Association between nasal colonization of Staphylococcus aureus and surgical site infections in spinal surgery patients: a systematic review and meta-analysis.

OBJECTIVE: The study aimed at examining the relationship between nasal colonization of Staphylococcus aureus (SA) or methicillin-resistant Staphylococcus aureus (MRSA) and the risk of SSI after spinal surgeries MATERIALS AND METHODS: PubMed, CENTRAL, Scopus, Web of Science, and Embase databases up to 24th September 2022 for articles on nasal colonization of SA/MRSA and spine surgeries. RESULTS: Ten studies were included. Meta-analysis revealed that the incidence of SSI was not significantly different between SA-positive and SA-negative patients (RR: 0.75, 95% CI: 0.47, 1.18 I2=2% p=0.21). It was noted that when no decolonization was done, there was no statistically significant difference in the risk of SSI between MRSA positive and MRSA negative patients, but a tendency of higher SSI in MRSA carriers (RR: 2.40, 95% CI: 0.91, 6.32, I2=37% p=0.08). However, in the subgroup analysis with decolonization, the risk of SSI was significantly higher in the MRSA-positive group (RR: 2.99, 95% CI: 1.27, 7.03, I2=24% p=0.01). Specifically, the risk of MRSA-SSI was significantly higher in MRSA carriers with (RR: 6.05, 95% CI: 1.14, 31.99, I2=43% p=0.03) and without decolonization (RR: 7.54, 95% CI: 1.43, 39.85, I2=38% p=0.02). CONCLUSIONS: Evidence from observational studies indicates that only MRSA nasal colonization increases the risk of SSIs in spinal surgery patients. Nasal decolonization was unable to reduce the risk of overall or MRSA-specific SSIs in MRSA carriers. Evidence was biased due to the extremely small number of MRSA-positive patients in the studies and the lack of adjustment of confounding factors.

RT-PCR detection of the expression of the polymerase gene of a novel reptilian herpesvirus in tumor tissues of green turtles with fibropapilloma.

An alpha-herpesvirus has recently been associated with green turtle fibropapilloma (FP). To further understand the etiological role of this newfound green turtle herpesvirus (GTHV) in the pathogenesis of FP, expression of GTHV polymerase ( pol) gene was determined in tumors and normal-appearing nontumor tissues and organs from five green turtles suffering multiple fibropapillomas, using reverse transcription-polymerase chain reaction (RT-PCR). Amplification of RNA prepared from tumor tissues evidenced the substantial expression of GTHV DNA pol gene in all specimens tested (15/15). However, GTHV pol gene expression in normal-appearing tissues and organs of affected animals was limited (4/45), and GTHV mRNA was detected only in periorbital tissue (1/2), gall bladder (2/5) and lung (1/5) by nested RT-PCR. By contrast, RT-PCR evaluation of RNA isolated from non-tumored turtles revealed undetectable expression of this herpesvirus gene. cDNA sequence analysis revealed that GTHV gene sequences were identical in different tumors. Our data represent the first evidence of the replication of this putative turtle herpesvirus in affected green turtles and fibropapilloma tissues are always active sites of GTHV mRNA synthesis. These findings extend and substantiate the pathogenic association of GTHV with FP.

Tandem peptide ligation for synthetic and natural biologicals.

We describe the concept and methods of peptide ligation and tandem peptide ligation for preparing synthetic and natural biologicals. Peptide ligation is a segment coupling method for free peptides or proteins through an amide bond without the use of a coupling reagent or a protecting group scheme. Because unprotected peptides or proteins prepared from either a chemical or biochemical source are being used as building blocks, the ligation removes the size limitation for peptide and protein synthesis. A key feature of the peptide ligation is that the coupling reaction is orthogonal, i.e. it is specific to a particular alpha-amino terminus (NT). This NT-amino acid-specific feature permits the development of a tandem peptide ligation method employing three unprotected peptide segments containing different NT-amino acids to form consecutively two amide bonds, an Xaa-SPro (thiaproline) and then an Xaa-Cys. This strategy was tested in peptides ranging from 28 to 70 amino acid residues, including analogues of somatostatins and two CC-chemokines MIP-1alpha and MIP-1beta. The thiaproline replacements in these peptides and proteins did not result in altered biological activity. By eliminating the protecting group scheme and coupling reagents, tandem ligation of multiple free peptide segments in aqueous solutions enhances the scope of protein synthesis and may provide a useful approach for preparing protein biologicals and synthetic vaccines.

