Synthesis of cyclic Herpes simplex virus peptides containing 281-284 epitope of glycoprotein D-1 in endo- or exo-position

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.

Synthesis, solution structure analysis and antibody binding of cyclic epitope peptides from glycoprotein D of Herpes simplex virus type I

Two cyclic peptides with a thioether bond have been synthesised corresponding to the 9-22 (9LKMADPNRFRGKDL(22)) sequence of glycoprotein D (gD-1) of Herpes simplex virus. The role of the secondary structure in protein-specific monoclonal antibody recognition was investigated. The sequence selected for this study comprises a strongly antigenic site adopting a beta-turn at residues 14Pro-(15)Asn. Thioether bond was formed between the free thiol group of cysteine or homocysteine inserted in position 11 and the chloroacetylated side chain of lysine in position 18. We report here the preparation of cyclic peptides containing Cys or Hcy in position 11, differing only in one methylene group. The linear precursor peptides were synthesised by Boc/Bzl strategy on MBHA resin, and the cyclisation was carried out in alkaline solution. The secondary structure of the peptides was studied by CD, FT-IR and NMR spectroscopy. The CD and FT-IR data have revealed fundamental changes in the solution conformation of the two compounds. The CH(2) group difference significantly resulted in the altered turn structure at the 12Ala and 13Asp as identified by NMR spectroscopy. The antibody binding properties of the cyclopeptides studied by gD-specific monoclonal antibody (A16) in direct and competition enzyme-linked immunosorbent assay (ELISA) were also not the same. We found that peptide LK[HcyADPNRFK]GKDL exhibited higher affinity to Mab A16 than peptide LK[CADPNRFK]GKDL, however, their reactivity was significantly lower compared to the linear ones. Our results clearly show the importance of secondary structure in an antibody binding and demonstrate that even a slight modification of the primary structure dramatically could influence the immune recognition of the synthetic antigens.

Conformational study of linear and cyclic peptides corresponding to the 276-284 epitope region of HSV gD-1

The results of conformational analysis of linear and cyclic peptides from the 276SALLEDPVG(284) sequence of glycoprotein D of Herpes simplex virus are presented. The epitope peptides were synthesized by SPPS and on resin cyclization was applied for preparation of cyclic compounds. Circular dichroism spectroscopy, Fourier-transform infrared spectroscopy and nuclear magnetic resonance (NMR) were used to determine of the solution structure of both linear and cyclic peptides. The results indicated that the cyclopeptides containing the core of the epitope (DPVG) as a part of the cycle have more stable beta-turn structure than the linear peptides or the cyclic analogues, where the core motif is not a part of the cycle. NMR study of H-SALLc(EDPVGK)-NH(2) confirm presence of a type I beta-turn structure which includes the DPVG epitope core.

Design, synthesis and biological evaluation of cyclic angiotensin II analogues with 3,5 side-chain bridges. Role of C-terminal aromatic residue and ring cluster for activity and implications in the drug design of AT1 non-peptide antagonists

The novel amide linked angiotensin II (ANG II) cyclic analogues: gamma, epsilon -cyclo(3, 5)-[Sar(1)-Glu(3)-Lys(5)-Ile(8)] ANG II (I) and gamma, epsilon -cyclo(3, 5)-[Sar(1)-Glu(3)-Lys(5)-Phe(8)] ANG II (II) have been designed, synthesized and bioassayed in anesthetized rabbits in order to unravel structural ring cluster characteristics important for receptor activation. Analogue I with Ile at position 8 was an inhibitor of Angiotensin II while analogue II with Phe at position 8 was found to be an agonist. Similar results were reported for cyclic compounds that have reversed the linking between positions 3 and 5. The overall results show that positions 3 and 5 do not govern the biological activity of the synthetic analogues. It also appears that the aromatic ring cluster (Tyr-His-Phe) in agonist peptides is an essential stereo-electronic feature for Angiotensin II to exert its biological activity. A non-peptide mimetic of ANG II, 1-[2'-[(N-benzyl)tetrazol-5-yl]biphenyl-4-yl]methyl]-2-hydroxymethylbenzimidazole (BZI8) has been designed and synthesized. This molecule is more rigid and much less active than AT(1) non-peptide mimetic losartan probably because it lacks to mimic the orientation of tetrazole and the pharmacophore segments of butyl chain and imidazole ring.

