Novel anoplin-based (lipo)-peptide models show potent antimicrobial activity.

The subject of this study is the synthesis and biological evaluation of anoplin-based (Gly-Leu-Leu3 -Lys-Arg5 -Ile-Lys-Thr8 -Leu-Leu-NH2 )-designed (lipo)-peptides, aiming at the development of new antibiotic substances. The design of synthetic compounds based on natural bioactive molecules is an optimistic strategy for the development of new pharmaceutics. Antimicrobial peptides (AMPs) and (lipo)-peptides are two classes of promising compounds, with characteristics that allow them to express their activity by differentiated mechanisms of action. On this basis, anoplin, a natural AMP, was used as a scaffold to design five peptides and seven lipopeptide analogs of them. Substitutions were made on residues Leu3 and Arg5 of the interphase and on Thr8 of the polar phase, as well as N-terminus conjunctions with octanoic and decanoic acid. The outcome of the biological evaluation revealed that some analogs might have substantial clinical potential. Specifically, Ano 1-F, Ano 3-F, Ano 4-C10 , and Ano 5-F are strongly active against Gram-negative bacteria at minimum inhibitory concentration (MIC) values of 3 µg/ml, while Ano 4-F is active against Gram-positive bacteria at 1 µg/ml. Ano 2-C10 , C10 -Gly-Leu-Lys3 -Lys-Ile5 -Ile-Lys-Lys8 -Leu-Leu-NH2 , is the most promising compound (MIC = 0.5 µg/ml) for the development of new pharmaceutics. The conformational features of the synthetic peptides were investigated by circular dichroism spectroscopy, and their physicochemical parameters were calculated. Our study shows that appropriate substitutions in the anoplin sequence in combination with Nα -acylation may lead to new effective AMPs.

Cationic amphipathic peptide analogs of cathelicidin LL-37 as a probe in the development of antimicrobial/anticancer agents.

Cathelicidin LL-37 belongs to the class of human defense peptides and is overexpressed in many cancers. Segments of LL-37 derived through biochemical processes have a wide range of activities. In this study, novel analogs of the 13-amino acid cathelicidin 17-29 amide segment F17 KRIV21 QR23 IK25 DF27 LR-NH2 were prepared and examined for their antimicrobial and hemolytic activities, as well as for their cytotoxicity on cancer bronchial epithelial cells. Selected substitutions were performed on residues R23 and K25 in the hydrophilic side, V21 and F27 in the hydrophobic side of the interphase, and F17 that interacts with cell membranes. Specific motifs IIKK and LLKKL with anticancer and antimicrobial activities isolated from animals were also inserted into the 17-29 fragment to investigate how they affect activity. Substitution of the amino-terminal positive charge by acetylation and replacement of lysine by the aliphatic leucine in the peptide analog Ac-FKRIVQRIL25 DFLR-NH2 resulted in significant cytotoxicity against A549 cancer cells with an IC50 value 3.90 µg/mL, with no cytotoxicity to human erythrocytes. The peptide Ac-FKRIVQI23 IKK26 FLR-NH2 , which incorporates the IIKK motif and the peptides FKRIVQL23 L24 KK26 L27 LR-NH2 and Ac-FKRIVQL23 L24 KK26 L27 LR-NH2 , which incorporate the LLKKL motif, displayed potent antimicrobial activity against gram-negative bacteria (MIC 3-7.5 µg/mL) and substantial cytotoxicity against bronchial epithelial cancer cells, (IC50 12.9-9.8 µg/mL), with no cytotoxic activity for human erythrocytes. The helical conformation of the synthetic peptides was confirmed by circular dichroism. Our study shows that appropriate substitutions, mainly in positions of the interphase, as well as the insertion of the motifs IIKK and LLKKL in the cathelicidin 17-29 segment, may lead to the preparation of effective biological compounds.

Synthesis and biological activity of lipophilic analogs of the cationic antimicrobial active peptide anoplin.

