[Research on salivary proteins: from properties to functions].

Saliva does more than merely contribute to the digestion of food. It is essential to the health of the oral cavity and with that, indirectly, of the entire body. In the 1970s and 1980s, the most important proteins and peptides in saliva were identified and characterised.

Staphylococcus aureus Sortase A-Mediated Incorporation of Peptides: Effect of Peptide Modification on Incorporation.

The endogenous Staphylococcus aureus sortase A (SrtA) transpeptidase covalently anchors cell wall-anchored (CWA) proteins equipped with a specific recognition motif (LPXTG) into the peptidoglycan layer of the staphylococcal cell wall. Previous in situ experiments have shown that SrtA is also able to incorporate exogenous, fluorescently labelled, synthetic substrates equipped with the LPXTG motif (K(FITC)LPETG-amide) into the bacterial cell wall, albeit at high concentrations of 500 μM to 1 mM. In the present study, we have evaluated the effect of substrate modification on the incorporation efficiency.

Sortase-mediated backbone cyclization of proteins and peptides.

Backbone cyclization has a profound impact on the biological activity and thermal and proteolytic stability of proteins and peptides. Chemical methods for cyclization are not always feasible, especially for large peptides or proteins. Recombinant Staphylococcus aureus sortase A shows potential as a new tool for the cyclization of both proteins and peptides.

Sphingoid bases inhibit acid-induced demineralization of hydroxyapatite.

Calcium hydroxyapatite (HAp), the main constituent of dental enamel, is inherently susceptible to the etching and dissolving action of acids, resulting in tooth decay such as dental caries and dental erosion. Since the prevalence of erosive wear is gradually increasing, there is urgent need for agents that protect the enamel against erosive attacks. In the present study we studied in vitro the anti-erosive effects of a number of sphingolipids and sphingoid bases, which form the backbone of sphingolipids.

Antimicrobial defense systems in saliva.

The oral cavity is one of the most heavily colonized parts of our body. The warm, nutrient-rich and moist environment promotes the growth of a diverse microflora. One of the factors responsible for the ecological equilibrium in the mouth is saliva, which in several ways affects the colonization and growth of bacteria.

Chimerization of lactoferricin and lactoferrampin peptides strongly potentiates the killing activity against Candida albicans.

Bovine lactoferrin harbors 2 antimicrobial sequences (LFcin and LFampin), situated in close proximity in the N1-domain. To mimic their semi parallel configuration we have synthesized a chimeric peptide (LFchimera) in which these sequences are linked in a head-to-head fashion to the α- and ε-amino group, respectively, of a single lysine. In line with previously described bactericidal effects, this peptide was also a stronger candidacidal agent than the antimicrobial peptides LFcin17-30 and LFampin265-284, or a combination of these 2.

Structure-activity analysis of histatin, a potent wound healing peptide from human saliva: cyclization of histatin potentiates molar activity 1,000-fold.

Wounds in the mouth heal faster and with less scarification and inflammation than those in the skin. Saliva is thought to be essential for the superior oral wound healing, but the involved mechanism is still unclear. We have previously discovered that a human-specific peptide, histatin, might be implicated in the wound-healing properties of saliva.

Histatins are the major wound-closure stimulating factors in human saliva as identified in a cell culture assay.

Wounds in the oral cavity heal much faster than skin lesions. Among other factors, saliva is generally assumed to be of relevance to this feature. Rodent saliva contains large amounts of growth factors such as epidermal growth factor (EGF) and nerve growth factor (NGF).

Bactericidal activity of LFchimera is stronger and less sensitive to ionic strength than its constituent lactoferricin and lactoferrampin peptides.

The innate immunity factor lactoferrin harbours two antimicrobial moieties, lactoferricin and lactoferrampin, situated in close proximity in the N1 domain of the molecule. Most likely they cooperate in many of the beneficial activities of lactoferrin. To investigate whether chimerization of both peptides forms a functional unit we designed a chimerical structure containing lactoferricin amino acids 17-30 and lactoferrampin amino acids 265-284.

Histatin-derived monomeric and dimeric synthetic peptides show strong bactericidal activity towards multidrug-resistant Staphylococcus aureus in vivo.

Homodimerization of histatin-derived peptides generally led to improved bactericidal activity against Staphylococcus aureus in vitro. In vivo, monomers and dimers were equally active in killing bacteria in mice with a soft tissue infection. Altogether, these peptides are promising compounds for the development of novel therapeutics against infections with drug-resistant bacteria.

Distinct bactericidal activities of bovine lactoferrin peptides LFampin 268-284 and LFampin 265-284: Asp-Leu-Ile makes a difference.

Two lactoferrampin (LFampin) peptides derived from bovine lactoferrin were compared with respect to their bactericidal activities. LFampin 265-284 killed a set of Gram-positive bacteria that were resistant to LFampin 268-284. The presence of 265Asp-Leu-267Ile did not simply lead to an overall increased potency, since higher concentrations of LFampin 265-284 than LFampin 268-284 were needed to kill the Gram-negative bacteria that were tested.

Ultrastructural effects of antimicrobial peptides from bovine lactoferrin on the membranes of Candida albicans and Escherichia coli.

Antimicrobial peptides allegedly exert their action on microbial membranes. Bovine lactoferrin enfold two antimicrobial domains, lactoferricin B (LFcin B) and lactoferrampin (LFampin). Effects of representative peptides thereof on the membranes of Candida albicans and Escherichia coli were investigated.

Lactoferrampin, an antimicrobial peptide of bovine lactoferrin, exerts its candidacidal activity by a cluster of positively charged residues at the C-terminus in combination with a helix-facilitating N-terminal part.

