Suppression of collagen induced arthritis by oral administration of type II collagen: changes in immune and arthritic responses mediated by active peripheral suppression

Undenatured type II collagen protects against collagen-induced arthritis by restoring gut-joint homeostasis and immunity

Oral administration of harmless antigens can induce suppression of reactive immune responses, a process that capitalises on the ability of the gastrointestinal tract to tolerate exposure to food and commensal microbiome without triggering inflammatory responses. Repeating exposure to type II collagen induces oral tolerance and inhibits induction of arthritis, a chronic inflammatory joint condition. Although some mechanisms underlying oral tolerance are described, how dysregulation of gut immune networks impacts on inflammation of distant tissues like the joints is unclear. We used undenatured type II collagen in a prophylactic regime -7.33 mg/kg three times/week- to describe the mechanisms associated with protective oral immune-therapy (OIT) in gut and joint during experimental Collagen-Induced Arthritis (CIA). OIT reduced disease incidence to 50%, with reduced expression of IL-17 and IL-22 in the joints of asymptomatic mice. Moreover, whilst the gut tissue of arthritic mice shows substantial damage and activation of tissue-specific immune networks, oral administration of undenatured type II collagen protects against gut pathology in all mice, symptomatic and asymptomatic, rewiring IL-17/IL-22 networks. Furthermore, gut fucosylation and microbiome composition were also modulated. These results corroborate the relevance of the gut-joint axis in arthritis, showing novel regulatory mechanisms linked to therapeutic OIT in joint disease.

Collagen Supplementation for Joint Health: The Link between Composition and Scientific Knowledge

Osteoarthritis (OA) is the most common joint disease, generating pain, disability, and socioeconomic costs worldwide. Currently there are no approved disease-modifying drugs for OA, and safety concerns have been identified with the chronic use of symptomatic drugs. In this context, nutritional supplements and nutraceuticals have emerged as potential alternatives. Among them, collagen is being a focus of particular interest, but under the same term different types of collagens coexist with different structures, compositions, and origins, leading to different properties and potential effects. The aim of this narrative review is to generally describe the main types of collagens currently available in marketplace, focusing on those related to joint health, describing their mechanism of action, preclinical, and clinical evidence. Native and hydrolyzed collagen are the most studied collagen types for joint health. Native collagen has a specific immune-mediated mechanism that requires the recognition of its epitopes to inhibit inflammation and tissue catabolism at articular level. Hydrolyzed collagen may contain biologically active peptides that are able to reach joint tissues and exert chondroprotective effects. Although there are preclinical and clinical studies showing the safety and efficacy of food ingredients containing both types of collagens, available research suggests a clear link between collagen chemical structure and mechanism of action.

Therapeutic Effect of Nile Tilapia Type II Collagen on Rigidity in CD8+ Cells by Alleviating Inflammation and Rheumatoid Arthritis in Rats by Oral Tolerance

Fibrillins are microfibril-associated macro glycoproteins found in connective tissues and structurally related to latent TGF-β-binding proteins (LTBPs). The special cellular immunity and blocking glycoprotein receptors IIb and IIIa of fibrillins are emerging topics in recent years. In this study, Nile Tilapia type IIcollagen (NTCII) was extracted and purified from the skull cartilages by a pepsin-soluble method. Amino acid analysis indicated that NTCII consisted of 315/1000 glycine residues, 72/1000 hydroxyproline residues and 108/1000 proline residues. SDS-PAGE analysis showed that NTCII was composed of three identical 130 kDa α-chains. The results of glycoprotein/carbohydrate assay indicated that the total polysaccharide content of NTCII was 5.6–19.0%. The IR spectrum of NTCII displayed five characteristic peaks of amide I, II, III, A, B. NTCII at 10–100 μg/mL concentration downregulated the content of cytokines in the presence or absence of LPS, especially the secretion of cytokines IL-6, IL-1β and TNF-α. Interestingly, NTCII promoted the secretion of Fas/Apo-1 compared to the control group and 25 μg/mL of NTCII resulted in a higher Fas/Apo-1 secretion level in CD8⁺ T cells. FITC-TCII fluorescence images confirmed that NTCII could bind to the membrane surface of CD8⁺ T cells, leading to the induction of rigidity. NTCII could bind to the membrane surface of CD8⁺ T cells that leads to the induction of rigidity, as evidenced by the FITC-NTCII fluorescence images. The qRT-PCR gene expression analysis of caspase-8 collected with Fas/Apo-1 was upregulated significantly in the 1 and 50 μg/mL NTCII-treated groups compared with the control group. Overall, the results conclude that the rigidity did not lead to an increase in inflammatory factors in CD8⁺ T cells treated with NTCII. The oral administration of NTCII 3 mg/kg dosage caused more prominent repair of damaged ankle cartilage than the 1 mg/kg dosage in Freund’s adjuvant-induced model of arthritis in rats. Therefore, this study disclosed the immunological and anti-arthritic effect of fibrillar collagen, which could be a potential biomaterial for practical applications with lower toxicity.

Advances in Pancreatic Islet Transplantation Sites for the Treatment of Diabetes

Diabetes is a complex disease that affects over 400 million people worldwide. The life-long insulin injections and continuous blood glucose monitoring required in type 1 diabetes (T1D) represent a tremendous clinical and economic burdens that urges the need for a medical solution. Pancreatic islet transplantation holds great promise in the treatment of T1D; however, the difficulty in regulating post-transplantation immune reactions to avoid both allogenic and autoimmune graft rejection represent a bottleneck in the field of islet transplantation. Cell replacement strategies have been performed in hepatic, intramuscular, omentum, and subcutaneous sites, and have been performed in both animal models and human patients. However more optimal transplantation sites and methods of improving islet graft survival are needed to successfully translate these studies to a clinical relevant therapy. In this review, we summarize the current progress in the field as well as methods and sites of islet transplantation, including stem cell-derived functional human islets. We also discuss the contribution of immune cells, vessel formation, extracellular matrix, and nutritional supply on islet graft survival. Developing new transplantation sites with emerging technologies to improve islet graft survival and simplify immune regulation will greatly benefit the future success of islet cell therapy in the treatment of diabetes.

