Characterization of histatin 5 with respect to amphipathicity, hydrophobicity, and effects on cell and mitochondrial membrane integrity excludes a candidacidal mechanism of pore formation

Histatin 5 is a 24-residue peptide from human saliva with antifungal properties. We recently demonstrated that histatin 5 translocates across the yeast membrane and targets to the mitochondria, suggesting an unusual antifungal mechanism (Helmerhorst, E. J., Breeuwer, P., van't Hof, W., Walgreen-Weterings, E., Oomen, L. C. J. M., Veerman, E. C. I., Nieuw Amerongen, A. V., and Abee, T. (1999) J. Biol. Chem. 274, 7286-7291). The present study used specifically designed synthetic analogs of histatin 5 to elucidate the role of peptide amphipathicity, hydrophobicity, and the propensity to adopt alpha-helical structures in relation to membrane permeabilization and fungicidal activity. Studies included circular dichroism measurements, evaluation of the effects on the cytoplasmic transmembrane potential and on the respiration of isolated mitochondria, and analysis of the peptide hydrophobicity/amphipathicity relationship (Eisenberg, D. (1984) Annu. Rev. Biochem. 53, 595-623). The 14-residue synthetic peptides used were dh-5, comprising the functional domain of histatin 5, and dhvar1 and dhvar4, both designed to maximize amphipathic characteristics. The results obtained show that the amphipathic analogs exhibited a high fungicidal activity, a high propensity to form an alpha-helix, dissipated the cytoplasmic transmembrane potential, and uncoupled the respiration of isolated mitochondria, similar to the pore-forming peptide PGLa (Peptide with N-terminal Glycine and C-terminal Leucine-amide). In contrast, histatin 5 and dh-5 showed fewer or none of these features. The difference in these functional characteristics between histatin 5 and dh-5 on the one hand and dhvar1, dhvar4, and PGLa on the other hand correlated well with their predicted affinity for membranes based on hydrophobicity/amphipathicity analysis. These data indicate that the salivary protein histatin 5 exerts its antifungal function through a mechanism other than pore formation.     

DS6: anticandidal,antibiofilm peptide against Candida tropicalis and exhibit synergy with commercial drug

Antifungal peptides have gained interest as therapeutic agents in recent years because of increased multidrug resistance against present antifungal drugs. This study designed, synthesized and characterized antifungal activity of a small peptide analogue, DS6. This peptide was designed using the template from the N‐terminal part of the antifungal protein, Aspergillus giganteous. DS6 inhibited Candida tropicalis (ATCC 13803), as well as its clinical isolates. DS6 was found to be a fungicidal, killing the fungus very rapidly. DS6 is also non‐toxic to human cells. Synergistic interactions of DS6 with amphotericin B and fluconazole were also evident. DS6 is membrane lytic and exhibits antibiofilm activity against C. tropicalis. In conclusion, DS6 may have utility as an alternative antifungal therapy for C. tropicalis. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.     

Synthesis,biological activity and conformational analysis of head‐to‐tail cyclic analogues of LL37 and histatin 5

LL37 and histatin 5 are antimicrobial peptides. LL37 exhibits killing activity against a broad spectrum of pathogens, whereas histatin 5 is primarily an antifungal agent. Head‐to‐tail cyclization of histatin 5 did not affect its antimicrobial and haemolytic activity. The cyclic LL37 exhibits identical antifungal and haemolytic activity as does LL37. Its antimicrobial activity varied in one dilution depending on the kind of bacteria. The structure of cyclic peptides was studied by circular dichroism spectroscopy. Both peptides undergo a conformational change leading to stabilisation of their α‐helical structure in the presence of negatively charged sodium dodecyl sulfate micelles. However, with cyclic histatin 5, the presence of Zn²⁺ ions is also necessary to fuse the peptide to the micelle. The specific action of the Zn²⁺ ions is attributed to the presence of a zinc‐binding motif, His‐Glu‐X‐X‐His. It has been speculated that this zinc complexing may be related to the well‐established anticandidal activity. In the case of cyclic LL37, also the presence of a zwitterionic dodecylphosphocholine micelle induces formation of the helical structure. A microwave‐assisted procedure for the cleavage of a peptide from the 2‐chlorotrityl chloride resin was, for the first time, successfully used to obtain protected peptide fragments that can be applied to the preparation of head‐to‐tail cyclopeptides or to condensation of peptidic fragments. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Fungicidal activity of the human peptide hepcidin 20 alone or in combination with other antifungals against Candida glabrata isolates

