A mycobacterial 65-kD heat shock protein induces antigen-specific suppression of adjuvant arthritis, but is not itself arthritogenic

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.

Intraperitoneal Administration of Adjuvant Inhibits the Development of Adjuvant Arthritis in Rats

In recent years, considerable efforts have been made to develop effective therapy for autoimmune diseases by specific suppression of the autoreactive immune process without affecting the remainder of the immune system. In our study we evaluated the protective effects and therapeutic potential of Mycobacterium butyricum (Mb), the causative antigen inducing adjuvant arthritis (AA), an experimental model of autoimmune disease in the rat. The antigen was administered to rats by a different route and at concentrations 10 and 100 times lower than the inducing one. Arthritis was induced by injection of 0.6 mg of Mb in paraffin oil into the hindpaw, and the severity of disease was assessed by measurement of contralateral paw swelling every three days and primary and secondary lesions were scored on an arbitrary scale after 14, 21, and 28 days. Animals were assigned to different groups and treated intraperitoneally with different doses and schedules of Mb. The administration of 60 μg of Mb every two days, starting 6 days before arthritogenic injection until the second day after, led to a significant inhibition of the arthritic process (p< 0.001 of the arthritic index). Treatment of animals with 60 μg of Mb every two days, from day 2 to day 21 after arthritis induction caused almost total suppression of lesions. However, in both treatment schedules, animals showed important signs of peritoneal inflammation. The administration of single injection of 60 or 6 μg of Mb 10 days after arthritis induction led to an inhibition of arthritic index reaching the maximum percentage on day 14 (26% and 24% with 60 and 6 μg respectively) and was able to delay the development of oedema foot volume, without signs of local inflammation. These results confirm the ability to modulate the autoimmune process even when the immunological response is far advanced, suggesting new strategies in the therapy of human autoimmune diseases.

Specific Antibodies to Om-89 Can Account for its Clinical Anti-Inflammatory Properties

The glycoprotein rich extract of E.coli, OM-89, has immunomodulatory properties and is used in the treatment of rheumatoid arthritis. One property ascribed to OM-89 is polyclonal B cell activation, however, less clear is whether administration of the drug results in the appearance of specific B-cell responses. Immunoprecipitation was used to demonstrate that OM-89 reactive antibody compexes could be formed in serum following oral (40mg/kg) or parenteral administration of OM-89. ELISAs were developed to measure OM-89 specific antibody isotypes (IgM, IgG1, IgG2a, IgG2b and IgG2c) in serum from orally dosed rats (4, 40 and 400mg/kg, 3 times a week for 6 weeks). A significant (p<0.05) increase in OM-89 specific IgG2a was observed at a dose of 40mg/kg, a dose shown previously to be efficacious in animal models of inflammation. These animals had significant elevations in IgG2a anti-GroEL (p<0.05) and anti-DnaK (p<0.05), major immunogenic epitopes in the drug. The possibility that these antibodies could be protective against chronic inflammation was investigated by examining the effect of serum transfer from OM-89 sensitised rabbits on granuloma weight in the cotton pellet model of chronic inflammation in rats. Serum from immune animals reduced granuloma weight by 22% (p<0.05) compared to untreated controls and by 33% (p<0.001) compared to controls dosed with the pre-immune serum. These results suggest that the induction of protective/blocking antibodies represents one mechanism in the therapeutic action of OM-89.

The danger model approach to the pathogenesis of the rheumatic diseases

The danger model was proposed by Polly Matzinger as complement to the traditional self-non-self- (SNS-) model to explain the immunoreactivity. The danger model proposes a central role of the tissular cells' discomfort as an element to prime the immune response processes in opposition to the traditional SNS-model where foreignness is a prerequisite. However recent insights in the proteomics of diverse tissular cells have revealed that under stressful conditions they have a significant potential to initiate, coordinate, and perpetuate autoimmune processes, in many cases, ruling over the adaptive immune response cells; this ruling potential can also be confirmed by observations in several genetically manipulated animal models. Here, we review the pathogenesis of rheumatic diseases such as systemic lupus erythematous, rheumatoid arthritis, spondyloarthritis including ankylosing spondylitis, psoriasis, and Crohn's disease and provide realistic approaches based on the logic of the danger model. We assume that tissular dysfunction is a prerequisite for chronic autoimmunity and propose two genetically conferred hypothetical roles for the tissular cells causing the disease: (A) the Impaired cell and (B) the paranoid cell. Both roles are not mutually exclusive. Some examples in human disease and in animal models are provided based on current evidence.