The Spleen as an Optimal Site for Islet Transplantation and a Source of Mesenchymal Stem Cells

This review demonstrates the unique potential of the spleen as an optimal site for islet transplantation and as a source of mesenchymal stem cells. Islet transplantation is a cellular replacement therapy used to treat severe diabetes mellitus; however, its clinical outcome is currently unsatisfactory. Selection of the most appropriate transplantation site is a major factor affecting the clinical success of this therapy. The spleen has long been studied as a candidate site for islet transplantation. Its advantages include physiological insulin drainage and regulation of immunity, and it has recently also been shown to contribute to the regeneration of transplanted islets. However, the efficacy of transplantation in the spleen is lower than that of intraportal transplantation, which is the current representative method of clinical islet transplantation. Safer and more effective methods of islet transplantation need to be established to allow the spleen to be used for clinical transplantation. The spleen is also of interest as a mesenchymal stem cell reservoir. Splenic mesenchymal stem cells contribute to the repair of damaged tissue, and their infusion may thus be a promising therapy for autoimmune diseases, including type 1 diabetes mellitus and Sjogren’s syndrome.

Antigen-based immunotherapy for autoimmune disease: current status

Autoimmune diseases are common chronic disorders that not only have a major impact on the quality of life but are also potentially life-threatening. Treatment modalities that are currently favored have conferred significant clinical benefits, but they may have considerable side effects. An optimal treatment strategy for autoimmune disease would specifically target disease-associated antigens and limit systemic side effects. Similar to allergen-specific immunotherapy for allergic rhinitis, antigen-specific immunotherapy for autoimmune disease aims to induce immune deviation and promote tolerance to specific antigens. In this review, we present the current status of studies and clinical trials in both human and animal hosts that use antigen-based immunotherapy for autoimmune disease.

Skin tolerance is supported by the spleen

The repeated application of antigens results in the induction of tolerance. Lymph nodes are responsible for this reaction by producing suppressor cells. Using an in vivo transplantation model, we showed recently that stromal cells from different lymph nodes induce different cell populations for suppression, which all produce a tolerogenic phenotype. In this study, we were interested in the role of the spleen in these tolerance reactions. Therefore, tolerance was induced via feeding or injecting ovalbumin several times in control and splenectomized mice. The delayed-type hypersensitivity (DTH) was measured as well as the cell subset composition of the spleen. The spleen of peripherally tolerized mice showed higher proliferation activity and a specific antibody production compared with orally tolerized mice, where regulatory T cells were predominantly found. Tolerance induction after removal of the spleen resulted in a reduced DTH response in antigen fed animals, whereas skin tolerance induction failed. In conclusion, the results illustrate that lymph nodes from different areas employ their individual pathways for similar immune reactions, and the spleen is part of this reaction initiated at the peripheral site.

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.

Type II collagen oral tolerance; mechanism and role in collagen-induced arthritis and rheumatoid arthritis

Oral tolerance means a diminished immune response to previously fed antigens. Repeated oral administrations of type II collagen (CII) induce oral tolerance and inhibit the development of collagen-induced arthritis (CIA). Dendritic cells (DCs) in the gut-associated lymphoid tissue (GALT) take up the CII and then present it to T cells to generate regulatory T cells (Tregs), which induce systemic immune tolerance to CII. Inhibitory cytokines, such as transforming growth factor (TGF)-beta and interleukin (IL)-10, and several immune regulatory molecules, including indoleamine 2,3-dioxygenase (IDO) and retinoic acid, play an important role in Treg generation. Each DC subset may play different roles, and CD11c+CD11b+DCs and IDO+DCs are important in the generation of antigen-inducible Tregs in CII oral tolerance. Upon stimulation with the antigen involved in its generation, Treg is activated and regulates the immune response through inhibitory cytokine production, cell-to-cell contact-dependent mechanisms, DC modification, and bystander suppression. The DCs and Tregs are deeply involved in oral tolerance through reciprocal interactions. Several clinical trials have been conducted in RA patients to examine the efficacy of CII oral tolerance. An understanding the mechanism of oral tolerance to CII would give clinicians new insights into the development of natural immune tolerance and new therapeutic approaches for the treatment of autoimmune diseases.

Systemic administration of tolerogenic dendritic cells ameliorates murine inflammatory arthritis

The expression of various cell surface molecules and the production of certain cytokines are important mechanisms by which dendritic cells (DC) are able to bias immune responses. This paper describes the effects of the inflammatory cytokine tumor necrosis factor (TNF)-α on DC phenotype and function. TNF-α treatment resulted in upregulation of MHC class II and CD86 in the absence of increased cell surface CD40 and CD80 or the production of IL-12. Additionally TNF-α treated cells were able to bias T cell responses towards an anti-inflammatory profile. On a note of caution this tolerogenic phenotype of the DC was not stable upon subsequent TLR-4 ligation as a 4 hour pulse of the TNF-α treated DC with lipopolysaccharide (LPS) resulted in the restoration of IL-12 production and an enhancement of their T cell stimulatory capacity which resulted in an increased IFN-γ production. However, TNF-α treated DC, when administered in vivo, were shown to ameliorate disease in collagen induced arthritis, an experimental model of inflammatory joint disease. Mice receiving TNF-α treated DC but not LPS matured DC had a delayed onset, and significantly reduced severity, of arthritis. Disease suppression was associated with reduced levels of collagen specific IgG2a and decreased inflammatory cell infiltration into affected joints. In summary the treatment of DC with TNF-α generates an antigen presenting cell with a phenotype that can reduce the pro-inflammatory response and direct the immune system towards a disease modifying, anti-inflammatory state.

Antigen-specific therapy of rheumatoid arthritis

BACKGROUND

Immunotherapy offers the promise of antigen-specific suppression of pathological immune responses in conditions such as autoimmunity and organ transplantation. Substantial advances have been made in recent years in terms of understanding basic immunological mechanisms of autoreactivity, as well as clinically implementing immune-based therapies that are antigen nonspecific.

OBJECTIVE

To provide an integrated overview of the current state of the art in terms of antigen-specific tolerance induction, as well as to predict future directions for the field.

METHODS

Examples of successes and failures of antigen-specific immunotherapy were sought. Particular attention was paid to the well-established collagen II-induced model of arthritis.

RESULTS/CONCLUSIONS

Previous failures of antigen-specific immunotherapy were associated with lack of identification of clinically relevant antigens, as well as inappropriate tolerogenic methodologies. The advances in proteomics combined with novel gene-specific immune modulatory techniques place today's translational researchers in a unique position to tackle the problem of antigen-specific immunotherapeutic protocols.