Activation barriers to structural transition determine deposition rates of Alzheimer's disease a beta amyloid.

Brain amyloid composed of the approximately 40-amino-acid human beta-amyloid peptide A beta is integral to Alzheimer's disease pathology. To probe the importance of a conformational transition in Abeta during amyloid growth, we synthesized and examined the solution conformation and amyloid deposition activity of A beta congeners designed to have similar solution structures but to vary substantially in their barriers to conformational transition. Although all these peptides adopt similar solution conformations, a covalently restricted Abeta congener designed to have a very high barrier to conformational rearrangement was inactive, while a peptide designed to have a reduced barrier to conformational transition displayed an enhanced deposition rate relative to wild-type A beta. The hyperactive peptide, which is linked to a heritable A beta amyloidosis characterized by massive amyloid deposition at an early age, displayed a reduced activation barrier to deposition consistent with a larger difference in activation entropy than in activation enthalpy relative to wild-type A beta. These results suggest that in Alzheimer's disease, as in the prion diseases, a conformational transition in the depositing peptide is essential for the conversion of soluble monomer to insoluble amyloid, and alterations in the activation barrier to this transition affect amyloidogenicity and directly contribute to human disease.

Design of salt-insensitive glycine-rich antimicrobial peptides with cyclic tricystine structures.

Cyclic peptide backbone and cystine constraints were used to develop a broadly active salt-insensitive antimicrobial peptide [Gly(6)]ccTP 1a with eight Gly residues in an 18-residue sequence. The importance of rigidity and amphipathicity imparted by the cyclic and cystine constraints was examined in two peptide series based on tachyplesin, a known beta-stranded antimicrobial peptide. The first series, which retained the charge and hydrophobic amino acids of tachyplesin, but contained zero to four covalent constraints, included a cyclic tricystine tachyplesin (ccTP 1). Corresponding [Gly(6)] analogues were prepared in a parallel series with all six bulky hydrophobic amino acids in their sequences replaced with Gly. Circular dichroism measurements showed that ccTP 1 and [Gly(6)]ccTP 1a exhibited well-ordered beta-sheet structures, while the less constrained [Gly(6)] analogues were disordered. Except for linear peptides assayed under high-salt conditions, peptides with increased or decreased conformational constraints retained broad activity spectra with small variations in potency of 2-10-fold compared to that of tachyplesin. In contrast, Gly replacement analogues resulted in large variations in activity spectra and significant decreases in potency that roughly correlated with the decreases in conformational constraints. Except against Escherichia coli, the Gly-rich analogues with two or fewer covalent constraints were largely inactive under high-salt conditions. Remarkably, the most constrained [Gly(6)]ccTP 1a retained a broad activity spectrum against all 10 test microbes in both low- and high-salt assays. Collectively, our results show that [Gly(6)]ccTP 1acould serve as a template for further analogue study to improve potency and specificity through single or multiple replacements of hydrophobic or unnatural amino acids.

Marked increase in membranolytic selectivity of novel cyclic tachyplesins constrained with an antiparallel two-beta strand cystine knot framework.

