Antagonistic effects of human cyclic MBP(87-99) altered peptide ligands in experimental allergic encephalomyelitis and human T-cell proliferation

Development and characterization of a novel conjugated methamphetamine vaccine

BACKGROUND

Methamphetamine (METH) addiction is a major public health concern globally with limited management options. The development of a METH vaccine through hapten design has received significant attention as a promising platform for the potential treatment of METH addiction and overdose, however there is yet to be a successful candidate in human trials.

RESEARCH DESIGN AND METHODS

In this study, we developed a novel conjugated METH vaccine using oxidized mannan (a polymannose) as an immunogenic carrier. A METH hapten was synthesized by using amphetamine and conjugated to mannan with a (Lysine-Glycine-Lysine-Glycine-lysine-Glycine-Lysine-Glycine-Lysine-Glycine) (KG)₅ peptide linker.

RESULTS

The reaction between amphetamine and (KG)₅, oxidation of mannan, and conjugation of amphetamine-(KG)₅ with oxidized mannan were confirmed by color tests, Fourier-transform infrared spectroscopy, gas and liquid chromatography mass spectrometry, thin-layer chromatography, and ultraviolet spectrophotometer. Additionally, the ability of the vaccine to generate antibodies was confirmed in C57BL/6 mice.

CONCLUSIONS

The successful development and characterization of the METH-mannan conjugate vaccine, provides a potential therapeutic intervention to curb METH substance use disorders. Each step of vaccine development was characterized to aid in future research on these vaccines, and the immunogenicity shown in the animal models supports future evaluation of the approach. Future studies of the conjugated METH vaccine should evaluate the efficacy in animal models of acute and chronic METH to pave the way for human studies.

An Overview of Peptide-Based Molecules as Potential Drug Candidates for Multiple Sclerosis

Multiple sclerosis (MS) belongs to demyelinating diseases, which are progressive and highly debilitating pathologies that imply a high burden both on individual patients and on society. Currently, several treatment strategies differ in the route of administration, adverse events, and possible risks. Side effects associated with multiple sclerosis medications range from mild symptoms, such as flu-like or irritation at the injection site, to serious ones, such as progressive multifocal leukoencephalopathy and other life-threatening events. Moreover, the agents so far available have proved incapable of fully preventing disease progression, mostly during the phases that consist of continuous, accumulating disability. Thus, new treatment strategies, able to halt or even reverse disease progression and specific for targeting solely the pathways that contribute to the disease pathogenesis, are highly desirable. Here, we provide an overview of the recent literature about peptide-based systems tested on experimental autoimmune encephalitis (EAE) models. Since peptides are considered a unique therapeutic niche and important elements in the pharmaceutical landscape, they could open up new therapeutic opportunities for the treatment of MS.

Antigen-Specific Treatment Modalities in MS: The Past, the Present, and the Future

Antigen-specific therapy for multiple sclerosis may lead to a more effective therapy by induction of tolerance to a wide range of myelin-derived antigens without hampering the normal surveillance and effector function of the immune system. Numerous attempts to restore tolerance toward myelin-derived antigens have been made over the past decades, both in animal models of multiple sclerosis and in clinical trials for multiple sclerosis patients. In this review, we will give an overview of the current approaches for antigen-specific therapy that are in clinical development for multiple sclerosis as well provide an insight into the challenges for future antigen-specific treatment strategies for multiple sclerosis.

Characterization of Asparagine Deamidation in Immunodominant Myelin Oligodendrocyte Glycoprotein Peptide Potential Immunotherapy for the Treatment of Multiple Sclerosis

Mannan (polysaccharide) conjugated with a myelin oligodendrocyte glycoprotein (MOG) peptide, namely (KG)5MOG35-55, represents a potent and promising new approach for the immunotherapy of Multiple Sclerosis (MS). The MOG35-55 epitope conjugated with the oxidized form of mannan (poly-mannose) via a (KG)5 linker was found to inhibit the symptoms of MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) in mice using prophylactic and therapeutic vaccinated protocols. Deamidation is a common modification in peptide and protein sequences, especially for Gln and Asn residues. In this study, the structural solution motif of deaminated peptides and their functional effects in an animal model for MS were explored. Several peptides based on the MOG35-55 epitope have been synthesized in which the Asn53 was replaced with Ala, Asp, or isoAsp. Our results demonstrate that the synthesized MOG peptides were formed to the deaminated products in basic conditions, and the Asn53 was mainly modified to Asp. Moreover, both peptides (wild type and deaminated derivative) conjugated with mannan (from Saccharomyces cerevisiae) independently inhibited the development of neurological symptoms and inflammatory demyelinating spinal cord lesions in MOG35-55-induced EAE. To conclude, mannan conjugated with a deamidated product did not affect the efficacy of the parent peptide.

The Use of Electrochemical Voltammetric Techniques and High-Pressure Liquid Chromatography to Evaluate Conjugation Efficiency of Multiple Sclerosis Peptide-Carrier Conjugates

Recent studies have shown the ability of electrochemical methods to sense and determine, even at very low concentrations, the presence and quantity of molecules or analytes including pharmaceutical samples. Furthermore, analytical methods, such as high-pressure liquid chromatography (HPLC), can also detect the presence and quantity of peptides at very low concentrations, in a simple, fast, and efficient way, which allows the monitoring of conjugation reactions and its completion. Graphite/SiO₂ film electrodes and HPLC methods were previously shown by our group to be efficient to detect drug molecules, such as losartan. We now use these methods to detect the conjugation efficiency of a peptide from the immunogenic region of myelin oligodendrocyte to a carrier, mannan. The HPLC method furthermore confirms the stability of the peptide with time in a simple one pot procedure. Our study provides a general method to monitor, sense and detect the presence of peptides by effectively confirming the conjugation efficiency. Such methods can be used when designing conjugates as potential immunotherapeutics in the treatment of diseases, including multiple sclerosis.

