Suppression of experimental autoimmune myasthenia gravis and experimental allergic encephalomyelitis by oral administration of acetylcholine receptor and myelin basic protein: double tolerance

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.

Treatment of Mice with the Suppressor of Cytokine Signaling-1 Mimetic Peptide, Tyrosine Kinase Inhibitor Peptide, Prevents Development of the Acute Form of Experimental Allergic Encephalomyelitis and Induces Stable Remission in the Chronic Relapsing/Remitting Form

We have previously characterized a novel tyrosine kinase inhibitor peptide (Tkip) that is a mimetic of suppressor of cytokine signaling 1 (SOCS-1) and inhibits JAK2 phosphorylation of the transcription factor STAT1alpha. We show in this study that Tkip protects mice against experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis. Mice are immunized with myelin basic protein (MBP) for induction of disease. Tkip (63 mug) administered every other day suppressed the development of acute EAE in 75% of New Zealand White (NZW) mice. Furthermore, Tkip completely protected SJL/J mice, which where induced to get the relapsing/remitting form of EAE, against relapses compared with control groups in which >70% of the mice relapsed after primary incidence of disease. Protection of mice by Tkip was similar to that seen with the type I IFN, IFN-tau. Protection of mice correlated with lower MBP Ab titers in Tkip-treated groups as well as suppression of MBP-induced proliferation of splenocytes taken from EAE-afflicted mice. Cessation of Tkip and IFN-tau administration resulted in SJL/J mice relapsing back into disease. Prolonged treatment of mice with Tkip produced no evidence of cellular toxicity or weight loss. Consistent with its JAK2 inhibitory function, Tkip also inhibited the activity of the inflammatory cytokine TNF-alpha, which uses the STAT1alpha transcription factor. The data presented in this study show that Tkip, like the type I IFN, IFN-tau, inhibits both the autoreactive cellular and humoral responses in EAE and ameliorates both the acute and chronic relapsing/remitting forms of EAE.

Interleukin-12 enhances clinical experimental autoimmune myasthenia gravis in susceptible but not resistant mice

Experimental autoimmune myasthenia gravis (EAMG) is induced by antibodies against the nicotinic acetylcholine receptor (AChR). Studies indicate a role for interferon-gamma (IFN-gamma) in EAMG. We examined the effect of IL-12, a major inducer of IFN-gamma production, on EAMG in C57BL/6 mice. Five doses of IL-12 accelerated and enhanced clinical disease in AChR-immunized mice. Control B6 mice, IFN-gamma gene-knockout mice, and EAMG-resistant bm12 mice showed no enhancement of disease. Shifting to a Th1-type antibody isotype distribution was insufficient to cause disease. Other factors, such as direct effects of Th1 cytokines on muscle tissue, may be involved in EAMG susceptibility.

The application of gene therapy in autoimmune diseases

The application of gene therapy in autoimmune disease represents a novel use of this technology. The goal of gene therapy in the treatment of autoimmune disease is to restore 'immune homeostasis' by countering the pro-inflammatory effects of the CD4+ T cells in the lesions of autoimmunity. This can be accomplished by adoptive therapy with transduced T cells which can specifically home to the site of inflammation and secrete 'regulatory' protein(s) to ameliorate the inflammation or by direct targeting of the retroviral vector to activated T cells in the sites of inflammation. Transduction of autoantigen recognizing CD4+ T cells, to secrete anti-inflammatory products, may become the 'magic bullet' to combat the ravages of autoimmune inflammation and tissue destruction. Gene Therapy (2000) 7, 9-13.

Oral immunization with enterocoated microbeads induces antigen-specific cytolytic T-cell responses

A cytolytic T-lymphocyte (CTL) response has been generated to a protein antigen via oral administration in an experimental murine system. This was achieved by the formulation of the test antigen ovalbumin (OVA) in a pH-sensitive microsphere particle (microbead) with an acrylic-based coating to avoid its degradation by gastric enzymes. Comparative studies of orally administered enterocoated microbead-OVA particles, versus the more traditional formulation of OVA in adjuvant (DETOX-PC) given subcutaneously as immunogen, were conducted; both elicited comparable responses in the generation of antigen-specific lymphoproliferative and CTL responses. CTL lines generated via oral administration of antigen were shown to be CD3(+), CD4(-), and CD8(+). CTL lysis of OVA peptide-pulsed targets was shown to be inhibited by anti-CD8 antibody. Whereas oral administration of pH-sensitive enterocoated microbeads containing proteins has previously been shown to elicit antibody and lymphoproliferative T-cell responses to protein antigens, this is the first demonstration of the generation of an antigen-specific cytolytic T-cell response via oral administration of a protein immunogen formulated in such microbeads.

