A T cell receptor antagonist peptide induces T cells that mediate bystander suppression and prevent autoimmune encephalomyelitis induced with multiple myelin antigens

A novel combination approach to effectively reduce inflammation and neurodegeneration in multiple sclerosis models

Multiple sclerosis (MS) is an autoimmune disease characterized by immune-mediated attacks on the central nervous system (CNS), resulting in demyelination and recurring T-cell responses. Unfortunately, there is no cure for it. Current therapies that target immunomodulation and/or immunosuppression show only modest beneficial effects, have many side effects, and do not block neurodegeneration or progression of the disease. Since neurodegeneration and in particular axonal degeneration is implicated in disability in progressive MS, development of novel therapeutic strategies to attenuate the neurodegenerative processes is imperative. This study aims to develop new safe and efficacious treatments that address both the inflammatory and neurodegenerative aspects of MS using its animal model, experimental allergic encephalomyelitis (EAE). In EAE, the cysteine protease calpain is upregulated in CNS tissue, and its activity correlates with neurodegeneration. Our immunologic studies on MS have indicated that increased calpain activity promotes pro-inflammatory T helper (Th)1 cells and the severity of the disease in EAE, suggesting that calpain inhibition could be a novel target to combat neurodegeneration in MS/EAE. While calpain inhibition by SNJ1945 reduced disease severity, treatment of EAE animals with a novel protease-resistant altered small peptide ligand (3aza-APL) that mimic myelin basic protein (MBP), also decreased the incidence of EAE, disease severity, infiltration of inflammatory cells, and protected myelin. A reduction in inflammatory T-cells with an increase in Tregs and myeloid suppressor cells is also found in EAE mice treated with SNJ1945 and 3aza-APL. Thus, a novel combination strategy was tested in chronic EAE mouse model in B10 mice which showed multiple pathological mechanisms could be addressed by simultaneous treatment with calpain inhibitor SNJ1945 and protease-resistant 3aza-APL to achieve a stronger therapeutic effect.

The good and the bad of T cell cross-reactivity: challenges and opportunities for novel therapeutics in autoimmunity and cancer

T cells are main actors of the immune system with an essential role in protection against pathogens and cancer. The molecular key event involved in this absolutely central task is the interaction of membrane-bound specific T cell receptors with peptide-MHC complexes which initiates T cell priming, activation and recall, and thus controls a range of downstream functions. While textbooks teach us that the repertoire of mature T cells is highly diverse, it is clear that this diversity cannot possibly cover all potential foreign peptides that might be encountered during life. TCR cross-reactivity, i.e. the ability of a single TCR to recognise different peptides, offers the best solution to this biological challenge. Reports have shown that indeed, TCR cross-reactivity is surprisingly high. Hence, the T cell dilemma is the following: be as specific as possible to target foreign danger and spare self, while being able to react to a large spectrum of body-threatening situations. This has major consequences for both autoimmune diseases and cancer, and significant implications for the development of T cell-based therapies. In this review, we will present essential experimental evidence of T cell cross-reactivity, implications for two opposite immune conditions, i.e. autoimmunity vs cancer, and how this can be differently exploited for immunotherapy approaches. Finally, we will discuss the tools available for predicting cross-reactivity and how improvements in this field might boost translational approaches.

Immune Modulation by Antigenic Peptides and Antigenic Peptide Conjugates for Treatment of Multiple Sclerosis

The immune system defends our body by fighting infection from pathogens utilizing both the innate and adaptive immune responses. The innate immune response is generated rapidly as the first line of defense. It is followed by the adaptive immune response that selectively targets infected cells. The adaptive immune response is generated more slowly, but selectively, by targeting a wide range of foreign particles (i.e., viruses or bacteria) or molecules that enter the body, known as antigens. Autoimmune diseases are the results of immune system glitches, where the body's adaptive system recognizes self-antigens as foreign. Thus, the host immune system attacks the self-tissues or organs with a high level of inflammation and causes debilitation in patients. Many current treatments for autoimmune diseases (i.e., multiple sclerosis (MS), rheumatoid arthritis (RA)) have been effective but lead to adverse side effects due to general immune system suppression, which makes patients vulnerable to opportunistic infections. To counter these negative effects, many different avenues of antigen specific treatments are being developed to selectively target the autoreactive immune cells for a specific self-antigen or set of self-antigens while not compromising the general immune system. These approaches include soluble antigenic peptides, bifunctional peptide inhibitors (BPI) including IDAC and Fc-BPI, polymer conjugates, and peptide-drug conjugates. Here, various antigen-specific methods of potential treatments, their efficacy, and limitations will be discussed along with the potential mechanisms of action.

A Modified Peptide Derived from Goodpasture Autoantigen Arrested and Attenuated Kidney Injuries in a Rat Model of Anti-GBM Glomerulonephritis

BACKGROUND

In Goodpasture disease, the noncollagenous domain 1 of the α3 chain (α3NC1) of type IV collagen is the main target antigen of antibodies against glomerular basement membrane (GBM). We previously identified a nephritogenic epitope, P14 (α3_127-148), that could induce crescentic nephritis in WKY rats, and defined its core motif. Designing a modified peptide, replacing critical pathogenic residues with nonpathogenic ones (on the basis of homologous regions in α1NC1 chain of type IV collagen, known to be nonpathogenic), might provide a therapeutic option for anti-GBM GN.

METHODS

We synthesized a modified peptide, replacing a single amino acid, and injected it into α3-P14-immunized rats from day 0 (the early-treatment group) or a later-treatment group (from days 17 to 21). A scrambled peptide administrated with the same protocol served as a control.

RESULTS

The modified peptide, but not the scrambled peptide, attenuated anti-GBM GN in both treatment groups, and halted further crescent formation even after disease onset. Kidneys from the modified peptide-treated rats exhibited reductions in IgG deposits, complement activation, and infiltration by T cells and macrophages. Treatment also resulted in an anti-inflammatory cytokine profile versus a proinflammatory profile for animals not receiving the modified peptide; it also reduced α3-P14-specific T cell activation, modulated T cell differentiation by decreasing Th17 cells and enhancing the ratio of Treg/Th17 cells, and inhibited binding of α3-P14 to antibodies and MHC II molecules.

CONCLUSIONS

A modified peptide involving alteration of a critical motif in a nephritogenic T cell epitope alleviated anti-GBM GN in a rat model. Our findings may provide insights into an immunotherapeutic approach for autoimmune kidney disorders such as Goodpasture disease.

Dynamic Mitochondrial Migratory Features Associated with Calcium Responses during T Cell Antigen Recognition

A T cell clone is able to distinguish Ags in the form of peptide-MHC complexes with high specificity and sensitivity; however, how subtle differences in peptide-MHC structures translate to distinct T cell effector functions remains unknown. We hypothesized that mitochondrial positioning and associated calcium responses play an important role in T cell Ag recognition. We engineered a microfluidic system to precisely manipulate and synchronize a large number of cell-cell pairing events, which provided simultaneous real-time signaling imaging and organelle tracking with temporal precision. In addition, we developed image-derived metrics to quantify calcium response and mitochondria movement. Using myelin proteolipid altered peptide ligands and a hybridoma T cell line derived from a mouse model of experimental autoimmune encephalomyelitis, we observed that Ag potency modulates calcium response at the single-cell level. We further developed a partial least squares regression model, which highlighted mitochondrial positioning as a strong predictor of calcium response. The model revealed T cell mitochondria sharply alter direction within minutes following exposure to agonist peptide Ag, changing from accumulation at the immunological synapse to retrograde movement toward the distal end of the T cell body. By quantifying mitochondria movement as a highly dynamic process with rapidly changing phases, our result reconciles conflicting prior reports of mitochondria positioning during T cell Ag recognition. We envision applying this pipeline of methodology to study cell interactions between other immune cell types to reveal important signaling phenomenon that is inaccessible because of data-limited experimental design.

