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

Aberrant immunity in the oral cavity-a link with rheumatoid arthritis?

There are well established epidemiological links between rheumatoid arthritis and periodontitis. Recent data have started to shed light on the mechanisms that might underlie the relationship between these two complex diseases. Unravelling the roles of distinct pathways involved in these mechanisms has the potential to yield novel preventative and therapeutic strategies for both diseases. Perhaps most intriguingly, this represents an area where understanding the biology in the oral cavity might reveal fundamental advances in understanding immune regulation and the relationships between the host and microbiome. Here we seek to discuss aspects of the adaptive immune response that might link periodontitis and rheumatoid arthritis.

Viewing Autoimmune Pathogenesis from the Perspective of Antigen Processing and Determinant Hierarchy

Autoimmunity results from the breakdown of immune tolerance to defined target self antigens. Like any foreign antigen, a self antigen is continuously processed by antigen-presenting cells (APCs) and its epitopes are displayed by the major histocompatibility complex on the cell surface (dominant epitopes). However, this self antigen fails to induce a T cell response as the T cells against its dominant epitopes have been purged in the thymus during negative selection. In contrast, the T cells against poorly processed (cryptic) self epitopes escape tolerance induction in the thymus and make it to the periphery. Such T cells are generally harmless as their cognate epitopes in the periphery are not presented efficiently. But, under conditions of inflammation and immune activation, previously cryptic epitopes can be revealed on the APC surface for activation of ambient T cells. This can initiate autoimmunity in individuals who are susceptible owing to their genetic and environmental constellation. Subsequent waves of enhanced processing of other epitopes on the same or different self antigens then cause "diversification" or "spreading" of the initial T cell response, resulting in propagation of autoimmunity. However, depending on the disease process and the self antigen involved, "epitope spreading" may instead contribute to natural regression of autoimmunity. This landmark conceptual framework developed by Eli Sercarz and his team ties together determinant hierarchy, selection of epitope-specific T cells, and the induction/progression of autoimmunity. I am extremely fortunate to have worked with Eli and to have been a part of this fascinating research endeavor.

Peptide-Based Vaccination Therapy for Rheumatic Diseases

Rheumatic diseases are extremely heterogeneous diseases with substantial risks of morbidity and mortality, and there is a pressing need in developing more safe and cost-effective treatment strategies. Peptide-based vaccination is a highly desirable strategy in treating noninfection diseases, such as cancer and autoimmune diseases, and has gained increasing attentions. This review is aimed at providing a brief overview of the recent advances in peptide-based vaccination therapy for rheumatic diseases. Tremendous efforts have been made to develop effective peptide-based vaccinations against rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), while studies in other rheumatic diseases are still limited. Peptide-based active vaccination against pathogenic cytokines such as TNF-α and interferon-α (IFN-α) is shown to be promising in treating RA or SLE. Moreover, peptide-based tolerogenic vaccinations also have encouraging results in treating RA or SLE. However, most studies available now have been mainly based on animal models, while evidence from clinical studies is still lacking. The translation of these advances from experimental studies into clinical therapy remains impeded by some obstacles such as species difference in immunity, disease heterogeneity, and lack of safe delivery carriers or adjuvants. Nevertheless, advances in high-throughput technology, bioinformatics, and nanotechnology may help overcome these impediments and facilitate the successful development of peptide-based vaccination therapy for rheumatic diseases.

Immunomodulation of autoimmune arthritis by pro-inflammatory cytokines

Pro-inflammatory cytokines promote autoimmune inflammation and tissue damage, while anti-inflammatory cytokines help resolve inflammation and facilitate tissue repair. Over the past few decades, this general feature of cytokine-mediated events has offered a broad framework to comprehend the pathogenesis of autoimmune and other immune-mediated diseases, and to successfully develop therapeutic approaches for diseases such as rheumatoid arthritis (RA). Anti-tumor necrosis factor-α (TNF-α) therapy is a testimony in support of this endeavor. However, many patients with RA fail to respond to this or other biologics, and some patients may suffer unexpected aggravation of arthritic inflammation or other autoimmune effects. These observations combined with rapid advancements in immunology in regard to newer cytokines and T cell subsets have enforced a re-evaluation of the perceived pathogenic attribute of the pro-inflammatory cytokines. Studies conducted by others and us in experimental models of arthritis involving direct administration of IFN-γ or TNF-α; in vivo neutralization of the cytokine; the use of animals deficient in the cytokine or its receptor; and the impact of the cytokine or anti-cytokine therapy on defined T cell subsets have revealed paradoxical anti-inflammatory and immunoregulatory attributes of these two cytokines. Similar studies in other models of autoimmunity as well as limited studies in arthritis patients have also unveiled the disease-protective effects of these pro-inflammatory cytokines. A major mechanism in this regard is the altered balance between the pathogenic T helper 17 (Th17) and protective T regulatory (Treg) cells in favor of the latter. However, it is essential to consider that this aspect of the pro-inflammatory cytokines is context-dependent such that the dose and timing of intervention, the experimental model of the disease under study, and the differences in individual responsiveness can influence the final outcomes. Nevertheless, the realization that pro-inflammatory cytokines can also be immunoregulatory offers a new perspective in fully understanding the pathogenesis of autoimmune diseases and in designing better therapies for controlling them.

Tanshinone IIA ameliorates chronic arthritis in mice by modulating neutrophil activities

Rheumatoid arthritis (RA) is a chronic immune inflammatory disease mediated by the influx of immune cells into the synovial joint space. As Tanshinone IIA (TIIA) has potent anti-oxidant and anti-inflammatory activities, we used the adjuvant-induced arthritis (AA) murine model of RA to investigate the impact of TIIA on RA and immune cell activation. The anti-arthritic activity of TIIA was investigated in an adjuvant-induced arthritis model of RA in mice. Myeloperoxidase and neutrophil elastase expression levels were assessed in ankle joints by immunohistochemistry analysis. Immune cell infiltration was evaluated in air pouch experiments. Proinflammatory cytokines expression levels were determined by quantitative real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assays. Neutrophil extracellular traps (NETs) were assessed by immunostaining and confocal microscopy. Treatment with TIIA alleviated cartilage erosion and neutrophil infiltration in the ankle joints of AA mice and reduced proinflammatory cytokine expression levels in sera. TIIA suppressed interleukin-6 and tumour necrosis factor-α expression and release in neutrophils and promoted neutrophil apoptosis. TIIA also inhibited the NET formation of neutrophils. Our findings demonstrated that TIIA can ameliorate RA effectively by targeting neutrophils, indicating that TIIA may act as a potential therapeutic for RA.