Antigen-specific suppression of established arthritis in mice by dendritic cells deficient in NF-kappaB

OBJECTIVE

NF-kappaB inhibitors applied to animal models of rheumatoid arthritis (RA) demonstrate the important role of NF-kappaB in the production of mediators of inflammation in the joint and their antiinflammatory effects. Because NF-kappaB is involved in the differentiation, activation, and survival of almost all cells, its prolonged inhibition might have unwanted adverse effects. Therefore, we sought to apply NF-kappaB inhibitors more specifically, targeting dendritic cell (DC) differentiation, in order to influence the outcome of the autoimmune response, rather than to produce a broad antiinflammatory effect. We tested whether DCs treated with the NF-kappaB inhibitor BAY 11-7082 and exposed to arthritogenic antigen would suppress established arthritis in C57BL/6 mice.

METHODS

Antigen-induced arthritis was generated in C57BL/6 mice by injection of methylated bovine serum albumin (mBSA). After mBSA challenge, mouse knee joints were injected with antigen-exposed BAY 11-7082-treated DCs or with soluble tumor necrosis factor receptor (sTNFR). Intraarticular injection of interleukin-1 (IL-1) was used to induce disease flare.

RESULTS

Inflammation and erosion were suppressed in mice that received mBSA-exposed BAY 11-7082-treated DCs, but not in those that received keyhole limpet hemocyanin-exposed BAY 11-7082-treated DCs. Clinical improvement was dependent on IL-10 and was associated with antigen-specific suppression of the delayed-type hypersensitivity (DTH) reaction and switching of anti-mBSA antibody isotype from IgG2b to IgG1 and IgA. Suppression of the DTH reaction or arthritic disease was not impaired by concomitant administration of sTNFR. Suppression could be reversed with intraarticular administration of IL-1beta and could be restored by a second injection of mBSA-exposed BAY 11-7082-treated DCs.

CONCLUSION

BAY 11-7082-treated DCs induce antigen-specific immune suppression in this model of inflammatory arthritis, even after full clinical expression of the disease. Such DCs have potential as antigen-specific therapy for autoimmune inflammatory arthritis, including RA.

Oral tolerance: therapeutic implications for autoimmune diseases

Oral tolerance is classically defined as the suppression of immune responses to antigens (Ag) that have been administered previously by the oral route. Multiple mechanisms of tolerance are induced by oral Ag. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral Ag induces Th2 (IL-4/IL-10) and Th3 (TGF-β) regulatory T cells (Tregs) plus CD4+CD25+ regulatory cells and LAP+T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-β, cholera toxin B subunit (CTB), Flt-3 ligand, anti-CD40 ligand and continuous feeding of Ag. In addition to oral tolerance, nasal tolerance has also been shown to be effective in suppressing inflammatory conditions with the advantage of a lower dose requirement. Oral and nasal tolerance suppress several animal models of autoimmune diseases including experimental allergic encephalomyelitis (EAE), uveitis, thyroiditis, myasthenia, arthritis and diabetes in the nonobese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, colitis and stroke. Oral tolerance has been tested in human autoimmune diseases including MS, arthritis, uveitis and diabetes and in allergy, contact sensitivity to DNCB, nickel allergy. Positive results have been observed in phase II trials and new trials for arthritis, MS and diabetes are underway. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time and Ag-specific mechanism of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy and early therapy.

Effect of rat kidney fraction 3 (rKF3) antigen and specific IgM antibody against rKF3 on the progression of slowly progressive Heymann nephritis

The aim of the present study was to find out if specific IgM (M) antibody (directed against rat kidney fraction 3 (rKF3)) or rKF3 antigen were able to influence disease progression in an experimental autoimmune kidney disease called slowly progressive Heymann nephritis (SPHN). The level of circulating autoantibodies (aabs) and the morphological and functional changes to the kidney were studied in six groups of rats. All of the treatment components (except post-treatment with M) used in the SPHN pre- and post-treated rats and post-treated-only rats had measurable beneficial effects (even during restimulation with the chemically modified renal antigen, 22 weeks after the induction of the disease) as demonstrated by diminished pathogenic IgG aab production, less severe kidney lesions, and proteinuria reductions. The injected rKF3 minimized progression best in this experiment, especially when administered in a pre- and post-treatment regimen. It is thought that the effect of rKF3 in the reduced progression of SPHN was due to increased production of specific IgM aabs, which in turn limited pathogenic aab production and continuous buildup of immune complexes in the glomeruli by facilitating removal or blockage of nephritogenic autoantigens from the circulation.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

Oral administration of type II collagen suppresses pro-inflammatory mediator production by synoviocytes in rats with adjuvant arthritis

The objective of this study was to investigate the effect of the oral administration of type II collagen (CII) on pro-inflammatory mediator production by synoviocytes in rats with adjuvant arthritis (AA). Sprague-Dawley rats were fed with bovine CII either before immunization with Complete Freund's adjuvant (CFA) or after initiation of arthritis. Hind paw secondary swelling was measured and synoviocytes were harvested. Sera from portal vein of oral tolerized rats were collected and in vitro synoviocytes culture or synoviocytes-Peyer's Patches (PP) cells coculture system were developed. Interleukin (IL)-1 activity was measured by a mouse thymocyte activation assayed by MTT dye reduction and tumour necrosis factor (TNF) activity was measured by an L929 cytotoxicity bioassay. Nitric oxide (NO) and malondialdehyde (MDA) levels were measured by biochemical methods. We found that feeding with CII (5, 50 and 500 micro g/kg) for 7 days before immunization significantly suppressed hind paw secondary swelling measured at day 16, 20, 24 and 28 (all P < 0.01) and pro-inflammatory mediator (IL-1, TNF, NO and MDA) production by synoviocytes (all P < 0.01) in rats with AA. Feeding with CII (5, 50 and 500 micro g/kg) for 7 days after initiation of arthritis had a similar effect. CII (1, 10, 100 micro g/ml) had no effect on IL-1 and TNF production by synoviocytes in vitro, but CII 10 micro g/ml suppressed IL-1 and TNF production by synoviocytes-PP cells coculture system (P < 0.01), which was antagonized by anti-TGF-beta antibody (10 micro g/ml) (P < 0.01). Portal serum (1 : 10) from oral tolerized rats suppressed IL-1 and TNF production by synoviocytes (P < 0.01), which was also antagonized by anti-TGF-beta antibody (10 micro g/ml) (P < 0.01). We conclude that oral administration of CII had prophylactic and therapeutic effects on AA and over-production of IL-1, TNF, NO and MDA by synoviocytes was suppressed. Bystander active suppression may be the main mechanism of oral CII in the suppression of synoviocyte function.