Candida glabrata infections are often difficult to eradicate due to the intrinsically low susceptibility to azoles of this species. In addition, C. glabrata has also been shown to be insensitive to several cationic peptides, which have been shown to be promising novel therapeutic candidates for the treatment of fungal infection. In this study, the in vitro fungicidal activity of the human cationic peptide hepcidin 20 (Hep-20) was evaluated against clinical isolates of C. glabrata with different levels of fluconazole susceptibility. Interestingly, all isolates were susceptible to Hep-20 (100–200 μg/ml) at pH 7.4, whereas the fungicidal effect of the peptide was higher (50 μg/ml) at acidic pH values. In addition, an increased antifungal activity was observed for Hep-20 with amphotericin B and a synergistic effect was demonstrated for the Hep-20/fluconazole and Hep-20/caspofungin combinations.     

Molecular Analysis and Susceptibility Profiling of Candida albicans Isolates from Immunocompromised Patients in South India

The genetic diversity and in vitro antifungal susceptibility profiles of 55 Candida albicans from immunocompromised patients were studied. PCR based analysis of the transposable intron in the 25S rDNA revealed 39 genotype A, 4 genotype B and 12 genotype C isolates. Serotype analysis categorized 52 isolates as serotype A and 3 as serotype B. All strains were susceptible to micafungin, 5-flucytosine and miconazole, whereas resistance against amphotericin B (3.6%), fluconazole (3.6%), itraconazole (7.3%) and voriconazole (5.5%) was observed. No association was seen between antifungal resistance and genotype/serotype status.     

Antifungal activity of Coriandrum sativum essential oil, its mode of action against Candida species and potential synergism with amphotericin B

The increasing incidence of drug-resistant pathogens and toxicity of existing antifungal compounds has drawn attention towards the antimicrobial activity of natural products. The aim of the present study was to evaluate the antifungal activity of coriander essential oil according to classical bacteriological techniques, as well as with flow cytometry. The effect of the essential oil upon germ tube formation, seen as an important virulence factor, and potential synergism with amphotericin B were also studied. Coriander essential oil has a fungicidal activity against the Candida strains tested with MLC values equal to the MIC value and ranging from 0.05 to 0.4% (v/v). Flow cytometric evaluation of BOX, PI and DRAQ5 staining indicates that the fungicidal effect is a result of cytoplasmic membrane damage and subsequent leakage of intracellular components such as DNA. Also, concentrations bellow the MIC value caused a marked reduction in the percentage of germ tube formation for C. albicans strains. A synergetic effect between coriander oil and amphotericin B was also obtained for C. albicans strains, while for C. tropicalis strain only an additive effect was observed. This study describes the antifungal activity of coriander essential oil on Candida spp., which could be useful in designing new formulations for candidosis treatment.     

Screening Antimicrobial Activities of Basic Protein Fractions from Dry and Germinated Wheat Seeds

Two small cationic peptide fractions (5 kDa) were isolated from dry and germinated seeds of wheat, named WAP and GWAP, respectively. The antifungal and antibacterial activities of the peptides were analyzed using disk diffusion and turbidity measurement assays. The peptides in vitro exhibited effective antifungal activity against four plant pathogenic fungi at minimum concentration of 15 g(protein) cm^–3. Their antimicrobial activity was negatively affected by the presence of 5 mM CaCl₂. The peptides were less effective against Gram-negative bacterium Erwinia carotovora subsp. carotovora, but they demonstrated inhibitory activity against Gram-positive bacterium Clavibacter michiganensis subsp. sepedonicus. The antimicrobial activity of GWAP was more effective than WAP.     

Effect of Ansamitocins on Growth of Yeasts

Ansamitocins in combination with amphotericin B produced synergistic inhibition on the growth of several yeasts in liquid cultures, Ansamitocin P–3 at 5 µg/ml completely suppressed the growth of Saccharomyces cerevisiae whereas ansamitocin P–3 alone at 50 µg/ml hardly affected growth. Ansamitocin P–4 and maytansine also showed synergistic activity with amphotericin B against S. cerevisiae. The synergism also occurred in cultures of Candida albicans and Hansenula anomala. Combinations of ansamitocin P–3 with various agents revealed that the synergism depended on the specific property of amphotericin B. Ansamitocins showed no interfering activity against regeneration of protoplasts of S. cerevisiae. These results suggest that the limited activity of ansamitocins against these yeasts is due to the membrane permeability barrier of these cells.     