Modulation of Adjuvant Arthritis by Cellular and Humoral Immunity to Hsp65

Heat shock proteins (Hsps) are highly conserved, and their expression is upregulated in cells by heat and other stressful stimuli. These proteins play a vital role in preserving the structural and functional integrity of cells under stress. Despite the ubiquitous expression of Hsps in an individual, the immune system is not fully tolerant to them. In fact, Hsps are highly immunogenic in nature, and immune response to these proteins is observed in various inflammatory and autoimmune diseases. Studies on the immunopathogenesis of autoimmune arthritis in the rat adjuvant arthritis (AA) model of human rheumatoid arthritis (RA) as well as observations in patients with RA and juvenile idiopathic arthritis (JIA) have unraveled immunoregulatory attributes of self-Hsp65-directed immunity. Notable features of Hsp65 immunity in AA include protection rather than disease induction following immunization of Lewis rats with self (rat)-Hsp65; the diversification of T cell response to mycobacterial Hsp65 during the course of AA and its association with spontaneous induction of response to self-Hsp65; the cross-reactive T cells recognizing foreign and self homologs of Hsp65 and their role in disease suppression in rats; the suppressive effect of antibodies to Hsp65 in AA; and the use of Hsp65, its peptides, or altered peptide ligands in controlling autoimmune pathology. The results of studies in the AA model have relevance to RA and JIA. We believe that these insights into Hsp65 immunity would not only advance our understanding of the disease process in RA/JIA, but also lead to the development of novel therapeutic approaches for autoimmune arthritis.

Tinospora cordifolia inhibits autoimmune arthritis by regulating key immune mediators of inflammation and bone damage

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the joints leading to tissue damage. Despite the availability of potent drugs including the biologics, many patients fail to respond to them, whereas others suffer adverse effects following long-term use of these drugs. Accordingly, the use of natural herbal products by RA patients has been increasing over the years. However, limited information about the mechanism of action of these natural products is a major shortcoming that prevents the widespread acceptance of herbal therapy by professionals and patients alike. In this study, we demonstrated the anti-arthritic activity of Tinospora cordifolia extract (TCE) using the rat adjuvant-induced arthritis model of human RA and elaborated the immune mechanisms underlying this effect. TCE treatment suppressed arthritic inflammation and bone and cartilage damage. The anti-inflammatory effect of TCE was mediated via reduction of the pro-inflammatory cytokines such as: IL-1β, TNF-α, IL-6, and IL-17; the frequency of IL-17-producing T cells; and the production of chemokines such as RANTES. Furthermore, TCE treatment limited bone damage by shifting the balance of mediators of bone remodeling (e.g., receptor activator of nuclear factor-kB ligand [RANKL] and MMP-9) in favor of anti-osteoclastic activity. Our results suggest that TCE and its bioactive components should be evaluated for their utility as therapeutic adjuncts to conventional drugs against RA.

Heat shock proteins can be targets of regulatory T cells for therapeutic intervention in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterised by excessive immune responses resulting in inflammation of the joints. Although current therapies can be successful in dampening inflammation, a long-lived state of tolerance is seldom achieved. Therefore, novel therapies are needed that restore and maintain tolerance in patients with RA. Targeting regulatory T cells (Tregs) is a successful strategy to achieve tolerance, as was shown in studies performed in animal models and in human clinical trials. The antigen-specificity of Tregs is crucial for their effectiveness and allows for very specific targeting of these cells. However, which antigen is suitable for autoimmune diseases such as RA, for which the autoantigens are largely unknown? Heat shock proteins (HSPs) are ubiquitously expressed and can be up-regulated during inflammation. Additionally, HSPs, or HSP-derived peptides are immunogenic and can be recognised by a variety of immune cells, including Tregs. Therefore, this review highlights the potential of HSP-specific Tregs to control inflammatory immune responses. Targeting HSP-specific Tregs in RA can be achieved via the administration of HSPs (derived peptides), thereby controlling inflammatory responses. This makes HSPs attractive candidates for therapeutic intervention in chronic autoimmune diseases, with the ultimate goal of inducing long-lasting tolerance.

Osteoconductive action of alendronate after implantation of beta tricalcium phosphate in rat adjuvant-induced arthritis

The aim of the study was to determine the effect of alendronate on resorption of β-tricalcium phosphate (β-TCP) and bone formation in rats with adjuvant-induced arthritis (AIA). After preparation of a model of AIA in rats (day 0), alendronate or vehicle was injected intraperitoneally once daily five times in a week. Cylindrical β-TCP was implanted into the rat femoral condyle on day 7. Rats were killed on days 12, 15, and 21, and specimens and serum samples were collected. Specimens were analyzed by tartrate-resistant acid phosphate (TRAP) staining, immunohistochemistry of the ED1 protein, and in situ hybridization with digoxigenin-labeled α1 chain of type I procollagen (COL1A1). Mineralized bone sections were analyzed by Villanueva bone stain. The serum osteocalcin level was measured using an enzyme-linked immunosorbent assay kit. Alendronate decreased the number of TRAP-positive cells attached to β-TCP, the numbers of ED1-positive multinucleated giant cells, and resorption of β-TCP. In AIA rats treated with alendronate, COL1A1 mRNA-positive cells adhered to β-TCP were round or cuboid whereas the cells in untreated AIA rats were fibroblast-like cells. Alendronate increased calcification of newly formed bone whereas it did not restore the bone formation suppressed with inflammation. These results suggest that alendronate has the potential to conduct mature bone after implantation of β-TCP in AIA. Alendronate may help to reduce insufficiency of newly formed bone after implantation of β-TCP in diseases characterized by increased bone resorption such as rheumatoid arthritis.