Induction of oral tolerance in experimental antiphospholipid syndrome by feeding with polyclonal immunoglobulins

Intravenous immunoglobulins (IVIG) contain a wide spectrum of anti-idiotypes associated with autoimmune diseases. Since part of these anti-idiotypes may bear an internal image of the eliciting antigen, IVIG might be suitable for induction of oral tolerance. In the current study we attempted to induce tolerance in an experimental model of anti-phospholipid syndrome (APS) by oral administration of IVIG. Naive mice were fed with IVIG, or anti-beta 2GPI-specific anti-idiotypic IVIG(alpha Id). Significantly diminished humoral response was noted in mice IVIG/ IVIG-F(ab')(2)or IVIG(alpha Id)-tolerized mice, accompanied by a significant attenuation of clinical manifestations. The maximal effect was achieved in the mice tolerized before disease induction. Abrogation of T lymphocyte proliferation to beta 2GPI was detected in the mice fed with IVIG prior to beta 2GPI immunization, mediated by TGFbeta and IL-10 secretion. The tolerance induced by IVIG-feeding was nonspecific and could be adoptively transferred to syngeneic mice by CD8alpha (+) cells. These CD8alpha (+) T cells, were found to secrete high levels of TGFbeta and IL-10. In summary, IVIG-induced oral tolerance has a nonspecific immunomodulatory effect in experimental APS, mediated by TGFbeta and IL-10-secreting CD8alpha (+) cells. Our results point to a possible application of IVIG in the induction of oral tolerance against various autoimmune diseases.

Importance of dose of type II collagen in suppression of collagen-induced arthritis by nasal tolerance

OBJECTIVE

To determine the influence of the dose of collagen given nasally on the induction of specific mucosal tolerance in collagen-induced arthritis.

METHODS

The severity of clinical arthritis induced in DBA/1 mice was studied after the nasal administration (before disease induction) of 1 of 4 doses (across a 2-log range) of bovine type II collagen (CII). Parameters of immunity included lymphocyte proliferation and cytokine production in vitro in response to antigen stimulation, and the production of anticollagen IgG antibody subclasses.

RESULTS

The 3 highest doses (20, 80, and 320 microg) ameliorated disease severity, whereas the lowest dose (5 microg) aggravated disease. These findings correlated well with antigen-specific T cell proliferation and cytokine and antibody production. T cell proliferation was suppressed by the higher doses of CII, whereas the low dose enhanced T cell proliferation, indicating it primed the T cells. Suppression of T cell proliferation could be overcome by the addition of exogenous interleukin-2 (IL-2) to these cultures. Decreased T cell proliferation was associated with suppression of both Th1 (interferon-gamma [IFNgamma]) and Th2 (IL-4) cytokines and all the subclasses of anticollagen IgG in mice receiving 20, 80, or 320 microg of collagen. Overall, the highest dose of collagen (320 microg) was less effective at suppressing the immune response and disease than the 20-microg or 80-microg doses. There was an increased production of antibodies of all IgG isotypes, and of the Th1-associated cytokines IFNgamma and IL-2, in animals that had received the lowest dose of 5 microg collagen nasally.

CONCLUSION

Nasal administration of antigens is effective in inducing tolerance and reducing disease severity, but the effects are dose dependent. Low doses can prime the immune system and aggravate disease; high doses may not suppress disease. Suppression of the immune response, which correlates with suppression of disease, is not obviously associated with a type I to type II T cell switch, but rather with an overall suppression of both forms of T cell response, with a potential role for anergy of T cells in this process.

Oral administration of collagen conjugated with cholera toxin induces tolerance to type II collagen and suppresses chondritis in an animal model of autoimmune ear disease

B10.RIII (H-2r) mice were orally administered cyanogen bromide peptide 11 (CB11) or cholera toxin B (CTB)-conjugated CB11 to induce tolerance in collagen-induced autoimmune ear disease. Oral administration of a high dosage of CB11 provided partial protection from chondritis. However, administration of a tiny amount of CTB-CB11 conjugate effectively suppressed chondritis. Oral administration of CTB-CB11 conjugate did not alter the stimulation of T cells in vitro or the fine specificities of B cells. The oral administration of CTB-CB11 caused a higher level of type II collagen-specific IgG and its subclass. Interestingly, increases of TH1 cytokine (interferon-gamma) in Peyer's patches and of TH1/TH2 cytokines (interleukin-2 and interleukin-4) in lymph nodes were detected in mice that had been fed CTB-CB11. An increase of CD8+ T cells in the Peyer's patches with a decrease of CD8+ T cells in lymph nodes was seen in mice that had been fed CTB-CB11. These results suggest that protection from chondritis by oral administration of minute amounts of CTB-CB11 conjugate can be achieved by a mechanism distinct from that of conventional oral tolerance induction.

The role of dendritic cells, B cells, and M cells in gut-oriented immune responses

Although induction of T cell responses to fed Ag (oral tolerance) is thought to happen within the organized lymphoid tissue of the gut, we found that mice lacking Peyer's patches, B cells, and the specialized Ag-handling M cells had no defect in the induction of T cell responses to fed Ag, whether assayed in vitro by T cell proliferation or cytokine production, or in vivo by delayed-type hypersensitivity or bystander suppression against mycobacterial Ags in CFA. Feeding of Ag had a major influence on dendritic cells from fed wild-type or muMT mice, such that these APCs were able to elicit a different class of response from naive T cells in vitro. These results suggest that systemic immune responses to soluble oral Ags do not require an organized gut-associated lymphoid tissue but are most likely induced by gut-conditioned dendritic cells that function both to initiate the gut-oriented response and to impart the characteristic features that discriminate it from responses induced parenterally.

Prevention of autoimmunity by induction of cutaneous tolerance

Autoimmune gastritis develops in 20-60% of BALB/c mice following thymectomy at 3 days after birth (3dnTx). Previously we identified the gastric H+/K+ ATPase as the causative autoantigen and mapped the immunoreactive T cell epitope to a carboxyl-terminal peptide on the gastric H+/K+ ATPase beta subunit. Here we show that autoimmune gastritis can be suppressed by immunizing 3dnTx mice through neonatal skin with the beta subunit peptide, in combination with the contact sensitizer TNCB. When spleen cells were transferred from suppressed mice to nude mice a proportion of recipient mice developed gastritis. These results indicate that pathogenic T cells were still present in the 3dnTx mice but the absence of gastritis indicates that their activity can be regulated following induction of cutaneous tolerance by immunizing through neonatal skin. We propose that cutaneous tolerance is induced through mediation of immature Langerhans cells in neonatal skin and that this tolerance prevented the autoreactivity of pathogenic T cells. This procedure will have implications for strategies to suppress autoimmunity.