A Journey to the Conformational Analysis of T-Cell Epitope Peptides Involved in Multiple Sclerosis

Multiple sclerosis (MS) is a serious central nervous system (CNS) disease responsible for disability problems and deterioration of the quality of life. Several approaches have been applied to medications entering the market to treat this disease. However, no effective therapy currently exists, and the available drugs simply ameliorate the destructive disability effects of the disease. In this review article, we report on the efforts that have been conducted towards establishing the conformational properties of wild-type myelin basic protein (MBP), myelin proteolipid protein (PLP), myelin oligodendrocyte glycoprotein (MOG) epitopes or altered peptide ligands (ALPs). These efforts have led to the aim of discovering some non-peptide mimetics possessing considerable activity against the disease. These efforts have contributed also to unveiling the molecular basis of the molecular interactions implicated in the trimolecular complex, T-cell receptor (TCR)–peptide–major histocompatibility complex (MHC) or human leucocyte antigen (HLA).

Systemic immunization with altered myelin basic protein peptide produces sustained antidepressant-like effects

Immune dysregulation, specifically of inflammatory processes, has been linked to behavioral symptoms of depression in both human and rodent studies. Here, we evaluated the antidepressant effects of immunization with altered peptide ligands of myelin basic protein (MBP)-MBP_87-99[A⁹¹, A⁹⁶], MBP_87-99[A⁹¹], and MBP_87-99[R⁹¹, A⁹⁶]-in different models of depression and examined the mechanism by which these peptides protect against stress-induced depression. We found that a single dose of subcutaneously administered MBP_87-99[A⁹¹, A⁹⁶] produced antidepressant-like effects by decreasing immobility in the forced swim test and by reducing the escape latency and escape failures in the learned helplessness paradigm. Moreover, immunization with MBP_87-99[A⁹¹, A⁹⁶] prevented and reversed depressive-like and anxiety-like behaviors that were induced by chronic unpredictable stress (CUS). However, MBP_87-99[R⁹¹, A⁹⁶] tended to aggravate CUS-induced anxiety-like behavior. Chronic stress increased the production of peripheral and central proinflammatory cytokines and induced the activation of microglia in the prelimbic cortex (PrL), which was blocked by MBP_87-99[A⁹¹, A⁹⁶]. Immunization with MBP-derived altered peptide ligands also rescued chronic stress-induced deficits in p11, phosphorylated cyclic adenosine monophosphate response element binding protein, and brain-derived neurotrophic factor expression. Moreover, microinjections of recombinant proinflammatory cytokines and the knockdown of p11 in the PrL blunted the antidepressant-like behavioral response to MBP_87-99[A⁹¹, A⁹⁶]. Altogether, these findings indicate that immunization with altered MBP peptide produces prolonged antidepressant-like effects in rats, and the behavioral response is mediated by inflammatory factors (particularly interleukin-6), and p11 signaling in the PrL. Immune-neural interactions may impact central nervous system function and alter an individual's response to stress.

The Long Road of Immunotherapeutics against Multiple Sclerosis

This commentary highlights novel immunomodulation and vaccine-based research against multiple sclerosis (MS) and reveals the amazing story that triggered this cutting-edge MS research in Greece and worldwide. It further reveals the interest and solid support of some of the world's leading scientists, including sixteen Nobel Laureates who requested from European leadership to take action in supporting Greece and its universities in the biggest ever financial crisis the country has encountered in the last decades. This support endorsed vaccine-based research on MS, initiated in Greece and Australia, leading to a worldwide network aiming to treat or manage disease outcomes. Initiatives by bright and determined researchers can result in frontiers science. We shed light on a unique story behind great research on MS which is a step forward in our efforts to develop effective treatments for MS.

Design of Linear and Cyclic Mutant Analogues of Dirucotide Peptide (MBP82⁻98) against Multiple Sclerosis: Conformational and Binding Studies to MHC Class II

Background: Multiple sclerosis (MS) is an autoimmune disorder of the central nervous system. MS is a T cell-mediated disease characterized by the proliferation, infiltration, and attack of the myelin sheath by immune cells. Previous studies have shown that cyclization provides molecules with strict conformation that could modulate the immune system. Methods: In this study, we synthesized peptide analogues derived from the myelin basic protein (MBP)_82–98 encephalitogenic sequence (dirucotide), the linear altered peptide ligand MBP_82–98 (Ala⁹¹), and their cyclic counterparts. Results: The synthesized peptides were evaluated for their binding to human leukocyte antigen (HLA)-DR2 and HLA-DR4 alleles, with cyclic MBP_82–98 being a strong binder with the HLA-DR2 allele and having lower affinity binding to the HLA-DR4 allele. In a further step, conformational analyses were performed using NMR spectroscopy in solution to describe the conformational space occupied by the functional amino acids of both linear and cyclic peptide analogues. This structural data, in combination with crystallographic data, were used to study the molecular basis of their interaction with HLA-DR2 and HLA-DR4 alleles. Conclusion: The cyclic and APL analogues of dirucotide are promising leads that should be further evaluated for their ability to alter T cell responses for therapeutic benefit against MS.