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

The immunodominant myelin basic protein (MBP) peptide comprising residues 87-99 is a self-antigen in multiple sclerosis (MS). In Lewis rats this epitope induces experimental allergic encephalomyelitis (EAE), a demyelinating disease of the central nervous system, and is a model of MS. Structure-activity studies have shown that Lys(91) and Pro(96) residues are important for encephalitogenicity. Replacement of Lys and/or Pro residues with Arg and/or Ala, respectively, results in suppression of EAE. A potent linear altered peptide ligand of the immunodominant sequence MBP(83-99) has been selected for clinical trial (Nat. Med. 2000, 6, 1167, 1176). In the present report, two cyclic analogues, cyclo(91-99)[Ala(96)]MBP(87-99) and cyclo(87-99)[Arg(91), Ala(96)]MBP(87-99) were designed by NMR and molecular modeling data on human MBP(87-99) epitope (Val(87)-His-Phe-Phe-Lys-Asn-Ile-Val-Thr-Pro-Arg-Thr-Pro(99)) and its linear antagonist peptide analogue [Arg(91), Ala(96)]MBP(87-99). These analogues (altered peptide ligands) inhibited EAE in Lewis rats and decreased inflammation in the spinal cord. In addition, the analogue cyclo(87-99)[Arg(91), Ala(96)]MBP(87-99) induced proliferation of human peripheral blood T-cells. These cyclic MBP(87-99) peptide analogues may lead to the design of potent antagonist mimetics for treating MS.

Manipulation of epitope function by modification of peptide structure: a minireview

We have explored various approaches to modify the immunrecognition of linear peptides representing sequential or continuous topographic B-cell or T-cell epitopes. For these studies, epitopes from herpes simplex virus (HSV) glycoprotein D (gD) and from mucin 1 and mucin 2 glycoproteins or T-cell epitopes from 16 kDa and 38 kDa proteins of Mycobacterium tuberculosis were selected. To increase antigenicity and immunogenicity we have prepared cyclic and chimaeric peptide variants as well as epitope peptides with altered flanking regions and epitope-carrier conjugates containing multiple epitope copies.

Treatment of experimental allergic encephalomyelitis (EAE) by a rationally designed cyclic analogue of myelin basic protein (MBP) epitope 72-85

In this report the rational design, synthesis and pharmacological properties of an amide-linked cyclic antagonist analogue of the guinea pig myelin basic protein epitope MBP(72-85) are described. Design of the potent cyclic analogue was based on 2D NOESY nuclear magnetic resonance and molecular dynamics studies carried out in the linear antagonist Ala81MBP(72-85). The cyclic antagonist completely prevented the induction of experimental allergic/autoimmune encephalomyelitis when coinjected with linear and cyclic agonist analogues MBP(72-85) and cyclo(2-9)MBP(72-85).

Design, synthesis, and biological activity of a cyclic peptide: an inhibitor of HIV-1 tat-TAR interactions in human cells

Replication of human immunodeficiency virus type 1 (HIV-1) requires specific interactions of Tat protein with the transactivation responsive region (TAR) RNA, a 59-base stem-loop structure located at the 5'-end of all HIV mRNAs. A number of cyclic peptides are known to possess antibiotic activity and increased biological stability. Here we report the design, synthesis, and biological activity of a cyclic peptide (2), which inhibits transcriptional activation by Tat protein in human cells with an IC50 of approximately 40 nM. Cyclic peptides that can target specific RNA structures provide a new class of small molecules that can be used to control cellular processes involving RNA-protein interactions in vivo.