IgG and IgA antibody titers against human heat-shock protein (hsp60) in sera of rheumatoid arthritis and osteoarthritis patients

Abstract To learn whether heat-shock proteins (HSP) are involved in the pathogenesis of rheumatoid arthritis (RA), antirecombinant human heat-shock protein 60 (hsp60) IgG and IgA in sera of RA and osteoarthritis (OA) patients were investigated. Only the anti-hsp60 IgG titer of seropositive (RF-positive) patients was found to be elevated. Although RF titers of the sera of seropositive RA patients were increased, there was no correlation between the individual anti-hsp60 IgG titer and the corresponding RF titer. In contrast, all the anti-hsp60 IgA titers of the sera of OA, seronegative RA, and seropositive RA patients were found to be elevated. Among them, only the serum IgA concentration of seropositive RA patients was increased. Thus, it was suggested that the increased anti-hsp60 IgG reflects the pathogenesis of RA and its activity. It was also suggested that the increased anti-hsp60 IgA response reflects an involvement of hsp60 in the pathogenesis of arthritides rather than the pathogenesis of RA.

Dendritic cells and the promise of antigen-specific therapy in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory disease resulting from an autoimmune response to self-antigens, leading to inflammation of synovial tissue of joints and subsequent cartilage and bone erosion. Current disease-modifying anti-rheumatic drugs and biologic inhibitors of TNF, IL-6, T cells and B cells block inflammation nonspecifically, which may lead to adverse effects, including infection. They do not generally induce long-term drug-free remission or restoration of immune tolerance to self-antigens, and lifelong treatment is usual. The development of antigen-specific strategies in RA has so far been limited by insufficient knowledge of autoantigens, of the autoimmune pathogenesis of RA and of the mechanisms of immune tolerance in man. Effective tolerance-inducing antigen-specific immunotherapeutic strategies hold promise of greater specificity, of lower toxicity and of a longer-term solution for controlling or even preventing RA. This paper reviews current understanding of autoantigens and their relationship to immunopathogenesis of RA, and emerging therapeutics that aim to leverage normal tolerance mechanisms for implementation of antigen-specific therapy in RA.

Expression of Mycobacterium leprae HSP65 in tobacco and its effectiveness as an oral treatment in adjuvant-induced arthritis

Transgenic plants are able to express molecules with antigenic properties. In recent years, this has led the pharmaceutical industry to use plants as alternative systems for the production of recombinant proteins. Plant-produced recombinant proteins can have important applications in therapeutics, such as in the treatment of rheumatoid arthritis (RA). In this study, the mycobacterial HSP65 protein expressed in tobacco plants was found to be effective as a treatment for adjuvant-induced arthritis (AIA). We cloned the hsp65 gene from Mycobacterium leprae into plasmid pCAMBIA 2301 under the control of the double 35S promoter from cauliflower mosaic virus. Agrobacterium tumefaciens bearing the pChsp65 plasmid was used to transform tobacco plants. Incorporation of the hsp65 gene was confirmed by PCR, reverse transcription-PCR, histochemistry, and western blot analyses in several transgenic lines of tobacco plants. Oral treatment of AIA rats with the HSP65 protein allowed them to recover body weight and joint inflammation was reduced. Our results suggest a synergistic effect between the HSP65 expressed protein and metabolites presents in tobacco plants.

A novel heat-shock protein coinducer boosts stress protein Hsp70 to activate T cell regulation of inflammation in autoimmune arthritis

OBJECTIVE

Stress proteins, such as members of the heat-shock protein (HSP) family, are up-regulated by cells in inflamed tissue and can be viewed functionally as "biomarkers" for the immune system to monitor inflammation. Exogenous administration of stress proteins has induced immunoregulation in various models of inflammation and has also been shown to be effective in clinical trials in humans. This study was undertaken to test the hypothesis that boosting of endogenous HSP expression can restore effective immunoregulation through T cells specific for stress proteins.

METHODS

Stress protein expression was manipulated in vivo and in vitro with a food component (carvacrol), and immune recognition of stress proteins was studied.

RESULTS

Carvacrol, a major compound in the oil of many Origanum species, had a notable capacity to coinduce cellular Hsp70 expression in vitro and, upon intragastric administration, in Peyer's patches of mice in vivo. As a consequence, carvacrol specifically promoted T cell recognition of endogenous Hsp70, as demonstrated in vitro by the activation of an Hsp70-specific T cell hybridoma and in vivo by amplified T cell responses to Hsp70. Carvacrol administration also increased the number of CD4+CD25+FoxP3+ T cells, systemically in the spleen and locally in the joint, and almost completely suppressed proteoglycan-induced experimental arthritis. Furthermore, protection against arthritis could be transferred with T cells isolated from carvacrol-fed mice.

CONCLUSION

These findings illustrate that a food component can boost protective T cell responses to a self stress protein and down-regulate inflammatory disease, i.e., that the immune system can respond to diet.

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.

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.

A measles-derived peptide treats and vaccinates against adjuvant arthritis

Measles vaccine and porcine myelin basic protein were both found to ameliorate or abolish the symptoms of adjuvant arthritis (AA) in Lewis rats whether inoculated at the time of adjuvant administration or after the onset of arthritis. These results are consistent with clinical observations that measles infection can sometimes cause remission of juvenile rheumatoid arthritis. The fact that measles virus proteins and myelin basic protein have significant regions of homology allowed peptides based on these regions to be synthesized. A twenty-amino acid sequence exhibits significant anti-arthritic activity when inoculated into rats with pre-existing AA and it also prevented onset of AA when a single dose was preinoculated three weeks prior to AA induction. These data suggest the possibility of developing novel therapeutic vaccines against some forms of arthritis.