A case of mistaken identity: HSPs are no DAMPs but DAMPERs

Until recently, the immune system was seen solely as a defense system with its primary task being the elimination of unwanted microbial invaders. Currently, however, the functional significance of the immune system has obtained a much wider perspective, to include among others the maintenance and restoration of homeostasis following tissue damage. In this latter aspect, there is a growing interest in the identification of molecules involved, such as the so-called danger or damage-associated molecular patterns (DAMPs), also called alarmins. Since heat shock proteins are archetypical molecules produced under stressful conditions, such as tissue damage or inflammation, they are frequently mentioned as prime examples of DAMPs (Bianchi, J Leukoc Biol 81:1-5, 2007; Kono and Rock, Nat Rev Immunol 8:279-289, 2008; Martin-Murphy et al., Toxicol Lett 192:387-394, 2010). See for instance also a recent review (Chen and Nunez, Science 298:1395-1401, 2010). Contrary to this description, we recently presented some of the arguments against a role of heat shock protein as DAMPs (Broere et al., Nat Rev Immunol 11:565-c1, 2011). With this perspective and reflection article, we hope to elaborate on this debate and provide additional thoughts to further ignite this discussion on this critical and evolving issue.

Bystander suppression of experimental arthritis by nasal administration of a heat shock protein peptide

OBJECTIVES

Mucosal immune therapy with disease-inducing antigens is an effective way to prevent experimental arthritis, but in humans these antigens are unknown. In juvenile idiopathic arthritis, however, T cell recognition of a so-called bystander antigen, heat shock protein 60 (HSP60), is associated with a good prognosis. Recently epitopes derived from HSP60, a microbial peptide (p1) and its self-homologue (p2) were reported to induce tolerogenic T cell responses in vitro in patients with arthritis. A study was undertaken to determine whether mucosal administration of these bystander epitopes can be similarly effective in suppressing arthritis.

METHODS

Rats were treated nasally with p1, p2 or phosphate-buffered saline before arthritis induction. Arthritis scores were assessed and peptide-specific proliferative responses, phenotypic analysis, cytokine production and in vitro suppressive capacity of cells were measured in lymph nodes and spleens. CD4 spleen T cells from p1- or p2-treated rats were adoptively transferred into naïve rats that were subsequently injected with complete Freund's adjuvant for arthritis induction.

RESULTS

Nasal administration of p1 prevented experimental arthritis whereas treatment with the self-homologue p2 did not. Adoptive transfer of CD4 T cells protected against experimental arthritis. Treatment with p1 increased peptide-specific and self-crossreactive interferon γ (IFNγ) production. Tumour necrosis factor α (TNFα) levels were reduced at the site of inflammation. Forkhead box P3 (FoxP3) expression remained stable but the suppressive capacity of T regulatory cells in p1-treated rats was enhanced.

CONCLUSION

p1 immune therapy induces a population of CD4 T cells with reduced TNFα and increased peptide-specific IFNγ production at the site of inflammation. This population expresses FoxP3 and has potent suppressive capacity which, upon transfer, protects against arthritis. The bystander epitope p1 may therefore be a suitable candidate for antigen-specific immunotherapy in arthritis.

Pediatric Sepsis - Part V: Extracellular Heat Shock Proteins: Alarmins for the Host Immune System

Heat shock proteins (HSPs) are molecular chaperones that facilitate the proper folding and assembly of nascent polypeptides and assist in the refolding and stabilization of damaged polypeptides. Through these largely intracellular functions, the HSPs maintain homeostasis and assure cell survival. However, a growing body of literature suggests that HSPs have important effects in the extracellular environment as well. Extracellular HSPs are released from damaged or stressed cells and appear to act as local "danger signals" that activate stress response programs in surrounding cells. Importantly, extracellular HSPs have been shown to activate the host innate and adaptive immune response. With this in mind, extracellular HSPs are commonly included in a growing list of a family of proteins known as danger-associated molecular patterns (DAMPs) or alarmins, which trigger an immune response to tissue injury, such as may occur with trauma, ischemia-reperfusion injury, oxidative stress, etc. Extracellular HSPs, including Hsp72 (HSPA), Hsp27 (HSPB1), Hsp90 (HSPC), Hsp60 (HSPD), and Chaperonin/Hsp10 (HSPE) are especially attractrive candidates for DAMPs or alarmins which may be particularly relevant in the pathophysiology of the sepsis syndrome.

The gene expression profile of preclinical autoimmune arthritis and its modulation by a tolerogenic disease-protective antigenic challenge

Introduction

Autoimmune inflammation is a characteristic feature of rheumatoid arthritis (RA) and other autoimmune diseases. In the natural course of human autoimmune diseases, it is rather difficult to pinpoint the precise timing of the initial event that triggers the cascade of pathogenic events that later culminate into clinically overt disease. Therefore, it is a challenge to examine the early preclinical events in these disorders. Animal models are an invaluable resource in this regard. Furthermore, considering the complex nature of the pathogenic immune events in arthritis, microarray analysis offers a versatile tool to define the dynamic patterns of gene expression during the disease course.

Methods

In this study, we defined the profiles of gene expression at different phases of adjuvant arthritis (AA) in Lewis rats and compared them with those of antigen mycobacterial heat shock protein 65 (Bhsp65)-tolerized syngeneic rats. Purified total RNA (100 ng) extracted from the draining lymph node cells was used to generate biotin-labeled fragment cRNA, which was then hybridized with an oligonucleotide-based DNA microarray chip. Significance analysis of microarrays was used to compare gene expression levels between the two different groups by limiting the false discovery rate to < 5%. Some of the data were further analyzed using a fold change ≥2.0 as the cutoff. The gene expression of select genes was validated by quantitative real-time PCR.

Results

Intriguingly, the most dramatic changes in gene expression in the draining lymphoid tissue ex vivo were observed at the preclinical (incubation) phase of the disease. The affected genes represented many of the known proteins that participate in the cellular immune response. Interestingly, the preclinical gene expression profile was significantly altered by a disease-modulating, antigen-based tolerogenic regimen. The changes mostly included upregulation of several genes, suggesting that immune tolerance suppressed disease by activating disease-regulating pathways. We identified a molecular signature comprising at least 12 arthritis-related genes altered by Bhsp65-induced tolerance.

Conclusions

This is the first report of microarray analysis in the rat AA model. The results of this study not only advance our understanding of the early phase events in autoimmune arthritis but also help in identifying potential targets for the immunomodulation of RA.