We have developed a highly constrained 18-residue cyclic peptide template based on the antimicrobial peptide tachyplesin-1 that features an end-to-end peptide backbone and a cystine knot-like motif with three evenly spaced disulfide bonds to cross-brace the antiparallel beta-strands and to approximate an amphiphatic "beta-tile"-like structure. Six beta-tile analogs were prepared to correlate different topological patterns with membranolytic specificity. Their conformations and antimicrobial and hemolytic activities were compared with tachyplesin-1 and the recently discovered Rhesus monkey theta defensin (RTD) which contains similar beta-tile structural elements. The beta-tile peptides and RTD retained broad spectrum antimicrobial activities. In general, they were less active than tachyplesin-1 in 10 tested organisms but their activity increased under high-salt (100 mM NaCl) rather than in low-salt conditions. The beta-tile peptides are highly nontoxic to human erythrocytes with EC(25) ranging from 600 to 4000 microM. Collectively, our results show that the design of a highly rigid peptide template is useful for further analog study to dissociate antimicrobial activity from cytotoxicity which would be helpful in discovering clinical applications for peptide antibiotics.

An unusual structural motif of antimicrobial peptides containing end-to-end macrocycle and cystine-knot disulfides.

Four macrocyclic cystine-knot peptides of 29-31 residues, kalata, circulin A and B (CirA and CirB), and cyclopsychotride, have been isolated from coffee plants but have undetermined physiological functions. These macrocycles and 10 of their analogs prepared by chemical synthesis were tested against nine strains of microbes. Kalata and CirA were specific for the Gram-positive Staphylococcus aureus with a minimum inhibition concentration of approximately 0.2 microM. They were relatively ineffective against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. However, CirB and cyclopsychotride were active against both Gram-positive and Gram-negative bacteria. In particular, CirB showed potent activity against E. coli with a minimum inhibitory concentration of 0.41 microM. All four cyclic peptides were moderately active against two strains of fungi, Candida kefyr and Candida tropicalis, but were inactive against Candida albicans. These macrocycles are cytotoxic and lysed human red blood cell with a lethal dose 50% of 400 microM. Modifying the Arg residue in kalata with a keto aldehyde significantly reduced its activity against S. aureus whereas blocking the arg in CirA produced no significant effect. The two-disulfide variants and their scrambled disulfide isomers exhibited antimicrobial profiles and potency similar to their native peptides. However, in high-salt assays (100 mM NaCl), few of these macrocyclic peptides, natives or analogs, retained antimicrobial activity. These results show that the macrocyclic peptides possess specific and potent antimicrobial activity that is salt-dependent and that their initial interactions with the microbial surfaces may be electrostatic, an effect commonly found in defensin antimicrobial peptides. Furthermore, their end-to-end cyclic structure with a cystine-knot motif represents a molecular structure of antimicrobials and may provide a useful template for the design of novel peptide antibiotics.

A biomimetic strategy in the synthesis and fragmentation of cyclic protein.

This paper describes a simple biomimetic strategy to prepare small cyclic proteins containing multiple disulfide bonds. Our strategy involves intramolecular acyl transfer reactions to assist both the synthesis and fragmentation of these highly constrained cyclic structures in aqueous solution. To illustrate our strategy, we synthesized the naturally occurring circulin B and cyclopsychotride (CPT), both consisting of 31 amino acid residues tightly packed in a cystine-knot motif with three disulfide bonds and an end-to-end cyclic form. The synthesis of these small cyclic proteins can be achieved by orthogonal ligation of free peptide thioester via the thia zip reaction, which involves a series of reversible thiol-thiolactone exchanges to arrive at an alpha-amino thiolactone, which then undergoes an irreversible, spontaneous ring contraction through an S,N-acyl migration to form the cyclic protein. A two-step disulfide formation strategy is employed for obtaining the desired disulfide-paired products. Partial acid hydrolysis through intramolecular acyl transfer of X-Ser, X-Thr, Asp-X, and Glu-X sequences is used to obtain the assignment of the circulins disulfide bond connectives. Both synthetic circulin B and CPT are identical to the natural products and, thus, the total synthesis confirms the disulfide connectivity of circulin B and CPT contain a cystine-knot motif of 1-4, 2-5, and 3-6. In general, our strategy, based on the convergence of chemical proteolysis and aminolysis of peptide bonds through acyl transfer, is biomimetic and provides a useful approach for the synthesis and characterization of large end-to-end cyclic peptides and small proteins.