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.

Antigenic complementarity in the induction of autoimmunity: A general theory and review

The mechanism by which tolerance is broken in the induction of autoimmunity is unknown. Simple, well-characterized antigens suggest that molecular complementarity may play a key role in breaking tolerance. Experimental allergic encephalomyelitis can be induced using myelin basic protein combined with muramyl dipeptide. These molecules bind specifically to each other. Insulin antibodies can be induced when insulin is combined with glucagon, to which it binds. These cases suggest that molecular complementarity may alter the processing of "self" proteins. Antigenic complementary yields molecularly complementary immune responses (i.e., idiotypic-anti-idiotypic), undermining immune system regulation. In addition, complementarity insures that the antibodies (or T cells) directed against one antigen will molecularly mimic the other antigen, and vice versa, so that "self" and "nonself" will be confused. If at least one complementary antigen mimics a "self" protein, then an unregulated, self-sustaining immune response against tissue results. This testable theory of antigenic complementarity in autoimmunity is reviewed.

Antigenic complementarity in the origins of autoimmunity: a general theory illustrated with a case study of idiopathic thrombocytopenia purpura

We describe a novel, testable theory of autoimmunity, outline novel predictions made by the theory, and illustrate its application to unravelling the possible causes of idiopathic thrombocytopenia purpura (ITP). Pairs of stereochemically complementary antigens induce complementary immune responses (antibody or T-cell) that create loss of regulation and civil war within the immune system itself. Antibodies attack antibodies creating circulating immune complexes; T-cells attack T-cells creating perivascular cuffing. This immunological civil war abrogates the self-nonself distinction. If at least one of the complementary antigens mimics a self antigen, then this unregulated immune response will target host tissues as well. Data demonstrating that complementary antigens are found in some animal models of autoimmunity and may be present in various human diseases, especially ITP, are reviewed. Specific mechanisms for preventing autoimmunity or suppressing existing autoimmunity are derived from the theory, and critical tests proposed. Finally, we argue that Koch's postulates are inadequate for establishing disease causation for multiple-antigen diseases and discuss the possibility that current research has failed to elucidate the causes of human autoimmune diseases because we are using the wrong criteria.

Heat shock proteins in autoimmune diseases

Heat shock proteins (hsp's) are among the most conserved proteins in evolution. They have been identified as important pathogen-related antigens as well as autoantigens suitable for construction of novel vaccines. The high evolutionary homology of hsp's has raised the question about the safety of such vaccines. Experimental and clinical observations have confirmed that hsp proteins are involved in the regulation of some autoimmune disease such as autoimmune arthritis, type 1 diabetes mellitus, atherosclerosis, multiple sclerosis, and other autoimmune reactions. It has been shown in experimental animals that some hsp proteins (especially hsp60, hsp70, and hsp10) can either induce or prevent autoimmune reactions depending on the circumstances. This article discusses the involvement of hsp proteins in the etiology of autoimmune diseases and it presents promising experimental data on the effects of immunization with hsp proteins in the prevention and therapy of autoimmune diseases.

Heat shock protein 60 activates B cells via the TLR4-MyD88 pathway

We recently reported that soluble 60-kDa heat shock protein (HSP60) can directly activate T cells via TLR2 signaling to enhance their Th2 response. In this study we investigated whether HSP60 might also activate B cells by an innate signaling pathway. We found that human HSP60 (but not the Escherichia coli GroEL or the Mycobacterial HSP65 molecules) induced naive mouse B cells to proliferate and to secrete IL-10 and IL-6. In addition, the HSP60-treated B cells up-regulated their expression of MHC class II and accessory molecules CD69, CD40, and B7-2. We tested the functional ability of HSP60-treated B cells to activate an allogeneic T cell response and found enhanced secretion of both IL-10 and IFN-gamma by the responding T cells. The effects of HSP60 were found to be largely dependent on TLR4 and MyD88 signaling; B cells from TLR4-mutant mice or from MyD88 knockout mice showed decreased responses to HSP60. Care was taken to rule out contamination of the HSP60 with LPS as a causative factor. These findings add B cells to the complex web of interactions by which HSP60 can regulate immune responses.

