Human lactoferrin binds and removes the hemoglobin receptor protein of the periodontopathogen Porphyromonas gingivalis

The Antimicrobial Activity of Human Defensins at Physiological Non-Permeabilizing Concentrations Is Caused by the Inhibition of the Plasma Membrane H+-ATPases

Human defensins are cysteine-rich peptides (Cys-rich peptides) of the innate immune system. Defensins contain an ancestral structural motif (i.e., γ-core motif) associated with the antimicrobial activity of natural Cys-rich peptides. In this study, low concentrations of human α- and β-defensins showed microbicidal activity that was not associated with cell membrane permeabilization. The cell death pathway was similar to that previously described for human lactoferrin, also an immunoprotein containing a γ-core motif. The common features were (1) cell death not related to plasma membrane (PM) disruption, (2) the inhibition of microbicidal activity via extracellular potassium, (3) the influence of cellular respiration on microbicidal activity, and (4) the influence of intracellular pH on bactericidal activity. In addition, in yeast, we also observed (1) partial K+-efflux mediated via Tok1p K+-channels, (2) the essential role of mitochondrial ATP synthase in cell death, (3) the increment of intracellular ATP, (4) plasma membrane depolarization, and (5) the inhibition of external acidification mediated via PM Pma1p H+-ATPase. Similar features were also observed with BM2, an antifungal peptide that inhibits Pma1p H+-ATPase, showing that the above coincident characteristics were a consequence of PM H+-ATPase inhibition. These findings suggest, for the first time, that human defensins inhibit PM H+-ATPases at physiological concentrations, and that the subsequent cytosolic acidification is responsible for the in vitro microbicidal activity. This mechanism of action is shared with human lactoferrin and probably other antimicrobial peptides containing γ-core motifs.

Acquired Pellicle and Biofilm Engineering by Rinsing with Hemoglobin Solution

INTRODUCTION

The identification of acid-resistant proteins, including hemoglobin (Hb), within the acquired enamel pellicle (AEP) led to the proposition of the "acquired pellicle engineering" concept, which involves the modification of the AEP by incorporating specific proteins, presenting a novel strategy to prevent dental demineralization.

OBJECTIVE

Combining in vivo and in vitro proof-of-concept protocols, we sought to reveal the impact of AEP engineering with Hb protein on the biofilm microbiome and enamel demineralization.

METHODS

In the in vivo studies, 10 volunteers, in 2 independent experiments, rinsed (10 mL,1 min) with deionized water-negative control or 1.0 mg/mL Hb. The AEP and biofilm formed along 2 or 3 h, respectively, were collected. AEP was analyzed by quantitative shotgun-label-free proteomics and biofilm by 16S-rRNA next-generation sequencing (NGS). In in vitro study, a microcosm biofilm protocol was employed. Seventy-two bovine enamel specimens were treated with (1) phosphate-buffered solution (PBS), (2) 0.12% chlorhexidine, (3) 500 ppm NaF, (4) 1.0 mg/mL Hb, (5) 2.0 mg/mL Hb, and (6) 4.0 mg/mL Hb. The biofilm was cultivated for 5 days. Resazurin, colony forming units (CFU), and transversal microradiography were performed.

RESULTS

Proteomics and NGS analysis revealed that Hb increased proteins with antioxidant, antimicrobial, acid-resistance, hydroxyapatite-affinity, calcium-binding properties and showed a reduction in oral pathogenic bacteria. In vitro experiments demonstrated that the lowest Hb concentration was the most effective in reducing bacterial activity, CFU, and enamel demineralization compared to PBS.

CONCLUSION

These findings suggest that Hb could be incorporated into anticaries dental products to modify the oral microbiome and control caries, highlighting its potential for AEP and biofilm microbiome engineering.