Predicting the effects of potentially therapeutic modified peptides on polyclonal T cell populations in a mouse model of multiple sclerosis

Altered peptide ligands (APLs) have routinely been studied in clonal populations of Th cells that express a single T cell receptor (TCR), but results generated in this manner poorly predict the effects of APLs on polyclonal Th cells in vivo, contributing to the failure of phase II clinical trials of APLs in autoimmune diseases such as multiple sclerosis (MS). We have used a panel of APLs derived from an encephalitogenic epitope of myelin proteolipid protein to investigate the relationship between antigen cross-reactivity in a polyclonal environment, encephalitogenicity, and the capacity of an APL to provide protection against experimental autoimmune encephalomyelitis (EAE) in SJL mice. In general, polyclonal Th cell lines specific for encephalitogenic APLs cross-reacted with other encephalitogenic APLs, but not with non-encephalitogenic APLs, and vice versa. This, alongside analysis of TCR Vβ usage, suggested that encephalitogenic and non-encephalitogenic subgroups of APLs expand largely non-cross-reactive Th cell populations. As an exception to the rule, one non-encephalitogenic APL, L188, induced proliferation in polyclonal CD4⁺ T cells specific for the native encephalitogen, with minimal induction of cytokine production. Co-immunization of L188 alongside the native encephalitogen slightly enhanced disease development. In contrast, another APL, A188, which induced IL-10 production without proliferation in CD4⁺ T cells specific for the native encephalitogen, was able to protect against development of EAE in a dose-dependent fashion when co-immunized alongside the native encephalitogen. These results suggest that testing against polyclonal Th cell lines in vitro may be an effective strategy for distinguishing between potentially therapeutic and non-therapeutic APLs.

Association of Autophagy in the Cell Death Mediated by Dihydrotestosterone in Autoreactive T Cells Independent of Antigenic Stimulation

Gender disparity is well documented in the mouse model of experimental autoimmune encephalomyelitis (EAE) induced with proteolipid protein (PLP) 139-151, in which female, but not male, SJL mice show a chronic relapsing-remitting paralysis. Furthermore, dihydrotestosterone (DHT) has been shown to ameliorate the severity of EAE, but the underlying mechanisms of its protective effects are unclear. Using major histocompatibility complex (MHC) class II dextramers for PLP 139-151, we tested the hypothesis that DHT selectively modulates the expansion and functionalities of antigen-specific T cells. Unexpectedly, we noted that DHT induced cell death in antigen-specific, autoreactive T cells, but the effects were not selective, because both proliferating and non-proliferating cells were equally affected independent of antigenic stimulation. Furthermore, DHT-exposed PLP 139-151-specific T cells did not show any shift in cytokine production; rather, frequencies of cytokine-producing PLP-specific T cells were significantly reduced, irrespective of T helper (Th) 1, Th2, and Th17 subsets of cytokines. By evaluating cell death and autophagy pathways, we provide evidence for the induction of autophagy to be associated with cell death caused by DHT. Taken together, the data provide new insights into the role of DHT and indicate that cell death and autophagy contribute to the therapeutic effects of androgens in autoreactive T cells.

The anergy induction of M3 muscarinic acetylcholine receptor-reactive CD4+ T cells suppresses experimental sialadenitis-like Sjögren's syndrome

OBJECTIVE

Autoreactive CD4+ T cells are involved in the pathogenesis of Sjögren's syndrome (SS). The aim of the present study was to clarify the dominant T cell epitopes of M3 muscarinic acetylcholine receptor (M3R) and to establish a new antigen-specific therapy for SS using an experimental mouse model.

METHODS

Production of cytokines from M3R-reactive CD4+ T cells, after culture with various M3R peptides, was analyzed by enzyme-linked immunosorbent assay. Adoptive cell transfer was performed using splenocytes from M3R(-/-) mice that were immunized with M3R peptides or phosphate buffered saline plus H37Ra as a control. Rag1(-/-) mice were inoculated with the splenocytes and examined for the development of sialadenitis. Altered peptide ligands (APLs) of the T cell epitopes, with substitutions in amino acid residues at T cell receptor contact sites, were synthesized, and the ability of the APLs to suppress sialadenitis was evaluated. The mechanisms underlying such effects were assessed.

RESULTS

CD4+ M3R-reactive T cells produced interleukin-17 (IL-17) and interferon-γ (IFNγ) in response to the N-terminal 1 (N1) and 1st extracellular loop peptides of M3R, and Rag1(-/-) mice that received N1- and/or 1st peptide-immunized splenocytes developed sialadenitis. Among the designed APLs, N1-APL7 (N→S at amino acid 15) significantly suppressed IFNγ production in vitro, and also suppressed sialadenitis in vivo. Levels of early growth response 2 in CD4+ T cells from the cervical lymph nodes of N1-APL7-treated mice were significantly higher than those of control mice, and cell proliferation was reversed by administration of exogenous IL-2. Levels of the anergy-related molecules itchy homolog E3 ubiquitin-protein ligase, Casitas B-lineage lymphoma b, gene related to anergy in lymphocytes, and Deltex-1 were significantly higher in CD4+ T cells cultured with N1-APL7.

CONCLUSION

The major T cell epitopes were from the N1 and 1st peptide regions. Moreover, N1-APL7, selected as the antagonistic APL in vitro, also suppressed sialadenitis through the induction of anergy. This is a potentially useful strategy for regulating pathogenic T cell infiltration in SS.

Effects of active immunisation with myelin basic protein and myelin-derived altered peptide ligand on pain hypersensitivity and neuroinflammation

Neuropathic pain is a debilitating condition in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). Specific myelin basic protein (MBP) peptides are encephalitogenic, and myelin-derived altered peptide ligands (APLs) are capable of preventing and ameliorating EAE. We investigated the effects of active immunisation with a weakly encephalitogenic epitope of MBP (MBP87-99) and its mutant APL (Cyclo-87-99[A(91),A(96)]MBP87-99) on pain hypersensitivity and neuroinflammation in Lewis rats. MBP-treated rats exhibited significant mechanical and thermal pain hypersensitivity associated with infiltration of T cells, MHC class II expression and microglia activation in the spinal cord, without developing clinical signs of paralysis. Co-immunisation with APL significantly decreased pain hypersensitivity and neuroinflammation emphasising the important role of neuroimmune crosstalk in neuropathic pain.

Taming the TCR: antigen-specific immunotherapeutic agents for autoimmune diseases

Current treatments for autoimmune diseases are typically non-specific anti-inflammatory agents that affect not only the autoreactive cells but also the parts of the immune system that are required to maintain health. There is a need for the development of antigen-specific therapeutic agents that can effectively prevent the autoimmune attack while leaving the rest of the immune system functioning as normal. The simplest way to achieve this is using the autoantigen itself as a tolerizing agent; however, there is some risk involved with administering a potentially pathogenic antigen. In this review, we focus instead on the development and use of modified T cell receptor (TCR) ligands, in which the peptide ligand is modified to change the response by the T cell from a disease inducing to a protective response, and still retain the antigen-specificity necessary to target the autoreactive T cells. We review the use of modified TCR ligands as therapeutic agents in animal models of autoimmunity and in human autoimmune disease, and finally consider how they need to be improved in order to use them effectively in patients with autoimmune disease.