Susceptibility of <Emphasis Type="Italic">Candida</Emphasis> biofilms to histatin 5 and fluconazole

Candida-associated denture stomatitis has a high rate of recurrence. Candida biofilms formed on denture acrylic are more resistant to antifungals than planktonic yeasts. Histatins, a family of basic peptides secreted by the major salivary glands in humans, especially histatin 5, possess significant antifungal properties. We examined antifungal activities of histatin 5 against planktonic or biofilm Candida albicans and Candida glabrata. Candida biofilms were developed on poly(methyl methacrylate) discs and treated with histatin 5 (0.01–100 μM) or fluconazole (1–200 μM). The metabolic activity of the biofilms was measured by the XTT reduction assay. The fungicidal activity of histatin 5 against planktonic Candida was tested by microdilution plate assay. Biofilm and planktonic C. albicans GDH18, UTR-14 and 6122/06 were highly susceptible to histatin 5, with 50% RMA (concentration of the agent causing 50% reduction in the metabolic activity; biofilm) of 4.6 ± 2.2, 6.9 ± 3.7 and 1.7 ± 1.5 μM, and IC₅₀ (planktonic cells) of 3.0 ± 0.5, 2.6 ± 0.1 and 4.8 ± 0.5, respectively. Biofilms of C. glabrata GDH1407 and 6115/06 were less susceptible to histatin 5, with 50% RMA of 31.2 ± 4.8 and 62.5 ± 0.7 μM, respectively. Planktonic C. glabrata was insensitive to histatin 5 (IC₅₀ > 100 μM). Biofilm-associated Candida was highly resistant to fluconazole in the range 1–200 μM; e.g. at 100 μM only ~20% inhibition was observed for C. albicans, and ~30% inhibition for C. glabrata. These results indicate that histatin 5 exhibits antifungal activity against biofilms of C. albicans and C. glabrata developed on denture acrylic. C. glabrata is significantly less sensitive to histatin 5 than C. albicans.     

Enzymatic Activity,Sensitivity to Antifungal Drugs and <Emphasis Type="Italic">Baccharis dracunculifolia</Emphasis> Essential Oil by <Emphasis Type="Italic">Candida</Emphasis> Strains Isolated from the Oral Cavities of Breastfeeding Infants and in Their Mothers’ Mouths and Nipples

Candida strains can cause oral candidosis, as well as nipples candidosis and lead to premature weaning or yeast transmission. The aim of this study was to evaluate 51 Candida isolates obtained from the oral cavities of infants during breastfeeding and mothers’ oral cavities and nipples, their enzymatic activity and their sensitivity to amphotericin B, fluconazole and Baccharis dracunculifolia essential oil. Among the studied strains, 96.1% produced phospholipase and 78.4% produced proteinase. The antifungal resistance was only observed among isolates of C. albicans, for which three strains showed a resistant activity to fluconazole and one showed a resistant activity to amphotericin B. All strains were sensitive to B. dracunculifolia essential oil with MIC between 0.2 and 6.25 mg/ml. It was concluded that most of the strains showed significant enzymatic activity and were sensitive to amphotericin B and fluconazole. B. dracunculifolia essential oil inhibited the growth of all strains, including the ones resistant to commercial antifungal agents.     

Antifungal Activity and Action Mechanism of Histatin 5-Halocidin Hybrid Peptides against Candida ssp

The candidacidal activity of histatin 5 is initiated through cell wall binding, followed by translocation and intracellular targeting, while the halocidin peptide exerts its activity by attacking the Candida cell membrane. To improve antimicrobial activities and to understand the killing mechanism of two peptides, six hybrid peptides were designed by conjugating histatin 5 and halocidin. A comparative approach was established to study the activity, salt tolerance, cell wall glucan binding assay, cytotoxicity, generation of ROS and killing kinetics. CD spectrometry was conducted to evaluate secondary structures of these hybrid peptides. Furthermore the cellular localization of hybrid peptides was investigated by confocal fluorescence microscopy. Of the six hybrid congeners, di-PH2, di-WP2 and HHP1 had stronger activities than other hybrid peptides against all tested Candida strains. The MIC values of these peptides were 1–2, 2–4 and 2–4 μg/ml, respectively. Moreover, none of the hybrid peptides was cytotoxic in the hemolytic assay and cell-based cytotoxicity assay. Confocal laser microscopy showed that di-PH2 and HHP1 were translocated into cytoplasm whereas di-WP2 was accumulated on surface of C. albicans to exert their candidacidal activity. All translocated peptides (Hst 5, P113, di-PH2) were capable of generating intracellular ROS except HHP1. Additionally, the KFH residues at C-terminal end of these peptides were assumed for core sequence for active translocation.     