A Cyclic Altered Peptide Analogue Based on Myelin Basic Protein 87-99 Provides Lasting Prophylactic and Therapeutic Protection Against Acute Experimental Autoimmune Encephalomyelitis

In this report, amide-linked cyclic peptide analogues of the 87-99 myelin basic protein (MBP) epitope, a candidate autoantigen in multiple sclerosis (MS), are tested for therapeutic efficacy in experimental autoimmune encephalomyelitis (EAE). Cyclic altered peptide analogues of MBP_87-99 with substitutions at positions 91 and/or 96 were tested for protective effects when administered using prophylactic or early therapeutic protocols in MBP_72-85-induced EAE in Lewis rats. The Lys⁹¹ and Pro⁹⁶ of MBP_87-99 are crucial T-cell receptor (TCR) anchors and participate in the formation of trimolecular complex between the TCR-antigen (peptide)-MHC (major histocompability complex) for the stimulation of encephalitogenic T cells that are necessary for EAE induction and are implicated in MS. The cyclic peptides were synthesized using Solid Phase Peptide Synthesis (SPPS) applied on the 9-fluorenylmethyloxycarboxyl/tert-butyl Fmoc/tBu methodology and combined with the 2-chlorotrityl chloride resin (CLTR-Cl). Cyclo(91-99)[Ala⁹⁶]MBP_87-99, cyclo(87-99)[Ala^91,96]MBP_87-99 and cyclo(87-99)[Arg⁹¹, Ala⁹⁶]MBP_87-99, but not wild-type linear MBP_87-99, strongly inhibited MBP_72-85-induced EAE in Lewis rats when administered using prophylactic and early therapeutic vaccination protocols. In particular, cyclo(87-99)[Arg⁹¹, Ala⁹⁶]MBP_87-99 was highly effective in preventing the onset and development of clinical symptoms and spinal cord pathology and providing lasting protection against EAE induction.

Cyclization of PLP139-151 peptide reduces its encephalitogenic potential in experimental autoimmune encephalomyelitis

We report the novel synthesis of cyclic PLP_139-151 (cPLP) and its application in SJL/J mice to study its encephalitogenic effects. Our results indicate that the cPLP analog is minimally encephalitogenic when administered to induce experimental autoimmune encephalomyelitis (low disease burden, minimal inflammatory, demyelinating and axonopathic pathology compared to its linear counterpart). Proliferation assays confirmed the low stimulatory potential of the cPLP compared to linPLP (2.5-fold lower proliferation) as well as inducing lower antibody responses. Molecular modeling showed a completely different TCR recognition profile of cPLP in regard to linPLP, where H¹⁴⁷ replaces W¹⁴⁴ and F¹⁵¹-K¹⁵⁰ replace H¹⁴⁷ as TCR contacts, which may explain the difference on each peptide's response.

Design, synthesis and evaluation of an anthraquinone derivative conjugated to myelin basic protein immunodominant (MBP85-99) epitope: Towards selective immunosuppression

Anthraquinone type compounds, especially di-substituted amino alkylamino anthraquinones have been widely studied as immunosuppressants. The anthraquinone ring is part of mitoxandrone that has been used for the treatment of multiple sclerosis (MS) and several types of tumors. A desired approach for the treatment of MS would be the immunosuppression and elimination of specific T cells that are responsible for the induction of the disease. Herein, the development of a peptide compound bearing an anthraquinone derivative with the potential to specifically destroy the encephalitogenic T cells responsible for the onset of MS is described. The compound consists of the myelin basic protein (MBP) 85-99 immunodominant epitope (MBP_85-99) coupled to an anthraquinone type molecule (AQ) via a disulfide (S-S) and 6 amino hexanoic acid (Ahx) residues (AQ-S-S-(Ahx)₆MBP_85-99). AQ-S-S-(Ahx)₆MBP_85-99 could bind to HLA II DRB1*-1501 antigen with reasonable affinity (IC₅₀ of 56 nM) The compound was localized to the nucleus of Jurkat cells (an immortalized line of human T lymphocytes) 10 min after its addition to the medium and resulted in lowered Bcl-2 levels (apoptosis). Entrance of the compound was abolished when cells were pre-treated with cisplatin, an inhibitor of thioredoxin reductase. Accordingly, levels of free thiols were elevated in the culture supernatants of Jurkat cells exposed to N-succinimidyl 3-(2-pyridyldithio) propionate coupled to (Ahx)₆MBP_85-99 via a disulphide (SPDP-S-S-(Ahx)₆MBP_85-99) but returned to normal after exposure to cisplatin. These results raise the possibility of AQ-S-S-(Ahx)₆MBP_85-99 being used as an eliminator of encephalitogenic T cells via implication of the thioredoxin system for the generation of the toxic, thiol-containing moiety (AQ-SH). Future experiments would ideally determine whether SPDP-S-S-(Ahx)₆MBP_85-99 could incorporate into HLA II DRB1*-1501 tetramers and neutralize encephalitogenic T cell lines sensitized to MBP_85-99.

Biologically relevant conformational features of linear and cyclic proteolipid protein (PLP) peptide analogues obtained by high-resolution nuclear magnetic resonance and molecular dynamics

Proteolipid protein (PLP) is one of the main proteins of myelin sheath that are destroyed during the progress of multiple sclerosis (MS). The immunodominant PLP_139-151 epitope is known to induce experimental autoimmune encephalomyelitis (EAE, animal model of MS), wherein residues 144 and 147 are recognized by T cell receptor (TCR) during the formation of trimolecular complex with peptide-antigen and major histocompability complex. The conformational behavior of linear and cyclic peptide analogues of PLP, namely PLP_139-151 and cyclic (139-151) (L¹⁴⁴, R¹⁴⁷) PLP_139-151, have been studied in solution by means of nuclear magnetic resonance (NMR) methods in combination with unrestrained molecular dynamics simulations. The results indicate that the side chains of mutated amino acids in the cyclic analogue have different spatial orientation compared with the corresponding side chains of the linear analogue, which can lead to reduced affinity to TCR. NMR experiments combined with theoretical calculations pave the way for the design and synthesis of potent restricted peptides of immunodominant PLP_139-151 epitope as well as non peptide mimetics that rises as an ultimate goal.