Celastrus-derived celastrol suppresses autoimmune arthritis by modulating antigen-induced cellular and humoral effector responses

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation and articular damage. Proinflammatory cytokines, antibodies, and matrix-degrading enzymes orchestrate the pathogenic events in autoimmune arthritis. Accordingly, these mediators of inflammation are the targets of several anti-arthritic drugs. However, the prolonged use of such drugs is associated with severe adverse reactions. This limitation has necessitated the search for less toxic natural plant products that possess anti-arthritic activity. Furthermore, it is imperative that the mechanism of action of such products be explored before they can be recommended for further preclinical testing. Using the rat adjuvant-induced arthritis model of human RA, we demonstrate that celastrol derived from Celastrus has potent anti-arthritic activity. This suppression of arthritis is mediated via modulation of the key proinflammatory cytokines (IL-17, IL-6, and IFN-γ) in response to the disease-related antigens, of the IL-6/IL-17-related transcription factor STAT3, of antibodies directed against cyclic citrullinated peptides and Bhsp65, and of the activity of matrix metalloproteinase-9 and phospho-ERK. Most of the clinical and mechanistic attributes of celastrol are similar to those of Celastrus extract. Several studies have addressed the antitumor activity of celastrol. Our study highlights the anti-arthritic activity of Celastrus-derived celastrol and the underlying mechanisms. These results provide a strong rationale for further testing and validation of the use of celastrol and the natural plant extract from Celastrus as an adjunct (with conventional drugs) or alternative modality for the treatment of RA.

Immunomodulation of Autoimmune Arthritis by Herbal CAM

Rheumatoid arthritis (RA) is a debilitating autoimmune disease of global prevalence. The disease is characterized by synovial inflammation leading to cartilage and bone damage. Most of the conventional drugs used for the treatment of RA have severe adverse reactions and are quite expensive. Over the years, increasing proportion of patients with RA and other immune disorders are resorting to complementary and alternative medicine (CAM) for their health needs. Natural plant products comprise one of the most popular CAM for inflammatory and immune disorders. These herbal CAM belong to diverse traditional systems of medicine, including traditional Chinese medicine, Kampo, and Ayurvedic medicine. In this paper, we have outlined the major immunological pathways involved in the induction and regulation of autoimmune arthritis and described various herbal CAM that can effectively modulate these immune pathways. Most of the information about the mechanisms of action of herbal products in the experimental models of RA is relevant to arthritis patients as well. The study of immunological pathways coupled with the emerging application of genomics and proteomics in CAM research is likely to provide novel insights into the mechanisms of action of different CAM modalities.

Interleukin-27 and interferon-gamma are involved in regulation of autoimmune arthritis

Inflammation underlying immune pathology and tissue damage involves an intricate interplay between multiple immunological and biochemical mediators. Cytokines represent the key immune mediators that trigger a cascade of reactions that drive processes such as angiogenesis and proteolytic damage to tissues. IL-17 has now been shown to be a pivotal cytokine in many autoimmune diseases, supplanting the traditional Th1-Th2 paradigm. Also, the dual role of proinflammatory IFN-γ has unraveled new complexities in the cytokine biology of such disorders. A major hurdle in fully understanding the effector pathways in these disorders is the lack of information regarding the temporal kinetics of the cytokines during the course of the disease, as well as the interplay among the key cytokines. Using an experimental model of arthritic inflammation, we demonstrate that the temporal expression of cytokines during the incubation phase is a critical determinant of disease susceptibility. The susceptible rats raised a vigorous IL-17 response early, followed by IFN-γ and IL-27 response in that sequence, whereas the resistant rats displayed an early and concurrent response to these three cytokines. Accordingly, treatment with exogenous IFN-γ/IL-27 successfully controlled arthritic inflammation and inhibited the defined mediators of inflammation, angiogenesis, cell survival, apoptosis, and tissue damage. Furthermore, IFN-γ enhanced IL-27 secretion, revealing a cooperative interplay between the two cytokines. Our results offer a novel immunobiochemical perspective on the pathogenesis of autoimmune arthritis and its therapeutic control.

Suppression of ongoing experimental arthritis by a chinese herbal formula (huo-luo-xiao-ling dan) involves changes in antigen-induced immunological and biochemical mediators of inflammation

Rheumatoid arthritis (RA) is one of the major autoimmune diseases of global prevalence. The use of the anti-inflammatory drugs for the treatment of RA is associated with severe adverse reactions and toxicity. This limitation has necessitated the search for novel therapeutic products. We report here a traditional Chinese medicine-based herbal formula, Huo luo xiao ling dan (HLXL), which has potent antiarthritic activity as validated in the rat adjuvant-induced arthritis (AA) model. HLXL (2.3 g/Kg) was fed to Lewis (RT.1(1)) rats daily by gavage beginning at the onset of arthritis and then continued through the observation period. HLXL inhibited the severity of ongoing AA. This suppression of arthritis was associated with significant alterations in the T cell proliferative and cytokine responses as well as the antibody response against the disease-related antigen, mycobacterial heat-shock protein 65 (Bhsp65). There was a reduction in the level of the proinflammatory cytokines IL-17 and IL-1β but enhancement of the anti-inflammatory cytokine IL-10 level. In addition, there was inhibition of both the anti-Bhsp65 antibody response and the serum level of nitric oxide. Thus, HLXL is a promising CAM modality for further testing in RA patients.

Identification of immunological parameters associated with the alveolar bone level in periodontal patients

Purpose

The present study was performed to clarify the relationship between periodontal disease severity and selected immunological parameters consisting of serum IgG titer against periodontopathogenic bacteria, the expression of the helper T-cell cytokine by gingival mononuclear cells, and patients' immunoreactivity to cross-reactive heat shock protein (HSP) epitope peptide from P. gingivalis HSP60.

Methods

Twenty-five patients with moderate periodontitis had their gingival connective tissue harvested of gingival mononuclear cells during an open flap debridement procedure and peripheral blood was drawn by venipuncture to collect serum. The mean level of interproximal alveolar bone was calculated to be used as an index for periodontal disease severity for a given patient. Each of selected immunologic parameters was subject to statistical management to seek their correlations with the severity of periodontal disease.