Immune responses of linear and cyclic PLP139-151 mutant peptides in SJL/J mice: peptides in their free state versus mannan conjugation

BACKGROUND

The predominant proteins of the CNS are myelin basic protein, proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein. PLP139-151 is one of the major encephalitogenic epitopes of PLP. The epitope PLP139-151 binds to MHC class II (I-A(s)) of SJL/J mice and induces Th1 responses.

AIM

The aim was to synthesize and test the immunological activity and cyclic analogs of PLP139-151 peptide and determine the immunological differences between adjuvant and conjugation to mannan. Materials & methods: We designed and synthesized cyclic peptides based on the linear PLP139-151 epitope by mutating critical T-cell receptor contact sites of residues W(144) and H(147), resulting in the mutant peptides PLP139-151, [L(144), R(147)]PLP139-151 or cyclo(139-151)PLP139-151 and cyclo(139-151) [L(144), R(147)]PLP139-151. In this study, mice were immunized with mutant peptides either emulsified in complete Freund's adjuvant or conjugated to reduced mannan and responses were assessed.

RESULTS

Linear double-mutant peptide [L(144), R(147)]PLP139-151 induced high levels of IL-4 responses and low levels of IgG total, and cyclization of this analog elicited low levels of IFN-γ. Moreover, linear [L(144), R(147)]PLP139-151 conjugated to reduced mannan did not induce IFN-γ, whilst both linear agonist PLP139-151 and cyclic agonist cyclo(139-151)PLP139-151 induced IFN-γ-secreting T cells. Molecular dynamics simulations of linear and cyclic(139-151)PLP139-151 analogs indicated the difference in topology of the most important for biological activity amino acids.

CONCLUSION

Cyclic double-mutant analog cyclo(139-151) [L(144), R(147)]PLP139-151 has potential for further studies for the immunotherapy of multiple sclerosis.

Nanoparticle-based autoimmune disease therapy

The goal of immunotherapy against autoimmunity is to block pathogenic inflammation without impairing immunity against infections and tumours. Regulatory T-cells (Tregs) play a central role in maintaining immune homeostasis, and autoimmune inflammation is frequently associated with decreased numbers and/or function of these T-cells. Therapies harnessing Tregs to treat autoimmune inflammation remain under-developed with caveats ranging from the lack of antigenic and disease specificity to the potential phenotypic and functional instability of in vitro-expanded Treg cells in vivo. Here, we review nanotechnology-based approaches designed to promote immune tolerance through various mechanisms, ranging from systemic or local suppression of antigen-presenting cells and deletion of antigen-specific T-cells, to the systemic expansion of antigen- and disease-specific Treg cells in vivo.

Active immunization with myelin-derived altered peptide ligand reduces mechanical pain hypersensitivity following peripheral nerve injury

Background

T cells have been implicated in neuropathic pain that is caused by peripheral nerve injury. Immunogenic myelin basic protein (MBP) peptides have been shown to initiate mechanical allodynia in a T cell-dependent manner. Antagonistic altered peptide ligands (APLs) are peptides with substitutions in amino acid residues at T cell receptor contact sites and can inhibit T cell function and modulate inflammatory responses. In the present study, we studied the effects of immunization with MBP-derived APL on pain behavior and neuroinflammation in an animal model of peripheral nerve injury.

Methods

Lewis rats were immunized subcutaneously at the base of the tail with either a weakly encephalitogenic peptide of MBP (cyclo-MBP_87-99) or APL (cyclo-(87-99)[A⁹¹,A⁹⁶]MBP_87-99) in complete Freund’s adjuvant (CFA) or CFA only (control), following chronic constriction injury (CCI) of the left sciatic nerve. Pain hypersensitivity was tested by measurements of paw withdrawal threshold to mechanical stimuli, regulatory T cells in spleen and lymph nodes were analyzed by flow cytometry, and immune cell infiltration into the nervous system was assessed by immunohistochemistry (days 10 and 30 post-CCI). Cytokines were measured in serum and nervous tissue of nerve-injured rats (day 10 post-CCI).

Results

Rats immunized with the APL cyclo-(87-99)[A⁹¹,A⁹⁶]MBP_87-99 had significantly reduced mechanical pain hypersensitivity in the ipsilateral hindpaw compared to cyclo-MBP_87-99-treated and control rats. This was associated with significantly decreased infiltration of T cells and ED1+ macrophages in the injured nerve of APL-treated animals. The percentage of anti-inflammatory (M2) macrophages was significantly upregulated in the APL-treated rats on day 30 post-CCI. Compared to the control rats, microglial activation in the ipsilateral lumbar spinal cord was significantly increased in the MBP-treated rats, but was not altered in the rats immunized with the MBP-derived APL. In addition, immunization with the APL significantly increased splenic regulatory T cells. Several cytokines were significantly altered after CCI, but no significant difference was observed between the APL-treated and control rats.

Conclusions

These results suggest that immune deviation by active immunization with a non-encephalitogenic MBP-derived APL mediates an analgesic effect in animals with peripheral nerve injury. Thus, T cell immunomodulation warrants further investigation as a possible therapeutic strategy for the treatment of peripheral neuropathic pain.

Single β³-amino acid substitutions to MOG peptides suppress the development of experimental autoimmune encephalomyelitis

CD4(+) T-cells play a key role in the pathogenesis of multiple sclerosis (MS). Altered peptide ligands capable of modulating T-cell autoreactivity are considered a promising strategy for development of antigen-specific therapies for MS. Since peptides are inherently unstable, the current study explored single β-amino acid substitution as a means of stabilizing an epitope of myelin oligodendrocyte glycoprotein. β-Amino acid substitution at position 44, the major T-cell receptor contact residue, increased the half-life of active metabolites. Vaccination with one altered peptide, MOG44βF, conferred protection from EAE, decreased T-cell autoreactivity and pro-inflammatory cytokine production. Additional studies using MOG44βF in an oral treatment regimen, administered after EAE induction, also attenuated disease severity. Thus, altered peptides such as those reported here may lead to the development of novel and more specific treatments for MS.

Thiopalmitoylation of altered peptide ligands enhances their protective effects in an animal model of multiple sclerosis

Previously, we have shown that conjugation of a palmitic chain via a thioester bond to a cysteine residue in weakly or nonencephalitogenic or neuritogenic peptides markedly enhances their ability to induce autoimmune disease in an MHC class II-restricted manner. From those studies, however, it was not clear whether thiopalmitoylation of the peptides was merely enhancing their disease-inducing potential or whether the lipid was itself playing a pathogenic role. To investigate this further, we have now tested the effects of thiopalmitoylation on MHC class II-restricted altered peptide ligands (APLs), which are normally protective in experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis. We hypothesized that if thiopalmitoylation of a peptide merely enhances its innate potential, then thiopalmitoylated APLs (S-palmAPLs) should show enhanced protective effects. Alternatively, if thiopalmitoylation itself can make a peptide pathogenic, then S-palmAPLs should have decreased therapeutic potential. We synthesized APLs and corresponding S-palmAPLs and showed that the S-palmAPLs were much more effective than the nonconjugated APL at inhibiting the development of experimental autoimmune encephalomyelitis. This was due to several features of the S-palmAPL:S-palmAPL-primed cells show an enhanced ability to proliferate and produce the anti-inflammatory cytokine, IL-10, in vitro. Furthermore, the bioavailability of S-palmAPL was greatly enhanced, compared with the nonpalmitoylated APL, and S-palm APL was taken up more rapidly into dendritic cells and channeled into the MHC class II processing pathway. These results show that thiopalmitoylation of MHC class II-restricted peptides is a simple way to enhance their effects in vivo and could have wide therapeutic application.