Identification of immunodominant autoantigens in rat autoimmune orchitis

Infection and inflammation of the genital tract are amongst the leading causes of male infertility. Experimental autoimmune orchitis (EAO) in the rat serves as a model for the investigation of inflammatory testicular impairment. In this study, experiments were conducted to identify the molecules that are responsible for eliciting the autoimmune attack on the testis. EAO was induced in in-bred Wistar rats by active immunization with testis homogenates (EAO group I). Development of disease was observed using histological techniques and a new non-invasive three-dimensional (3D) imaging technology for in vivo monitoring, termed flat-panel volumetric computed tomography (fpvCT). Examination of control and EAO testes demonstrated the superior image quality of high-resolution fpvCT. A proteomics approach using 2D SDS-PAGE and immunoblotting analysis with EAO sera identified 12 spots. Seven were subsequently identified by mass spectrometry as heat shock proteins 60 (Hsp60) and 70 (Hsp70), disulphide isomerase ER-60, alpha-1-anti-trypsin, heterogeneous nuclear ribonucleoprotein H1 (hnRNP H1), sperm outer dense fibre major protein 2 (ODF-2), and phosphoglycerate kinase 1. Hsp70, ODF-2, hnRNP H1, and ER-60 were identified by all EAO sera studied. To test the capacity of the identified proteins to elicit testicular autoimmune disease, recombinant proteins were used either individually or in combination to immunize rats (EAO group II). In all groups, the incidence of EAO was 25%. Inflammatory-type (ED1+) and resident (ED2+) macrophages, lymphocytes (CD45RA+), and dendritic cells (Ox-62+) were strongly increased in EAO group II animals, comparable to the testes of EAO I rats. Pre-immunization with a low dose of recombinant Hsp 70, hnRNP H1 or ODF-2 before induction of EAO with testis homogenate significantly delayed the onset of EAO but could not prevent disease. The identification of testicular autoantigens will allow a better understanding of disease pathogenesis and could provide a basis for the development of novel therapies for inflammation-based male infertility.

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.

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 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.

Resistance to adjuvant arthritis is due to protective antibodies against heat shock protein surface epitopes and the induction of IL-10 secretion

Adjuvant arthritis (AA) is an experimental model of autoimmune arthritis that can be induced in susceptible strains of rats such as inbred Lewis upon immunization with CFA. AA cannot be induced in resistant strains like Brown-Norway or in Lewis rats after recovery from arthritis. We have previously shown that resistance to AA is due to the presence of natural as well as acquired anti-heat shock protein (HSP) Abs. In this work we have studied the fine specificity of the protective anti-HSP Abs by analysis of their interaction with a panel of overlapping peptides covering the whole HSP molecule. We found that arthritis-susceptible rats lack Abs to a small number of defined epitopes of the mycobacterial HSP65. These Abs are found naturally in resistant strains and are acquired by Lewis rats after recovery from the disease. Active vaccination of Lewis rats with the protective epitopes as well as passive vaccination with these Abs induced suppression of arthritis. Incubation of murine and human mononuclear cells with the protective Abs induced secretion of IL-10. Analysis of the primary and tertiary structure of the whole Mycobacterium tuberculosis HSP65 molecule indicated that the protective epitopes are B cell epitopes with nonconserved amino acid sequences found on the outer surface of the molecule. We conclude that HSP, the Ag that contains the pathogenic T cell epitopes in AA, also contains protective B cell epitopes exposed on its surface, and that natural and acquired resistance to AA is associated with the ability to respond to these epitopes.

Preventive administration of Mycobacterium tuberculosis 10-kDa heat shock protein (hsp10) suppresses adjuvant arthritis in Lewis rats

Adjuvant arthritis (AA) can be induced in Lewis rats by immunization with Mycobacterium tuberculosis (Mt) in oil. We have investigated the modulation of AA by mycobacterial 10-kDa heat shock protein (hsp10), administered according to several protocols known to induce immune tolerance and immune deviation. Subcutaneous immunization with hsp10 in aqueous solution did not induce a cellular immune response, evaluated as delayed-type hypersensitivity (DTH) reaction, although anti-hsp10 antibodies, mainly of the IgG2a isotype, were detected in serum of treated animals. When rats were pretreated with hsp10 in aqueous solution before AA induction, no effects were seen on arthritis-induced joint swelling, although osteolysis and lymphocyte infiltration were slightly decreased. When other routes of administration were attempted, the strongest suppression was seen in the group of animals which received four intranasal (i.n.) administrations of protein and a subsequent challenge of hsp10 in incomplete Freund's adjuvant (IFA). We also found that the extent of disease suppression among the different groups of animals correlated with serum anti-hsp10 antibody levels. These antibodies mostly belonged to the IgG2a subtype, suggesting that immune deviation may play a role in the mechanism of disease suppression by hsp10.

Prevention of experimental myointimal hyperplasia by immunomodulation

INTRODUCTION

we have tested the hypothesis that treatment with a mycobacterial preparation that modulates the antibody response, would diminish restenosis in a rat angioplasty model.

MATERIALS/METHODS

male Sprague-Dawley rats were used. All immunisations were given subcutaneously. Group A (control) received normal saline on days 0, 21, and 42. Group B received SRL172 on days 0, 21, and 42. Group C received SRL172 on days 0, 21, and 42, and hsp65/Incomplete Freund's on days 21 and 42. Group D received hsp65/Freund's on days 21 and 42. Right common carotid arteries were balloon-injured on day 63 using a standard technique known to produce MIH and animals were sacrificed on day 77. For each carotid 6 microm cross sections were cut from paraffin blocks. Cross-sectional areas were measured by computerised planimetry.