Anoplin is a short natural cationic antimicrobial peptide which is derived from the venom sac of the solitary wasp, Anoplius samariensis. Due to its short sequence G1 LLKR5 IKT8 LL-NH2 , it is ideal for research tests. In this study, novel analogs of anoplin were prepared and examined for their antimicrobial, hemolytic activity, and proteolytic stability. Specific substitutions were introduced in amino acids Gly1 , Arg5 , and Thr8 and lipophilic groups with different lengths in the N-terminus in order to investigate how these modifications affect their antimicrobial activity. These cationic analogs exhibited higher antimicrobial activity than the native peptide; they are also nontoxic at their minimum inhibitory concentration (MIC) values and resistant to enzymatic degradation. The substituted peptide GLLKF5 IKK8 LL-NH2 exhibited high activity against Gram-negative bacterium Zymomonas mobilis (MIC = 7 µg/ml), and the insertion of octanoic, decanoic, and dodecanoic acid residues in its N-terminus increased the antimicrobial activity against Gram-positive and Gram-negative bacteria (MIC = 5 µg/ml). The conformational characteristics of the peptide analogs were studied by circular dichroism. Structure activity studies revealed that the substitution of specific amino acids and the incorporation of lipophilic groups enhanced the amphipathic α-helical conformation inducing better antimicrobial effects. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Collagen and keratin polypeptide models for assessing the natural and artificial protein decay of organic materials.

Among the materials constituting the natural and cultural heritage, organic materials of proteinaceous origin as bone (collagen), parchment and woolen textiles (keratin) are the most susceptible to damage and decay because of their exposure to air pollution, inappropriate values of ambient temperature, humidity and light. Aiming at contributing to the development of a reliable and reproducible immunoassay for the evaluation of collagen and keratin decay, three polypeptide models of these proteins were designed, synthesized and studied. Polypeptide [Pro-Ser(OBzl)-Gly]n incorporates the typical motif Pro-X-Gly of collagen; polypeptide [Pro-Cys(Acm)-Gly]n is a model of the C-terminal domain of type I keratin, corresponding to the repeating unit Pro-Cys-X of keratin, while polypeptide Ac-YRSGGGFGYRSGGGFGYRS-ßAla-NH2 encloses the characteristic repeating sequence GGGFGYRS of the N-terminal part of Type II keratin. These polypeptides may be considered as simplified models that mimic fragments of collagen and keratin resulting from artificial and natural ageing or decay. It is concluded that high recognition of anti-polypeptide antibodies, produced after immunizations, by the bone, parchment and textile samples is indicative of high deterioration, while high anti-collagen or anti-keratin recognition is indicative of low deterioration. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Palmitoylated peptide, being derived from the carboxyl-terminal sequence of the integrin αIIb cytoplasmic domain, inhibits talin binding to αIIbß3.

The αIIb cytoplasmic domain of platelet integrin αIIbß3 contains an unorganized acidic membrane-distal (1000)LEEDDEEGE(1008) region. We have shown that a platelet permeable peptide corresponding to the above region the palmitoyl-K-LEEDDEEGE (pal-K-1000-1008) inhibits platelet aggregation induced by thrombin or by pal-K-989-995, a palmitoylated peptide corresponding to the membrane-proximal αIIb cytoplasmic domain (989)KVGFFKR(995). We now tested the anti-aggregatory activity of (i) a lipid-modified scrambled acidic peptide (pal-K-GDDEELEEE), (ii) two smaller peptides derived from the acidic amino sequence: palmitoyl-K-(1000)LEEDDE(1005) (pal-K-1000-1005) and palmitoyl-K-(1005)EEGE(1008) (pal-K-1005-1008) and (iii) lipid-modified palmitoyl-acidic peptides with alanine (Ala) substitution at residues 1001, 1003, 1004 and 1005 and one peptide with a double Ala substitution at residues 1001 and 1004 of the 1000-1008 sequence. All the peptides tested showed an inhibitory activity, however, the palmitoylated peptide with the natural and the whole acidic sequence, being the most active. Our results suggest that the whole acidic sequence, rather than some specific amino acids, contributes to the aggregation inhibitory activity. The inhibitory peptide, pal-K-1000-1008, inhibited the association of talin with αIIbß3 in thrombin-activated platelets, as demonstrated by co-immunoprecipitation experiments, while the scrambled peptide was inefficient. We suggest that, by interacting with αIIb cytoplasmic domain, pal-K-1000-1008 has an anti-aggregatory inhibitory activity due to a specific inhibition of talin binding to αIIbß3.