Effects of vaccination with altered Peptide ligand on chronic pain in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis

Neuropathic pain is a chronic symptom of multiple sclerosis (MS) and affects nearly half of all MS sufferers. A key instigator of this pain is the pro-inflammatory response in MS. We investigated the behavioral effects of immunization with a mutant peptide of myelin basic protein (MBP), termed altered peptide ligand (APL), known to initiate immune deviation from a pro-inflammatory state to an anti-inflammatory response in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Male and female Lewis rats were injected with vehicle control or with varying doses of 50 or 100 μg guinea pig MBP in combination with or without APL. APL-treated animals established significantly lower disease severity compared to encephalitogenic MBP-treated animals. Animals with EAE developed mechanical, but not thermal pain hypersensitivity. Mechanical pain sensitivities were either improved or normalized during periods of clinical disease in male and female APL-treated animals as compared to the encephalitogenic group. No significant changes to thermal latency were observed upon co-immunization with APL. Together these data indicate that APL ameliorates disease states and selectively mediates an analgesic effect on EAE animals.

APL-1, an altered peptide ligand derived from human heat-shock protein 60, selectively induces apoptosis in activated CD4+ CD25+ T cells from peripheral blood of rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a chronic T-cell mediated autoimmune disease that affects primarily the joints. The induction of immune tolerance through antigen-specific therapies for the blockade of pathogenic CD4+ T cells constitutes a current focus of research. In this focus it is attempted to simultaneously activate multiple regulatory mechanisms, such as: apoptosis and regulatory T cells (Tregs). APL-1 is an altered peptide ligand derived from a novel CD4+ T-cell epitope of human heat-shock protein of 60kDa, an autoantigen involved in the pathogenesis of RA. Previously, we have reported that APL-1 induces CD4+ CD25(high)Foxp3+ Tregs in several systems. Here, we investigated the ability of APL-1 in inducing apoptosis in PBMCs from RA patients, who were classified as active or inactive according to their DAS28 score. APL-1 decreased the viability of PBMCs from active but not from inactive patients. DNA fragmentation assays and typical morphological features clearly demonstrated that APL-1 induced apoptosis in these cells. Activated CD4+ CD25+ T cells but not resting CD4+ CD25- T cells were identified as targets of APL-1. Furthermore, CD4+ T-cell responses to APL-1 were found to be dependent on antigen presentation via the HLA-DR molecule. Thus, APL-1 is a regulatory CD4+ T cell epitope which might modulate inflammatory immune responses in PBMCs from RA patients by inducing CD4+ CD25(high)Foxp3+ Tregs and apoptosis in activated CD4+ T cells. These results support further investigation of this candidate drug for the treatment of RA.

Role of inactivated influenza vaccine in regulation of autoimmune processes in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is characterized by appearance of anti-myelin autoantibodies in the blood and with the increased expression of MHC (major histocompatibility complex) class I and II antigens in the brain tissue. Although there is an evidence of possible linkage between influenza vaccination and development of autoimmune processes, the precise mechanisms of action of this vaccine on EAE-induction is still unclear. In this study, effects of influenza vaccine on clinical sign, antimyelin antibody titer in the blood by ELISA test and expression of MHC class I and II molecules immunohistochemistry were examined in the brain of C57BL mice with EAE. EAE was induced by MOG 35-55 protein in 16 of 32 mice. Influenza split vaccine was administered to eight MOG-induced EAE mice and to eight previously nontreated mice. A significant increase of anti-influenza antibody was detected in vaccinated mice compared to nontreated mice. Also, significant increase of antimyelin antibodies was detected in mice with EAE compared to vaccinated group without EAE and control group, respectively. In EAE-influenza vaccinated mice, a mild but not significant increase of antimyelin antibodies was detected, compared to EAE mice. High expression of MHC-II and mild expression of MHC-I were detected in the brain of mice with EAE. No expressions were detected in vaccinated and normal intact brains. Similar staining was found between EAE-vaccinated and EAE group in both MHC-I and MHC-II expression. The results obtained show that influenza vaccine has no significant influence on EAE induction and severity of autoimmune processes.

Controlling immune response and demyelination using highly potent bifunctional peptide inhibitors in the suppression of experimental autoimmune encephalomyelitis

In this study, we investigated the efficacy of new bifunctional peptide inhibitors (BPIs) in suppressing experimental autoimmune encephalomyelitis (EAE) in an animal model. BPI [e.g. proteolipid protein-cyclo(1,8)-CPRGGSVC-NH2 (PLP-cIBR)] is a conjugate between the PLP139-151 peptide derived from proteolipid protein (PLP) and the cIBR7 peptide derived from domain-1 (D1) of intercellular adhesion molecule-1 (ICAM-1). PLP-cIBR is designed to bind to major histocompatibility complex (MHC)-II and leucocyte function-associated antigen-1 (LFA-1) simultaneously to inhibit the formation of the immunological synapse and alter the differentiation and activation of a subpopulation of T cells, thus inducing immunotolerance. The results show that PLP-cIBR is highly potent in ameliorating EAE, even at low concentrations and less frequent injections. Mice treated with PLP-cIBR had a higher secretion of cytokines related to regulatory and/or suppressor cells compared to phosphate-buffered saline (PBS)-treated mice. In contrast, T helper type 1 (Th1) cytokines were higher in mice treated with PBS compared to PLP-cIBR, suggesting that it suppressed Th1 proliferation. Also, we observed significantly less demyelination in PLP-cIBR-treated mice compared to the control, further indicating that PLP-cIBR promoted protection against demyelination.

Immune modulating peptides for the treatment and suppression of multiple sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease in which the immune system recognizes proteins of the myelin sheath as antigenic, thus initiating an inflammatory reaction in the central nervous system. This leads to demyelination of the axons, breakdown of the blood-brain barrier, and lesion formation. Current therapies for the treatment of MS are generally non-specific and weaken the global immune system, thus making the individual susceptible to opportunistic infections. Antigenic peptides and their derivatives are becoming more prevalent for investigation as therapeutic agents for MS because they possess immune-specific characteristics. In addition, other peptides that target vital components of the inflammatory immune response have also been developed. Therefore, the objectives of this review are to (a) summarize the immunological basis for the development of MS, (b) discuss specific and non-specific peptides tested in EAE and in humans, and (c) briefly address some problems and potential solutions with these novel therapies.