RESULTS

balloon injury resulted in MIH in all animals. Data represents mean+/-SEM for the percentage of area enclosed within the internal elastic lamina occupied by MIH (% MIH); which for groups A, B, C, and D was 85+/-11, 24+/-3, 27+/-7, and 17+/-3 respectively. All the treatment groups had significantly less MIH when compared to the control group but no statistically significant difference was found between any of the treatment groups.

CONCLUSIONS

this is the first report that immunomodulation with mycobacterial material suitable for use in man, can reduce MIH. Since such modulation has low risk, this raises the prospect of an important new therapeutic modality to combat restenosis.

Induction of IL-10 and inhibition of experimental arthritis are specific features of microbial heat shock proteins that are absent for other evolutionarily conserved immunodominant proteins

Bacterial heat shock proteins (hsp) are evolutionary conserved immunodominant proteins that manifest amino acid homologies with hsp present in mammalian cells. Preimmunization with mycobacterial hsp65 has been found to protect against various forms of experimental arthritis. As these protective effects have previously been attributed to induction of self homologue cross-reactive T cell responses, the question was raised as to whether this protective effect could be extended to other highly conserved and immunodominant microbial Ags with mammalian homologues. Therefore, we immunized Lewis rats with conserved bacterial Ags (superoxide dismutase, aldolase, GAPDH, and hsp70). Although all Ags appeared highly immunogenic, we only found a protective effect in experimental arthritis after immunization with bacterial hsp70. The protective effect of hsp70 was accompanied with a switch in the subclasses of hsp70-specific Abs, suggesting the induction of Th2-like response. The most striking difference between immunization with hsp70 and all other immunodominant Ags was the expression of IL-10 found after immunization with hsp70. Even more, while immunization with hsp70 led to Ag-induced production of IL-10 and IL-4, immunization with aldolase led to increased production of IFN-gamma and TNF-alpha. Thus, the protective effect of conserved immunodominant proteins in experimental arthritis seems to be a specific feature of hsp. Therefore, hsp may offer unique possibilities for immunological intervention in inflammatory diseases.

Heat shock proteins, anti-heat shock protein reactivity and allograft rejection

Heat shock proteins are families of highly conserved immunodominant molecules, reactivity to which has been implicated in the pathogenesis of a number of autoimmune and vascular disease states. However, heat shock proteins are cytoprotective, and in clinical and experimental arthritis, anti-heat shock protein reactivity can down modulate immune responses via a self-Hsp reactive, Th2-type mechanism. Despite a number of studies associating heat shock protein expression and anti-heat shock protein reactivity with allograft rejection, the balance between protective and damaging effects and the precise influence of these responses on graft outcome is unclear. This article reviews current knowledge surrounding heat shock proteins, autoimmunity, and allograft rejection and presents a perspective on the potential influence of these proteins and the stress response on allograft outcome.

Connectivity patterns in tuberculosis and leprosy patients are indistinguishable from that of healthy donors

Connectivity, the self-defined interactions between antigen-recognising molecules in a network system can in part be assessed by measuring the reactivity of a given serum against an ordered set of immunoglobulin (Ig)G F(ab')2 fractions, separated by means of isoelectric focusing so that, the serum reactivity against the whole set of fractions defines a characteristic pattern of connectivity. Deviations from the normal condition (healthy donors) have so far been documented for two autoimmune diseases: systemic lupus erythematosus (SLE) and pemphigus vulgaris, as well as for human immunodeficiency virus (HIV)-1 infection. We tested here if bacterial infections lead to alterations in connectivity. In addition, we wanted to test if two antigenically related bacteria would produce similar or otherwise distinctive connectivity patterns. Connectivity analysis was applied on the sera from tuberculosis and leprosy patients and the sera from healthy donors were used as control. No statistically significant differences between the three groups studied were found. These results have implications for theories that set the origin of autoimmune diseases in microbial infections. To the best of our knowledge, this is the first attempt to analyze the connectivity status in bacterial infections.

Immune responses in tuberculosis: antibodies and CD4-CD8 lymphocytes with vascular adhesion molecules and cytokines (chemokines) cause a rapid antigen-specific cell infiltration at sites of bacillus Calmette-Guérin reinfection