Antibodies to Lysophosphatidylcholine Are Decreased in Borderline Hypertension

-Atherosclerosis is characterized by infiltration in the lesions of cytokine-producing T cells and macrophages, where oxidized LDL may play an important role. However, little is known about the role of the immune system in the development of hypertension. Lysophosphatidylcholine (LPC) is formed by phospholipase A(2)-induced hydrolysis and/or by oxidation of LDL and other phospholipid-containing membranes. The objective of the present study was to investigate the role of antibodies to LPC in borderline hypertension (BHT). Seventy-five men with BHT were compared with 75 age-matched normotensive (NT) men (diastolic blood pressure 85 to 94 and <80 mm Hg, respectively). Antibody levels to LPC of IgM and IgG isotypes and IgG subclasses were determined with ELISAs. BHT men had significantly lower anti-LPC antibody levels of both IgG class (P:=0.0002) and IgM class (P:=0.0003) than did NT controls. Subclass analysis indicated that IgG(1) (P:=0.0005), but not IgG(2), was decreased. Anti-LPC antibodies or immunoglobulin subclasses thereof were negatively associated with atherosclerosis on the basis of intima-media thickness (P:=0.02), metabolic factors (P:=0.02), smoking (P:=0.02), and endothelin (P:=0.03). LPC has proinflammatory properties and is toxic at higher concentrations and thus may play a role in atherogenesis. Furthermore, LPC functions as a vasoconstrictor in experimental systems by inhibiting NO-mediated vasorelaxation. An intriguing possibility is that anti-LPC antibodies counteract these effects. Taken together, our data indicate that anti-LPC antibodies may constitute a novel factor in the development of hypertension and atherosclerosis.

Suppression of systemic lupus erythematosus disease in mice by oral administration of kidney extract

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the increased production of antibodies reactive with a variety of self and non-self antigens. A number of immunomodulatory therapies have been investigated for the disease process. Intragastric administration of low dose kidney extract (KE) three times weekly for 5 weeks and then weekly until 6 months of age in SLE mice, showed decreased anti-dsDNA antibody levels, less kidney damage and significantly prolonged survival compared with control phosphate buffered saline (PBS)-fed mice. The KE-fed mice also exhibited reduced T cell proliferative response to KE in comparison with PBS-fed controls. Serum isotype distribution of the anti-dsDNA antibodies revealed a marked reduction of IgG1 and IgG3 responses in the KE-fed mice. While the renal inflammatory cell infiltration and expression of interleukin-4 (IL-4) and IL-10 were markedly suppressed, no local enhancement of transforming growth factor-beta (TGF-beta) was detected. Oral administration of low dose KE, however, upregulated expression of IL-2, IFN-gamma and TNF-alpha in the kidneys and suppressed glomerulonephritis. These findings suggest that oral KE affects the disease process in SLE and raise the possibility that oral administration of KE or other potential autoantigens may provide a new approach for the treatment of SLE.

Suppression of collagen-induced arthritis by oral or nasal administration of type II collagen

We directly compared the effects of oral and nasal administration of collagen type II (CII) on disease progression, cytokine production and T cell responses in DBA/1 mice. Lymphocytes were assayed for proliferation and cytokine production and cell lines established. T cells from fed or nasally treated groups proliferated significantly less and produced markedly less IFN-gamma than the non-fed immunized group 10 days after immunization and prior to onset of arthritis. T cell lines established from fed or nasally treated mice showed a pattern of cytokine production involving IL-4, IL-10 and TGF-beta, whereas T cell lines from the control group produced more IFN-gamma and IL-2. Suppression of clinical measures of arthritis was equivalent in the nasal and orally treated groups. Animals were then tested for IFN-gamma production 70 days after a booster immunization at a time when disease was apparent. Mucosally treated animals secreted less IFN-gamma as compared to controls, even at this late time point. Suppression of collagen induced arthritis (CIA) by nasal treatment of mice with CII was associated with diminished levels of TNF-alpha and IL-6 mRNA expression in the joints of tolerized mice, two cytokines known to be involved in the inflammatory and pathological process of CIA. These results demonstrate the induction of antigen specific Th2 and TGF-beta secreting regulatory cells following both oral and nasal treatment, which is associated with suppression of local inflammation in the joints and decreased Th1 type responses in the periphery throughout the course of the illness.

Effect of multiple antigenic exposures in the gut on oral tolerance and induction of antibacterial systemic immunity

We have analyzed oral tolerance of microbial antigens in an experimental model in which mice are treated orally with a single small dose of soluble antigen and challenged systemically with the antigen in complete Freund's adjuvant. We found that, while oral administration of sonicated extracts of either Leishmania major, Leishmania donovani, or Staphylococcus aureus was tolerogenic, as was administration of the nominal antigen ovalbumin or conalbumin, oral administration of Escherichia coli or Salmonella typhimurium sonicated extract was not. Since E. coli is an enteric commensal that colonizes the intestine soon after birth, these data suggested that lack of demonstrable oral tolerance may be related to the frequency of oral exposure to an antigen. In support of this, we found that multiple oral doses of ovalbumin or S. aureus or L. donovani antigens did not increase systemic hyporesponsiveness beyond that achieved with a single oral dose. We have also tested the ability of mice fed with sonicates of the tolerogenic S. aureus or the nontolerogenic S. typhimurium to clear a subsequent systemic infection with the homologous bacteria and found that, while clearance of S. aureus was unaffected by prior feeding, clearance of S. typhimurium was actually enhanced. The data suggest that frequent oral antigenic exposure may eventually lead to induction of systemic immunity in tolerant mice.