Blood stage Plasmodium falciparum antigens induce T cell independent immunoglobulin production via B cell activation factor of the TNF family (BAFF) pathway

T independent (TI) antigens (Ags) activate monocytes to produce a cytokine, termed B cell activation factor (BAFF), involved in immunoglobulin (Ig) production. This study aimed to investigate whether the soluble schizont fraction of Plasmodium falciparum antigen (sPfAg) and hemozoin (HZ) could act as TI Ag to induce P. falciparum (Pf) specific Ig production via BAFF pathway. Co-cultures of monocytes and naïve B cells from 6 healthy donors were stimulated with sPfAg (10mg/ml) or HZ (10μM). At interval times, the expressions of BAFF on activated monocytes, BAFF receptor (BAFF-R) and proliferation nuclear Ag in activated B cells were determined by flow cytometry. The soluble BAFF (sBAFF), total and specific IgG levels in the supernatants were assessed by enzyme-linked immunosorbent assay (ELISA). The finding revealed both sPfAg and HZ could activate monocytes to express BAFF on surface and release sBAFF in the supernatant within 72h of stimulation. The B cells responded to specific activation, indicated by BAFF-R expression on the surface within 72h, marked proliferation on day 7, and final production of total and specific IgG during days 7-12. Comparing to sPfAg, HZ stimulated monocyte and B cell co-culture to express higher levels of BAFF and sBAFF during 24-48h, more BAFF-R on HZ activated B cells within 24h and induced marked proliferation of B cells with higher Pf specific IgG level. However, stimulation with sPfAg showed a more significant correlation between BAFF expression on the activated monocytes at 72h and the Pf specific IgG level on day 12 (r=0.961, p=0.039, Pearson Correlation). In conclusion, it is possible that both sPfAg and HZ stimulated B cells to produce specific IgG with BAFF involvement.

Comprehensive, quantitative mapping of T cell epitopes in gluten in celiac disease

Celiac disease is a genetic condition that results in a debilitating immune reaction in the gut to antigens in grain. The antigenic peptides recognized by the T cells that cause this disease are incompletely defined. Our understanding of the epitopes of pathogenic CD4(+ )T cells is based primarily on responses shown by intestinal T-cells in vitro to hydrolysates or polypeptides of gluten, the causative antigen. A protease-resistant 33-amino acid peptide from wheat alpha-gliadin is the immunodominant antigen, but little is known about the spectrum of T cell epitopes in rye and barley or the hierarchy of immunodominance and consistency of recognition of T-cell epitopes in vivo. We induced polyclonal gluten-specific T cells in the peripheral blood of celiac patients by feeding them cereal and performed a comprehensive, unbiased analysis of responses to all celiac toxic prolamins, a class of plant storage protein. The peptides that stimulated T cells were the same among patients who ate the same cereal, but were different after wheat, barley and rye ingestion. Unexpectedly, a sequence from omega-gliadin (wheat) and C-hordein (barley) but not alpha-gliadin was immunodominant regardless of the grain consumed. Furthermore, T cells specific for just three peptides accounted for the majority of gluten-specific T cells, and their recognition of gluten peptides was highly redundant. Our findings show that pathogenic T cells in celiac disease show limited diversity, and therefore suggest that peptide-based therapeutics for this disease and potentially other strongly HLA-restricted immune diseases should be possible.

A novel probiotic mixture exerts a therapeutic effect on experimental autoimmune encephalomyelitis mediated by IL-10 producing regulatory T cells

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system (CNS). One potential therapeutic strategy for MS is to induce regulatory cells that mediate immunological tolerance. Probiotics, including lactobacilli, are known to induce immunomodulatory activity with promising effects in inflammatory diseases. We tested the potential of various strains of lactobacilli for suppression of experimental autoimmune encephalomyelitis (EAE), an animal model of MS.

METHODOLOGY/PRINCIPAL FINDINGS

The preventive effects of five daily-administered strains of lactobacilli were investigated in mice developing EAE. After a primary screening, three Lactobacillus strains, L. paracasei DSM 13434, L. plantarum DSM 15312 and DSM 15313 that reduced inflammation in CNS and autoreactive T cell responses were chosen. L. paracasei and L. plantarum DSM 15312 induced CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) in mesenteric lymph nodes (MLNs) and enhanced production of serum TGF-beta1, while L. plantarum DSM 15313 increased serum IL-27 levels. Further screening of the chosen strains showed that each monostrain probiotic failed to be therapeutic in diseased mice, while a mixture of the three lactobacilli strains suppressed the progression and reversed the clinical and histological signs of EAE. The suppressive activity correlated with attenuation of pro-inflammatory Th1 and Th17 cytokines followed by IL-10 induction in MLNs, spleen and blood. Additional adoptive transfer studies demonstrated that IL-10 producing CD4(+)CD25(+) Tregs are involved in the suppressive effect induced by the lactobacilli mixture.

CONCLUSIONS/SIGNIFICANCE

Our data provide evidence showing that the therapeutic effect of the chosen mixture of probiotic lactobacilli was associated with induction of transferable tolerogenic Tregs in MLNs, but also in the periphery and the CNS, mediated through an IL-10-dependent mechanism. Our findings indicate a therapeutic potential of oral administration of a combination of probiotics and provide a more complete understanding of the host-commensal interactions that contribute to beneficial effects in autoimmune diseases.

Altered peptide ligands inhibit arthritis induced by glucose-6-phosphate isomerase peptide

INTRODUCTION

Immunosuppressants, including anti-TNFalpha antibodies, have remarkable effects in rheumatoid arthritis; however, they increase infectious events. The present study was designed to examine the effects and immunological change of action of altered peptide ligands (APLs) on glucose-6-phosphate isomerase (GPI) peptide-induced arthritis.

METHODS

DBA/1 mice were immunized with hGPI325-339, and cells of draining lymph node (DLN) were stimulated with hGPI325-339 to investigate the T-cell receptor (TCR) repertoire of antigen-specific CD4+ T cells by flow cytometry. Twenty types of APLs with one amino acid substitution at a TCR contact site of hGPI325-339 were synthesized. CD4+ T cells primed with human GPI and antigen-presenting cells were co-cultured with each APL and cytokine production was measured by ELISA to identify antagonistic APLs. Antagonistic APLs were co-immunized with hGPI325-339 to investigate whether arthritis could be antigen-specifically inhibited by APL. After co-immunization, DLN cells were stimulated with hGPI325-339 or APL to investigate Th17 and regulatory T-cell population by flow cytometry, and anti-mouse GPI antibodies were measured by ELISA.

RESULTS

Human GPI325-339-specific Th17 cells showed predominant usage of TCRVbeta8.1 8.2. Among the 20 synthesized APLs, four (APL 6; N329S, APL 7; N329T, APL 12; G332A, APL 13; G332V) significantly reduced IL-17 production by CD4+ T cells in the presence of hGPI325-339. Co-immunization with each antagonistic APL markedly prevented the development of arthritis, especially APL 13 (G332V). Although co-immunization with APL did not affect the population of Th17 and regulatory T cells, the titers of anti-mouse GPI antibodies in mice co-immunized with APL were significantly lower than in those without APL.

CONCLUSIONS

We prepared antagonistic APLs that antigen-specifically inhibited the development of experimental arthritis. Understanding the inhibitory mechanisms of APLs may pave the way for the development of novel therapies for arthritis induced by autoimmune responses to ubiquitous antigens.