Rabbit primary dermal bacillus Calmette-Guérin (BCG) lesions were compared with reinfection BCG lesions in order to gain insight into how immune responses protect against clinical tuberculosis. As early as 3 hr, a marked infiltration of macrophages and lymphocytes occurred in the reinfection group, while very little cell infiltration occurred in the primary group. It seems that only an antigen-antibody reaction could produce such an immediate pronounced antigen-specific chemotactic effect, because very few lymphocytes are normally present in the skin. Therefore, antibodies hasten the accumulation of an expanded antigen-specific T-lymphocyte population (memory cells) at sites of bacillary lodgement. By 1-2 days, the primary and reinfection BCG lesions differed 400- to 500-fold in size. By 4-5 days, the size of the reinfection lesions had declined, while the size of the primary lesions had increased, so that, grossly, both types of lesion were similar. At 8 days in reinfection lesions and at 12 days in primary lesions, small secondary peaks in size occurred, which were probably caused by cell-mediated immune responses. In rabbits with primary BCG lesions, skin tests with Old Tuberculin were positive at 9 days, accompanied by a rise in the levels of antibodies to the secreted antigen, phosphate-specific transport protein 1, but the levels of antibodies to the constitutive antigens, purified protein derivative and heat-shock protein 65, did not increase appreciably until some time after 23 days. In tissue sections of reinfection BCG lesions, the percentage of mononuclear cells labelled, by in situ hybridization techniques, for the mRNA of monocyte chemoattractant protein 1 (MCP-1), a chemokine, peaked at 3 hr and then was down-regulated, whereas in primary lesions, this percentage was down-regulated only after 2 days. [The percentage in the tissue sections for the mRNAs of interleukins 1beta and 8, as well as the proteins of MCP-1 and tumor necrosis factor alpha (TNF-alpha), followed a somewhat similar time-course to that of MCP-1 mRNA.] A high percentage of mononuclear cells containing the MCP-1 mRNA 'factory' would favour enlargement of the lesions and a low percentage would favour their regression. At 5 days, the percentage of CD4 and CD8 lymphocytes, stained by immunohistochemical techniques, and the amount of microvasculature stained similarly for vascular cell adhesion molecule 1 were higher in the reinfection group, indicating that prior immunization caused a more rapid (antigen-dependent) up-regulation of these factors. Tuberculin reactions resembled early reinfection BCG lesions in almost every factor evaluated herein. In brief, the production of chemokines began soon after BCG reinfection, peaked within a few hours and was markedly down-regulated by 24 hr, a time at which the lesions of reinfection were of maximal size. Therefore, the amount of cell infiltration was tightly controlled, probably by the variety of mechanisms listed herein.

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.

Treatment of adjuvant-induced arthritis by oral administration of mycobacterial Hsp65 during disease

OBJECTIVE

Oral administration of antigen prior to disease induction has been shown to induce peripheral tolerance in several experimental autoimmune diseases. However, the clinical benefit of pretreatment with antigens is limited. The aim of this study was to investigate whether adjuvant-induced arthritis (AIA) could be treated by oral administration of mycobacterial heat-shock protein 65 (Hsp65) during ongoing disease.

METHODS

AIA was induced in Lewis rats by immunization with Mycobacterium tuberculosis in Freund's incomplete adjuvant. Oral feeding of Hsp65 in the presence or absence of soybean trypsin inhibitor (SBTI) was started on day 11 after immunization. Arthritis was monitored visually, and joint pathology was examined radiologically.

RESULTS

Oral treatment with Hsp65 during ongoing disease significantly reduced the activity of AIA. However, treatment with Hsp65 was only successful when SBTI was coadministered to prevent breakdown of the Hsp65. The beneficial effect of Hsp65/SBTI treatment during AIA was also represented by a clear reduction of articular destruction, as visualized by radiography. Moreover, feeding Hsp65/SBTI resulted in a lower number of both spleen and mesenteric lymph node (MLN) cells expressing the costimulatory molecule CD80 (B7-1). The number of cells expressing CD86 (B7-2) was not altered. Furthermore, MLN cells from AIA animals treated with Hsp65/SBTI contained a lower number of T cells expressing the activation marker CD134 (Ox-40). In addition, treatment with Hsp65/ SBTI was accompanied by an increased proliferative response of spleen cells to the Hsp65 antigen in vitro. Moreover, Hsp65/SBTI-treated rats showed less Hsp65-specific interferon-gamma and increased production of interleukin-10.

CONCLUSION

Ongoing AIA activity can be reduced by oral administration of Hsp65 only when protein breakdown in the gastrointestinal tract is inhibited.

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.

Antibodies against mycobacterial antigens in the synovial fluid of patients with temporomandibular disorders

In the absence of active pulmonary disease, mycobacterial infection frequently causes arthritis and can be considered to initiate autoimmune diseases such as rheumatoid arthritis. Temporomandibular disorder (TMD) is a disease in which pain and impaired mandibular movement appear to arise directly from degenerative or inflammatory changes within the temporomandibular joint, but its precise pathogeny has not been elucidated. Here we examined whether mycobacterial infection is related to the pathology of TMD. The antibody levels against mycobacterial antigen in the synovial fluid (SF) of patients with TMD were assessed by enzyme-linked immunosorbent assay (ELISA). Six of 17 TMD patients (35%) were found to possess mycobacterial antigen-specific immunoglobulin (Ig) G but not IgM, while the six healthy volunteers possessed neither. Western-blot analysis was used to isolate the reacted antigen, and the IgG reacted strongly to 44-kDa antigen. The first 14 N-terminal amino acid sequences were determined, and computer analysis revealed that it was homologous to translational elongation factor Tu (EF-Tu) of Mycobacterium tuberculosis, which was a major target antigen for these antibodies. The 44-kDa protein of Mycobacterium bovis BCG (BCG) was identical with the EF-Tu of M. tuberculosis. We cloned the gene encoding the EF-Tu of BCG by using the synthesized oligonucleotide primers by means of polymerase chain-reaction. The gene was expressed in Escherichia coli. The protein was purified, and the antibody levels against this recombinant protein in the SF of TMD patients were assessed by ELISA. Our findings suggest that some cases of TMD are concerned with the synovial IgG against the EF-Tu of M. tuberculosis, and that the existence of the antibody is a clinical indication of TMD.

