Peptide carriers: A helicoid-type sequential oligopeptide carrier (SOC(n)) for multiple anchoring of antigenic/immunogenic peptides

Peptide dendrimers as valuable biomaterials in medical sciences

Peptides are oligomers of amino acids, which have been used in a wide range of applications, particularly in medical and pharmaceutical sciences. Linear peptides have been extensively developed in various fields of medicine as therapeutics or targeting agents. The branched structure of peptide dendrimers with peptide (commonly, poly l‑Lysine) or non-peptide (commonly poly‑amidoamine) core, often exhibits valuable novel features, improves stability and enhances the functionality of peptide in comparison with small linear peptides. The potential applications of Branched and hyper-branched peptidic structures which are known as peptide dendrimers in biomedical sciences have been approved vastly. A peptide dendrimer contains three distinct parts including core, building blocks and branching units or surface functional groups. These structures provide a lot of opportunities in the pharmaceutical field, particularly for novel drug development. In this review, a brief summary of different biomedical applications of peptide dendrimers is presented, and peptide dendrimers as active pharmaceutical ingredients and drug delivery carriers are discussed. Applications of peptide dendrimers in vaccines and diagnostic tools are also presented, in brief. Generally, peptide dendrimers are promising biomaterials with high evolution rate for clinical and non-clinical applications in medicine.

A complementary La/SSB epitope anchored to Sequential Oligopeptide Carrier regulates the anti-La/SSB response in immunized animals

Complementary peptide epitopes, derived from complementary RNA sequences, have been used for suppressing the autoimmune response in experimental autoimmune diseases as myasthenia gravis, allergic neuritis and allergic encephalomyelitis. Aiming at contributing to the development of a tool that could regulate the autoantibody production against La/SSB, which is the main target of autoantibodies in Sjogren's syndrome (SS) and systemic lupus erythematosus (SLE), the complementary epitope, cpep349-364, of the minor T/major B cell epitope of La/SSB, pep349-364, was utilized for the induction of neutralizing anti-cpep349-364 antibodies in rabbit immunizations. Complementary peptides were coupled to an artificial carrier, developed in our laboratory, in order to enhance the complementary potency of cpep349-364 and its counterpart. This carrier, named Sequential Oligopeptide Carrier, SOC(n), formed by the repeating tripeptide Lys-Aib-Gly, adopts helical conformation, which allows the anchored peptide epitopes to preserve their initial reactivity such as molecular recognition, antigenicity/immunogenicity. Our study provides proof of evidence of specific interactions between idiotypic (Id)/anti-idiotypic (anti-Id) antibodies generated in immunized animals by the sense epitope (conjugate I) of La/SSB and its complementary counterpart (conjugate II). It was also demonstrated that the Id/anti-Id association is specifically disrupted by adding either the sense epitope (conjugate I) or its complementary counterpart (conjugate II). A mutual neutralization of Id/anti-Id antibodies was observed in vivo, which implies that generation of anti-Id antibodies by immunization with the complementary La/SSB epitope could scavenge the anti-La/SSB response.

A palmitoyl-tailed sequential oligopeptide carrier for engineering immunogenic conjugates

The main guideline in designing effective immunogens as vaccine candidates capable of eliciting potent and specific immune responses is to combine B/T cell epitopes and adjuvants as immunostimulators on the same carrier that links the major histocompatibility complex with T cell receptors. Aiming at contributing to the development of carriers for human usage a helicoid type sequential oligopeptide carrier, SOC(n)-II, formed by the repeating tetrapeptide unit (Aib-Lys-Aib-Gly)(n), n=2-7, elongated from the amino-terminus by the palmitoyl group, known for its adjuvanticity, is now presented. The main B cell epitope, PPGMRPP, of the Sm autoantigen against which the majority of antibodies in patients with systemic lupus erythematosus is directed, was coupled to the Lys-N(epsilon)H(2) groups of the carrier in four copies and the resulting conjugate Palm-SOC(4)-II-Sm(4) was subjected to animal immunizations without utilizing any adjuvant. The induced immune response was comparable with that produced when Ac-SOC(4)-II-Sm(4) was administered in animals following the conventional immunization protocol of complete/incomplete Freund's adjuvant. High titers of anti-Palm-SOC(4)-II-Sm(4) antibodies were generated, which recognize the priming immunogenic conjugate, as well as reconstituted Sm mimics but not the carrier alone. It is concluded that Palm-SOC(n)-II carrier is a valuable tool for engineering immunogens eliciting enhanced and specific humoral immune responses.