Immunotherapy for the Prevention and Treatment of Type 1 Diabetes

A major effort has been on-going to develop immunotherapies to prevent and/or treat type 1 diabetes (T1D). This autoimmune disease is characterized by the selective loss of the insulin-producing beta cells via the cumulative effects of autoantigen-specific CD4(+) and CD8(+) T cells, autoantibodies, and activated antigen-presenting cells. To be applicable in a clinical setting, immunotherapies must suppress established beta-cell autoimmunity. Preclinical studies and recent clinical findings suggest that antigen-specific and systemic-based strategies can be effective in this regard. However, either approach alone may not be sufficient to block the diabetogenic response and establish long-term protection in the clinic. In this review, we will discuss the importance of both strategies and how a combinatorial approach to treat T1D is appealing.

The good, the bad and the ugly: how altered peptide ligands modulate immunity

BACKGROUND

The basis of T cell immune responses is the specific recognition of an immunogenic peptide epitope by a T cell receptor. Peptide alterations of such T cell epitopes with single or few amino acid variations can have drastic effects on the outcome of this recognition. These altered peptide ligands can act as modulators of immune responses as they are capable of downregulating or upregulating responses.

OBJECTIVE/METHODS

We review how altered peptide ligands can have 'good' 'bad' and 'ugly' outcomes in treating diseases.

RESULTS/CONCLUSION

Altered peptide ligands have been used as immunotherapeutics in autoimmune (and allergic) diseases, infectious diseases and cancer. In the next five years we anticipate seeing a number of altered peptide ligands in clinical trials, progressing from contradictory classifications of good, bad or ugly, to the exciting outcome of 'useful'.

Prospects for antigen-specific tolerance based therapies for the treatment of multiple sclerosis

A primary focus in autoimmunity is the breakdown of central and peripheral tolerance resulting in the survival and eventual activation of autoreactive T cells. As CD4(+) T cells are key contributors to the underlying pathogenic mechanisms responsible for onset and progression of most autoimmune diseases, they are a logical target for therapeutic strategies. One method for restoring self-tolerance is to exploit the endogenous regulatory mechanisms that govern CD4(+) T cell activation. In this review, we discuss tolerance strategies with the common goal of inducing antigen (Ag)-specific tolerance. Emphasis is given to the use of peptide-specific tolerance strategies, focusing on ethylene carbodiimide (ECDI)-peptide-coupled cells (Ag-SP) and nonmitogenic anti-CD3, which specifically target the T cell receptor (TCR) in the absence of costimulatory signals. These approaches induce a TCR signal of insufficient strength to cause CD4(+) T cell activation and instead lead to functional T cell anergy/deletion and activation of Ag-specific induced regulatory T cells (iTregs) while avoiding generalized long-term immunosuppression.

MHC variant peptide-mediated anergy of encephalitogenic T cells requires SHP-1

Our lab has demonstrated that encephalitogenic T cells can be effectively anergized by treatment with MHC variant peptides, which are analogues of immunogenic peptides containing an amino acid substitution at an MHC anchor residue. The MHC variant peptide of myelin oligodendrocyte glycoprotein (MOG)(35-55) proves an effective treatment as it does not induce symptoms of experimental autoimmune encephalomyelitis and fails to recruit macrophages or MOG(35-55)-specific T cells to the CNS. In this study, we sought to characterize the signaling pathways required for the induction of anergy by building upon the observations identifying the tyrosine phosphatase SHP-1 as a critical regulator of T cell responsiveness. Motheaten viable heterozygous mice, which contain a mutation in the SHP-1 gene resulting in a reduction in functional SHP-1, were challenged with MOG(35-55) or the MOG(35-55) MHC variant 45D. These mice display symptoms of experimental autoimmune encephalomyelitis upon immunization with MHC variant peptide and have significant CNS infiltration of tetramer-positive CD4(+) cells and macrophages, unlike B6 mice challenged with the variant peptide. The effects of SHP-1 are directly on the T cell as Motheaten viable heterozygous mice autoreactive T cells are not anergized in vitro. Lastly, we demonstrate no distinguishable difference in the initial interaction between the TCR and agonist or MHC variant. Rather, an unstable interaction between peptide and MHC attenuates the T cell response, seen in a decreased half-life relative to MOG(35-55). These results identify SHP-1 as a mediator of T cell anergy induced by destabilized peptide:MHC complexes.

Prophylactic and therapeutic suppression of experimental autoimmune encephalomyelitis by a novel bifunctional peptide inhibitor

The objective was to optimize and evaluate the in vivo activities of our novel bifunctional peptide inhibitor (BPI), which alters immune response in autoimmune diseases by modulating the immunological synapse formation. Previously, we have designed PLP-BPI and GAD-BPI by conjugating myelin proteolipid protein (PLP)(139-151) and glutamic acid decarboxylase (GAD)(208-217), respectively, with CD11a(237-246) via a spacer peptide. PLP-BPI and GAD-BPI suppressed the disease progression in experimental autoimmune encephalomyelitis (EAE) and in type-1 diabetes, respectively. In this study, various PLP-BPI derivatives were synthesized and evaluated in the EAE model. Intravenous injections of PLP-BPI derivatives prevented the disease progression more efficiently than did unmodified PLP-BPI. Production of IL-17, a potent proinflammatory cytokine found commonly among MS patients, was significantly low in Ac-PLP-BPI-NH(2)-2-treated mice. Treatment given after the disease onset could dramatically ameliorate the disease. BPI induced anaphylactic responses at a lower incidence than PLP(139-151). In conclusion, PLP-BPI derivatives can effectively suppress the disease severity and morbidity of EAE by post-onset therapeutic treatment as well as prophylactic use.

OSP/claudin-11-induced EAE in mice is mediated by pathogenic T cells primarily governed by OSP192Y residue of major encephalitogenic region OSP179-207

Pathogenic autoimmunity against oligodendrocyte-specific protein (OSP/claudin-11), recently implicated in multiple sclerosis (MS) pathophysiology, has been poorly investigated as compared to that against other myelin encephalitogens. Using recombinant soluble mouse OSP (smOSP) and overlapping peptides thereof, we show that smOSP-induced chronic EAE in C57BL/6J mice is primarily associated with CD4(+) T cells reactive against OSP179-207 and OSP22-46, the major and minor encephalitogenic regions, respectively, and with a predominant B cell response against OSP22-46. The encephalitogenic OSP179-207-specific T cells recognized OSP190-202 as minimal stimulatory epitope, while minimal encephalitogenic sequence was OSP191-199. Further delineation and structural bioinformatic analysis of the major encephalitogenic region suggested four overlapping potential I-A(b) core epitopes, predicting OSP192Y as major TCR-contact residue shared by OSP 188-196, OSP190-198, and OSP191-199 cores, albeit at different MHC-II pockets. Accordingly, substitution at OSP192Y yielded OSP188-192A-202, a non-stimulatory/non-encephalitogenic altered peptide ligand (APL) that was antagonistic for OSP188-202-specific encephalitogenic T cells. Systemic administration of OSP188-192A-202 suppressed OSP188-202-induced EAE and fully reversed smOSP-induced EAE. These data suggest that a single epitopic residue (OSP192Y) governs the selection and control of most pathogenic T cells associated with smOSP-induced EAE in H-2(b) mice. This may impact profoundly on peripheral self-tolerance to OSP and on potential APL-mediated therapy of OSP-related autoimmune pathogenesis.