A beta deposition inhibitor screen using synthetic amyloid.

The formation, growth, and maturation of brain amyloid "senile" plaques are essential pathological processes in Alzheimer's disease (AD) and key targets for therapeutic intervention. The process of in vitro deposition of A beta at physiological concentrations onto plaques in AD brain preparations has been well characterized, but is cumbersome for drug discovery. We describe here a high-through put screen for inhibitors of A beta deposition onto a synthetic template (synthaloid) of fibrillar A beta immobilized in a polymer matrix. Synthaloid is indistinguishable from plaques in AD brain (the natural template) in deposition kinetics, pH profile, and structure-activity relationships for both A beta analogs and inhibitors. Synthaloid, in contrast to current A beta aggregation screens, accurately predicted inhibitor potency for A beta deposition onto AD cortex preparations, validating its use in searching for agents that can slow the progression of AD and exposing a previously inaccessible target for drug discovery.

Restoration of the transcription activation function to mutant p53 in human cancer cells.

The p53 tumor suppressor gene product is a sequence-specific transcription activator frequently mutated in a variety of human malignancies. Typically, tumor-derived p53 missense mutants are defective in DNA binding and this is likely to result in a failure to active p53-regulated genes. Hence, restoring function to mutant p53 represents an attractive target to develop a novel cancer chemotherapeutic agent. We now show that a small chemically modified peptide derived from p53 restores sequence-specific DNA binding to a subset of p53 mutants. Moreover, when microinjected into human colon carcinoma cells this peptide restores the transcription activation function to endogenous mutant p53 protein. This is the first example showing that a small peptide molecule can reverse the effect of several inactivating missense mutations and restore protein function.

Point substitution in the central hydrophobic cluster of a human beta-amyloid congener disrupts peptide folding and abolishes plaque competence.

Alzheimer's disease (AD) is pathologically characterized by the presence of numerous insoluble amyloid plaques in the brain composed primarily of a 40-43 amino acid peptide, the human beta-amyloid peptide (A beta). The process of A beta deposition can be modeled in vitro by deposition of physiological concentrations of radiolabeled A beta onto preexisting amyloid in preparations of unfixed AD cerebral cortex. Using this model system, it has been shown that A beta deposition is biochemically distinct from A beta aggregation and occurs readily at physiological A beta concentrations, but which regions and conformations of A beta are essential to A beta deposition is poorly understood. We report here that an active congener, A beta (10-35)-NH2, displays time dependence, pH-activity profile, and kinetic order of deposition similar to A beta (1-40), and is sufficiently soluble for NMR spectroscopy in water under conditions where it actively deposits. To examine the importance of the central hydrophobic cluster of A beta (LVFFA, residues 17-21) for in vitro A beta deposition, an A beta (10-35)-NH2 analog with a single point substitution (F19T) in this region was synthesized and examined. Unlike A beta (10-35)-NH2, the F19T analog was plaque growth incompetent, and NMR analysis indicated that the mutant peptide was significantly less folded than wild-type A beta. These results support previous studies suggesting that the plaque competence of A beta correlates with peptide folding. Since compounds that alter A beta folding may reduce amyloid deposition, the central hydrophobic cluster of A beta will be a tempting target for structure-based drug design when high-resolution structural information becomes available.

Peptide synthesis using unprotected peptides through orthogonal coupling methods.