Influence of sequential oligopeptide carriers on the bioactive structure of conjugated epitopes: Comparative study of the conformation of aHerpes simplex virus glycoprotein gD-1 epitope in the free and conjugated form, and protein “built-in” crystal structure

Synthetic carriers play an important role in immunogen presentation, due to their ability of inducing improved and specific responses to conjugated epitopes. Their influence on the bioactive conformation of the epitope, though admittedly crucial for relevant in vitro and in vivo applications, is difficult to evaluate, given the usual lack of information on the complex conformational features determined by the nature of the carrier and the mode of ligation. Using the Herpes simplex virus glycoprotein D-1 epitope (Leu(9)-Lys-Nle-Ala-Asp-Pro-Asn-Arg-Phe-Arg-Gly-Lys-Asp-Leu(22)) as a model, we have performed a detailed conformational analysis on the free epitope peptide in solution and on three constructs in which the epitope was conjugated to sequential oligopeptide carriers {Ac-[Lys-Aib-Gly](4)-OH (SOC(4))} (through either a thioether or an amide bond; Ac: acetyl) and polytuftsin oligomers {H-[Thr-Lys-Pro-Lys-Gly](4)-NH(2) (T20)}, (through a thioether bond). The analysis of the epitope conformation in the parent protein, in carrier-conjugated and free form, suggests that the beta-turn structure of the -Asp(13)-Pro-Asn-Arg(16)- segment is highly conserved and independent of the epitope form. However, small conformational variations were observed at the C-terminal part of the epitope, depending on the nature of the carrier.

Sequential oligopeptide carriers, SOCn, as scaffolds for the reconstitution of antigenic proteins: applications in solid phase immunoassays

A new class of helicoid type sequential oligopeptide carriers (SOC), for anchoring antigenic epitopes, has been modeled from the repetitive Lys-Aib-Gly (SOC(n)-I) and Aib-Lys-Aib-Gly (SOC(n)-II) units aiming to the development of scaffolds with predetermined 3D structures. Conformational analysis showed that the SOC(n) carriers adopt 3(10)-helical structures, while the SOC(n)-conjugates retain their original active conformations and they interact neither to the carriers nor to each other. It is concluded that the helicoid structure of SOC(n) helps the reconstitution and/or mimicking of the native forms of the epitopes so that potent antigens are generated for developing specific, sensitive and reproducible immunoassays.

T cell help is required to induce idiotypic-anti-idiotypic autoantibody network after immunization with complementary epitope 289-308aa of La/SSB autoantigen in non-autoimmune mice

Immunotherapies against autoimmune diseases have been of limited success. Preventive vaccines could be developed on the basis to abrogate unwanted immune responses to defined autodeterminants. In this study it is shown that immunization of BALB/c mice with two linear T and B cell epitopes of the human La/SSB autoantigen (spanning the regions 289-308aa and 349-364aa) and their complementary forms specified by the complementary mRNA, results in characteristic B and T cell responses. Mice immunized with the 289-308aa epitope or its complementary peptide elicited specific antibodies against both epitopes. In contrast, mice immunized with the 349-364aa epitope or its complementary peptide mounted antibody titres against the immunizing peptide only. According to these data, the 289-308aa epitope and its complementary form were capable to generate an idiotypic-anti-idiotypic response, which were cross-regulated. Peptide-specific T cell proliferation and cytokine production in vitro revealed the induction of a two-stage T helper response (Th1-->Th2 type) after immunization with either the epitope 289-308 or its complementary peptide. IgG1 was the predominant subclass after immunization with the two forms of epitopes 289-308 and 349-364, while a response of the IgG2b > IgG2a was obtained after the immunization with the complementary form of 349-364 epitope reflecting the TH2/TH1 polarization, respectively. Our data suggest that the complementary peptides of two immunodominant epitopes of human LaSSB can mimic the autoantibodies against these epitopes and establish an active idiotypic-anti-idiotypic network.