Sialic acid and sialyl-lactose glyco-conjugates: design, synthesis and binding assays to lectins and swine influenza H1N1 virus.

The terminal parts of the influenza hemagglutinin (HA) receptors α2,6- and α2,3-sialyllactoses were conjugated to an artificial carrier, named sequential oligopeptide carrier (SOC(4) ), to formulate human and avian receptor mimics, respectively. SOC(4) , formed by the tripeptide unit Lys-Aib-Gly, adopts a rigid helicoids-type conformation, which enables the conjugation of biomolecules to the Lys-N(ε) H(2) groups. By doing so, it preserves their initial conformations and functionalities of the epitopes. We report that SOC(4) -glyco-conjugate bearing two copies of the α2,6-sialyllactose is specifically recognized by the biotinylated Sambucus nigra (elderberry) bark lectin, which binds preferentially to sialic acid in an α2,6-linkage. SOC(4) -glyco-conjugate bearing two copies of the α2,3-sialyllactose was not recognized by the biotinylated Maackia amurensis lectin, despite its well-known α2,3-sialyl bond specificity. However, preliminary immune blot assays showed that H1N1 virus binds to both the SOC(4) -glyco-conjugates immobilized onto nitrocellulose membrane. It is concluded that Ac-SOC(4) [(Ac)(2) ,(3'SL-Aoa)(2) ]-NH(2) 5 and Ac-SOC(4) [(Ac)(2) ,(6'SL-Aoa)(2) ]-NH(2) 6 mimic the HA receptors. These findings could be useful for easy screening of binding and inhibition assays of virus-receptor interactions.

Influenza virus H5N1 hemagglutinin (HA) T-cell epitope conjugates: design, synthesis and immunogenicity.

The influenza virus, major surface glycoprotein hemagglutinin (HA) is one of the principal targets for the development of protective immunity. Aiming at contributing to the development of a vaccine that remains the first choice for prophylactic intervention, a reconstituted model of HA, mimicking its antigenic properties was designed, synthesized and tested in mice for the induction of protective immunity. Four helper T lymphocyte [HTL (T(1) , T(3) , T(7) and T(8) )] and four cytotoxic lymphocyte [CTL (T(2) , T(4) , T(5) and T(6) )] epitopes were coupled in two copies each to an artificial carrier, SOC(4) , which was formed by the repeating tripeptide Lys-Aib-Gly. The helical conformation of the SOC(4) -conjugates preserves the initial topology of the attached epitopes, which is critical for their immunogenic properties. Survival of immunized animals, ranged from 30 to 50%, points out the induction of protective immunity by using the SOC(4) -conjugates.

Apolipoprotein A-I peptide models as probes to formulate potential inhibitors of the low-density lipoprotein oxidation.

Apolipoprotein A-I (apoA-I), which constitutes the principal protein component of high-density lipoprotein, is responsible for its major antiatherogenic functions. Aiming at contributing to the development of potent inhibitors of low-density lipoprotein (LDL) peptide models of helices 4,6 and 9,10 of apoA-I were designed and synthesized. Specific amino acid substitutions, resulting in transformation of the original helix class A and Y to G according to the Schiffer and Edmundson helical wheel representation, were introduced in order to validate the contribution of these modifications in the inhibitory activity of the synthesized peptide models against the LDL oxidation. The role of Met at positions 112 (helix 4) and 148 (helix 6) as oxidant scavenger was also investigated. The helical characteristics of all the peptide models were studied by CD in membrane-mimicking microenvironments and compared with the original helices.

Inhibition of platelet activation by peptide analogs of the beta(3)-intracellular domain of platelet integrin alpha(IIb)beta(3) conjugated to the cell-penetrating peptide Tat(48-60).

