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, ofatumumab, ocrelizumab, alemtuzumab, daclizumab) and emerging immune modulating approaches (stem cells, DNA vaccines, nanoparticles, altered peptide ligands) for the treatment of MS.
The use of antagonist peptides derived from the myelin sheath constitutes a promising therapeutic approach for multiple sclerosis (MS). Cyclization of peptide analogues is of great interest, since the limited stability of linear peptides restricts their potential as therapeutic agents. Herein, we designed and synthesized a number of cyclic peptides by mutating TCR contact sites of the MBP 83-99 epitope. A number of cyclic analogues were tested for their ability to inhibit (antagonize) Th1 (IFN-gamma) responses, and cyclo(83-99)[A (91)]MBP 83-99 mutant peptide was found to be the most efficient inhibitor. We demonstrated that cyclo(83-99)[A (91)]MBP 83-99 peptide emulsified in CFA enhanced Th2 (IL-4) and antibody responses in vivo. Moreover, immunization of mice with antagonist cyclo(83-99)[A (91)]MBP 83-99 peptide conjugated to reduced mannan enhanced IL-4 responses compared to cyclo(83-99)MBP 83-99 peptide. Thus, cyclized peptides, which offer greater stability and enhanced responses, are novel leads for the immunotherapy of many diseases, such as MS. In particular, cyclo(83-99)[A (91)]MBP 83-99 is a promising mutant peptide analogue for the potential treatment of MS.
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.
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