Activity of Combined Antifungal Agents Against Multidrug-Resistant <Emphasis Type="Italic">Candida glabrata</Emphasis> Strains

In this study, we evaluated the in vitro activity of echinocandins, azoles, and amphotericin B alone and in combination against echinocandin/azole-sensitive and echinocandin/azole-resistant Candida glabrata isolates. Susceptibility tests were performed using the broth microdilution method in accordance with the Clinical and Laboratory Standards Institute document M27-A3. The checkerboard method was used to evaluate the fractional inhibitory concentration index of the interactions. Cross-resistance was observed among echinocandins; 15% of the isolates resistant to caspofungin were also resistant to anidulafungin and micafungin. Synergistic activity was observed in 70% of resistant C. glabrata when anidulafungin was combined with voriconazole or posaconazole. Higher (85%) synergism was found in the combination of caspofungin and voriconazole. The combinations of caspofungin with fluconazole, posaconazole and amphotericin B, micafungin with fluconazole, posaconazole and voriconazole, and anidulafungin with amphotericin B showed indifferent activities for the majority of the isolates. Anidulafungin combined with fluconazole showed the same percentage of synergism and indifference (45%). Antagonism was detected in 50% of isolates when micafungin was combined with amphotericin B. Combinations of echinocandins and antifungal azoles have great potential for in vivo assays which are required to evaluate the efficacy of these combinations against multidrug-resistant C. glabrata strains.     

A novel bovine lactoferrin peptide, FKCRRWQWRM, suppresses Candida cell growth and activates neutrophils.

To identify potent new antifungal agents, the Candida cell growth inhibitory activities of six lactoferrin (Lf) peptides consisting of 6-25 amino acid residues (peptide 1, FKCRRWQWRMKKLGAPSITCVRRAF lactoferricin B; peptide 2, FKCRRWQWRM; peptide 2', FKARRWQWRM; peptide 3, GAPSITCVRRAF; peptide 4, RRWQWR; and peptide 5, RWQWRM) were examined. Of these, peptide 2 strongly suppressed the multiplication of Candida cells, but other peptides showed only weak activities. In two strains of C. albicans, the minimum inhibitory concentration 100 of peptide 2 (17.3+/-2.2 microM and 17.5+/-2.4 microM) was close to that of miconazole (13.0+/-1.7 microM and 13.1+/-1.6 microM) but markedly different from that of amphotericin B (0.52+/-0.09 microM and 0.56+/-0.11 microM). The suppression of Candida cell growth was additively increased by a combination of peptide 2 with amphotericin B and miconazole. Peptides 1, 3, 4 and 5 and Lf suppressed iron uptake by Candida cells, inversely correlated with their Candida cell growth inhibition activities. However, iron uptake was not inhibited by peptide 2. In addition, peptide 2 upregulated Candida cell killing activity of polymorphonuclear leukocytes (PMN) increasing their superoxide generation, protein kinase C activity, p38 MAPK activity and the expression of p47phox. These results indicated that the main antimicrobial activity of the Lf peptides is dependent on the N-terminal half of Lf and that the PMN upregulatory activity of peptide 2 and additive function of peptide 2 with antifungal drugs are useful for prophylaxis and control of candidiasis.     