T-cell anergy induced by clonotype-specific antibodies: modulation of an autoreactive human T-cell clone in vitro

Monoclonal antibodies (mAb) specific for the clonotype of an autoreactive T cell may be useful reagents in the modulation of autoimmune disease. We have previously reported the generation of a set of mAb specific for the clonotypic structure of a human T-cell clone recognizing an epitope of human cartilage gp-39. This glycoprotein was recently identified as a candidate autoantigen in rheumatoid arthritis. Here, we demonstrate for the first time that small amounts of immobilized anticlonotype mAb can induce anergy in the autoreactive clone. Following the anergic stimulus, T cells failed to proliferate upon restimulation as a result of a lack of interleukin-2 (IL-2) gene transcription. In addition, a diminished interferon-gamma (IFN-gamma) production was found. Our data indicate that anergy was not a result of T-cell receptor (TCR) downmodulation or the absence of free TCR. The anergic state was induced independent of costimulation or the presence of IL-2 and no protein synthesis was required for the induction of anergy. Anticlonotype mAb-induced anergy was prevented by cyclosporin A, suggesting that active signalling via the calcium/calcineurin pathway was required for the induction of anergy. In coculture experiments, anergic T cells were found to suppress the response of reactive cells from the same clone. This bystander suppression led to 90% inhibition of peptide-induced proliferation. Together, these findings suggest that mAb to the clonotypic structure of autoreactive T cells may be suitable reagents for the functional inactivation of these T cells in autoimmune diseases.

Modulation by cytokines of induction of oral tolerance to type II collagen

OBJECTIVE

To determine whether the simultaneous administration of drugs and/or cytokines such as transforming growth factor beta (TGFbeta) can render oral tolerance to type II collagen (CII) more effective in causing resistance to collagen-induced arthritis (CIA) in mice, and to investigate whether oral tolerance can still be induced when high levels of anti-CII are present.

METHODS

Tolerance was induced by intragastric feeding of low-dose CII to DBA/1 mice during a 2-week period, either before immunization with CII in Freund's complete adjuvant or after initiation of arthritis. Some mice were simultaneously injected with TGFbeta1 or with the H2 receptor agonist dimaprit.

RESULTS

Both TGFbeta1 and dimaprit increased the degree of oral tolerance obtained. TGFbeta1 augmented the induction of immunoregulatory CD8 T cells, which transferred the resistance to CIA induction to normal recipients. Feeding of CII for 2 weeks, starting after the onset of arthritis, still significantly ameliorated the course of CIA.

CONCLUSION

Administration of TGFbeta1 or dimaprit, both of which are believed to promote the development of immunoregulatory T cells, may reinforce induction of oral tolerance, even after the onset of arthritis.

Different therapeutic and bystander effects by intranasal administration of homologous type II and type IX collagens on the collagen-induced arthritis and pristane-induced arthritis in rats

To assess the efficiency of nasally administered cartilage-specific collagens as vaccination against development of arthritis and to ameliorate already established chronic arthritis, experimental models which develop chronic arthritis, pristane-induced arthritis (PIA), and homologous collagen-induced arthritis (CIA) in the rat were selected. Cartilage-specific collagens type IX (CIX) and type II (CII) were used for vaccination intranasally. A single dose of 250 microg CII instilled intranasally in rats with established PIA ameliorated the disease. For the prevention of disease, the same dose given before immunization was found to be most effective. Most importantly, the disease was more severe if this dose was given three times. For treatment of PIA, CIX was found to be more effective than CII, whereas for treatment of CIA only CII was effective. The amelioration of CIA was associated with a marked suppression of delayed type hypersensitivity and the flare reaction to CII and lower levels of IgG2b anti-CII antibodies in serum, i.e., with suppression of the TH1 rather than the TH2 response to CII. These findings, that cartilage proteins, if given intranasally, can both prevent and ameliorate established chronic arthritis in rats, are of significant importance for possible use in rheumatoid arthritis. The identification of two different cartilage-specific proteins (CII and CIX) effective against a disease induced with a well-defined nonimmunogenic adjuvant such as pristane will be of value for enhancing the effectiveness of the treatment.

Treatment with an Anti-IL-4 Monoclonal Antibody Blocks Suppression of Collagen-Induced Arthritis in Mice by Oral Administration of Type II Collagen

Oral administration of type II collagen (CII) has been shown to suppress collagen-induced arthritis (CIA) in experimental animals. However, the exact mechanism by which CIA is suppressed following administration of CII remains to be investigated, although it was demonstrated that active suppression by regulatory T cells might be involved in the suppression. Therefore, we have examined whether the inhibitory cytokine IL-4 plays a role in the suppression of CIA, by using an anti-IL-4 mAb (11B11 mAb). Mice were fed daily with CII over a period of 10 days before immunization with CII. 11B11 mAb was i.p. injected 30 min before each oral administration of CII. The results showed that treatment with 11B11 mAb markedly blocked suppression of CIA by the oral Ag. The blockade of suppression of CIA by the anti-IL-4 mAb was associated with the blockade of augmentation of IL-4 secretion in CII-fed mice. The treatment with 11B11 mAb also resulted in the prevention of decreases in anti-CII IgG2a Ab production, DTH responses to CII, proliferation of lymphoid cells to CII, and IFN-γ secretion in mice given CII orally. Thus, the neutralization of IL-4 by an anti-IL-4 Ab appears to be effective in blocking suppression of CIA by oral administration of CII, suggesting that IL-4 may be critically involved in its suppression.

Nasal administration of retinal antigens maintains immunosuppression of uveoretinitis in cyclosporin-A-treated Lewis rats: future treatment of endogenous posterior uveoretinitis?

PURPOSE

Current treatment of autoimmune endogenous posterior uveoretinitis (EPU) is limited by drug toxicity, unpredictable relapses on dose reduction and resistance to therapy. Administration of autoantigens via gastrointestinal or respiratory mucosa prior to antigen exposure induces immune hyporesponsiveness (mucosal tolerance) to further antigen sensitisation. In this study we assessed whether mucosal tolerance induction was possible after immunisation with retinal antigens in experimental autoimmune uveoretinitis (EAU) in animals that were short-term immunosuppressed with cyclosporin A (CsA) to determine whether mucosal administration of retinal antigens can maintain immunosuppression in sensitised and immunosuppressed individuals.

METHODS

Female Lewis rats were immunised with retinal extract (RE) and then treated as follows. Group 1 received no specific therapy and served as control; group 2 were fed CsA from day 7 to day 20 post-immunisation; group 3 received inhalational tolerance therapy with RE in addition to CsA; tolerance therapy was continued after day 20 when CsA was stopped. Experiments varying the timing and dosage of both tolerising and immunising antigen were also performed, the details of which are described. Incidence, day of onset and clinical activity were recorded and histopathological assessment of intraocular inflammation, in particular the extent of autoimmune target-organ damage, was graded semiquantitatively.