Sjogrens syndrome as failed local immunohomeostasis: prospects for cell-based therapy

Sjogrens syndrome has been estimated to affect between 0.2% and 2% or more of the population. It is an autoimmune disease with the hallmark histopathology of focal, periductal, and perivascular CD4(+) cell infiltration of the lacrimal and salivary glands. The immunohistopathology is typically associated with severe lacrimal and salivary dysfunctions, which contribute to debilitating ocular surface and oral symptoms. The quality of life of patients with Sjogrens syndrome often is degraded further by serious, multisystemic manifestations, and they are subject to a forty-fold increased risk of developing B cell lymphomas. In normal lacrimal glands, secretory epithelial cells, autoimmune effector lymphocytes, and regulatory lymphocytes can be seen as collaborating to maintain a local immunohomeostasis. The epithelium contributes by secreting immunomodulatory paracrine factors and also by continuously exposing autoantigens, which thereby become available for uptake by professional antigen presenting cells (APCs). Local or systemic perturbations may initiate autoimmune pathophysiology by impairing the replacement of normally-turning-over regulatory cells, by altering epithelial production of immunomodulatory paracrine factors, by inducing intact epithelial cells to begin secreting previously cryptic epitopes (epitopes that previously were not available to bind to major histocompatibility complex (MHC) molecules and so could not be recognized by T cell antigen receptors), and by inducing epithelial cells to begin expressing MHC Class II molecules and presenting formerly cryptic epitopes directly to CD4(+) cells. This process has been modeled ex vivo with mixed cell reactions comprised of isolated epithelial cells and autologous lymphocytes. This development has occurred as studies of anterior chamber-associated immune deviation (ACAID) and other immunoregulatory phenomena have elucidated the origins and functions of several different kinds of regulatory lymphocytes and shown that regulatory lymphocytes can be generated ex vivo. It now is possible to envision strategies for exploiting each possible mode of epithelial autoantigen exposure to produce therapeutic regulatory cells that might be capable of re-establishing normal immunohomeostasis. Consideration of the hypothetical therapies identifies a number of basic questions that warrant investigation.

Antigen-specific tolerance strategies for the prevention and treatment of autoimmune disease

The development of safe and effective antigen-specific therapies is needed to treat patients with autoimmune diseases. These therapies must allow for the specific tolerization of self-reactive immune cells without altering host immunity to infectious insults. Experimental models and clinical trials for the treatment of autoimmune disease have identified putative mechanisms by which antigen-specific therapies induce tolerance. Although advances have been made in the development of efficient antigen-specific therapies, translating these therapies from bench to bedside has remained difficult. Here, we discuss the recent advances in our understanding of antigen-specific therapies for the treatment of autoimmune diseases.

Comparison of Proposed Putative Active Conformations of Myelin Basic Protein Epitope 87−99 Linear Altered Peptide Ligands by Spectroscopic and Modelling Studies: The Role of Positions 91 and 96 in T-Cell Receptor Activation

This work proposes a structural motif for the inhibition of experimental autoimmune encephalomyelitis (EAE) by the linear altered peptide ligands (APLs) [Ala91,96] MBP87-99 and [Arg91,Ala96] MBP87-99 of myelin basic protein. Molecular dynamics was applied to reveal distinct populations of EAE antagonist [Ala91,96] MBP87-99 in solution, in agreement with NOE data. The combination of the theoretical and experimental results led to the identification of a putative active conformation. This approach is of value as no crystallographic data is available for the APL-receptor complex. TCR contact residue Phe89 has an altered topology in the putative bioactive conformations of both APLs with respect to the native peptide, as found via crystallography; it is no longer prominent and solvent exposed. It is proposed that the antagonistic activity of the APLs is due to their binding to MHC, preventing the binding of self-myelin epitopes, with the absence of an immunologic response as the loss of some interactions with the TCR hinders activation of T-cells.

A putative bioactive conformation for the altered peptide ligand of myelin basic protein and inhibitor of experimental autoimmune encephalomyelitis [Arg91, Ala96] MBP87–99

[Arg(91), Ala(96)] MBP(87-99) is an altered peptide ligand (APL) of myelin basic protein (MBP), shown to actively inhibit experimental autoimmune encephalomyelitis (EAE), which is studied as a model of multiple sclerosis (MS). The APL has been rationally designed by substituting two of the critical residues for recognition by the T-cell receptor. A conformational analysis of the APL has been sought using a combination of 2D NOESY nuclear magnetic resonance (NMR) experiments and detailed molecular dynamics (MD) calculations, in order to comprehend the stereoelectronic requirements for antagonistic activity, and to propose a putative bioactive conformation based on spatial proximities of the native peptide in the crystal structure. The proposed structure presents backbone similarity with the native peptide especially at the N-terminus, which is important for major histocompatibility complex (MHC) binding. Primary (Val(87), Phe(90)) and secondary (Asn(92), Ile(93), Thr(95)) MHC anchors occupy the same region in space, whereas T-cell receptor (TCR) contacts (His(88), Phe(89)) have different orientation between the two structures. A possible explanation, thus, of the antagonistic activity of the APL is that it binds to MHC, preventing the binding of myelin epitopes, but it fails to activate the TCR and hence to trigger the immunologic response. NMR experiments coupled with theoretical calculations are found to be in agreement with X-ray crystallography data and open an avenue for the design and synthesis of novel peptide restricted analogues as well as peptide mimetics that rises as an ultimate goal.

Future of multiple sclerosis therapy: combining antigen-specific immunotherapy with strategies to promote myelin repair

Persistent CNS inflammation and the failure of myelin repair during multiple sclerosis (MS) trigger a progressive deterioration in neurophysiological function and permanent clinical debilitation. Current treatment consists of immunosuppressive therapies targeted against the immune response, which have only been moderately successful in ameliorating disease relapses and have little or no benefit in slowing disease progression or enhancing remyelination. Recent breakthroughs have revealed new targets and more selective techniques for inhibiting autoreactive T-cell responses and promoting lesion repair in animal models of MS. In light of these new findings and the limitations of current treatments, the authors hypothesize that the future of MS therapy will progress towards the development of a combinatorial therapeutic strategy that consists of specific tolerance of autoreactive T cells, myelin repair and axonal protection.

Nitric oxide contributes to the resistance of young SJL/J mice to experimental autoimmune encephalomyelitis

EAE development in SJL/J mice is age and sex dependent: young males are EAE resistant; females and adult males are EAE susceptible. By studying splenocytes' IFNgamma and NO production and the induction or the suppression of actively induced EAE by manipulating NO systemic levels, we provide evidence that the failure of young male SJL/J mice to develop EAE lies in the activation of the innate immune system by the immunising stimulus.

Targeting the TCR: T-cell receptor and peptide-specific tolerance-based strategies for restoring self-tolerance in CNS autoimmune disease

A principal theme in autoimmunity is the breakdown of central tolerance resulting in the persistence and eventual activation of autoreactive T cells. Because CD4(+) T cells are key contributors to the underlying pathogenic mechanisms responsible for the onset and progression of most autoimmune diseases, they are a logical target for therapeutic interventions. One technique for restoring self-tolerance is to exploit the endogenous regulatory mechanisms that govern CD4(+) T-cell activation. In this review, we discuss promising techniques with the common goal of inducing antigen (Ag)-specific tolerance. Emphasis is given to the use of non-mitogenic anti-CD3 and peptide-specific tolerance strategies that specifically target the T-cell receptor (TCR) in the absence of costimulatory signals. These approaches produce a TCR signal of insufficient strength to cause CD4(+) T-cell activation and instead induce functional T-cell anergy or deletion while avoiding generalized long-term immunosuppression.