Synergism of Antimicrobial Frog Peptides Couples to Membrane Intrinsic Curvature Strain

Mixtures of the frog peptides magainin 2 and PGLa are well-known for their pronounced synergistic killing of Gram-negative bacteria. We aimed to gain insight into the underlying biophysical mechanism by interrogating the permeabilizing efficacies of the peptides as a function of stored membrane curvature strain. For Gram-negative bacterial-inner-membrane mimics, synergism was only observed when the anionic bilayers exhibited significant negative intrinsic curvatures imposed by monounsaturated phosphatidylethanolamine. In contrast, the peptides and their mixtures did not exhibit significant activities in charge-neutral mammalian mimics, including those with negative curvature, which is consistent with the requirement of charge-mediated peptide binding to the membrane. Our experimental findings are supported by computer simulations showing a significant decrease of the peptide-insertion free energy in membranes upon shifting intrinsic curvatures toward more positive values. The physiological relevance of our model studies is corroborated by a remarkable agreement with the peptide’s synergistic activity in Escherichia coli. We propose that synergism is related to a lowering of a membrane-curvature-strain-mediated free-energy barrier by PGLa that assists membrane insertion of magainin 2, and not by strict pairwise interactions of the two peptides as suggested previously.     

Synthesis and antibacterial activity of amphiphilic lysine-ligated neomycin B conjugates

Amphiphilic lysine-ligated neomycin B building blocks were prepared by reductive amination of a protected C5″-modified neomycin B-based aldehyde and side chain-unprotected lysine or lysine-containing peptides. It was demonstrated that a suitably protected lysine-ligated neomycin B conjugate (NeoK) serves as a building block for peptide synthesis, enabling incorporation of aminoglycoside binding sites into peptides. Antibacterial testing of three amphiphilic lysine-ligated neomycin B conjugates against a representative panel of Gram-positive and Gram-negative strains demonstrates that C5″-modified neomycin-lysine conjugate retains antibacterial activity. However, in most cases the lysine-ligated neomycin B analogs display reduced potency against Gram-positive strains when compared to unmodified neomycin B or unligated peptide. An exception is MRSA where an eightfold enhancement was observed. When compared to unmodified neomycin B, the prepared lysine-neomycin conjugates exhibited a 4–8-fold enhanced Gram-negative activity against Pseudomonas aeruginosa and up to 12-fold enhanced activity was observed when compared to unligated reference peptides.     

Biological activity and structural aspects of PGLa interaction with membrane mimetic systems

Peptidyl-glycine-leucine-carboxyamide (PGLa), isolated from granular skin glands of Xenopus laevis, is practically devoid of secondary structure in aqueous solution and in the presence of zwitterionic phospholipids, when added exogenously, but adopts an α-helix in the presence of anionic lipids. The peptide was shown to exhibit antifungal activity and to have antimicrobial activity towards both Gram-negative and Gram-positive bacteria. As a broad variety of peptides is found in the secretions of amphibian skin combinatorial treatment of PGLa and magainin 2 was studied showing enhanced activity by a heterodimer formation. Thus production of mutually recognizing peptides seems to be an effective way in nature to increase selective membrane activity. Biophysical studies on membrane mimics demonstrated that PGLa can discriminate between different lipid species, preferentially interacting with negatively charged lipids, which are major components of bacterial but not mammalian cell membranes. This emphasizes the role of electrostatic interactions as a major determinant to trigger the affinity of antimicrobial peptides towards bacterial membranes. PGLa induced the formation of a quasi-interdigitated phase in phosphatidylglycerol bilayers below their chain melting transition, which is due to the creation of voids below the peptide being aligned parallel to the membrane surface. In the fluid phase of phosphatidylglycerol the peptide inserts perpendicularly into the bilayer above a threshold concentration, which results in a hydrophobic mismatch of the peptide length and bilayer core for lipids ≤ C16. This mismatch is compensated by stretching of the acyl chains and in turn thickening of the bilayer demonstrating that membrane thinning cannot be taken generally as the hallmark of pore formation by antimicrobial peptides. Furthermore, PGLa was shown to affect membrane curvature strain of phosphatidylethanolamine, another main lipid component of bacterial membranes, where a cubic phase coexists with the fluid bilayer phase. Investigations on living Escherichia coli showed distinct changes in cell envelope morphology, when treated with the peptide. In a first stage loss of surface stiffness and consequently of topographic features was observed, followed in a second stage by permeabilization of the outer membrane and rupture of the inner (cytoplasmic) membrane supposedly by the mechanism(s) derived from model studies.     