Activation of the platelet integrin-receptor alpha(IIb)beta(3) is the final pathway of platelet aggregation, regardless of the initiating stimulus. Many studies suggest that there are several cytoplasmic proteins such as talin and beta(3)-endonexin that bind to N(744)PLY(747) and N(756)ITY(759) motif of the beta(3) cytoplasmic tail and play the major role in the receptor activation. In this study, we investigated the role of the membrane distal region of human beta(3) cytoplasmic tail and specifically the N(743)NPLYKEA(750) and T(755)NITYRGT(762) sequence that contains an NXXY motif, in platelet aggregation, secretion, alpha(IIb)beta(3) activation (PAC-1 binding) and fibrinogen binding. We synthesized two peptides corresponding to the above sequences as well as their conjugates with the Tat(48-60) cell-penetrating peptide. The capability of conjugates to penetrate the platelet membrane was investigated with confocal laser scanning microscopy using carboxyfluorescein (CF)-labeled peptides. Our results showed that the conjugated with the Tat(48-60) sequence peptides penetrate the platelet membrane and inhibit platelet aggregation in both PRP and washed platelets in a dose-dependent manner. The Tat-beta(3)743-750 conjugate exhibited similar inhibitory activity in PRP and in washed platelets whereas the Tat-beta(3)755-762 conjugate was more potent inhibitor of aggregation in washed platelets than in PRP. Both conjugated peptides were also able to inhibit P-selectin membrane expression as well as PAC-1 and fibrinogen binding to the platelets, the Tat-beta(3)755-762 conjugate being more potent than Tat-beta(3)743-750. The Tat(48-60) peptide and the peptides beta(3)743-750 and beta(3)755-762, which were not conjugated to the Tat(48-60) sequence, did not exhibit any inhibitory effect on the above parameters. In conclusion, the present study shows for the first time that the peptide analogs of the intracellular domain of the beta(3) subunit beta(3)743-750 and beta(3)755-762 conjugated to the cell-penetrating peptide Tat(48-60) are capable of penetrating the platelet membrane and expressing biological activity by inhibiting the activation of alpha(IIb)beta(3), the fibrinogen binding to the activated receptor as well as platelet aggregation. Further studies are necessary to support whether such conjugated peptides may be useful tools for the development of potent antiplatelet agents acting intracellularly through the platelet integrin alpha(IIb)beta(3).

A palmitoylated peptide, derived from the acidic carboxyl-terminal segment of the integrin alphaIIb cytoplasmic domain, inhibits platelet activation.

Platelet integrin alpha(IIb)beta(3) contains an acidic membrane distal motif, 1000LEEDDEEGE1008, in the cytoplasmic domain of the alpha(IIb) subunit. We showed that a lipid-modified peptide corresponding to the above region, palmitoyl-K-LEEDDEEGE (pal-K-1000-1008), is platelet permeable and has inhibited platelet aggregation induced by 0.4 U/ml of thrombin (IC50 = 164 microM). Moreover the peptide inhibited both Fibrinogen and PAC-1, binding to activated platelets. The non palmitoylated analog was inactive. A modified, scrambled acidic peptide (palmitoyl-K-GDDEELEEE), showed significant lower inhibitory activity than pal-K-1000-1008. A palmitoylated peptide corresponding to the membrane proximal cytoplasmic domain of alpha(IIb), 989KGVFFKR995 (pal-989-995), is known to specifically induce platelet aggregation. Pal-K-1000-1008 was an inhibitor of human washed platelet aggregation induced by pal-K-989-995 (IC50 = 15 microM). Moreover, pal-K-1000-1008 inhibited phosphorylation of ERK and FAK, two protein kinases involved in platelet activation and aggregation. Our results favour the assumption that the interaction of the membrane proximal sequence 989KGVFFKR995 of the cytoplasmic domain of alpha(IIb) with the acidic terminal 1000LEEDDEEGE1008 motif may be an important structural factor in platelet signaling, leading to platelet activation and aggregation.

Innovative, multifunctional sequential oligopeptide carriers Soc(n)-I and SOC(n)-II: functions-technology-perspectives.