The role of microbiome-host interactions in the development of Alzheimer´s disease

Alzheimer`s disease (AD) is the most prevalent cause of dementia. It is often assumed that AD is caused by an aggregation of extracellular beta-amyloid and intracellular tau-protein, supported by a recent study showing reduced brain amyloid levels and reduced cognitive decline under treatment with a beta-amyloid-binding antibody. Confirmation of the importance of amyloid as a therapeutic target notwithstanding, the underlying causes of beta-amyloid aggregation in the human brain, however, remain to be elucidated. Multiple lines of evidence point towards an important role of infectious agents and/or inflammatory conditions in the etiology of AD. Various microorganisms have been detected in the cerebrospinal fluid and brains of AD-patients and have thus been hypothesized to be linked to the development of AD, including Porphyromonas gingivalis (PG) and Spirochaetes. Intriguingly, these microorganisms are also found in the oral cavity under normal physiological conditions, which is often affected by multiple pathologies like caries or tooth loss in AD patients. Oral cavity pathologies are mostly accompanied by a compositional shift in the community of oral microbiota, mainly affecting commensal microorganisms and referred to as 'dysbiosis'. Oral dysbiosis seems to be at least partly mediated by key pathogens such as PG, and it is associated with a pro-inflammatory state that promotes the destruction of connective tissue in the mouth, possibly enabling the translocation of pathogenic microbiota from the oral cavity to the nervous system. It has therefore been hypothesized that dysbiosis of the oral microbiome may contribute to the development of AD. In this review, we discuss the infectious hypothesis of AD in the light of the oral microbiome and microbiome-host interactions, which may contribute to or even cause the development of AD. We discuss technical challenges relating to the detection of microorganisms in relevant body fluids and approaches for avoiding false-positives, and introduce the antibacterial protein lactoferrin as a potential link between the dysbiotic microbiome and the host inflammatory reaction.

Intestinal amoebiasis: 160 years of its first detection and still remains as a health problem in developing countries

Amoebiasis is a parasitic disease caused by Entamoeba histolytica (E. histolytica), an extracellular enteric protozoan. This infection mainly affects people from developing countries with limited hygiene conditions, where it is endemic. Infective cysts are transmitted by the fecal-oral route, excysting in the terminal ileum and producing invasive trophozoites (amoebae). E. histolytica mainly lives in the large intestine without causing symptoms; however, possibly as a result of so far unknown signals, the amoebae invade the mucosa and epithelium causing intestinal amoebiasis. E. histolytica possesses different mechanisms of pathogenicity for the adherence to the intestinal epithelium and for degrading extracellular matrix proteins, producing tissue lesions that progress to abscesses and a host acute inflammatory response. Much information has been obtained regarding the virulence factors, metabolism, mechanisms of pathogenicity, and the host immune response against this parasite; in addition, alternative treatments to metronidazole are continually emerging. An accesible and low-cost diagnostic method that can distinguish E. histolytica from the most nonpathogenic amoebae and an effective vaccine are necessary for protecting against amoebiasis. However, research about the disease and its prevention has been a challenge due to the relationship between E. histolytica and the host during the distinct stages of the disease is multifaceted. In this review, we analyze the interaction between the parasite, the human host, and the colon microbiota or pathogenic microorganisms, which together give rise to intestinal amoebiasis.

Effects of lactoferrin and lactoperoxidase-containing food on the oral hygiene status of older individuals: A randomized, double blinded, placebo-controlled clinical trial

AIM

Lactoferrin and lactoperoxidase have antimicrobial effects against oral pathogens. This randomized, double-blinded, placebo-controlled parallel group study tested the efficacy of a lactoferrin and lactoperoxidase-containing tablet (LF + LPO tablet) in improving the oral hygiene status of older individuals.

METHODS

A total of 46 participants (31 nursing home residents and 15 healthy older individuals) were randomly assigned to receive either lactoferrin and lactoperoxidase-containing tablets or placebo tablets, and were asked to suck on a tablet after every meal for 8 weeks. Oral and bacteriological assessments were carried out at baseline, 4 weeks and 8 weeks.

RESULTS

A total of 47 participants (test group n = 20; mean age 80.4 ± 6.4 years; placebo group n = 17; mean age 85.9 ± 6.7 years) were included in the efficacy analysis. In the test group, the total number of bacteria in the tongue coating was significantly reduced at 4 and 8 weeks compared with that at baseline, and the number of Porphyromonas gingivalis and Fusobacterium nucleatum was significantly reduced at 8 weeks. The total number of bacteria and the number of P. gingivalis in the supragingival plaque were significantly reduced at 8 weeks. Furthermore, there was a significant difference in the change in the number of P. gingivalis in supragingival plaque at 8 weeks between the two groups.

