Properties of myelin altered peptide ligand cyclo(87-99)(Ala91,Ala96)MBP87-99 render it a promising drug lead for immunotherapy of multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system, and it has been established that autoreactive T helper (Th) cells play a crucial role in its pathogenesis. Myelin basic protein (MBP) epitopes are major autoantigens in MS, and the sequence MBP87-99 is an immunodominant epitope. We have previously reported that MBP87-99 peptides with modifications at principal T-cell receptor (TCR) contact sites suppressed the induction of EAE symptoms in rats and SJL/J mice, diverted the immune response from Th1 to Th2 and generated antibodies that did not cross react with the native MBP protein. In this study, the linear and cyclic analogs of the MBP87-99 epitope, namely linear (Ala91,Ala96)MBP87-99 (P2) and cyclo(87-99)(Ala91,Ala96)MBP87-99 (P3), were evaluated for their binding to HLA-DR4, stability to lysosomal enzymes, their effect on cytokine secretion by peripheral blood mononuclear cells (PBMC) derived from MS patients or healthy subjects (controls), and their effect in rat EAE. P1 peptide (wild-type, MBP87-99) was used as control. P2 and P3 did not alter significantly the cytokine secretion by control PBMC, in contrast to P1 that induced moderate IL-10 production. In MS PBMC, P2 and P3 induced the production of IL-2 and IFN-γ, with a simultaneous decrease of IL-10, whereas P1 caused a reduction of IL-10 secretion only. The cellular response to P3 indicated that cyclization did not affect the critical TCR contact sites in MS PBMC. Interestingly, the cyclic P3 analog was found to be a stronger binder to HLA-DR4 compared to linear P2. Moreover, cyclic P3 was more stable to proteolysis compared to linear P2. Finally, both P2 and P3 suppressed EAE induced by an encephalitogenic guinea pig MBP74-85 epitope in Lewis rats whereas P1 failed to do so. In conclusion, cyclization of myelin altered peptide ligand (Ala91,Ala96)MBP87-99 improved binding affinity to HLA-DR4, resistance to proteolysis and antigen-specific immunomodulation, rendering cyclo(87-99)(Ala91,Ala96)MBP87-99 an important candidate drug for MS immunotherapy.

Citrullination of linear and cyclic altered peptide ligands from myelin basic protein (MBP(87-99)) epitope elicits a Th1 polarized response by T cells isolated from multiple sclerosis patients: implications in triggering disease.

Derangement of cellular immunity is central in the pathophysiology of multiple sclerosis (MS) and is often manifested by abnormal cytokine production. We investigated cytokine secretion in peripheral blood mononuclear cells (PBMC) of 18 MS patients and 15 controls and correlated cytokine polarization with the nature of antigenic stimulus. We synthesized two novel citrullinated peptides, linear [Cit(91), Ala(96), Cit(97)]MBP(87-99) and cyclo(87-99)[Cit(91), Ala(96), Cit(97)]MBP(87-99) that resulted from citrullination of 91,97 Arg residues in antagonists, linear [Arg(91), Ala(96)]MBP(87-99) and cyclo(87-99)[Arg(91), Ala(96)]MBP(87-99) peptides. PBMC from MS patients and controls were cultured with citrullinated peptides, and both peptides caused a Th1 polarization in all MS patients studied. In contrast, culture with noncitrullinated MBP peptides resulted in heterogeneous cytokine secretion that differed between individual patients. Thus, citrullination of self-antigens may potentially trigger disease in susceptible individuals. This finding may open new avenues in drug design of new substances that inhibit citrullination and arrest epitope spreading and worsening of MS.

Current therapeutic leads for the treatment of autoimmune diseases: stem cell transplantation and inhibition of post-translational modifications of autoantigens.