An innovative type of multifunctional helicoid artificial carriers, formed by the repetitive Lys-Aib-Gly (SOC(n)-I) or by the Aib-Lys-Aib-Gly (SOC(n)-II), with structural rigidity and regularity were successfully applied in our laboratory for anchoring antigenic/immunogenic peptides. The carriers, designed to display a predetermined 3D structure, adopt the 3(10) helical conformation, while the attached peptides preserve their original "active" conformation. The constructed conjugates were used as substrates in solid phase immunoassays, as well as for generating potent and specific immune responses.

Zinc ion dependent B-cell epitope, associated with primary Sjogren's syndrome, resides within the putative zinc finger domain of Ro60kD autoantigen: physical and immunologic properties.

The Ro/La ribonucleoprotein (RNP) complex is composed of the proteins Ro60kD, Ro52kD, and La48kD that are in association with one small cytoplasmic RNA (YRNA). Specific protein-RNA and protein-protein interactions are thought to occur through the RNP and zinc-finger secondary structure elements of the Ro60kD protein. The aim of our study was to investigate the antigenic properties of the zinc finger domain of the Ro60KD autoantigen and its contribution to the formation of Ro/La RNP complex. It was found that the peptide VSLVCEKLCNEKLLKKARIHPFHILIA (Zif-1), which corresponds to the natural sequence of the zinc finger domain (301-327), and the peptide C(Acm)NEKLLKKARIC(Acm), analogous to the intermediate loop 310-319 (Zif-3) of the same domain of Ro60KD, are recognized by the majority of anti-Ro/SSA and anti-La/SSB positive sera (82.6% and 77.1%, respectively) in the absence of zinc ions. The same sera failed to react with Zif-1 peptide in the presence of Zn2+. In contrast, the addition of zinc ions was necessary for the binding of Zif-1 to recombinant Ro52KD as shown by direct binding experiments of the recombinant protein with synthetic peptides. Our data suggest the zinc finger domain of Ro60kD contains a B-cell epitope with high specificity for primary Sjogren's syndrome. Furthermore, depending on the presence of zinc ions, the zinc finger domain of the Ro60KD protein can exist in two different conformational states favoring either an interaction with the Ro52KD protein or binding with autoantibodies.

Complementary peptide epitopes and anti-idiotypic antibodies in autoimmunity.

Application of complementary B and T cell epitopes in inducing anti-idiotypic and anti-clonotypic antibodies capable of regulating or suppressing the autoimmune responses in experimental autoimmune myasthenia gravis (EAMG), allergic neuritis (EAN) and allergic encephalomyelitis (EAE) has been the stimulus of many research efforts. Studies on the idiotypic/anti-idiotypic network of anti-La/SSB positive sera from patients with Sjogren's Syndrome (SS) and Systemic Lupus Erythematosus (SLE) and on animals immunized with the complementary epitopes are presented.

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.

Prime boost vaccination approaches with different conjugates of a new HIV-1 gp41 epitope encompassing the membrane proximal external region induce neutralizing antibodies in mice.

Peptide mimics of epitopes for pathogen-specific antibodies present in patient sera can be selected based on the phage display technology. Such mimotopes potentially represent vaccine candidates in case they are able to induce neutralizing antibodies upon vaccination. Here we analyze the immunogenicity of different conjugates of epitope EC26-2A4 localizing to the membrane proximal external region (MPER) of the HIV-1 transmembrane protein gp41. The EC26-2A4 epitope, which overlaps with that of the broadly neutralizing monoclonal antibody (mAb) 2F5, was coupled to sequential oligopeptide carriers (SOC) or to palmitoyl acid for better immunogenicity. Upon prime-boost immunizations of mice, the peptide conjugates induced EC26-2A4 specific antibodies in all settings and mice sera neutralized HIV-1SF162.LS in standardized neutralization assays. Thus, the EC26-2A4 MPER epitope represents a promising vaccine candidate for further analysis in larger animals with respect to the breadth of the neutralizing antibodies induced.

Physical activity and natural anti-VIP antibodies: potential role in breast and prostate cancer therapy.