RESULTS

Compared with controls and group 2, group 3 showed both a marked delay in disease onset and a reduction in disease severity. This effect was both dose and dose-timing dependent. Tissue damage assessed in terms of preservation of rod outer segments was significantly less in group 3.

CONCLUSIONS

The success of combination therapy, clinically, remains unknown at present but these results support continuing present clinical trials of mucosal tolerance therapy and in particular have future implications for either maintaining or inducing immunosuppression in autoimmune diseases in combination with present immunosuppressive therapies.

Effect of a monoclonal antibody against interleukin-4 on collagen-induced arthritis in mice

1 The present study was undertaken to investigate the effect of a monoclonal antibody (11B11 mAb) against interleukin-4 (IL-4) on collagen-induced arthritis (CIA) in mice. 2 11B11 mAb was daily injected intraperitoneally over a period of 10 days, commencing on the day of immunization with type II collagen (CII). 3 The results showed that the anti-IL-4 mAb markedly augmented both the incidence and the severity of CIA. The augmentation of the disease was associated with a significant increase in anti-CII IgG2a antibody production, proliferative responses of lymph node cells to CII and interferon-gamma (IFN-gamma) secretion from the lymphoid cells. The production of anti-CII IgG1 antibodies the secretion of IL-4 was markedly reduced in the mAb-treated mice. 4 Thus, the neutralization of IL-4 by 11B11 mAb appears to be effective in augmenting CIA.

Expression and characterization of recombinant human type II collagens with low and high contents of hydroxylysine and its glycosylated forms

Insect cells coinfected with two baculoviruses, one coding for the pro alpha chains of human type II procollagen and the other for both the alpha and beta subunits of human prolyl 4-hydroxylase, produced the cartilage-specific type II collagen with a stable triple helix. The highest expression levels, up to 50 mg/l of type II collagen, were obtained in suspension culture using a modified construct in which sequences coding for the signal peptide and N propeptide of type II procollagen had been replaced by those for type III procollagen. The type III N propeptide artificially generated into type II procollagen was found to be cleaved at a much higher rate than the wild-type type II N propeptide, probably because the former interacted poorly with the triple-helical domain of type II procollagen. The amino acid composition of the recombinant type II collagen was very similar to that of the non-recombinant protein, but the hydroxylysine content was only 17% and that of glycosylated hydroxylysines was equally low. The hydroxylysine content was increased to the level found in the non-recombinant collagen by using an additional baculovirus coding for lysyl hydroxylase, and a substantial increase was also found in the glycosylated hydroxylysine content. No difference in thermal stability was found between the low- and high-hydroxylysine collagens.

Prevention of autoimmune disease due to lymphocyte modulation by the B-subunit of Escherichia coli heat-labile enterotoxin

We demonstrate that the receptor binding moiety of Escherichia coli heat-labile enterotoxin (EtxB) can completely prevent autoimmune disease in a murine model of arthritis. Injection of male DBA/1 mice at the base of the tail with type II collagen in the presence of complete Freund's adjuvant normally leads to arthritis, as evidenced by inflammatory infiltration and swelling of the joints. A separate injection of EtxB at the same time as collagen challenge prevented leukocyte infiltration, synovial hyperplasia, and degeneration of the articular cartilage and reduced clinical symptoms of disease by 82%. The principle biological property of EtxB is its ability to bind to the ubiquitous cell surface receptor GM1 ganglioside, and to other galactose-containing glycolipids and galactoproteins. The importance of receptor interaction in mediating protection from arthritis was demonstrated by the failure of a non-receptor-binding mutant of EtxB to elicit any protective effect. Analysis of T cell responses to collagen, in cultures of draining lymph node cells, revealed that protection was associated with a marked increase in interleukin 4 production concomitant with a reduction in interferon gamma levels. Furthermore, in protected mice there was a significant reduction in anti-collagen antibody levels as well as an increase in the IgG1/IgG2a ratio. These observations show that protection is associated with a shift in the Th1/Th2 balance as well as a general reduction in the extent of the anti-type II collagen immune response. This suggests that EtxB-receptor-mediated modulation of lymphocyte responses provides a means of preventing autoimmune disease.

Interphotoreceptor retinoid binding protein is a potent tolerogen in Lewis rat: suppression of experimental autoimmune uveoretinitis is retinal antigen specific

AIMS

Administration of unfractionated retinal antigen(s) (retinal extract, RE) suppresses RE induced experimental autoimmune uveoretinitis (EAU) and offers a potential therapeutic alternative to non-specific immunosuppressive therapies for posterior uveitis and autoimmune diseases. S-Ag and interphotoreceptor retinoid binding protein (IRBP) are two major autoantigens within soluble RE. It was aimed to assess, firstly, as has previously been shown with S-Ag, if IRBP can induce intranasal tolerance and, secondly, the contribution of both these major autoantigens to tolerance induction by whole RE.

METHODS

Animals were tolerised by intranasal administration with S-Ag or IRBP, either alone or in combination, or RE before immunisation with either IRBP or RE. Control animals were administered nasally either PBS or MBP. Daily clinical responses were recorded biomicroscopically and histological grades were obtained using a semiquantitative scoring system. Weekly serum antibody levels to retinal antigens were measured by ELISA and delayed hypersensitivity responses (DTH) were assessed by skin reactivity to intradermal inoculation with retinal or non-specific antigens.

RESULTS

Microgram doses of IRBP successfully suppressed both clinically and histologically IRBP induced EAU. This suppression was accompanied by reduced antigen specific DTH reactivity but maintained T cell dependent (IgG2a) antibody responses. Furthermore, combined S-Ag and IRBP administration afforded equal suppression of RE induced EAU when compared with RE therapy alone. Suppression of RE induced EAU was not achieved with administration of a non-retinal specific autoantigen, MBP. Although individually, both S-Ag and IRBP suppressed RE induced EAU, whole RE was unable to protect against IRBP induced disease.

CONCLUSIONS

Intranasal administration of IRBP suppressed IRBP induced EAU in the Lewis rat. S-Ag and IRBP are the major contributors to the tolerogenicity within RE, despite the known uveogenicity of other retinal antigens within RE and induction of tolerance was retinal antigen specific. Furthermore, suppression induced by single antigen administration is antigen specific although concomitant bystander suppression may also play a role. RE was unable to protect against IRBP induced disease despite tolerogenic levels of antigen within RE. Although this may be due in part to a dose effect of either tolerising or immunising antigen, further investigation into the possible antigen dominance of IRBP or mucosal processing of combinations of antigens is necessary so that the full efficacy of mucosal tolerance therapy can be assessed.