Results

A significant correlation could not be identified between serum IgG titers against specific bacteria (Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans, and Streptococcus mutans) and the severity of periodontal disease. Expression of interleukin (IL)-10 by gingival mononuclear cells was statistically significant in the group of patients who had higher levels of alveolar bone height. However, a similar correlation could not be demonstrated in cases for IL-4 or interferon-γ. Patients' serum reactivity to cross-reactive epitope peptide showed a significant correlation with the amount of alveolar bone.

Conclusions

It was concluded that expression of IL-10 by gingival mononuclear cells and patients' sero-reactivity to the cross-reactive HSP peptide of P. gingivalis HSP60 were significantly correlated with alveolar bone height.

The involvement of heat-shock proteins in the pathogenesis of autoimmune arthritis: a critical appraisal

OBJECTIVES

To review the literature on the role of heat-shock proteins (HSPs) in the pathogenesis of autoimmune arthritis in animal models and patients with rheumatoid arthritis (RA).

METHODS

The published literature in Medline (PubMed), including our published work on the cell-mediated as well as humoral immune response to various HSPs, was reviewed. Studies in the preclinical animal models of arthritis as well as RA were examined critically and the data are presented.

RESULTS

In experimental arthritis, disease induction by different arthritogenic stimuli, including an adjuvant, led to immune response to mycobacterial HSP65 (BHSP65). However, attempts to induce arthritis by a purified HSP have not met with success. There are several reports of a significant immune response to HSP65 in RA patients. However, the issue of cause and effect is difficult to address. Nevertheless, several studies in animal models and a couple of clinical trials in RA patients have shown the beneficial effect of HSPs against autoimmune arthritis.

CONCLUSIONS

There is a clear association between immune response to HSPs, particularly HSP65, and the initiation and propagation of autoimmune arthritis in experimental models. The correlation is relatively less convincing in RA patients. In both cases, the ability of HSPs to modulate arthritis offers support, albeit an indirect one, for the involvement of these antigens in the disease process.

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.

The determinants of susceptibility/resistance to adjuvant arthritis in rats

Adjuvant arthritis (AA) serves as an excellent model for human rheumatoid arthritis. AA is readily inducible in certain rat strains, but not in others. Susceptibility/resistance to AA is determined by multiple factors. Among the genetic factors, both MHC and non-MHC genes contribute to arthritis susceptibility, and specific quantitative trait loci show association with the severity of the disease. Differential T-cell proliferative and cytokine responses, as well as antibody responses, to heat-shock proteins are evident when comparing AA-susceptible and AA-resistant rats. In addition, neuroendocrine factors and the housing environment can further modulate arthritis susceptibility/severity in particular rat strains.

Tolerization with Hsp65 induces protection against adjuvant-induced arthritis by modulating the antigen-directed interferon-gamma, interleukin-17, and antibody responses

OBJECTIVE

Pretreatment of Lewis rats with soluble mycobacterial Hsp65 affords protection against subsequent adjuvant-induced arthritis (AIA). This study was aimed at unraveling the mechanisms underlying mycobacterial Hsp65-induced protection against arthritis, using contemporary parameters of immunity.

METHODS

Lewis rats were given 3 intraperitoneal injections of mycobacterial Hsp65 in solution prior to the initiation of AIA with heat-killed Mycobacterium tuberculosis. Thereafter, mycobacterial Hsp65-specific T cell proliferative, cytokine, and antibody responses were tested in tolerized rats. The roles of anergy and the indoleamine 2,3 dioxygenase (IDO)-tryptophan pathway in tolerance induction were assessed, and the frequency and suppressive function of CD4+FoxP3+ Treg cells were monitored. Also tested was the effect of mycobacterial Hsp65 tolerization on T cell responses to AIA-related mycobacterial Hsp70, mycobacterial Hsp10, and rat Hsp65.

RESULTS

The AIA-protective effect of mycobacterial Hsp65-induced tolerance was associated with a significantly reduced T cell proliferative response to mycobacterial Hsp65, which was reversed by interleukin-2 (IL-2), indicating anergy induction. The production of interferon-gamma (but not IL-4/IL-10) was increased, with concurrent down-regulation of IL-17 expression by mycobacterial Hsp65-primed T cells. Neither the frequency nor the suppressive activity of CD4+FoxP3+ T cells changed following tolerization, but the serum level of anti-mycobacterial Hsp65 antibodies was increased. However, no evidence was observed for a role of IDO or cross-tolerance to mycobacterial Hsp70, mycobacterial Hsp10, or rat Hsp65.

CONCLUSION

Tolerization with soluble mycobacterial Hsp65 leads to suppression of IL-17, anergy induction, and enhanced production of anti-mycobacterial Hsp65 antibodies, which play a role in protection against AIA. These results are relevant to the development of effective immunotherapeutic approaches for autoimmune arthritis.

Regulation of autoimmune arthritis by self-heat-shock proteins

Heat-shock proteins (hsps) are highly conserved and immunogenic, and they are generally perceived to be attractive initiators or targets of a pathogenic immune response, and as such, have been implicated in the pathogenesis of autoimmune arthritis. However, studies in animal models and arthritis patients have unraveled the disease-regulating attributes of self-hsp65. We propose that the self-hsp65 induces a protective and beneficial immune response because of its ubiquitous distribution, stress inducibility and participation in tolerogenic processes. By contrast, the foreign hsp65 that does not influence the above processes and that resides admixed with microbial ligands for innate receptors generates an inflammatory pathogenic response. The regulatory properties of self-hsps need be fully explored and might be used for therapeutic purposes.

Antigen-specific tolerogenic and immunomodulatory strategies for the treatment of autoimmune arthritis

OBJECTIVES

To review various antigen-specific tolerogenic and immunomodulatory approaches for arthritis in animal models and patients in regard to their efficacy, mechanisms of action, and limitations.

METHODS

We reviewed the published literature in Medline (PubMed) on the induction of antigen-specific tolerance and its effect on autoimmune arthritis, as well as the recent work on B-cell-mediated tolerance from our laboratory. The prominent key words used in different combinations included arthritis, autoimmunity, immunotherapy, innate immunity, tolerance, treatment, and rheumatoid arthritis (RA). Although this search spanned the years 1975 to 2007, the majority of the short-listed articles belonged to the period 1990 to 2007. The relevant primary as well as cross-referenced articles were then collected from links within PubMed and reviewed.