BACKGROUND: The complexity of autoimmune diseases is reflected on their clinicopathological heterogeneity and the failure to find treatments that cure them after over a century of research. Conventional treatments help ameliorate disease activity but they treat the symptoms whereas the diseases remain incurable in the vast majority of patients. OBJECTIVE: To confront diseases of such nature it is essential to discover therapeutics that will lead to the induction of tolerance or the specific deletion of autoreactive lymphocytes. Current basic and clinical research strategies focus on the better identification of self-antigens, the induction of T regulatory cells that can suppress autoreactive cell activities or, more radically, the 'reformatting' of the immune system through hematopoietic stem cell transplantation (HSCT). METHODS: We analyzed literature on autoimmune disease therapeutics, focusing on new antigens that may arise from post-translational modifications of common proteins and, also, the area of HSCT. RESULTS/CONCLUSIONS: With the recent discovery that citrullination of self-epitopes may be a major pathogenic mechanism for, at least, certain types of autoimmune diseases, it becomes apparent that potentially any self-antigen in the body can be a target of an autoimmune attack. In addition, although the available data on HSCT applied to patients suffering from severe refractory autoimmune diseases do not allow for the determination of the efficacy of the various methods employed to re-educate the immune system, they contribute to our understanding of disease pathogenesis and the improvement on the therapeutic approaches.

Anti-TNF-alpha antibody therapies in autoimmune diseases.

Autoimmune diseases affect about 3% of the world population, more frequently women than men, and their incidence is attributed to an immune response of a genetically predisposed individual to an environmental pathogen, under the influence of inadequate immuno-regulatory mechanisms. Advances in understanding the cellular activity pathways and cytokine expression profiles have led to new therapeutic regiments, like soluble receptors, monoclonal antibodies and molecular mimetics that have been employed to enhance or replace conventional immunosuppressive therapies. Among new biologicals that have been developed to target defined pathways of the adaptive immune response are TNF-alpha inhibitors. TNF-alpha is a proinflammatory cytokine elevated in many autoimmune lesions, and its deregulation characterizes many autoimmune diseases. TNF-alpha seems to exhibit an immunoregulatory role that can alter the balance of T regulatory cells and orchestrate acute immunological responses. More than half a million autoimmune patients have received therapy with anti-TNF-alpha antibodies, usually because they were refractory to conventional treatments. This review offers an update on TNF-alpha-targeted therapies used in patients suffering from various autoimmune diseases, based on the current knowledge of disease pathogenesis, with emphasis on the efficacy and safety that clinical trials have shown until now.

Advances in the treatment of autoimmune diseases; cellular activity, type-1/type-2 cytokine secretion patterns and their modulation by therapeutic peptides.

Autoimmune diseases are many, have an overall prevalence of about 3% of the world population, affecting more women than men, and their incidence is influenced by genetics and the environment. It is currently thought that the immune response of a genetically predisposed individual to an environmental pathogen, under the influence of inadequate or non-functional immunoregulatory mechanisms, can lead to the development of an autoimmune disease. Advances in the treatment of autoimmune diseases follow a better understanding of the abnormalities in the cellular activity pathways and the resulting, often permanent, imbalance of the pro- and anti-inflammatory cytokine expression profiles. Over the past few years, there has been a dramatic change in the therapeutic regimens employed in autoimmune diseases, with soluble receptors, monoclonal antibodies and molecular mimetics enhancing or gradually replacing conventional immunosuppressive therapies. New biologicals have been developed, targeting defined pathways of the adaptive immune response. One approach towards the therapeutic management of autoimmune diseases involves the design and use of peptide analogs of disease-associated epitopes to be used as immunomodulatory drugs. Peptides can target cell-functions directly, by interfering with the formation of the tri-molecular complex MHC-Peptide-TCR, and/or they can target soluble mediators such as cytokines or their receptors, eventually replacing monoclonal antibody therapies. This review offers an update on the treatment modalities of certain prototypic autoimmune diseases, based on the current knowledge of disease pathogenesis, with emphasis on cell activation and cytokine expression profiles.

Design and synthesis of a novel potent myelin basic protein epitope 87-99 cyclic analogue: enhanced stability and biological properties of mimics render them a potentially new class of immunomodulators.