Oral tolerance for the treatment of autoimmune diseases

Orally administered autoantigens suppress autoimmunity in animal models, including experimental allergic encephalomyelitis, collagen and adjuvant-induced arthritis, uveitis, and diabetes in the non-obese diabetic mouse. Low doses of oral antigen induce antigen-specific regulatory T-cells in the gut, which act by releasing inhibitory cytokines such as transforming growth factor-beta, interleukin-4, and interleukin-10 at the target organ. Thus, one can suppress inflammation at a target organ by orally administering an antigen derived from the site of inflammation, even if it is not the target of the autoimmune response. Initial human trials of orally administered antigen have shown positive findings in patients with multiple sclerosis and rheumatoid arthritis. A double-blind, placebo-controlled, phase III multi-center trial of oral myelin in 515 relapsing-remitting multiple sclerosis patients is in progress, as are phase II clinical trials investigating the oral administration of type II collagen in rheumatoid arthritis, S-antigen in uveitis, and insulin in type I diabetes.

Mucosal tolerance and suppression of collagen-induced arthritis (CIA) induced by nasal inhalation of synthetic peptide 184-198 of bovine type II collagen (CII) expressing a dominant T cell epitope

The purpose of the study was to map the dominant T cell epitope of the CB11 sequence of CII in RTlu haplotype rats and to determine if, when used as a synthetic peptide, it would induce tolerance to protect against CIA. A dominant epitope corresponding to residues 184-198 included in the sequence of the CB11 fragment of bovine CII was identified in proliferation assay using peptides in an epitope scanning system using synthetic peptides of 15 amino acids, overlapping by 12 amino acids. This epitope is bovine-specific, but cross-reacts with the corresponding rat peptide. Minor epitopes in the bovine CB11 sequence was also autoantigenic. Use of independently synthesized and purified 184-198 peptide confirmed its dominance in the T cell responses of arthritic rats. The peptide itself was not arthritogenic. Cells from lymph nodes draining arthritic feet were particularly responsive to the dominant peptide sequence, and showed evidence of epitope spreading to include reactions to at least four subdominant epitopes. Mucosal tolerance was successfully induced by instilling CII into the nose of rats before induction of CIA: this was found to delay the onset of disease, reduce mean disease severity, shift the anti-CII antibody response to favour antibodies of the IgG1, rather than the IgG2b isiotype, and to reduce T cell reactivity to both CII and to the 184-198 peptide. The dominant 184-198 peptide itself had the same tolerogenic effects when given nasally to rats daily, on the 4 days immediately preceding the induction of CIA. Two forms of CIA with acute and delayed disease onset were each modified by pre-treatment with the peptide. This study demonstrates that mucosal tolerance to CII can be induced by delivering it nasally in a way similar to that achieved previously by oral delivery, and that the use of an immunodominant epitope contained in a synthetic peptide will also suppress the immunologic and arthritic responses to collagen.

Oral tolerance: mechanisms and possible role in inflammatory joint diseases

Decreased systemic immune responsiveness to a specific antigen following exposure to that antigen by the enteric route is termed 'oral tolerance.' Oral tolerance is revealed when attempts are made to parenterally immunize the host to the same antigen that was previously administered orally or intragastrically. A similar phenomenon is also seen following antigen exposure via the nasal mucosa and a related phenomenon is seen following antigen exposure in the upper respiratory tract. There has been a marked renewal of interest in the mechanisms that underlie oral tolerance because of its potential role for preventing and treating autoimmune and inflammatory diseases and IgE-mediated allergic disorders. The specific factors that determine whether or not the host develops mucosal tolerance to an antigen administered by the mucosal route are also of substantial importance for those involved in mucosal vaccine development. Furthermore, putative abnormalities in the ability of the host to develop mucosal tolerance may play a pathogenetic role in certain autoimmune and allergic diseases and disorders. Several well-defined immunological mechanisms mediate oral tolerance. These include the induction, following mucosal antigen exposure, of regulatory populations of T-cells that can down-regulate specific immune responses (e.g. DTH) via the production of specific cytokines (e.g. TGF-beta 1, IL-10 and IL-4). In addition, clonal anergy, clonal deletion and antibody-mediated suppression can be shown to play a role in the induction and maintenance of mucosal tolerance in several experimental systems. In animal studies, the onset of collagen-induced, adjuvant-induced, antigen-induced and pristane-induced arthritis has been delayed and the severity of ongoing disease diminished following feeding collagen type II. Mucosal tolerance has been clearly demonstrated in humans and clinical studies have been undertaken to treat rheumatoid arthritis using a similar approach. Results of initial clinical studies in rheumatoid arthritis indicated a modest improvement and further studies are ongoing in this and other autoimmune diseases (e.g. multiple sclerosis, autoimmune uveitis and insulin-dependent diabetes). This approach, if successful, could offer a new and novel therapeutic modality for preventing autoimmune and allergic disorders, and modulating ongoing disease.

Suppression of antigen-induced arthritis in Lewis rats by oral administration of type II collagen

OBJECTIVE

To assess the effect of orally administered type II collagen (CII) in antigen-induced arthritis (AIA).

METHODS

Arthritis was induced in Lewis rats by immunization with methylated bovine serum albumin (mBSA) in Freund's complete adjuvant, followed by an intraarticular injection of mBSA 2 weeks later. Different doses of CII, mBSA, and an unrelated control protein, keyhole limpet hemocyanin (KLH), were orally administered 5 times over several days prior to the induction of arthritis. Ankle joint swelling and delayed-type hypersensitivity (DTH) responses were measured.

RESULTS

Joint swelling was significantly reduced at a dose of 3 micrograms and 30 micrograms of CII, but not at 300 micrograms. The most prominent suppression of AIA was observed when rats were fed 10 mg of mBSA, whereas oral KLH had no effect. DTH responses were significantly reduced in the mBSA-fed rats, but not in rats that were fed CII or KLH.

CONCLUSION

Oral CII can suppress arthritis in an animal model in which immunity to collagen does not play a role. The effect is dose dependent and occurs at lower doses of CII. These results demonstrate the biologic relevance of bystander suppression associated with oral tolerance, and the potential use of this approach to treat human inflammatory joint disease.