Modulation of pristane-induced arthritis by mycobacterial antigens

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.

Tolerization against atherosclerosis using heat shock protein 60

Atherosclerosis is a chronic inflammatory disease of the artery wall, and both innate and adaptive immunity play important roles in the pathogenesis of this disease. In several experimental and human experiments of early atherosclerotic lesions, it has been shown that the first pathogenic event in atherogenesis is intimal infiltration of T cells at predilection sites. These T cells react to heat shock protein 60 (HSP60), which is a ubiquitous self-antigen expressed on the surface of endothelial cells (ECs) together with adhesion molecules in response to classical risk factors for atherosclerosis. When HSP60 is expressed on the EC surface, it can act as a "danger-signal" for both cellular and humoral immune reactions. Acquired by infection or vaccination, beneficial protective immunity to microbial HSP60 and bona fide autoimmunity to biochemically altered autologous HSP60 is present in all humans. Thus, the development of atherosclerosis during aging is paid by the price for lifelong protective preexisting anti-HSP60 immunity by harmful (auto)immune cross-reactive attack on arterial ECs maltreated by atherosclerosis risk factors. This is supported by experiments, which shows that bacterial HSP60 immunization can lead and accelerate experimental atherosclerosis. This review article presents accumulating proof that supports the idea that tolerization with antigenic HSP60 protein or its peptides may arrest or even prevent atherosclerosis by increased production of regulatory T cells and/or anti-inflammatory cytokines. Recent data indicates that HSP60, or more likely some of its derivative peptides, has immunoregulatory functions. Therefore, these peptides may have important potential for being used as diagnostic agents or therapeutic targets.

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.

Mycobacterium tuberculosis infection precipitates SLE in patients from endemic areas

In a cohort of 70 systemic lupus erythematosus (SLE) patients diagnosed over 2 years period, 14 patients were found to have confirmed antecedent tuberculosis (20.0%) which was 40 times higher (p < 0.001, 95%CI 36.2-48.6) than the prevalence of tuberculosis in the local population. Demonstration of anti-histone antibodies in similar proportion of SLE patients with and without antecedent anti-TB treatment and similar proportion of renal involvement (36 vs. 40%) between anti-TB drug exposed and non-exposed patients ruled out the drugs to be causative factors in precipitating SLE in these patients with antecedent history of tuberculosis. A cohort of 30 confirmed pulmonary tuberculosis patients were also studied in parallel to demonstrate high incidence of autoantibodies in these patients but no SLE. This study suggests a role of prior tuberculosis in precipitating SLE in genetically predisposed patients.

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.

Heat shock proteins induce T cell regulation of chronic inflammation

The significance of immune responses to certain heat shock proteins (HSPs) that develop in virtually all inflammatory diseases is only now becoming clear. In experimental models, HSPs prevent or arrest inflammatory damage, and initial clinical trials in chronic inflammatory disease have shown HSP peptides to promote production of anti-inflammatory cytokines-indicating immunoregulatory potential. HSPs are ubiquitous self-antigens that are highly expressed in inflamed tissues. The prokaryotic homologous proteins, present in every bacterial species, are dominantly immunogenic. This is striking, especially as these proteins have large areas of sequence homologies with the host (mammalian) counterparts. In several experimental models of autoimmune diseases, immunisation with bacterial HSPs inhibited disease development, as did oral/nasal administration. Based on the experimental evidence so far, it is tempting to speculate that: firstly, exposure to homologues of these self-antigens, as present in, for instance, the bacterial intestinal flora, has a decisive impact on the regulation of self-tolerance at the level of T cells; and secondly, such proteins or their derivative peptides may have a role in an antigen specific immunotherapy approach involving modulation of relevant T cells, without the immediate necessity of defining disease specific autoantigens. Recent findings in experimental asthma and atherosclerosis have indicated that the field of application of such immunotherapy can be broader than just autoimmunity.

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.

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 and arthritis--new readers start here

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

Influence of microbial stimulation on hypergammaglobulinemia and autoantibody production in pristane-induced lupus

Pristane induces a lupus-like syndrome characterized by autoantibody production and glomerulonephritis in nonautoimmune strains of mice. Although it has been suggested that this syndrome results from nonspecific immune activation, there is little evidence so far that B cells are activated nonspecifically by pristane or that this promotes autoimmunity. In this study, we examined whether polyclonal hypergammaglobulinemia occurs in pristane-induced lupus, and its relationship to the production of anti-DNA, nRNP/Sm, and Su autoantibodies. In conventionally housed mice, there was a marked increase in total IgM and IgG3 2 weeks after i.p. pristane injection, followed by increased IgG1, IgG2a, and IgG2b levels. IgM levels were higher in pristane-treated specific pathogen-free (SPF) mice than in conventionally housed mice, whereas IgG and IgA levels were reduced. Pristane induced anti-nRNP/Sm and Su autoantibodies in SPF mice, but their onset was delayed and levels were lower than those in conventionally housed mice. There was no consistent relationship between total IgG1, 2a, and 2b hypergammaglobulinemia and production of anti-nRNP/Sm and Su autoantibodies. Moreover, the total Ig levels were similar in the anti-nRNP/Sm-positive and -negative groups. In contrast, production of IgM anti-ssDNA antibodies paralleled IgM hypergammaglobulinemia in some, but not all, mice. These studies indicate that pristane-induced lupus is associated with marked hypergammaglobulinemia, the magnitude of which is influenced by the microbial environment. However, anti-nRNP/Sm and Su autoantibody production is at least partly independent of polyclonal B cell activation. The data strongly suggest that pristane-induced lupus is not exclusively the consequence of nonspecific immune stimulation. They also point to the importance of microbial stimulation in the development of hypergammaglobulinemia in this inducible lupus model.