A self-hsp60 peptide acts as a partial agonist inducing expression of B7-2 on mycobacterial hsp60-specific T cells: a possible mechanism for inhibitory T cell regulation of adjuvant arthritis?

We previously reported that resistance to the induction of adjuvant arthritis after preimmunization with mycobacterial hsp60 was mediated by T cells recognizing a conserved epitope (M256-270) of mycobacterial hsp60. These T cells were cross-reactive with the homologous rat hsp60 peptide sequence and the natural self-epitope on stressed antigen-presenting cells. Recognition of peptide M256-265, the conserved core of peptide M256-270, was shown to be essential for the generation of self-reactive T cells. The rat homologue of peptide M256-265, peptide R256-265, differs with three conservative amino acid substitutions from the mycobacterial core peptide. Thus peptide R256-265 could act as an altered peptide ligand with the potential of inducing a different functional phenotype in M256-270-specific T cells. We now show that peptide R256-265 was recognized by M256-270-specific T cells as a partial agonist, inducing TCR down-regulation and up-regulation of activation/adhesion molecules in the absence of proliferative responses. Peptide R256-265 did not induce anergy but induced B7-2 (but not B7-1) expression on M256-270-specific T cells, as opposed to the mycobacterial peptide, which preferentially induced B7-1. These effects were more pronounced at low peptide concentrations. Therefore also in vivo at the more relevant low physiological level of expression, the self-hsp could induce such phenotype. It is discussed how this selective up-regulation of B7-2 expression on (self-hsp60) autoreactive T cells might be a way by which destructive autoimmune responses are controlled.

Molecular cloning, purification and immunological responses of recombinants GroEL and DnaK from Streptococcus pyogenes

To better understand the roles of heat shock proteins in streptococcal diseases, the groEL and dnaK genes from Streptococcus pyogenes were cloned and their products (GroEL and DnaK) and derivatives (F2GroEL, F3GroEL and C1DnaK) purified as His-tagged fusion proteins. Western blot analysis of the purified proteins with sera from individuals with streptococcal diseases demonstrated that 29 out of 36 sera tested were reactive with GroEL and eight recognized DnaK. Rabbit antiserum against myosin recognized both GroEL and DnaK. Antibodies raised against purified F2GroEL and DnaK reacted with myosin in the ELISA but not in a Western immunoblot. These data indicate that the S. pyogenes GroEL and DnaK may be important immunogens during streptococcal infections. Furthermore, we provide evidence of an immunogenic relatedness of the GroEL and DnaK proteins with myosin that could play a role in the pathogenesis of streptococcal non-suppurative sequelae.

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.

Activation of T Cells Recognizing an Epitope of Heat-Shock Protein 70 Can Protect Against Rat Adjuvant Arthritis

We have previously reported that CD4+ T cells recognizing a peptide comprising residues 234–252 of the heat shock protein (HSP)70 of Mycobacterium tuberculosis (M.tb) in the context of RT1.B MHC class II molecule emerged in the peritoneal cavity during the course of Listeria monocytogenes infection in rats and suppressed the inflammatory responses against listerial infection via IL-10 production. We report in this work that pretreatment with peptide 234–252 of HSP70 derived from M.tb suppressed the development of adjuvant arthritis (AA) in Lewis rats induced using heat-killed M.tb. T cells from rats pretreated with peptide 234–252 produced a significant amount of IL-10 in response to the epitope. T cells from rats pretreated with the peptide and immunized with M.tb produced the larger amount of IL-10 in response to the peptide, but only a marginal level of IFN-γ in response to purified protein derivative of M.tb. Administration of anti-IL-10 Ab partly inhibited the suppressive effect of pretreatment with peptide 234–252 on the development of AA. Furthermore, transfer of a T cell line specific for the epitope at the time of AA induction markedly suppressed AA. These findings suggested that T cells recognizing peptide 234–252 may play a regulatory role in inflammation during AA via the production of suppressive cytokines including IL-10.

Behçet's disease and antibody titers to various heat-shock protein 60s

It has been suggested that the 65 kDa heat-shock protein (HSP) of Streptococcus in recurrent aphthae within the oral cavity may be involved in the uveoretinitis of Behçet's disease, possibly through sensitization of the immune system. To investigate this possibility, we examined serum antibody titers for various members of the 60 kDa family of HSPs and their implications with regard to a role for HSP60s in Behçet's disease. We isolated HSP60 of Streptococcus pyogenes from the margin of oral aphthae in one Behçet's disease patient with severe uveoretinitis and the HSP60s of Yersinia enterocolitica, retinoblastoma cell line clone Y79, and bovine retinal extract and investigated the reaction of each of these HSP60s with 100-fold diluted serum samples from 20 Behçet's disease patients using anti-HSP60 antibody titers determined by ELISA. The anti- Streptococcus HSP60 antibody and anti-retinal HSP60 antibody titers of the 100-fold diluted serum samples from the Behçet's disease patients were both significantly higher than those of similarly diluted serum samples from healthy donors. The results of the ELISA antibody titer assay showed that, although the various HSP60s share a common basic antigenicity, they differed in reactivity to the anti-HSP60 antibodies in the sera of the Behçet's disease patients. The results indicate that subtle but significant differences exist in the antigenicity of the various HSP60s tested, all of which share a common basic antigenicity and are of approximately the same molecular weight, and suggest that an immuno-cross-reaction between retinal and streptococcal HSPs and a related autoimmune response may be involved in the development of Behçet's disease.

