis. In this article, three possibilities are considered. Firstly, an excessive immune response to bacterial hsp could be arthritogenic - as may occur in reactive arthritis. In these circumstances therapy would be directed to down-regulating this immune response, or altering the nature of the immune response e.g. by changing cytokine production from interferon-g to IL-4. However this approach depends on the immune response to bacterial hsp not being critical for control of the bacterial infection. Secondly, an immune response to bacterial hsp may induce autoimmunity by cross-reactivity, e.g. with the homologous human. This could also be modulated in the same way with a lower likelihood of interfering with control of the infectious agent, since only a component of the immune response against the bacterial hsp will be cross-reactive with self. Thirdly, recent experiments raise the possibility that joint inflammation might be controlled by T cells which recognizes self hsp, particularly hsp60. Therapies might enhance this response; protection from experimental arthritis by prior immunization with hsp60 is well established. Whether similar approaches will be viable after arthritis is established remains to be seen.

Heat shock proteins and arthritis--new readers start here

The possible roles of heat shock proteins in the pathogenesis of inflammatory arthritis have been discussed for a number of years, and investigated intensively in both animal models and human disease. This review surveys evidence which has pointed, on the one hand, to hsp as targets of a pathogenic immune response, and on the other, to an immunoregulatory role for T cell recognition of self hsp. The extent to which findings in experimental animals have led to further insights applicable to human disease is also emphasised.

Vaccination with plasmid DNA encoding mycobacterial antigen 85A stimulates a CD4+ and CD8+ T-cell epitopic repertoire broader than that stimulated by Mycobacterium tuberculosis H37Rv infection

Vaccination of mice with plasmid DNA carrying the gene for the major secreted mycobacterial antigen 85A (Ag85A) from Mycobacterium tuberculosis is a powerful technique for generating robust specific Thl helper T-cell responses, CD8+-mediated cytotoxicity, and protection against M. tuberculosis challenge (K. Huygen et al., Nat. Med. 2:893-898, 1996). We have now analyzed in more detail the antigen-specific immune CD4+- and CD8+-T-cell responses induced in BALB/c mice vaccinated with Ag85A DNA and have compared these responses to those generated by intravenous infection with M. tuberculosis. T-cell-epitope mapping, as measured by interleukin-2 and gamma interferon secretion from splenic T cells restimulated in vitro with synthetic 20-mer peptides spanning the complete mature sequence of Ag85A, demonstrated that DNA vaccination stimulated a stronger and broader T-cell response than did M. tuberculosis infection. Moreover, elevated cytotoxic T lymphocyte (CTL) activity against Ag85A-transfected and peptide-pulsed P815 target cells could be generated exclusively by vaccination with plasmid DNA, not following M. tuberculosis infection. By using DNA vaccination, three Ag85A CTL epitopes with predicted major histocompatibility complex class I binding motifs were defined. One of them was previously reported as a dominant, promiscuously recognized T-cell epitope in healthy humans with primary infections. These data strengthen the potential of DNA vaccination with respect to inducing antituberculous immunity in humans.

Genetic vaccination against tuberculosis

New weapons are needed in the fight against tuberculosis. Recent research indicates that a vaccine better than BCG may be within reach. A diverse range of protein antigens can give encouragingly high levels of protective immunity in animal models when administered with adjuvants or as DNA vaccines. Accelerated arrest of bacterial multiplication followed by sustained decline in bacterial numbers are key parameters of protection and so the vaccine must target antigens produced by both actively multiplying and growth-inhibited bacteria. Consistent with this, the protective antigens have been found among secreted and stress proteins (e.g. Ag85, ESAT-6, hsp65, hsp70). Species-specific antigens are not needed, hence these remain available for diagnostic tests. Adoptive transfer of protection from vaccinated or infected mice into naive mice by transfer of purified T cells and clones shows that protection is expressed by antigen-specific cytotoxic T cells that produce interferon-gamma and lyse infected macrophages. These cells are produced in response to endogenous antigen. DNA vaccination appears to be an excellent way of generating these cells and may be able to give long-lasting protection.