Characterization of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> inhibitory lipopeptide from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> IB

Bacillus subtilis strain IB exhibiting inhibitory activity against the Fusarium head blight disease fungus Fusarium graminearum was isolated and identified. The major inhibitory compound was purified from the culture broth through anion exchange, hydrophobic interaction, and reverse phase high-performance liquid chromatography (RP-HPLC) steps. It was a 1,463-Da lipopeptide and had an amino acid composition consisting of Ala, Glx, Ile, Orn, Pro, Thr, and Tyr at a molar ratio of 1:3:1:1:1:1:2. Electrospray ionization mass spectrometry/mass spectrometry (ESI MS/MS) analyses of the natural and the ring-opened peptides showed the antagonist was fengycin, a kind of macrolactone molecule with antifungal activity produced by several Bacillus strains. Fluorescence microscopic analysis indicated this peptide permeabilized and disrupted F. graminearum hyphae.     

Role of Oxidative Phosphorylation in Histatin 5-Induced Cell Death in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The succeptibility of Saccharomyces cerevisiae to the anti-microbial peptide, histatin 5, was tested after pre-growth in fermentable and non-fermentable carbon sources and in the absence or presence of the uncoupler of oxidative phosphorylation, carbonyl cyanide m-chlorophenylhydrazone (CCCP). S. cerevisiae was more resistant to histatin 5 when grown on a fermentable carbon source compared to growth on a non-fermentable carbon source, indicating an important role for oxidative phosphorylation in histatin 5-induced cell death. Oxidative phosphorylation is a pre-requisite for histatin 5-induced cell death in Candida albicans but this is not the case in S. cerevisiae. Incubation of CCCP-treated S. cerevisiae cells with histatin 5 still resulted in cell death. These results suggest that histatin 5-induced cell death in S. cerevisiae differs from that in C. albicans.Revisions received 28 September 2004     

Salivary histatin 5: dependence of sequence, chain length, and helical conformation for candidacidal activity

Histatin 5 (Asp1-Ser-His-Ala4-Lys-Arg-His-His8-Gly-Tyr-Lys-Arg12-Lys-Ph e-His-Glu16-Lys-His - His-Ser20-His-Arg-Gly-Tyr24), one of the basic histidine-rich peptides present in human parotid saliva and several of its fragments, 1-16 (N16), 9-24 (C16), 11-24 (C14), 13-24 (C12), 15-24 (C10), and 7-16 (M10), were synthesized by solid-phase procedures. Native histatin 5 from human parotid saliva was also purified. Their antifungal activities on two strains of Candida albicans have been studied and their conformational preferences both in aqueous and non-aqueous solutions examined by circular dichroism. The synthetic histatin 5, C16, and C14 peptides were highly active and inhibited the growth of C. albicans. The candidacidal activity data of synthetic histatin 5 were comparable to the values of the native histatin 5 isolated from parotid saliva and those reported previously, although the assay system used and the strains examined were different. The C16 fragment was as active as the whole peptide itself, whereas the N16 fragment was far less active than C14, suggesting that the sequence at the C-terminal is important for its fungicidal activity. An increase in the chain length of the C-terminal sequence from 12 to 16 residues increased the candidacidal activity, thereby indicating that a peptide chain length of at least 12 residues is necessary to elicit optimum biological activity. The CD spectra of these linear peptides showed that they are structurally more flexible, and they adopt different conformations depending on the solvent environment. CD studies provided evidence that histatin 5 and the longer fragments, C16, N16, and C14 preferred alpha-helical conformations in non-aqueous solvents such as trifluoroethanol and methanol, while in water and pH 7.4 phosphate buffers, they favored random coil structures. The shorter sequences seemed to adopt either turn structures or unordered structures both in aqueous and non-aqueous solutions. It appears that the sequence at the C-terminal of histatin 5 with a minimum chain length of 14 residues and alpha-helical conformation are the important structural requirements for appreciable candidacidal activity.     

Induction of Antimeningitis Immunity by Synthetic Peptides: III. Immunoactive Synthetic Fragments of the NspA Protein from Neisseria meningitidis

Four potentially immunoactive peptide fragments of the NspA protein from the outer membrane of the Neisseria meningitidis bacterium were synthesized in order to create a synthetic vaccine against meningococcal infection by the serogroup B bacterium. Mice of various lines were immunized with free peptides nonconjugated with a protein carrier. All the synthetic peptides were shown to induce the production of the antipeptide antibodies in mice. A peptide capable of inducing a decrease in the number of bacteria in blood and the protection of infected animals from death was found in the experiments on the protection of the animals infected with two strains of the Neisseria meningitidis serogroup B.