Multiple Sclerosis: Immunopathology and Treatment Update

The treatment of multiple sclerosis (MS) has changed over the last 20 years. All immunotherapeutic drugs target relapsing remitting MS (RRMS) and it still remains a medical challenge in MS to develop a treatment for progressive forms. The most common injectable disease-modifying therapies in RRMS include β-interferons 1a or 1b and glatiramer acetate. However, one of the major challenges of injectable disease-modifying therapies has been poor treatment adherence with approximately 50% of patients discontinuing the therapy within the first year. Herein, we go back to the basics to understand the immunopathophysiology of MS to gain insights in the development of new improved drug treatments. We present current disease-modifying therapies (interferons, glatiramer acetate, dimethyl fumarate, teriflunomide, fingolimod, mitoxantrone), humanized monoclonal antibodies (natalizumab, ofatumumb, ocrelizumab, alentuzumab, daclizumab) and emerging immune modulating approaches (stem cells, DNA vaccines, nanoparticles, altered peptide ligands) for the treatment of MS.

Cyclic MOG35-55 ameliorates clinical and neuropathological features of experimental autoimmune encephalomyelitis

EAE is induced to susceptible mice using linear peptides of myelin proteins of the central nervous system. Specific peptide motifs within the peptide-binding groove of the MHC peptide-complex determines the affinity of the peptide in each animal and the consequent T-cell receptor recognition and activation of the cell. Altered peptide ligand (APL) vaccination is a novel approach based on an effort to induce T-cell tolerance or alter cytokine profile from pro-inflammatory to anti-inflammatory. In the present study we synthesized the MOG_35-55 peptide and altered its 3-dimensional conformation to make it a cyclic one (c-MOG_35-55). EAE was induced in C57BL/6 mice and pathology was studied on acute and chronic phase of the disease. Our data indicates that c-MOG_35-55 peptide alone induces a mild transient acute phase without chronic axonopathy. Administration of the c-MOG_35-55 peptide at a 1:1 ratio during disease induction significantly ameliorates clinical disease and underlying pathology, such as demyelination and axonopathy in the acute and chronic phases. Binding and structural studies revealed milder interactions between the c-MOG_35-55 and mouse or human MHC class II alleles (H2-IA^b and HLA-DR2). Collectively, we provide data supporting for the first time the concept that the cyclic modification of an established encephalitogenic peptide ameliorates the clinical outcomes and underlying pathological processes of EAE. Such a cyclic modification of linear peptides could provide a novel treatment approach for future, patient-selective, immunomodulative treatments of multiple sclerosis.

Matrix metalloproteinases - From the cleavage data to the prediction tools and beyond

Understanding the physiological role of any protease requires identification of both its cleavage substrates and their relative cleavage efficacy as compared with other substrates and other proteinases. Our review manuscript is focused on the cleavage preferences of the individual matrix metalloproteinases (MMPs) and the cleavage similarity and distinction that exist in the human MMP family. The recent in-depth analysis of MMPs by us and many others greatly increased knowledge of the MMP biology and structural-functional relationships among this protease family members. A better knowledge of cleavage preferences of MMPs has led us to the development of the prediction tools that are now capable of the high throughput reliable prediction and ranking the MMP cleavage sites in the peptide sequences in silico. Our software unifies and consolidates volumes of the pre-existing data. Now this prediction-ranking in silico tool is ready to be used by others. The software we developed may facilitate both the identification of the novel proteolytic regulatory pathways and the discovery of the previously uncharacterized substrates of the individual MMPs. Because now the MMP research may be based on the mathematical probability parameters rather than on either random luck or common sense alone, the researchers armed with this novel in silico tool will be better equipped to fine-tune or, at least, to sharply focus their wet chemistry experiments. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

Cyclic citrullinated MBP87-99 peptide stimulates T cell responses: Implications in triggering disease

Amino acid mutations to agonist peptide epitopes of myelin proteins have been used to modulate immune responses and experimental autoimmune encephalomyelitis (EAE, animal model of multiple sclerosis). Such amino acid alteration are termed, altered peptide ligands (APL). We have shown that the agonist myelin basic protein (MBP) 87-99 epitope (MBP_87-99) with crucial T cell receptor (TCR) substitutions at positions 91 and 96 (K⁹¹,P⁹⁶ (TCR contact residues) to R⁹¹,A⁹⁶; [R⁹¹,A⁹⁶]MBP_87-99) results in altered T cell responses and inhibits EAE symptoms. In this study, the role of citrullination of arginines in [R⁹¹,A⁹⁶]MBP_87-99 peptide analog was determined using in vivo experiments in combination with computational studies. The immunogenicity of linear [Cit⁹¹,A⁹⁶,Cit⁹⁷]MBP_87-99 and its cyclic analog - cyclo(87-99)[Cit⁹¹,A⁹⁶,Cit⁹⁷]MBP_87-99 when conjugated to the carrier mannan (polysaccharide) were studied in SJL/J mice. It was found that mannosylated cyclo(87-99)[Cit⁹¹,A⁹⁶,Cit⁹⁷]MBP_87-99 peptide induced strong T cell proliferative responses and IFN-gamma cytokine secretion compared with the linear one. Moreover, the interaction of linear and cyclic peptide analogs with the major histocompatibility complex (MHC II, H2-IA^s) and TCR was analyzed using molecular dynamics simulations at the receptor level, in order to gain a better understanding of the molecular recognition mechanisms that underly the different immunological profiles of citrullinated peptides compared to its agonist native counterpart MBP_87-99 epitope. The results demonstrate that the citrullination of arginine in combination with the backbone conformation of mutated linear and cyclic analogs are significant elements for the immune response triggering the induction of pro-inflammatory cytokines.