RESULTS

Antigen-specific tolerance has been successful in the prevention and/or treatment of arthritis in animal models. The administration of soluble native antigen or an altered peptide ligand intravenously, orally, or nasally, and the delivery of the DNA encoding a particular antigen by gene therapy have been the mainstay of immunomodulation. Recently, the methods for in vitro expansion of CD4+CD25+ regulatory T-cells have been optimized. Furthermore, interleukin-17 has emerged as a promising new therapeutic target in arthritis. However, in RA patients, non-antigen-specific therapeutic approaches have been much more successful than antigen-specific tolerogenic regimens.

CONCLUSION

An antigen-specific treatment against autoimmune arthritis is still elusive. However, insights into newly emerging mechanisms of disease pathogenesis provide hope for the development of effective and safe immunotherapeutic strategies in the near future.

The dynamics of articular leukocyte trafficking and the immune response to self heat-shock protein 65 influence arthritis susceptibility

INTRODUCTION

Adjuvant arthritis (AA) shares several features with human rheumatoid arthritis, and it can be induced in the Lewis (LEW) rat but not the Wistar Kyoto (WKY) rat (both RT.1(l)) by immunization with heat-killed Mycobacterium tuberculosis (Mtb). We set out to unravel the mechanisms underlying the differential susceptibility to AA of these MHC-compatible rat strains.

MATERIALS AND METHODS

We compared the levels of T-cell proliferative and cytokine response to the immunoregulatory self (rat) hsp65 (Rhsp65) after an arthritogenic (Mtb) challenge and the kinetics of migration of adoptively transferred, (111)Indium-labeled, Mtb-primed leukocytes into the hind paw joints of recipient rats.

RESULTS AND DISCUSSION

The WKY rats raised a significantly higher level of T-cell proliferative response coupled with a temporally opposite cytokine profile against the disease-regulating Rhsp65 compared to that of LEW rats. Moreover, the arthritogenic leukocytes accumulated into the joints of WKY rats at significantly lower numbers than that in LEW rats.

CONCLUSIONS

These results offer novel insights into the immune events influencing the pathogenesis of autoimmune arthritis.

Celastrus aculeatus Merr. suppresses the induction and progression of autoimmune arthritis by modulating immune response to heat-shock protein 65

Complementary and alternative medicine products are increasingly being used for the treatment of autoimmune diseases. However, the mechanisms of action of these agents are not fully defined. Using the rat adjuvant arthritis (AA) model of human rheumatoid arthritis, we determined whether the ethanol extract of Celastrus aculeatus Merr. (Celastrus), a Chinese herb, can down-modulate the severity of AA, and also examined the Celastrus-induced changes in immune responses to the disease-related antigen mycobacterial heat-shock protein 65 (Bhsp65). AA was induced in the Lewis (LEW; RT.1^l) rat by immunization subcutaneously with heat-killed M. tuberculosis H37Ra (Mtb). Celastrus was fed to LEW rats by gavage daily, beginning either before Mtb challenge (preventive regimen) or after the onset of AA (therapeutic regimen). An additional group of rats was given methotrexate for comparison. All rats were graded regularly for the signs of arthritis. In parallel, the draining lymph node cells of Celastrus-treated rats were tested for proliferative and cytokine responses, whereas their sera were tested for the inflammatory mediator nitric oxide. Celastrus feeding suppressed both the induction as well as the progression of AA, and the latter effect was comparable to that of methotrexate. Celastrus treatment induced relative deviation of the cytokine response to anti-inflammatory type and enhanced the production of anti-Bhsp65 antibodies, which are known to be protective against AA. Celastrus feeding also reduced the levels of nitric oxide. On the basis of our results, we suggest further systematic exploration of Celastrus as an adjunct therapeutic modality for rheumatoid arthritis.

Exogenous tumour necrosis factor alpha induces suppression of autoimmune arthritis

Introduction

Our previous studies showed that arthritic Lewis (LEW) rats produced the highest levels of tumour necrosis factor (TNF)α in the recovery phase of adjuvant arthritis (AA), suggesting a correlation between high TNFα levels and reduced severity of arthritis. To further explore this correlation, we compared the TNFα secretion profile of the AA-resistant Wistar Kyoto (WKY) rats with that of LEW rats, determined the effect of exogenous TNFα on the course of AA in LEW rats, and examined various mechanisms involved in TNFα-induced disease modulation.

Methods

A cohort each of LEW and WKY rats was immunised subcutaneously with heat-killed Mycobacterium tuberculosis H37Ra (Mtb). At different time points thereafter, subgroups of rats were killed and their draining lymph node cells were tested for cytokine production. Another group of LEW rats was injected with TNFα intraperitoneally daily for a total of 10 injections, 3 before and 6 after Mtb challenge, and then observed for signs of AA. In parallel, TNFα-treated rats were examined for changes in other cytokines, in CD4+CD25+ T cell frequency, and in indoleamine 2,3-dioxygenase (IDO) mRNA expression levels.

Results

LEW rats displayed a TNFα secretion profile that was opposite to that of the WKY rats. Furthermore, TNFα treatment significantly downmodulated the severity of AA in LEW rats, and decreased the interferon (IFN)-γ secretion in response to the pathogenic determinant of the disease-related antigen. No significant alterations were observed in other parameters tested.

Conclusion

The role of endogenous TNFα in the induction and propagation of arthritis is well established. However, exogenous TNFα can downmodulate the course of AA, displaying an immunoregulatory functional attribute of this cytokine.

Regulation of autoimmune arthritis by the pro-inflammatory cytokine interferon-gamma

The pathogenesis of T cell-mediated diseases like rheumatoid arthritis (RA) has typically been explained in the context of the Th1-Th2 paradigm: the initiation/propagation by pro-inflammatory cytokines, and downregulation by Th2 cytokines. However, in our study based on the adjuvant-induced arthritis (AA) model of RA, we observed that Lewis (LEW) (RT.1(l)) rats at the recovery phase of AA showed the highest level of IFN-gamma in recall response to mycobacterial heat-shock protein 65 (Bhsp65), whereas AA-resistant Wistar-Kyoto (WKY) (RT.1(l)) rats secreted high levels of IFN-gamma much earlier following disease induction. However, no significant secretion of IL-10 or TGF-beta was observed in either strain. Furthermore, pre-treatment of LEW rats with a peptide of self (rat) hsp65 (R465), which induced T cells secreting predominantly IFN-gamma, afforded protection against AA and decreased IL-17 expression by the arthritogenic epitope-restimulated T cells. These results provide a novel perspective on the pathogenesis of autoimmune arthritis.