HLA-DRB1 motifs and heat shock proteins in rheumatoid arthritis

Susceptibility to develop Rheumatoid arthritis (RA) maps to a highly conserved amino acid motif expressed in the third hypervariable region of different HLA-DRB1 alleles. This motif, namely QKRAA, QRRAA or RRRAA helps the development of RA by an unknown mechanism. In the past ten years, we have extensively studied the unique properties of the QKRAA motif of HLA-DRB1*0401 and have found: (1) That it can constitute B and T cell epitopes on many infectious agents; (2) That it can shape the T cell repertoire; (3) That it is overrepresented in protein databases; (4) That it constitutes a binding motif for the highly conserved family of 70 kD heat shock proteins. This may cause abnormal trafficking of HLA-DRB1*0401 in B cells and/or abnormal T cell responses to bacterial and human 70 kD heat shock proteins in people who express HLA-DRB1*0401.

Immunity to heat shock proteins and arthritic disorders

Adjuvant arthritis (AA) is a frequently used model of experimental arthritis. Because of its histopathology, which is reminiscent of rheumatoid arthritis in humans, AA is used as a model for the development of novel anti-inflammatory drugs. Recently, it has become evident that AA is a typical T-cell-mediated autoimmune condition. Therefore, novel immunotherapies targeted to T cells can be developed in this model. Analysis of responding T cells in AA have now led to the definition of various antigens with potential relevance to arthritis, including human arthritic conditions. One such antigen defined in AA is the 60kD heat shock protein. Both T-cell vaccination approaches and active antigen immunizations and antigen toleration approaches have turned out to be effective in suppressing AA.

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.

HSP-derived peptides inducing uveitis and IgG and IgA antibodies

Heat shock protein (HSP) 65 kD-derived peptides, which specifically stimulate T cells from patients with Behçet's disease (BD), are capable of inducing uveitis in rats. Mycobacterial HSP 65 kD and BD-specific peptides were injected into Lewis rats and the development of uveitis was monitored clinically and histologically, and IgG and IgA antibodies were measured using an enzyme-linked immunosorbent assay (ELISA). Rats immunized with HSP peptides that developed uveitis showed significantly higher serum IgG antibody levels to peptide 311-326 (P < 0.05) and the corresponding homologous human peptide 336-351 (P < 0.01) than rats without uveitis. Significant increases in serum IgA antibodies in rats with uveitis were also observed in those immunized with peptides 111-125, 311-326 and 336-351 (P < 0.05). Rats injected with HSP 65 kD showed a rise in IgG antibody levels to peptides 111-125, 154-172 and 311-326 and to a lesser extent, a rise in IgA antibody level to peptide 311-326. HSP showed almost complete inhibition of binding of IgG antibodies to HSP 65 kD, but peptides 111-125, 154-172, 311-326 and 336-351 showed inhibition to a lesser extent in a competitive assay. These results suggest that increases in IgG and IgA antibody levels to specific peptides within HSP, develop in rats with uveitis. The T and B cell epitopes responsible for the development of ocular disease in rats immunized with HSP-derived peptides, appear to be similar or identical to those found in patients with the ocular type of BD.

Diversification of response to hsp65 during the course of autoimmune arthritis is regulatory rather than pathogenic

Determinant spreading has been implicated in the pathogenesis of certain autoimmune diseases in animal models. We have observed that during the course of adjuvant arthritis (AA) in the Lewis rat, there is 'diversification' of response to the bacterial 65-kDa heat shock protein (Bhsp65) towards its carboxy-terminal determinants (BCTD). Strikingly, pretreatment of naive Lewis rats with BCTD affords significant protection from AA. Our preliminary studies indicate that the diversification of response to BCTD in the Lewis rat is probably triggered in vivo by the induction and enhanced processing of self(rat) hsp65. Thus, the self hsp65-directed T-cell responses appear to be involved in mediating natural remission from acute inflammatory arthritis induced by a foreign antigen, Mycobacterium tuberculosis. This the first report describing that the new T-cell specificities arising during the course of an autoimmune disease are regulatory/protective rather than pathogenic. Moreover, our results suggest that a final common mechanism involving BCTD might be recruited by other rat strains which either are resistant to AA (WKY rats) or whose susceptibility to AA is modulated significantly by microbial flora (Fisher rats). The results of this study would contribute significantly to understanding of the pathogenesis of human rheumatoid arthritis, and in devising new therapeutic strategies for this disease.