CD226 is specifically expressed on the surface of Th1 cells and regulates their expansion and effector functions

Surface molecules that are differentially expressed on Th1 and Th2 cells may be useful in regulating specific immune responses in vivo. Using a panel of mAbs, we have identified murine CD226 as specifically expressed on the surface of differentiated Th1 cells but not Th2 or Th0 cells. Although CD226 is constitutively expressed on CD8 cells, it is up-regulated on CD4 cells upon activation. Th1 differentiation results in enhanced CD226 expression, whereas expression is down-regulated upon Th2 polarization. We demonstrate that CD226 is involved in the regulation of T cell activation; in vivo treatment with anti-CD226 results in significant reduction of Th1 cell expansion and in the induction of APCs that inhibit T cell activation. Furthermore, anti-CD226 treatment delays the onset and reduces the severity of a Th1-mediated autoimmune disease, experimental autoimmune encephalomyelitis. Our data suggest that CD226 is a costimulatory molecule that plays an important role in activation and effector functions of Th1 cells.

MHC Class II–Mediated Apoptosis by a Nonpolymorphic MHC Class II Peptide Proceeds by Activation of Protein Kinase C

It was demonstrated previously that a peptide derived from a conserved region of MHC class II, HLA-DQA1, inhibits proliferation of allogeneic T cells in vitro. Administration of HLA-DQA1 in conjunction with allogeneic cells at the time of priming or at the time of rechallenge prevented the development of the delayed type hypersensitivity response in vivo. The immunomodulatory effects of HLA-DQA1 were associated with the induction of apoptosis in B cells, macrophages, and dendritic cells via a caspase-independent pathway. This study investigated the binding site and mechanism that mediates cell death induced by HLA-DQA1. It was demonstrated that HLA-DQA1 binds to MHC class II on the cell surface, causing MHC class II signaling, initiation of protein kinase C signaling, and mitochondrial membrane depolarization with resultant apoptosis. The data indicate that HLA-DQA1 binds to MHC class II outside the groove, in a manner similar to superantigen. These results suggest that HLA-DQA1 is a novel immunotherapy that may provide an effective means of targeting professional antigen-presenting cells, in particular B cells.

Multiple sclerosis

Multiple sclerosis (MS) is a complex genetic disease associated with inflammation in the central nervous system (CNS) white matter and is thought to be mediated by autoimmune processes. Clonal expansion of B cells, their antibody products, and T cells, hallmarks of inflammation in the CNS, are found in MS. The association of the disease with major histocompatibility complex genes, the inflammatory white matter infiltrates, similarities with animal models, and the observation that MS can be treated with immunomodulatory and immunosuppressive therapies support the hypothesis that autoimmunity plays a major role in the disease pathology. This review discusses the immunopathology of MS with particular focus given to regulatory T cells and the role of B cells and antibodies, immunomodulatory therapeutics, and finally new directions in MS research, particularly new methods to define the molecular pathology of human disease with high-throughput examination of germline DNA haplotypes, RNA expression, and protein structures that will allow the generation of a new series of hypotheses that can be tested to develop better understandings and therapies for this disease.

Peptide-based therapeutic vaccines for allergic and autoimmune diseases

Allergic and autoimmune diseases are forms of immune hypersensitivity that increasingly cause chronic ill health. Most current therapies treat symptoms rather than addressing underlying immunological mechanisms. The ability to modify antigen-specific pathogenic responses by therapeutic vaccination offers the prospect of targeted therapy resulting in long-term clinical improvement without nonspecific immune suppression. Examples of specific immune modulation can be found in nature and in established forms of immune desensitization. Understanding and exploiting common mechanisms such as the ability to induce antigen-specific regulatory cells should allow the development of effective therapeutic strategies for both forms of immunopathology. Targeting pathogenic T cells using vaccines consisting of synthetic peptides representing T cell epitopes is one such strategy that is currently being evaluated with encouraging results. Future challenges in the development of therapeutic vaccines include selection of appropriate antigens and peptides, optimization of peptide dose and route of administration and identifying strategies to induce bystander suppression.

Amelioration of established experimental autoimmune encephalomyelitis by an MHC anchor-substituted variant of proteolipid protein 139-151

Murine experimental autoimmune encephalomyelitis (EAE) is a CD4+ T cell-mediated autoimmune disorder directed against myelin proteins within the CNS. We propose that variant peptides containing amino acid substitutions at MHC anchor residues will provide a unique means to controlling the polyclonal autoimmune T cell response. In this study, we have identified an MHC variant of proteolipid protein (PLP) 139-151 (145D) that renders PLP(139-151)-specific T cell lines anergic in vitro, as defined by a significant reduction in proliferation and IL-2 production following challenge with wild-type peptide. In vivo administration of 145D before challenge with PLP(139-151) results in a significant reduction in disease severity and incidence. Importantly, we demonstrate the ability of an MHC variant peptide to ameliorate established EAE. An advantage to this treatment is that the MHC variant peptide does not induce an acute hypersensitivity reaction. This is in contrast to previous work in the PLP(139-151) model demonstrating that anaphylactic shock resulting in death occurs upon rechallenge with the encephalitogenic peptide. Taken together, these data demonstrate the effectiveness of MHC anchor-substituted peptides in the treatment of EAE and suggest their utility in the treatment of other autoimmune disorders.

Defining the parameters necessary for T-cell recognition of ligands that vary in potency

Identification of the mechanisms by which a T cell is able to sense ligands of varying strength, such as those that mediate tumor growth, viral evasion, and autoimmunity, is a major goal of T-cell activation studies. In recent years, parameters important for T-cell activation by strong ligands (agonists) are beginning to be characterized. Here, we review our current work on the factors that are critical for T-cell activation by ligands that differ in potency, typified by full agonists, weak agonists, partial agonists, and antagonists. Furthermore, we discuss mechanisms contributing to the lack of a full range of effector functions observed in T cells following their stimulation by suboptimal ligands. Finally, we present strategies for the design of peptide-based therapies to control activation of polyclonal, autoreactive T-cell populations.

Immunomodulation by the copolymer glatiramer acetate

Glatiramer acetate (GA; Copaxone, also known as Copolymer 1 or Cop-1), a copolymer of amino acids, is very effective in the suppression of experimental autoimmune encephalitis (EAE), the animal model for multiple sclerosis (MS), in various species including primates. The immunological cross-reaction between the myelin basic protein and GA serves as the basis for the suppressive activity of GA in EAE, by the induction of antigen-specific suppressor cells. The mode of action of GA is by initial strong promiscuous binding to major histocompatibility complex class II molecules and competition with MBP and other myelin proteins for such binding and presentation to T cells. Suppressor T cells induced by GA are of the Th2 type, migrate to the brain and lead to in situ bystander suppression. Clinical trials with GA, both phase II and phase III, were performed in relapsing-remitting MS (RRMS) patients, and demonstrated efficacy in reducing the relapse rate, decreasing MRI-assessed disease activity and burden and slowing progression of disability. GA is generally well tolerated and is not associated with influenza-like symptoms and formation of neutralizing antibodies seen with beta-interferons. It exerts its suppressive effect primarily by immunomodulation, and has recently shown ameliorating effect in a few additional autoimmune disorders as well as in graft rejection. At present GA is considered a valuable first-line treatment option for patients with RRMS.