Treatment with encapsulated Hsp60 peptide (p277) prolongs skin graft survival in a murine model of minor antigen disparity

The increased expression of heat shock protein (Hsp)60 in different kinds of graft tissues has been associated with a proinflammatory role and rejection. However, there are very few reports in which treatment with Hsp60 delays skin allograft rejection. The aim of this work was to evaluate the capacity of encapsulated human Hsp60-derived peptide p277 to delay graft rejection in two murine models of skin transplantation with minor antigen disparities. Briefly, BALB/c mice and C57BL/6 were intranasally pre-treated with five doses of Hsp60 p277 peptide encapsulated in polylactide-co-glycolide acid microspheres (PLGM), and received skin grafts from DBA2 mice and 129/B6 (F1) mice respectively. The treatment with the peptide increased skin graft survival more than 20 days in both the mouse strains, mainly in C57BL/6 recipients (P < 0.05). Also, p277-treated BALB/c and C57BL/6 mice showed IL-10 and IFN-gamma production, induced by p277 peptide. For the first time, a mucosal schedule using the Hsp60 C-terminal peptide p277 encapsulated in PLGM showed some survival prolongation of skin grafts bearing minor antigen disparities. Our results suggest a potential role for Hsp60-based therapy and the mucosal route as a useful tool to control the inflammatory response to allografts.

Diversity of physiological cell reactivity to heat shock protein 60 in different mouse strains

Heat shock proteins (Hsp) are families of highly conserved molecules and immunodominant antigens in some infections and in autoimmune diseases. Some reports suggest that different regions of the Hsp60 molecule induce distinct immune responses. However, there are no reports comparing physiological T-cell reactivity to Hsp60 in mice. In this study, we have analyzed T-cell proliferation and cytokine production induced by Hsp60, under physiological conditions, in three mouse strains bearing distinct major histocompatibility complex (MHC) backgrounds. Proliferative response predominantly was found in C57BL/6 mice, mostly induced by N-terminal and intermediate Hsp60 peptides (P < 0.0001). Interferon-gamma (IFNgamma) production was broadly induced by different regions of Hsp60 in all three mouse strains, although response was focused in different peptide groups in each strain. We did not observe an exclusive Th1 or Th2 cytokine profile induced by any particular region of Hsp60. However, we identified a strain hierarchy in IL-10 production induced by Hsp60 peptides from different regions, mostly detected in C3H/HePas, and in BALB/c, but not in C57BL/6 mice. In contrast, IL-4 production only was induced by the intermediate and C-terminal region peptides in both C3H/HePas and BALB/c mice. Our data give original information on physiological cellular reactivity to Hsp60. We also have identified peptides with the capacity to induce the production of anti-inflammatory cytokines, bringing perspectives for their use in immunotherapy of chronic inflammatory diseases and allograft rejection.

The major histocompatibility complex haplotypes dictate and the background genes fine-tune the dominant versus the cryptic response profile of a T-cell determinant within a native antigen: relevance to disease susceptibility and vaccination

The immune system of a healthy individual responds vigorously to foreign microbial antigens. However, all potentially immunogenic regions (determinants) within an antigen are not functionally of equal relevance in mediating host immunity against the pathogen. Moreover, some of these antigenic determinants are well processed and presented (immunodominant), while others are not revealed (cryptic) from the native antigen. Nevertheless, cryptic determinants are good immunogens in the pre-processed peptide form. Defining the factors influencing the dominance versus the crypticity of antigenic determinants is critical to advancing our understanding of the individual variations in host immunity to infection, autoantigens and vaccination. In this study based on a model antigen, hen eggwhite lysozyme (HEL), we describe that the major histocompatibility complex (MHC) haplotypes imprint and the non-MHC genes modify the dominance versus the crypticity of a specific antigenic determinant. Both the H-2(q)- and the H-2(d)-bearing mice raised potent response to native HEL, but responded differently to its determinant region 57-78, which was dominant in the H-2(q) but cryptic in the H-2(d) mice. The H-2(q)- but not the H-2(d)-bearing mice of three different genetic backgrounds yielded patterns of graded reactivity to epitope 57-78 showing the fine-tuning effect of the non-MHC genes. Interestingly, the F1 (H-2(q) x H-2(d)) mice retained the dominant response profile of the H-2(q) parent regardless of the contributing gender, and also responded to a new sub-determinant 61-75. These results highlight the genetic factors influencing the dominance/crypticity of a specific antigenic determinant.

Antibody responses to mycobacterial and self heat shock protein 65 in autoimmune arthritis: epitope specificity and implication in pathogenesis

Many autoimmune diseases are believed to involve primarily T cell-mediated effector mechanisms. There is increasing realization, however, that Abs may also play a vital role in the propagation of T cell-driven disorders. In this study, on the rat adjuvant-induced arthritis (AA) model of human rheumatoid arthritis, we examined the characteristics of serum Ab response to mycobacterial heat shock protein (hsp) 65 (Bhsp65), self (rat) hsp65 (Rhsp65), and linear peptides spanning these two molecules. The AA-resistant WKY (RT.1(l)) rat responded to the heat-killed Mycobacterium tuberculosis immunization with a rapid burst of Abs to both Bhsp65 and Rhsp65. These Abs reacted with numerous peptide epitopes; however, this response was reduced to a few epitopes with time. On the contrary, the susceptible Lewis (RT.1(l)) rat developed a relatively lower Ab response to Bhsp65, and Abs to Rhsp65 did not appear until the recovery from the disease. The Ab response in Lewis rats diversified with progression of AA, and there was an intriguing overlap between the repertoire of Bhsp65-reactive B and T cells during the recovery phase of AA. Nonetheless, subsets of the repertoire of the late Abs in both rat strains became focused on the same epitope regions of Bhsp65 and Rhsp65. The functional relevance of these Abs was evident from the results showing that sera from recovery phase Lewis or WKY rats, but not that of naive rats, afforded protection against subsequent AA. These results are of significance in further understanding of the role of humoral immunity in the pathogenesis of autoimmune arthritis.