We describe an approach to the synthesis of peptides from segments bearing no protecting groups through an orthogonal coupling method to capture the acyl segment as a thioester that then undergoes an intramolecular acyl transfer to the amine component with formation of a peptide bond. Two orthogonal coupling methods to give the covalent ester intermediate were achieved by either a thiol-thioester exchange mediated by a trialkylphosphine and an alkylthiol or a thioesterification by C alpha-thiocarboxylic acid reacting with a beta-bromo amino acid. With this approach, unprotected segments ranging from 4 to 37 residues were coupled to aqueous solution to give free peptides up to 54 residues long with high efficiency.

Pegylated peptides. IV. Enhanced biological activity of site-directed pegylated GRF analogs.

Conditions have been developed for the site-specific pegylation (NH2-terminus, side-chain and carboxy-terminus) of a potent analog of growth hormone-releasing factor, [Ala15]-hGRF(1-29)-NH2. These pegylated peptides were prepared by solid-phase peptide synthesis using the Fmoc/tBu strategy, and were fully characterized by analytical HPLC, amino-acid analysis, 1H-NMR spectroscopy and laser desorption mass spectrometry. Biological activities of hGRF analogs were determined in vitro utilizing stimulation of growth hormone release by cultured rat pituitary cells as an index. GH-releasing potencies of the pegylated hGRF analogs were compared to a series of model analogs of [Ala15]-hGRF(1-29)-NH2 that were acetylated or protected as the ethylamides at the pegylation sites. It was found that acetylation at the NH2-terminus resulted in reduced potency, which was not further affected when the NH2-terminus was pegylated, regardless of the size of poly(ethyleneglycol) (PEG) employed (e.g. PEG2000 or PEG5000). Pegylation at Asp8 or Lys12 decreased biological potency, a situation which was exacerbated by increasing the molecular weight of PEG. Pegylation at Lys21 or Asp25 did not significantly affect biological activity. The C-terminal model peptide, [Ala15,Orn(Ac)30]-hGRF(1-29)-NH2, was the most potent analog identified in this series (ca. 4-5-fold that of hGRF(1-44)-NH2. The COOH-terminal pegylated analogs retained this increased level of biological activity independent of PEG molecular weight. These studies demonstrate that a biologically active peptide can be pegylated and retain the full in vitro potency of the peptide. However, the biological activity is highly dependent on the site of pegylation and, in some cases, the molecular weight of PEG (degree of pegylation) moiety used.

1H NMR of A beta amyloid peptide congeners in water solution. Conformational changes correlate with plaque competence.

To begin to examine the structural basis for the deposition of soluble A beta amyloid peptide onto senile plaques in Alzheimer's disease, we have prepared A beta congeners and measured their activity in an in vitro plaque growth assay. The N-terminal fragment, A beta (1-28)-OH, was inactive at all pH values tested. While the central fragment, A beta (10-35)-NH2, and the full length peptide, A beta (1-40)-OH, were inactive below pH 4, both were active (plaque competent) between pH 5 and 9. The active and inactive fragments were studied by nuclear magnetic resonance spectroscopy in water at submillimolar concentrations at pH 2.1 and 5.6. Changes in chemical shifts, coupling constants, and nuclear Overhauser enhancements indicate a pH dependent folding transition in A beta (10-35)-NH2 as it becomes active. The conformation of the active fragment is not helical, and preliminary data indicate the presence of several turns and at least two short strands. In contrast, the inactive fragment A beta (1-28)-OH did not undergo a similar folding transition. Earlier nuclear magnetic resonance studies of amyloid peptides in fluorinated alcohols or detergent micelles at low pH described a helical conformation and proposed a helix to sheet transition in plaque formation; the present study demonstrates that no such conformations are present in water under conditions where the peptides can adhere to authentic amyloid plaques.

Immunization with synthetic peptide segments of a sperm protein impair fertility in rats.