Use of the 2-chlorotrityl chloride resin for microwave-assisted solid phase peptide synthesis

A fast and efficient microwave (MW)-assisted solid-phase peptide synthesis protocol using the 2-chlorotrityl chloride resin and the Fmoc/tBu methodology, has been developed. The established protocol combines the advantages of MW irradiation and the acid labile 2-chlorotrityl chloride resin. The effect of temperature during the MW irradiation, the degree of resin substitution during the coupling of the first amino acids and the rate of racemization for each amino acid were evaluated. The suggested solid phase methodology is applicable for orthogonal peptide synthesis and for the synthesis of cyclic peptides.

A Scalable and Facile Process for the Preparation of N-(Pyridin-4-yl) Piperazine-1-Carboxamide Hydrochloride

A scalable and facile synthetic process for N-(pyridin-4-yl)piperazine-1-carboxamide hydrochloride, a novel Rho kinase inhibitor with an unsymmetrical urea structure currently under investigation for the treatment of central nervous system disorders, was established. After optimisation of the reaction conditions, N-(pyridin-4-yl)piperazine-1-carboxamide hydrochloride was synthesised from 4-aminopyridine and N,N′-carbonyldiimidazole through acylation, deprotection and salt formation. This new procedure affords the product in 53% overall yield with high purity and it can be easily scaled up for production.

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.

Mannosylated Linear and Cyclic Single Amino Acid Mutant Peptides Using a Small 10 Amino Acid Linker Constitute Promising Candidates Against Multiple Sclerosis

Multiple sclerosis (MS) is a serious autoimmune demyelinating disease leading to loss of neurological function. The design and synthesis of various altered peptide ligands of immunodominant epitopes of myelin proteins to alter the autoimmune response, is a promising therapeutic approach for MS. In this study, linear and cyclic peptide analogs based on the myelin basic protein 83–99 (MBP_83–99) immunodominant epitope conjugated to reduced mannan via the (KG)₅ and keyhole limpet hemocyanin (KLH) bridge, respectively, were evaluated for their biological/immunological profiles in SJL/J mice. Of all the peptide analogs tested, linear MBP_83–99(F⁹¹) and linear MBP_83–99(Y⁹¹) conjugated to reduced mannan via a (KG)₅ linker and cyclic MBP_83–99(F⁹¹) conjugated to reduce mannan via KLH linker, yielded the best immunological profile and constitute novel candidates for further immunotherapeutic studies against MS in animal models and in human clinical trials.

Homo-β-amino acid containing MBP(85-99) analogs alleviate experimental autoimmune encephalomyelitis

MBP(85–99), an immuno-dominant epitope of myelin basic protein which binds to the major histocompatibility complex haplotype HLA-DR2 is widely implicated in the pathogenesis of multiple sclerosis. J5, an antagonist of MBP(85–99), that blocks the binding of MBP(85–99) to soluble HLA-DR2b much more efficiently than glatiramer acetate (a random copolymer comprising major MHC and T-cell receptor contact residues), was transformed into analogs with superior biological half-lives and antagonistic-activities by substitution of some of its residues with homo-β-amino acids. S18, the best analog obtained ameliorated symptoms of experimental autoimmune encephalomyelitis at least twice more effectively than glatiramer acetate or J5. S18 displayed marked resistance to proteolysis in-vitro; biological impact of which was evident in the form of delayed clinical onset of disease and prolonged therapeutic-benefits. Besides active suppression of MBP(85–99)-reactive CD4⁺ T-cells in-vitro and in-vivo S18 treatment also generated IL-4 producing CD4⁺ T-cell clones, through which protective effect could be transferred passively.

Rational design and synthesis of altered peptide ligands based on human myelin oligodendrocyte glycoprotein 35-55 epitope: inhibition of chronic experimental autoimmune encephalomyelitis in mice

Experimental autoimmune encephalomyelitis (EAE) is a demyelinating disease of the central nervous system and is an animal model of multiple sclerosis (MS). Although the etiology of MS remains unclear, there is evidence T-cell recognition of immunodominant epitopes of myelin proteins, such as the 35–55 epitope of myelin oligodendrocyte glycoprotein (MOG), plays a pathogenic role in the induction of chronic EAE. Cyclization of peptides is of great interest since the limited stability of linear peptides restricts their potential use as therapeutic agents. Herein, we have designed and synthesized a number of linear and cyclic peptides by mutating crucial T cell receptor (TCR) contact residues of the human MOG_35–55 epitope. In particular, we have designed and synthesized cyclic altered peptide ligands (APLs) by mutating Arg⁴¹ with Ala or Arg⁴¹ and Arg⁴⁶ with Ala. The peptides were synthesized in solid phase on 2-chlorotrityl chloride resin (CLTR-Cl) using the Fmoc/t-Bu methodology. The purity of final products was verified by RP-HPLC and their identification was achieved by ESI-MS. It was found that the substitutions of Arg at positions 41 and 46 with Ala results in peptide analogues that reduce the severity of MOG-induced EAE clinical symptoms in C57BL/6 mice when co-administered with mouse MOG_35–55 peptide at the time of immunization.

A novel synthetic luteinizing hormone-releasing hormone (LHRH) analogue coupled with modified β-cyclodextrin: insight into its intramolecular interactions

BACKGROUND

Cyclodextrins (CDs) in combination with therapeutic proteins and other bioactive compounds have been proposed as candidates that show enhanced chemical and enzymatic stability, better absorption, slower plasma clearance and improved dose-response curves or immunogenicity. As a result, an important number of therapeutic complexes between cyclodextrins and bioactive compounds capable to control several diseases have been developed.