Cellular autoreactivity against heat shock protein 60 in renal transplant patients: peripheral and graft-infiltrating responses

Autoreactivity to heat shock protein 60 (Hsp60) has been implicated in the pathogenesis and regulation of chronic inflammation, especially in autoimmune diseases. In transplantation, there is a lack of information regarding the cytokine profile and specificity of cells that recognize self-Hsp60 as well as the kinetics of autoreactivity following transplantation. We studied the cellular reactivity of peripheral and graft-infiltrating lymphocytes against Hsp60 in renal transplant patients. Cytokine production induced by this protein in peripheral blood mononuclear cells indicated a predominance of interleukin (IL)-10 during the late post-transplantation period, mainly in response to intermediate and C-terminal peptides. Patients with chronic rejection presented reactivity to Hsp60 with a higher IL-10/interferon (IFN)-gamma ratio compared to long-term clinically stable patients. Graft-infiltrating T cell lines, cocultured with antigen-presenting cells, preferentially produced IL-10 after Hsp60 stimulation. These results suggest that, besides its proinflammatory activity, autoreactivity to Hsp60 in transplantation may also have a regulatory role.

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.

Heat-shock protein 60 as a tool for novel therapeutic strategies that target the induction of regulatory T cells in human arthritis

In health, immune responses to self are abundantly available, but under strict control of mechanisms of peripheral tolerance. Occasionally the immune system loses control and an autoimmune disease develops. At present, treatment of autoimmune disease is based on generalised suppression of all immune responses, and is often needed to be lifelong, leading to long-term toxicities and suppression of protective immune responses against pathogens. A more targeted approach would be to reset the immune system via restoration of failing regulatory mechanisms, and redirect the immune system to a state of tolerance. Over the past decade there have been enormous advances in the understanding of basic processes that control immune tolerance, pushing regulatory T cells forward as targets for novel therapeutic strategies. This review describes the development of antigen-specific immunotherapy that targets the antigen-specific induction of regulatory T cells as a means to treat autoimmune disease. The 'holy grail' for autoimmunity is not the disease-causing antigen, but the disease-curing antigen.

Heat shock protein 65-reactive T cells are involved in the pathogenesis of non-antigenic dimethyl dioctadecyl ammonium bromide-induced arthritis

Dimethyl dioctadecyl ammonium bromide (DDA) (C(38)H(80)NBr) is a nonantigenic lipoid material. DDA-induced arthritis (DIA) in the Lewis (LEW) (RT.1(l)) rat is a new experimental model for human rheumatoid arthritis (RA). DIA is a T cell-mediated autoimmune disease. However, the precise self/foreign Ags associated with the disease process in DIA are not yet known. We observed that LEW rats with DIA spontaneously raised a vigorous T cell response both to 65-kDa self (rat) heat shock protein (Rhsp65) and mycobacterial hsp65 (Bhsp65), but not to another arthritis-related Ag, bovine collagen type II. The T cell response to Rhsp65 was focused predominantly on determinant regions 120-134 and 213-227 of the self protein. Interestingly, pretreatment of adult LEW rats using either a mixture of peptides 120-134 and 213-227 of Rhsp65 or a low nonarthritogenic dose of DDA induced protection against subsequent DIA. Intriguingly, the protection induced by the latter was associated with spontaneous priming of T cells specific for peptide 213-227 of Rhsp65. Similarly, LEW rats neonatally tolerized against either Rhsp65 or Bhsp65 were significantly protected from subsequently induced DIA at adult stage, showing the disease-modulating attribute of the hsp65-specific T cells. Taken together, the above findings demonstrate that the hsp65-directed T cell repertoire is of significance in the pathogenesis of autoimmune arthritis induced by nonantigenic DDA. Like other animal models of RA involving hsp65, these first insights into the disease-associated Ags in the DIA model would pave the way for further understanding of the immunological aspects of induction and regulation of RA.

Understanding crypticity is the key to revealing the pathogenesis of autoimmunity

In this opinion, we propose that the hierarchy of antigenic determinants within self-antigens is the major influence in molding the potentially autoreactive T-cell repertoire. The well processed and presented determinants constitute a 'dominant self', whereas the poorly processed and/or presented determinants will be invisible to T cells and comprise a 'cryptic self', which we consider a fundamental cornerstone of a theory of autoimmunity. It accounts for the large repertoire of self-reactive clones because a similar hierarchy is established in the thymus and controls positive and negative selection. Furthermore, this residual T-cell repertoire, largely directed against cryptic determinants, will contain some T cells with sufficient affinity for MHC and antigen that enables them to respond under inflammatory conditions, thus facilitating presentation of previously cryptic determinants.

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.

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.

The regulatory C-terminal determinants within mycobacterial heat shock protein 65 are cryptic and cross-reactive with the dominant self homologs: implications for the pathogenesis of autoimmune arthritis

The 65-kDa mycobacterial heat shock protein (Bhsp65) has been invoked in the pathogenesis of both adjuvant arthritis (AA) in the Lewis rat (RT.1(l)) and human rheumatoid arthritis. Arthritic Lewis rats in the late phase of AA show diversification of the T cell response to Bhsp65 C-terminal determinants (BCTD), and pretreatment of naive Lewis rats with a mixture of peptides representing these neoepitopes affords protection against AA. However, the fine specificity and physiologic significance of the BCTD-directed T cell repertoire, and the role of homologous self (rat) hsp65 (Rhsp65), if any, in spreading of the T cell response to Bhsp65 have not yet been examined. We observed that T cells primed by peptides comprising BCTD can adoptively transfer protection against AA to the recipient Lewis rats. However, these T cells can be activated by preprocessed (peptide) form of BCTD, but not native Bhsp65, showing that BCTD are cryptic epitopes. The BCTD-reactive T cells can be activated by the naturally generated (dominant) C-terminal epitopes of both exogenous and endogenous Rhsp65 and vice versa. Furthermore, certain individual peptides constituting BCTD and their self homologs can also induce protection against AA. These results support a model for the diversification of T cell response to Bhsp65 during the course of AA involving up-regulation of the display of cryptic BCTD coupled with spontaneous induction of T cell response to the cross-reactive dominant C-terminal epitopes of Rhsp65. The identification of disease-regulating cryptic determinants in Ags implicated in arthritis provides a novel approach for immunotherapy of rheumatoid arthritis.