The nucleotide sequence of the cDNA encoding a sperm protein (rSMP-B) was determined in a previous study. Two peptide segments corresponding to the extracellular domain of the deduced sperm polypeptide were synthesized as multiple antigen peptide (MAP) and designated as rSMP-229 and rSMP-230. Polyclonal antibodies were raised against the two MAPs. Sera obtained from rabbits immunized with rSMP-230 interacted with human and rabbit sperm membrane proteins with estimated molecular sizes of 72 and 20.1 kD, respectively. Adult female and male rats were immunized with the MAPs and their fertilities determined. Immunization of female rats with rSMP-229 and rSMP-230 induced infertility in 25% and 83% of the treated animals, respectively. All male rats immunized with rSMP-229 remained fertile; whereas animals immunized with rSMP-230 did not mate with normal cycling female rats. Three impotent male rats were found to regain their mating potency 45 days after the last booster injection. These findings demonstrated that immunization with rSMP-230 induced a reversible impotency in male rats. Serum testosterone and LH levels were reduced in rSMP-230-immunized male rats and were elevated in rSMP-229-immunized animals. Histopathological examination of sections of testes from male rats immunized with rSMP-230 showed impairment of spermatogenesis and sloughing of germ cells into the lumen of the seminiferous tubules. The testes of male rats immunized with rSMP-229 showed normal morphology and active spermatogenesis with scattered foci of nodular hyperplasia of Leydig cells in the interstitial areas. In conclusion, immunization with synthetic peptide segments corresponding to different domains of a deduced sperm protein induced infertility in a significant number of female rats and transient impotency in male rats.

Pegylated peptides. II. Solid-phase synthesis of amino-, carboxy- and side-chain pegylated peptides.

General procedures are presented for the site-specific pegylation of peptides at the NH2-terminus, side-chain positions (Lys or Asp/Glu) or COOH-terminus using solid-phase Fmoc/tBu methodologies. A model tridecapeptide fragment of interleukin-2, IL-2(44-56)-NH2, was chosen for this study since it possesses several trifunctional amino acids which serve as potential sites for pegylation. The pegylation reagents were designed to contain either Nle or Orn, which served as diagnostic amino acids for confirming the presence of 1 PEG unit per mole of peptide. NH2-Terminal pegylation was carried out by coupling PEG-CH2CO-Nle-OH to the free NH2-terminus of the peptide-resin. Side-chain pegylation of Lys or Asp was achieved by one of two pathways. Direct side-chain pegylation was accomplished by coupling with Fmoc-Lys(PEG-CH2CO-Nle)-OH or Fmoc-Asp(Nle-NH-CH2CH2-PEG)-OH, followed by solid-phase assemblage of the pegylated peptide-resin and TFA cleavage. Alternatively, allylic protective groups were introduced via Fmoc-Lys(Alloc)-OH or Fmoc-Asp(O-Allyl)-OH, and selectively removed by palladium-catalyzed deprotection after assemblage of the peptide-resin. Solid-phase pegylation of the side-chain of Lys or Asp was then carried out in the final stage with PEG-CH2CO-Nle-OH or H-Nle-NH-(CH2)2-PEG, respectively. COOH-Terminal pegylation was achieved through the initial attachment of Fmoc-Orn(PEG-CH2CO)-OH to the solid support, followed by solid-phase peptide synthesis using the Fmoc/tBu strategy. The pegylated peptides were purified by dialysis and preparative HPLC and were fully characterized by analytical HPLC, amino acid analysis, 1H-NMR spectroscopy and laser desorption mass spectrometry.

Pegylated peptides I: Solid-phase synthesis of N alpha-pegylated peptides using Fmoc strategy.

The feasibility of pegylating peptides by the solid-phase procedure was examined. Although polyethyleneglycol (PEG) was shown to be partially degraded by HF, the use of TFA was fully compatible with the PEG system. Therefore, the Fmoc/tBu solid-phase strategy was utilized for the synthesis of a series of model tetra-, octa- and dodecapeptides, and the corresponding N alpha-pegylated peptides, which were prepared from common peptide-resin intermediates. PEG-OCH2-CO-Nle-OH, 3, proved to be an ideal reagent for N-terminal pegylation. This intermediate served as a diagnostic for the determination of the number of PEG units/mole of peptide. Solid-phase coupling reactions proceeded by standard procedures using BOP-activation. The authentic pegylated peptides (readily purified by conventional methods of preparative HPLC) were fully characterized by amino acid analysis, 1H-NMR spectroscopy, analytical HPLC and laser desorption ionization mass spectrometry, leading to the values that are identical with the expected structures.