RESULTS

In this article, the synthesis and the structural study of a conjugate between a luteinizing hormone-releasing hormone (LHRH) analogue, related to the treatment of hormone dependent cancer and fertility, and modified β-cyclodextrin residue are presented. The results show that both the phenyl group of tyrosine (Tyr) as well as the indole group of tryptophan (Trp) can be encapsulated inside the cyclodextrin cavity. Solution NMR experiments provide evidence that these interactions take place intramolecularly and not intermolecularly.

CONCLUSIONS

The study of a LHRH analogue conjugated with modified β-cyclodextrin via high field NMR and MD experiments revealed the existence of intramolecular interactions that could lead to an improved drug delivery.

GENERAL SIGNIFICANCE

NMR in combination with MD simulation is of great value for a successful rational design of peptide-cyclodextrin conjugates showing stability against enzymatic proteolysis and a better pharmacological profile.

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.

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.

Divergent and convergent synthesis of polymannosylated dibranched antigenic peptide of the immunodominant epitope MBP(83-99)

Multiple antigenic peptide (MAP) systems are dendrimeric structures bearing multiple copies of identical or different peptide epitopes, and they have been demonstrated to show enhanced immunogenicity. Herein, we report the direct (divergent) and indirect (convergent) synthesis, using contemporary synthetic approaches, of a di-branched antigenic peptide (di-BAP) containing the immunodominant epitope MBP(83-99), which is implicated in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). The direct synthesis (di-BAP 1) was performed using microwave irradiation. The indirect synthesis (di-BAP 2) was carried out performing an efficient chemoselective coupling reaction through the formation of a thioether bond. Both di-BAPs were conjugated to polysaccharide mannan since mannosylation is a promising technique to achieve modulation in immune response. The conjugation was achieved through free amino groups of both di-BAPs via the formation of Schiff bases. The mannan-conjugated di-BAPs were further evaluated in vivo in a prophylactic vaccination protocol, prior to EAE induction in Lewis rats.

Rationally designed cyclic analogues of luteinizing hormone-releasing hormone: enhanced enzymatic stability and biological properties

This article describes the rational design, synthesis and pharmacological properties of amide-linked cyclic analogues of Luteinizing Hormone-Releasing Hormone (LHRH) with substitutions at positions 1 (Pro), 6 (D-Leu/D-Trp), 9 (Aze) and 10 (BABA/Acp). These LHRH analogues fulfil the conformational requirements that are known in the literature (bend in the 5-8 segment) to be essential for receptor recognition and activation. Although, they are characterised by an overall low binding affinity to the LHRH-I receptor, the cyclic analogues that were studied and especially the cyclo(1-10)[Pro(1), D-Leu(6), BABA(10)] LHRH, exhibit a profoundly enhanced in vitro and in vivo stability and improved pharmacokinetics in comparison with their linear counterpart and leuprolide. Upon receptor binding, cyclo(1-10)[Pro(1), D-Leu(6), BABA(10)] LHRH causes testosterone release in C57/B16 mice (in vivo efficacy) that is comparable to that of leuprolide. Testosterone release is an acutely dose dependent effect that is blocked by the LHRH-I receptor antagonist, cetrorelix. The pharmacokinetic advantages and efficacy of cyclo(1-10)[Pro(1), D-Leu(6), BABA(10)] LHRH render this analogue a promising platform for future rational drug design studies towards the development of non-peptide LHRH mimetics.

Immunodominant fragments of myelin basic protein initiate T cell-dependent pain

Background

The myelin sheath provides electrical insulation of mechanosensory Aβ-afferent fibers. Myelin-degrading matrix metalloproteinases (MMPs) damage the myelin sheath. The resulting electrical instability of Aβ-fibers is believed to activate the nociceptive circuitry in Aβ-fibers and initiate pain from innocuous tactile stimulation (mechanical allodynia). The precise molecular mechanisms, responsible for the development of this neuropathic pain state after nerve injury (for example, chronic constriction injury, CCI), are not well understood.

Methods and results

Using mass spectrometry of the whole sciatic nerve proteome followed by bioinformatics analyses, we determined that the pathways, which are classified as the Infectious Disease and T-helper cell signaling, are readily activated in the nerves post-CCI. Inhibition of MMP-9/MMP-2 suppressed CCI-induced mechanical allodynia and concomitant TNF-α and IL-17A expression in nerves. MMP-9 proteolysis of myelin basic protein (MBP) generated the MBP84-104 and MBP68-86 digest peptides, which are prominent immunogenic epitopes. In agreement, the endogenous MBP69-86 epitope co-localized with MHCII and MMP-9 in Schwann cells and along the nodes of Ranvier. Administration of either the MBP84-104 or MBP68-86 peptides into the naïve nerve rapidly produced robust mechanical allodynia with a concomitant increase in T cells and MHCII-reactive cell populations at the injection site. As shown by the genome-wide expression profiling, a single intraneural MBP84-104 injection stimulated the inflammatory, immune cell trafficking, and antigen presentation pathways in the injected naïve nerves and the associated spinal cords. Both MBP84-104-induced mechanical allodynia and characteristic pathway activation were remarkably less prominent in the T cell-deficient athymic nude rats.

Conclusions

These data implicate MBP as a novel mediator of pain. Furthermore, the action of MMPs expressed within 1 day post-injury is critical to the generation of tactile allodynia, neuroinflammation, and the immunodominant MBP digest peptides in nerve. These MBP peptides initiate mechanical allodynia in both a T cell-dependent and -independent manner. In the course of Wallerian degeneration, the repeated exposure of the cryptic MBP epitopes, which are normally sheltered from immunosurveillance, may induce the MBP-specific T cell clones and a self-sustaining immune reaction, which may together contribute to the transition of acute pain into a chronic neuropathic pain state.