Multiple anchoring of myelopeptides on sequential oligopeptide carriers (SOC(n)): synthesis, conformation and studies in human leukemia cells

Myelopeptides, MP-6 (Val-Asp-Pro-Pro) and MP-4 (Phe-Arg-Pro-Arg-Ile-Met-Thr-Pro), induce metabolic changes in human leukemia cells, HL-60, characteristic of the differentiation process, which should be regarded as a promising therapeutic approach in cancer and related diseases. With the aim to optimize the differentiation effect of MPs, they were coupled to the Lys-N(epsilon)H(2) groups of a sequential oligopeptide carrier Ac-(Lys-Aib-Gly)(4), SOC(4), and the constructs obtained were studied. The rigid 3(10) secondary structure of the carrier is preserved even after linkage of the MPs, which also maintain their initial conformations without interacting either with each other or with the carrier, as demonstrated by (1)H nuclear magnetic resonance (NMR) spectroscopy. It is concluded that the carrier accommodates the presentation of MPs, thus improving their differentiation effect on human leukemia cells.

A diepitopic sequential oligopeptide carrier (SOCn) as mimic of the sm autoantigen: synthesis, conformation and biological assays

Anti-Sm (Sm: U1-U6 RNA-protein complex) antibodies are usually considered highly specific for systemic lupus erythematosus (SLE), while anti-U1RNP (U1RNP: U1RNA-protein complex) are thought of as diagnostic criteria for the mixed connective tissue disease (MCTD). However, both antibody specificities coexist in SLE and MCTD, in varying percentages. Although the anti-Sm/anti-U1RNP immunological cross-reactivity has been initially attributed to a common motif, PPXY(Z)PP (where X, Y, Z are various amino acids), found in the Sm, U1-A and U1-C autoantigens, it appears that the conformational features of the Sm epitopes also play an important role in the immunoreactivity. The PPGMRPP and PPGIRGP main epitopes of the Sm antigen were coupled in duplicate to the tetrameric Ac-(Lys-Aib-Gly)4-OH, SOC4, carrier to form the [(PPGMRPP)2, (PPGIRGP)2]-SOC4 construct as a mimic of the native Sm. It was found that: (i) the 3(10) helical structure of SOC4 allows the epitopes to adopt an exposed orientation, similar to their free forms, that facilitates their recognition from the anti-Sm antibodies, and (ii) the U1-RNP cross-reactivity is minimized.

The position of the LysN epsilon H2-grafted antigens along the sequential oligopeptide carrier, Ac-(Aib-Lys-Aib-Gly)n (SOCn-II), influences the antibody recognition: application to the Sm main autoimmune epitope

A sequential oligopeptide carrier of antigenic peptides is presented, incorporating two Aib residues in each repetitive moiety: Ac-(Aib-Lys-Aib-Gly)(n) (SOC(n) -II; n = 2-4). The conformational study, by (1)H-nmr, CD, and Fourier transform ir spectroscopy, indicated that the SOC(n) -II carrier displays a pronounced 3(10)-helix, compared to the Ac-(Lys-Aib-Gly)(n) (SOC(n) -I) carrier of the same approximately backbone length, previously reported. One of the dominant autoimmune epitopes of the Sm and U1RNP cellular components, the PPGMRPP sequence, was coupled to the Lys-N(epsilon)H(2) groups of the SOC(n) -II carrier and used as antigenic substrate for detecting anti-Sm/U1RNP autoantibodies in ELISA assays. Anti-Sm antibodies are highly specific for systemic lupus erythematosus, while anti-U1RNP are specific for mixed connective tissue disease. The anti-(PPGMRPP)(5)-SOC(n) -II ELISA was compared with the anti-(PPGMRPP)(n) -SOC(n) -I ELISA, provided that both antigenic substrates possess the same amount of the epitope replicates. The significance of the lysine positions along the oligopeptide backbone of the carrier for a favorable antibody recognition of the anchored antigens is also examined.