The antimicrobial activity of bovine lactoferrin (bLF) is attributed to lactoferricin, which is situated in the N1-domain of bLF. Recently, another antimicrobial domain consisting of residues 268-284, designated lactoferrampin (LFampin), has been identified in the N1-domain of bLF, which exhibited antimicrobial activity against Candida albicans and several bacteria. In the present study, the candidacidal activity of a series of peptides spanning this antimicrobial domain was investigated in relation to the charge and the capacity to form a helical conformation in hydrophobic environments.

Degradation of antimicrobial histatin-variant peptides in Staphylococcus aureus and Streptococcus mutans.

Histidine-free variants of salivary histatin 5 have a broad antimicrobial activity against various bacteria. In relation to a possible therapeutic application, we were interested in the susceptibility of these small peptides (14 amino acids long) to microbial proteinases and whether this affects their antimicrobial activity. Analyses by SDS-PAGE of supernatants of peptide-bacteria incubation showed a reduction in protein bands within 15 minutes' incubation, as a result of cellular internalization.

Internalisation and degradation of histatin 5 by Candida albicans.

Histatins, salivary antimicrobial peptides, are susceptible to proteolytic degradation, often ascribed to host proteinases. In this study, we addressed the question whether proteolytic activity from microbial sources can contribute to this degradation. Candida albicans, an opportunistic yeast that is susceptible to the histatins, was used as target organism.

Effects of carbohydrate polymers applicable in saliva substitutes on the anti-Candida activity of a histatin-derived peptide.

The effects of polymers applicable in saliva substitutes on the anti-Candida activity of the cationic antimicrobial peptide dhvar1 were investigated. Dhvar1 is a derivative of the 14 C-terminal amino acids of histatin 5. The effects of the following polymers were tested: uncharged hydroxyethylcellulose (HEC), negatively charged xanthan (XG) and three types of negatively charged carboxymethylcellulose (CMC) of identical mass but different degrees of carboxylic acid-group substitution (DS).

Antimicrobial peptides: properties and applicability.

All organisms need protection against microorganisms, e. g. bacteria, viruses and fungi.

Cationic amphipathic peptides, derived from bovine and human lactoferrins, with antimicrobial activity against oral pathogens.

Peptides derived from the N-terminal domain that comprises an amphipathic alpha-helix in human lactoferrin (LFh 18-31 and LFh 20-38) and bovine lactoferrin (LFb 17-30 and LFb 19-37) were chemically synthesised. Since many positively charged amphipathic alpha-helices contain antimicrobial activity, the peptides were tested for their antimicrobial activity against various oral pathogens. Both peptides from bovine lactoferrin had more potent antimicrobial activities than the human equivalents.

Detection and quantification of MUC7 in submandibular, sublingual, palatine, and labial saliva by anti-peptide antiserum.

The large carbohydrate moiety of low-Mr salivary mucin MUC7 (originally referred to as MG2) is subject to variations. Biochemical analysis and quantification of MUC7 in saliva samples require recognition tools that are independent of the carbohydrate moiety. Therefore, we have evoked three antisera to synthetic peptides of MUC7.

The effects of histatin-derived basic antimicrobial peptides on oral biofilms.

Susceptibility of bacteria to antimicrobial agents is strongly reduced by the formation of complex biofilms. We investigated whether synthetic histatin analogs with broad-spectrum antibacterial activity in vitro were also active against these complex mixtures of bacteria, as present in saliva and plaque. In a simplified model system for dental plaque, hydroxyapatite discs were placed in a continuous culture system comprised of Streptococcus mutans, S.

A critical comparison of the hemolytic and fungicidal activities of cationic antimicrobial peptides.

The hemolytic and fungicidal activity of a number of cationic antimicrobial peptides was investigated. Histatins and magainins were inactive against human erythrocytes and Candida albicans cells in phosphate buffered saline, but displayed strong activity against both cell types when tested in 1 mM potassium phosphate buffer supplemented with 287 mM glucose. The HC50/IC50 ratio, indicative of the therapeutic index, was about 30 for all peptides tested.

IgE and IgG4 binding to synthetic peptides of the cat (Felis domesticus) major allergen Fel dI.

Specificities of IgE and IgG4 antibodies in 12 cat-allergic patients were compared with respect to their reactivity towards 3 IgE-binding synthetic peptides of Felis domesticus allergen 1 (Fel dI): peptides 25-38 and 46-59 of chain 1 and peptide 15-28 of chain 2. Peptides were coupled to Sepharose and anti-Fel dI antibodies were isolated by affinity chromatography. Fel dI-specific IgE- and IgG4 antibody activity in the peptide eluates was measured using Fel dI binding assays.

IgE epitopes on the cat (Felis domesticus) major allergen Fel d I: a study with overlapping synthetic peptides.

Background: The major cat allergen Fel d I is composed of two disulfide-linked polypeptide chains, chain 1 (70 amino acid residues) and chain 2 (92 amino acid residues). Reduction and alkylation of Fel d I eliminates almost all antigenic and allergenic activity, and detection of linear epitopes with synthetic peptides is therefore not expected.

Methods: We synthesized synthetic peptides of both chains of about 14 amino acid residues, overlapping by 7 residues.

T cell epitopes of house dust mite major allergen Der p II.

Recent work has indicated the significance of IL-4- and IL-5-secreting allergen-specific human Th2 lymphocytes in the control of immune responses to allergens in atopic individuals. The precise allergenic epitopes that activate these allergen-specific Th2 cells are, however, hardly known. We analyzed the epitope-specificity of T lymphocytes specific for Der p II, one of the major allergens of house dust mite Dermatophagoides pteronyssinus.