Effect of transforming growth factor-beta1 on interleukin-6 secretion in human myoblasts

Transforming growth factor-beta (TGF-beta) is involved in several autoimmune neurological diseases. It is still unclear whether its local action can be pro-inflammatory or anti-inflammatory in the muscle tissue, because of the few reports on this subject. We have previously shown that human myoblasts secrete interleukin-6 (IL-6) when stimulated with inflammatory cytokine such as interleukin-1beta (IL-1beta) or tumor necrosis factor alpha. In the present report, we show that TGF-beta1 can induce IL-6 production; moreover, costimulation or short term pre-incubation with TGF-beta1 increases IL-1beta effect, while a longer incubation inhibits its action.

IFN-tau suppresses both the autoreactive humoral and cellular immune responses and induces stable remission in mice with chronic experimental allergic encephalomyelitis

We have previously shown that interferon-tau (IFN-tau) pretreatment inhibits the development of both acute and chronic mouse experimental allergic encephalomyelitis (EAE), an animal model for the human demyelinating disease multiple sclerosis (MS). IFN-tau is a type I IFN that has pregnancy recognition hormone activity in ruminants. Here we show that IFN-tau induced remission in SJL/J mice that had ongoing chronic active EAE disease and protected mice against secondary relapses. IFN-tau treatment reversed lymphocyte infiltration and microglial activation in the central nervous system. Mice that were treated with IFN-tau had lower levels of anti-MBP antibodies than untreated mice in both chronic and acute forms of EAE. MBP induced proliferation in B cells from EAE mice, but treatment with IFN-tau either in vivo or in vitro blocked activation. Furthermore, IFN-tau inhibited MBP activation of T cells from EAE mice. Thus, IFN-tau inhibits the humoral arm as well as the cellular arm of the autoimmune disease EAE. The data presented here show that IFN-tau inhibits both B cell and T cell responses in EAE as well as active, chronic EAE, and this may help explain the effectiveness of type I IFNs in treatment of MS.

Nasal tolerance to experimental autoimmune myasthenia gravis: tolerance reversal by nasal administration of minute amounts of interferon-gamma

Tolerance to B cell-mediated experimental autoimmune myasthenia gravis (EAMG), an animal model for myasthenia gravis (MG) in humans, can be achieved by nasal administration of the autoantigen acetylcholine receptor (AChR). Nasal tolerance induction requires only 1/1000 of the amount of AChR used for oral tolerance induction, but is as effective in preventing EAMG. To investigate whether nasally induced tolerance to EAMG can be influenced by nasal administration of cytokines, recombinant rat IFN-gamma (total 5000 U/rat), a combination of AChR and IFN-gamma or AChR alone was given nasally to Lewis rats before immunization with AChR and complete Freund's adjuvant (CFA). One additional group of rats received the same amount of AChR nasally in conjunction with IFN-gamma (total 5000 U/rat) intraperitoneally. AChR given alone nasally induced effective tolerance to EAMG whereas rats receiving AChR + IFN-gamma by the nasal route exhibited a similar disease pattern, and similarly escalated T and B cell responses to AChR when compared to control EAMG rats. In contrast, administration of IFN-gamma i.p. together with AChR nasally did not affect the induction of tolerance to EAMG. IFN-gamma given alone nasally did not affect clinical EAMG. This study demonstrates that nasal tolerance can be modulated by nasal administration of minute amounts of IFN-gamma. Nasal administration of certain cytokines with beneficial effects might broaden the effectiveness of applying nasal tolerance as a potential therapeutic means of preventing autoimmune diseases.

Nasal administration of multiple antigens suppresses experimental autoimmune myasthenia gravis, encephalomyelitis and neuritis

Oral tolerization with acetylcholine receptor (AChR) and myelin basic protein (MBP) prior to immunization with AChR+MBP+ complete Freund's adjuvant (CFA) alleviated clinical signs of experimental autoimmune myasthenia gravis (EAMG)+experimental allergic encephalomyelitis (EAE) and AChR- or MBP-specific T and B cell responses. Tolerance induced via the nasal route needs much less tolerogen and may still be as effective as oral tolerance induction. We now immunized Lewis rats with AChR+MBP+bovine peripheral nerve myelin (BPM)+CFA, which resulted in a multiphasic clinical picture with a combination of clinical signs of the EAMG+EAE+experimental allergic neuritis (EAN), accompanied by massive macrophage infiltrations in sections of muscle, spinal cord and sciatic nerve, and strong T and B cell responses to AChR, MBP and BPM in lymphoid organs. Nasal administration of microg doses of AChR+MBP+BPM prior to immunization with a mixture of these antigens+CFA effectively suppressed the incidence and severity of clinical disease, reduced macrophage infiltrations in sections of muscle, spinal cord and sciatic nerve, and down-regulated autoreactive T cell responses to the three antigens in lymphoid organs. Numbers of AChR-, MBP-, BPM-reactive Th1 type of cytokine interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha mRNA expression in lymph node cells were markedly suppressed, while transforming growth factor-beta (TGF-beta) mRNA expression was upregulated from nasally tolerized rats, suggesting an active suppression mechanism may act partly in the induction of tolerance. The results implicate the possibility to establish multiple autoantigen-based vaccination for the prevention of autoimmune diseases in humans.