Conformational analysis of the ΜΒΡ83-99 (Phe91) and ΜΒΡ83-99 (Tyr91) peptide analogues and study of their interactions with the HLA-DR2 and human TCR receptors by using molecular dynamics

The two new synthetic analogues of the MBP(83-99) epitope substituted at Lys(91) (primary TCR contact) with Phe [MBP(83-99) (Phe(91))] or Tyr [MBP(83-99) (Tyr(91))], have been structurally elucidated using 1D and 2D high resolution NMR studies. The conformational analysis of the two altered peptide ligands (APLs) has been performed and showed that they adopt a linear and extended conformation which is in agreement with the structural requirements of the peptides that interact with the HLA-DR2 and TCR receptors. In addition, Molecular Dynamics (MD) simulations of the two analogues in complex with HLA-DR2 (DRA, DRB1*1501) and TCR were performed. Similarities and differences of the binding motif of the two analogues were observed which provide a possible explanation of their biological activity. Their differences in the binding mode in comparison with the MBP(83-99) epitope may also explain their antagonistic versus agonistic activity. The obtained results clearly indicate that substitutions in crucial amino acids (TCR contacts) in combination with the specific conformational characteristics of the MBP(83-99) immunodominant epitope lead to an alteration of their biological activity. These results make the rational drug design intriguing since the biological activity is very sensitive to the substitution and conformation of the mutated MBP epitopes.

Antigen processing and presentation in multiple sclerosis

CD4(+) T cells play a central role in the pathogenesis of multiple sclerosis (MS). Generation, activation and effector function of these cells crucially depends on their interaction with MHC II-peptide complexes displayed by antigen presenting cells (APC). Processing and presentation of self antigens by different APC therefore influences the disease course at all stages. Selection by thymic APC leads to the generation of autoreactive T cells, which can be activated by peripheral APC. Reactivation by central nervous system APC leads to the initiation of the inflammatory response resulting in demyelination. In this review we will focus on how MHC class II antigenic epitopes are created by different APC from the thymus, the periphery and from the brain, and will discuss the relevance of the balance between creation and destruction of such epitopes in the context of MS. A solid understanding of these processes offers the possibility for designing future therapeutic strategies.

Altered peptide ligands of myelin basic protein ( MBP87-99 ) conjugated to reduced mannan modulate immune responses in mice

Mutations of peptides to generate altered peptide ligands, capable of switching immune responses from T helper 1 (Th1) to T helper 2 (Th2), are promising candidates for the immunotherapy of autoimmune diseases such as multiple sclerosis (MS). We synthesized two mutant peptides from myelin basic protein 87-99 (MBP(87-99)), an immunodominant peptide epitope identified in MS. Mutations of residues K(91) and P(96), known to be critical T-cell receptor (TCR) contact sites, resulted in the mutant peptides [R(91), A(96)]MBP(87-99) and [A(91), A(96)]MBP(87-99). Immunization of mice with these altered peptide ligands emulsified in complete Freund's adjuvant induced both interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) responses compared with only IFN-gamma responses induced to the native MBP(87-99) peptide. It was of interest that [R(91), A(96)]MBP(87-99) conjugated to reduced mannan induced 70% less IFN-gamma compared with the native MBP(87-99) peptide. However, [A(91), A(96)]MBP(87-99) conjugated to reduced mannan did not induce IFN-gamma-secreting T cells, but elicited very high levels of interleukin-4 (IL-4). Furthermore, antibodies generated to [A(91), A(96)]MBP(87-99) peptide conjugated to reduced mannan did not cross-react with the native MBP(87-99) peptide. By molecular modelling of the mutant peptides in complex with major histocompatibility complex (MHC) class II, I-A(s), novel interactions were noted. It is clear that the double-mutant peptide analogue [A(91), A(96)]MBP(87-99) conjugated to reduced mannan is able to divert immune responses from Th1 to Th2 and is a promising mutant peptide analogue for use in studies investigating potential treatments for MS.

Inflammatory proprotein convertase-matrix metalloproteinase proteolytic pathway in antigen-presenting cells as a step to autoimmune multiple sclerosis

Multiple sclerosis (MS) is a disease of the central nervous system with autoimmune etiology. Susceptibility to MS is linked to viral and bacterial infections. Matrix metalloproteinases (MMPs) play a significant role in the fragmentation of myelin basic protein (MBP) and demyelination. The splice variants of the single MBP gene are expressed in the oligodendrocytes of the central nervous system (classic MBP) and in the immune cells (Golli-MBPs). Our data suggest that persistent inflammation caused by environmental risk factors is a step to MS. We have discovered biochemical evidence suggesting the presence of the inflammatory proteolytic pathway leading to MS. The pathway involves the self-activated furin and PC2 proprotein convertases and membrane type-6 MMP (MT6-MMP/MMP-25) that is activated by furin/PC2. These events are followed by MMP-25 proteolysis of the Golli-MBP isoforms in the immune system cells and stimulation of the specific autoimmune T cell clones. It is likely that the passage of these autoimmune T cell clones through the disrupted blood-brain barrier to the brain and the recognition of neuronal, classic MBP causes inflammation leading to the further up-regulation of the activity of the multiple individual MMPs, the massive cleavage of MBP in the brain, demyelination, and MS. In addition to the cleavage of Golli-MBPs, MMP-25 proteolysis readily inactivates crystallin alphaB that is a suppressor of MS. These data suggest that MMP-25 plays an important role in MS pathology and that MMP-25, especially because of its restricted cell/tissue expression pattern and cell surface/lipid raft localization, is a promising drug target in MS.