BACKGROUND: There is convincing evidence from numerous clinical and epidemiological studies that physical activity can reduce the risk for breast and prostate cancer. The biological mechanisms underlying this phenomenon remain elusive. Herein we suggest a role for naturally produced antibodies reactive with the vasoactive intestinal peptide (VIP) in the suppression of breast and prostate cancer, which we believe could offer a possible molecular mechanism underlying control of these cancers by physical exercise. METHODOLOGY AND RESULTS: We found that sera from individuals having breast and prostate cancers have decreased titers of VIP natural antibodies as demonstrated by a lower reactivity against peptide NTM1, having similar informational and structural properties as VIP. In contrast, sera collected from elite athletes, exhibited titers of natural NTM1-reactive antibodies that are significantly increased, suggesting that physical activity boosts production of these antibodies. SIGNIFICANCE: Presented results suggest that physical exercise stimulates production of natural anti-VIP antibodies and likely results in suppression of VIP. This, in turn, may play a protective role against breast and prostate cancers. Physical exercise should be further investigated as a potential tool in the treatment of these diseases.

HLA-DQ7 beta(1) and beta(2) derived peptides as immunomodulators.

Modulation of protein-protein interactions involved in the immune system by using small molecular mimics of the contact interfaces may lead to the blockage of the autoimmune response and the development of drugs for immunotherapy. The nonpolymorphic beta-regions, exposed to the microenvironment, of the modeled HLA-DQ7, which is genetically linked to autoimmune diseases, were determined. Peptides 132-141 and 58-67, located at the beta(1) and beta(2) domains of HLA-DQ7, respectively, were tested for their involvement in the interactions with CD4(+) T lymphocytes. Linear, cyclic, and dimeric analogs that mimic the exposed surfaces of HLA-DQ7 were designed and synthesized. Their immunosuppressory activities, found in the secondary, humoral immune response to sheep erythrocytes (SRBC) in mice in vitro, ranged from 11% to 53%. The significance of the total charge of the peptides, the pattern of the hydrogen bonding, and the presence of secondary structure were investigated in relation to the immunomodulatory effect of the peptides. Two dimeric analogs of the HLA-DQ7 58-67 fragment, consisting of the two monomers covalently linked by a polyethylene glycol (PEG) spacer, able to mimic the superdimers, were also synthesized and studied. As the 58-67 segment is located at the beta(1) region of HLA-DQ7, close to the major histocompatibility complex (MHC) groove, one may assume that the 58-67 peptide could accommodate the association between T-cell receptor (TCR) and human leukocyte antigen (HLA) by activating a co-stimulatory molecule of the TCR/HLA interaction. This hypothesis is supported by the confocal laser image of the fluorescein-labeled 58-67 peptide and by the fact that it is an immunostimulator at low concentration.

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.

Design and synthesis of cationic Aib-containing antimicrobial peptides: conformational and biological studies.

Development of antimicrobial peptides has attracted considerable attention in recent years due to the excessive use of antibiotics, which has led to multiresistant bacteria. Cationic amphiphilic Aib-containing peptide models Ac-(Aib-Arg-Aib-Leu)(n)-NH2, n = 1-4, and sequential cationic polypeptides (Arg-X-Gly)(n), X = Ala, Val, Leu, were prepared and studied for their antimicrobial and hemolytic activity, as well as for their proteolytic stability. Ac-(Aib-Arg-Aib-Leu)(n)-NH2, n = 2, 3 and the polypeptide (Arg-Leu-Gly)(n) exhibited significant antimicrobial activity, and they were nontoxic at their MIC values and resistant, in particular the Aib-peptide models, to enzymatic degradation. The conformational characteristics of the peptide models were studied by circular dichroism (CD). Structure-activity relationship studies revealed the importance of the amphipathic alpha-helical conformation of the reported peptides in inducing antimicrobial effects. It is concluded that peptide models comprising cationic amino acids (Arg), helicogenic and noncoding residues (Aib) and/or hydrophobic and helix-promoting components (Leu) may lead to the development of antimicrobial therapeutics.