Mucosal tolerance: a two-edged sword to prevent and treat autoimmune diseases

Mucosal administration of autoantigens results in the development of a state of peripheral immunological tolerance. Depending upon the dose of antigen administered, anergy/deletion of antigen-specific T cells (higher doses) and/or selective expansion of cells producing immunosuppressive cytokines (TGF-beta, IL-4, and IL-10) (lower doses) are two major mechanisms in mucosal tolerance induction. Mucosal tolerance is more effective after nasal compared to oral administration of antigens at the same dose. A large series of studies have demonstrated that mucosal tolerance by oral or nasal antigen administration effectively prevents several experimental disease models (EAE, EAMG, EAN, EAU, IDDM, and CIA). Mucosal antigen administration is superior in prevention to treatment of autoimmune diseases. To broaden the effectiveness of mucosal tolerance, a conjunction of tolerogens with cytokines/CTB might enhance suppression of clinical disease. Based on experimental experience with mucosal tolerance, trials in humans are ongoing in MS, RA, and uveitis. However, mucosal tolerance induction is related to the route of antigen administration (oral, nasal, parentetal), type of antigen (whole protein, peptide, altered peptide), and timing with regard to disease onset and may represent a two-edged sword. In particular, the risks of worsening an ongoing autoimmune disease by mucosal antigen administration have been incompletely addressed. Here we give an overview on some recent developments in this field where, however, much more studies are needed to define an ultimate and safe procedure.

Spontaneously hypertensive rat: cholera toxin converts suppression to immunity through a Th2 cell-IL-4 pathway

The spontaneously hypertensive rat (SHR) exhibits a number of T cell dysfunctions that develop concurrently with elevated blood pressure. Studies have shown a mitogen-induced lymphocyte suppression mediated in part by the production of interferon-gamma (IFN-gamma), which stimulated NO production by macrophages. To assess whether this immune suppression is reversible, SHR were immunized with diphtheria toxoid (DT) with or without cholera toxin (CT) as adjuvant. SHR immunized with DT only displayed weak serum immunoglobulin G (IgG) anti-DT titers, tenfold less than similarly treated normotensive Wistar-Kyoto rats (WKYR). SHR CD4+ T cells failed to proliferate upon in vitro stimulation with DT. In contrast, SHR coimmunized with DT and CT showed serum IgG antibody titers similar to WKYR and Brown Norway rats. Coimmunization with CT rescued SHR CD4+ T cells from suppression and supported DT- or B subunit of CT-specific proliferative responses, and these cells produced more interleukin-4 (IL-4) than IFN-gamma, and anti-IFN-gamma antibody treatment enhanced IL-4 production. Exogenous IL-4 increased the proliferation of antigen-specific CD4+ T cells, whereas IFN-gamma was inhibitory. This study shows that the adjuvant CT induces T helper 2-type responses, reversing the T cell dysfunction in the SHR.

Treatment of uveitis by oral administration of retinal antigens: results of a phase I/II randomized masked trial

PURPOSE

To evaluate the effect and safety of the oral administration of retinal antigens as a treatment of ocular inflammation.

METHODS

In a phase I/II randomized masked trial, patients with endogenous uveitis who were dependent on immunosuppressive agents were randomly assigned to receive either retinal S antigen alone (10 patients), retinal S antigen and a mixture of soluble retinal antigens (10 patients), a mixture of soluble retinal antigens alone (10 patients), or placebo (15 patients). An attempt was then made to taper patients completely off their standard immunosuppressive therapy over an 8 week period. The primary study endpoint was time to ocular inflammatory attack. The secondary study endpoint was the ability to taper patients completely off their immunosuppressive or cytotoxic medication within 8 weeks.

RESULTS

Time to development of the main study endpoint was not statistically significantly different for any of the four treatment groups. However, the group receiving the purified S antigen alone appeared to be tapered off their immunosuppressive medication more successfully compared with patients given placebo (P = .08), whereas all the other groups appeared to do worse than did those receiving placebo. No toxic effects attributable to any treatment were observed.

CONCLUSIONS

This phase I/II study is the first to test the use of orally administered S antigen in the treatment of uveitis. Although not statistically significant, patients given S antigen were more likely to be tapered off their chronically administered systemic immunosuppressive therapy than were the other groups tested.

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.