A cyclic analogue, [cyclo(87-99)MBP(87)(-)(99)], of the human immunodominant MBP(87)(-)(99) epitope, was designed based on ROESY/NMR distance information and modeling data for linear epitope 87-99, taking into account T-cell (Phe(89), Lys(91), Pro(96)) and HLA (His(88), Phe(90), Ile(93)) contact side-chain information. The cyclic analogue was found to induce experimental allergic encephalomyelitis (EAE), to bind HLA-DR4, and to increase CD4 T-cell line proliferation, like that of the conformationally related linear MBP(87)(-)(99) epitope peptide. The mutant cyclic peptides, the cyclo(91-99)[Ala(96)]MBP(87)(-)(99) and the cyclo(87-99)[Arg(91)Ala(96)]MBP(87)(-)(99), reported previously for suppressing, to a varying degree, autoimmune encephalomyelitis in a rat animal model, were found in this study to possess the following immunomodulatory properties: (i) they suppressed the proliferation of a CD4 T-cell line raised from a multiple sclerosis patient, (ii) they scored the best in vitro TH2/TH1 cytokine ratio in peripheral blood mononuclear cell cultures derived from 13 multiple sclerosis patients, inducing IL-10 selectively, and (iii) they bound to HLA-DR4, first to be reported for cyclic MBP peptides. In addition, cyclic peptides were found to be more stable to lysosomal enzymes and Cathepsin B, D, and H, compared to their linear counterparts. Taken together, these data render cyclic mimics as putative drugs for treating multiple sclerosis and potentially other Th1-mediated autoimmune diseases.

Leptin and its soluble receptor in plasma of patients suffering from remitting-relapsing multiple sclerosis (MS) In vitro effects of leptin on type-1 and type-2 cytokine secretion by peripheral blood mononuclear cells, T-cells and monocytes of MS patients.

Leptin is synthesized by adipocytes to regulate appetite. Leptin has also been implicated in the pathogenesis of multiple sclerosis (MS) leading to speculation about a beneficial effect of fasting to autoimmune patients. We measured plasma leptin and its soluble receptor (OB-Rs) in 52 MS patients and 50 controls. We also cultured MS and control peripheral blood mononuclear cells (PBMC), T-cells and monocytes +/- recombinant leptin (rleptin), to assess leptin's direct effect on pro- and anti-inflammatory cytokine secretion. We found similar leptin and OB-Rs plasma levels between patients and controls. Untreated patients in the acute phase or in remission, or patients treated with methylprednisolone, had lower leptin levels than patients in the acute phase or in remission receiving IFN-beta. OB-Rs levels were low in patients refractory to IFN-beta but higher in patients receiving methylprednisolone or patients in remission receiving IFN-beta. PBMC from untreated patients in the acute phase, secreted spontaneously IFN-gamma, TNF-alpha and IL-10. IFN-gamma was contributed by T-cells, TNF-alpha and IL-10 primarily by monocytes and to a lesser extent by T-cells. The overall effect of rleptin on PBMC was a net increase in IL-10 production and a net reduction in IFN-gamma production. These results do not warrant a beneficial effect of fasting to MS patients.

Immunotherapy for multiple sclerosis: basic insights for new clinical strategies.

Multiple Sclerosis (MS) is a chronic inflammatory degenerative disease of the central nervous system (CNS), first described over 100 years ago. MS is a clinically heterogeneous disease with an increasing incidence over time, and a population prevalence that increases with distance from the equator. It is postulated that environmental factors such as diet and population-specific genetics, influence the distribution of MS. Diagnosis is based on established clinical criteria, aided by magnetic resonance imaging, evoked potential recordings and cerebrospinal fluid examination. Whichever the type of clinical manifestation, MS is considered an organ-specific autoimmune disease, characterized by T-cell and macrophage infiltrates, triggered by CNS-specific CD4 T-cells. The prominent autoimmune etiology of MS is considered to be the aberrant activation of IFN-gamma-producing Th1 cells that recognize self-peptides of the myelin sheath, such as myelin basic protein (MBP) and proteolipid protein (PLP). Current treatments for MS aim primarily to suppress T-cell-mediated immune responses, albeit non-specifically. Experimental approaches towards the therapeutic management of MS involve the use of peptide analogs of disease-associated myelin epitopes or vaccines, to help shift T helper cell responses from Type-1 (secreting pro-inflammatory cytokines) to Type-2 (secreting anti-inflammatory cytokines) or induce peripheral T-cell tolerance. Animal models of MS have been useful to dissect disease mechanisms and evaluate new therapies. Experimental clinical trials, although few, are valuable to assess new treatment regimens and clarify possible conceptual mistakes about the disease. This review attempts to link the current knowledge of MS pathogenesis with clinical and experimental protocols of immunotherapy for MS.