NMR structural elucidation of myelin basic protein epitope 83-99 implicated in multiple sclerosis

Myelin basic protein peptide 83-99 (MBP83-99) is the most immunodominant epitope playing a significant role in the multiple sclerosis (MS), an autoimmune disease of the central nervous system. Many peptide analogues, linear or cyclic have been designed and synthesized based on this segment in order to inhibit the experimental autoimmune encephalomyelitis, the best well-known animal model of MS. In this study, the solution structural motif of MBP(83-99) has been performed using 2D (1)H-NMR spectroscopy in dimethyl sulfoxide. A rather extended conformation, along with the formation of a well defined alpha-helix spanning residues Val(87)-Phe(90) is proposed, as no long-range NOE are presented. Moreover, the residues of MBP peptide that are important for T-cell receptor recognition are solvent exposed. The spatial arrangement of the side chain all over the sequence of our NMR based model exhibits great similarity with the solid state model, while both TCR contacts occupy the same region in space.

Matrix metalloproteinase proteolysis of the myelin basic protein isoforms is a source of immunogenic peptides in autoimmune multiple sclerosis

Background

Matrix metalloproteinases (MMPs) play a significant role in the fragmentation of myelin basic protein (MBP) and demyelination leading to autoimmune multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). The classic MBP isoforms are predominantly expressed in the oligodendrocytes of the CNS. The splice variants of the single MBP gene (Golli-MBP BG21 and J37) are widely expressed in the neurons and also in the immune cells. The relative contribution of the individual MMPs to the MBP cleavage is not known.

Methodology/Principal Findings

To elucidate which MMP plays the primary role in cleaving MBP, we determined the efficiency of MMP-2, MMP-8, MMP-9, MMP-10, MMP-12, MT1-MMP, MT2-MMP, MT3-MMP, MT4-MMP, MT5-MMP and MT6-MMP in the cleavage of the MBP, BG21 and J37 isoforms in the in vitro cleavage reactions followed by mass-spectroscopy analysis of the cleavage fragments. As a result, we identified the MMP cleavage sites and the sequence of the resulting fragments. We determined that MBP, BG21 and J37 are highly sensitive to redundant MMP proteolysis. MT6-MMP (initially called leukolysin), however, was superior over all of the other MMPs in cleaving the MBP isoforms. Using the mixed lymphocyte culture assay, we demonstrated that MT6-MMP proteolysis of the MBP isoforms readily generated, with a near quantitative yield, the immunogenic N-terminal 1–15 MBP peptide. This peptide selectively stimulated the proliferation of the PGPR7.5 T cell clone isolated from mice with EAE and specific for the 1–15 MBP fragment presented in the MHC H-2^U context.

Conclusions/Significance

In sum, our biochemical observations led us to hypothesize that MT6-MMP, which is activated by furin and associated with the lipid rafts, plays an important role in MS pathology and that MT6-MMP is a novel and promising drug target in MS especially when compared with other individual MMPs.

Design and synthesis of a cyclic double mutant peptide (cyclo(87-99)[A91,A96]MBP87-99) induces altered responses in mice after conjugation to mannan: implications in the immunotherapy of multiple sclerosis

Altered peptide ligands that alter immune responses are a promising approach to the immunotherapy of multiple sclerosis. Cyclic peptides are of interest because the limited stability of linear peptides restricts their use in vivo. We designed and synthesized a cyclic double mutant peptide from MBP(87-99)-[cyclo(87-99)[A(91),A(96)]MBP(87-99)]. Immunization of mice, in CFA reduced Th1 responses. However, when conjugated to reduced mannan, a significant further reduction of Th1 responses and moderate Th2 responses were induced.

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'.

Towards immunotherapeutic drugs and vaccines against multiple sclerosis

Multiple sclerosis (MS) is an autoimmune, demyelinating disease of the central nervous system. Numerous treatment options are available to MS patients; however, these options need to be improved. Herein, we review the current drugs and therapeutic approaches available to MS patients, preclinical trial interventions and recent animal model studies for the potential therapy of MS. Since the current treatment of MS remains elusive and is limited, animal studies and clinical research offers an optimistic outlook.

Mannosylation of mutated MBP83-99 peptides diverts immune responses from Th1 to Th2

Multiple sclerosis (MS) is an autoimmune demyelinating disease mediated primarily by CD4+ T cells. The design of peptide mutants of disease-associated myelin epitopes to alter immune responses offers a promising avenue for the treatment of MS. We designed and synthesized a number of peptide analogs by mutating the principal TCR contact residue based on MBP83-99 epitope and these peptides were conjugated to reduced mannan. Immune responses were diverted from Th1 to Th2 in SJL/J mice and generated antibodies which did not cross-react with native MBP protein. Peptide [Y91]MBP83-99 gave the best cytokine and antibody profile and constitutes a promising candidate peptide for immunotherapy of MS. Structural alignment of existing crystal structures revealed the peptide binding motif of I-As. Molecular modeling was used to identify H-bonding and van der Waals interactions between peptides and MHC (I-A(s)).

Design of protease-resistant myelin basic protein-derived peptides by cleavage site directed amino acid substitutions

Multiple Sclerosis (MS) is considered to be a T cell-mediated autoimmune disease. An attractive strategy to prevent activation of autoaggressive T cells in MS, is the use of altered peptide ligands (APL), which bind to major histocompatibility complex class II (MHC II) molecules. To be of clinical use, APL must be capable of resisting hostile environments including the proteolytic machinery of antigen presenting cells (APC). The current design of APL relies on cost- and labour-intensive strategies. To overcome these major drawbacks, we used a deductive approach which involved modifying proteolytic cleavage sites in APL. Cleavage site-directed amino acid substitution of the autoantigen myelin basic protein (MBP) resulted in lysosomal protease-resistant, high-affinity binding peptides. In addition, these peptides mitigated T cell activation in a similar fashion as conventional APL. The strategy outlined allows the development of protease-resistant APL and provides a universal design strategy to improve peptide-based immunotherapeutics.