Immunogenicity of multiple antigen peptides containing B and non-repeat T cell epitopes of the circumsporozoite protein of Plasmodium falciparum.

We have characterized the immune response of mice to multiple Ag peptide systems (MAP) containing the immunodominant B cell epitope (NANP)3 and one of three distinct Th epitopes, Th2R, Th3R, and CS.T3, of the C terminal region of the circumsporozoite protein of Plasmodium falciparum, a human malaria parasite. Mice of three different MHC haplotypes (H-2k, H-2d, and H-2a) were immunized with the various MAP constructs. Mice of all three strains produced antibodies, but their anti-sporozoite titers were considerably lower than their anti-peptide titers as detected by ELISA. These antibodies reacted at high titers not only with the repeat polymer (NANP)50, but also with MAP that contained only the respective Th sequence. The antibody binding site within each of the Th sequences was mapped, using truncated peptides, in an inhibition assay. A primary antibody response, induced by a single i.v. inoculation of sporozoites, was greatly enhanced by the injection of MAP.

Infertility induced in rats by immunization with synthetic peptide segments of a sperm protein.

Three peptide segments (YAL-198, YAL-201 and YAL-212) corresponding to the extracellular domain of a human sperm protein designated as YWK-II antigen were synthesized as multiple antigen peptide (MAP). Male and female rats were immunized with the YWK-II-MAPs and fertility determined. In a group of 12 female rats immunized with YAL-198, seven animals were infertile and two animals were subfertile. When immunized with YAL-201 and YAL-212, 4 and 2 animals were infertile, respectively. In a group of 15 males immunized with YAL-198, 2 animals were infertile and 6 were subfertile. Two animals immunized with YAL-201 were subfertile. All control male and female rats immunized with bovine serum albumin and adjuvant were fertile. Sera obtained from infertile rats immunized with YAL-198 contained higher titers of antibodies compared to those obtained from fertile animals. The present study shows that immunization with synthetic peptide segments of a sperm protein can effectively reduce fertility.

A chemically defined synthetic vaccine model for HIV-1.

Multiple Ag peptide (MAP) system without the use of a protein carrier was used as a vaccine model in three species of animals. Synthetic peptides from the V3 region of the gp120 of IIIB, RF and MN HIV-1 isolates were used as the Ag. MAP consisting of various chain lengths, from 11 to 24 residues, were prepared in a monoepitope configuration containing four repeats of each individual peptide. In parallel, they were synthesized in a diepitope configuration adding at the carboxyl-terminus of the V3 peptides a conserved sequence, known to be a Th cell epitope of gp120. The antibody response elicited by the monoepitope constructs was species-dependent. Rabbits produced immunity against all nine peptides, whereas mice were strongly reactive mainly to the longest sequence of the IIIB isolate. The immune response of guinea pigs was intermediate to those of rabbits and mice. Diepitope MAPs were immunogenic in all three species and elicited significantly higher titers than those raised by the immunization with the monoepitope MAPs. The response was type specific; the high-titered antibodies were reactive mostly against the isolate from which the peptides were derived, with a small cross-reactivity in ELISA between IIIB and RF strains. The dominant antigenic site of the B cell epitope, IIIB sequence, was located at the amino and central part of the MAP and a sequence overlapping the putative V3 reverse-turn was particularly reactive with the raised antibodies. Moreover, sera from the immunized animals inhibited virus-dependent cell fusion. These results show that MAP, with a chemically defined structure and without the use of a protein carrier, can be potentially useful for the design of synthetic HIV-1 vaccine candidates.