CONCLUSIONS

Lactoferrin and lactoperoxidase-containing tablet ingestion showed antibacterial effects on periodontal bacteria present in the tongue coating and supragingival plaque, indicating that long-term ingestion could improve the oral hygiene of older individuals. Geriatr Gerontol Int 2017; 17: 714-721.

Effect of deletion of the rgpA gene on selected virulence of Porphyromonas gingivalis

Background/purpose

The most potent virulence factors of the periodontal pathogen Porphyromonas gingivalis are gingipains, three cysteine proteases (RgpA, RgpB, and Kgp) that bind and cleave a wide range of host proteins. Considerable proof indicates that RgpA contributes to the entire virulence of the organism and increases the risk of periodontal disease by disrupting the host immune defense and destroying the host tissue. However, the functional significance of this proteinase is incompletely understood. It is important to analyze the effect of arginine-specific gingipain A gene (rgpA) on selected virulence and physiological properties of P. gingivalis.

Materials and methods

Electroporation and homologous recombination were used to construct an rgpA mutant of P. gingivalis ATCC33277. The mutant was verified by polymerase chain reaction and sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Cell structures of the mutant were examined by transmission electron microscopy and homotypic biofilm formation was examined by confocal laser scanning microscopy.

Results

Gene analysis revealed that the rgpA gene was deleted and replaced by a drug resistance gene marker. The defect of the gene resulted in a complete loss of RgpA proteinase, a reduction of out membrane vesicles and hemagglutination, and an increase in homotypic biofilm formation.

Conclusion

Our data indicate that an rgpA gene deficient strain of P. gingivalis is successfully isolated. RgpA may have a variety of physiological and pathological roles in P. gingivalis.

Innate Humoral Defense Factors

Although innate immunity came into the research spotlight in the late 1990s when its instructive role in the adaptive immune response was recognized, innate humoral defense factors have a much older history. The exocrine secretions of the body contain a plethora of distinct soluble factors (lysozyme, lactoferrin, peroxidases, proline-rich proteins, histatins, etc.) that protect the body from mucosal microbial pathogens. More recent studies have established that the humoral arm of innate immunity contains a heterogeneous group of pattern-recognition molecules (e.g., pentraxins, collectins, and ficolins), which perform diverse host-defense functions, such as agglutination and neutralization, opsonization, control of inflammation, and complement activation and regulation. These pattern-recognition molecules, which act as functional predecessors of antibodies (“ante-antibodies”), and the classic soluble innate defense factors form an integrated system with complementary specificity, action, and tissue distribution, and they are the subject of this chapter.

Propeptide-mediated inhibition of cognate gingipain proteinases

Porphyromonas gingivalis is a major pathogen associated with chronic periodontitis. The organism’s cell-surface cysteine proteinases, the Arg-specific proteinases (RgpA, RgpB) and the Lys-specific proteinase (Kgp), which are known as gingipains have been implicated as major virulence factors. All three gingipain precursors contain a propeptide of around 200 amino acids in length that is removed during maturation. The aim of this study was to characterize the inhibitory potential of the Kgp and RgpB propeptides against the mature cognate enzymes. Mature Kgp was obtained from P. gingivalis mutant ECR368, which produces a recombinant Kgp with an ABM1 motif deleted from the catalytic domain (rKgp) that enables the otherwise membrane bound enzyme to dissociate from adhesins and be released. Mature RgpB was obtained from P. gingivalis HG66. Recombinant propeptides of Kgp and RgpB were produced in Escherichia coli and purified using nickel-affinity chromatography. The Kgp and RgpB propeptides displayed non-competitive inhibition kinetics with K_i values of 2.04 µM and 12 nM, respectively. Both propeptides exhibited selectivity towards their cognate proteinase. The specificity of both propeptides was demonstrated by their inability to inhibit caspase-3, a closely related cysteine protease, and papain that also has a relatively long propeptide. Both propeptides at 100 mg/L caused a 50% reduction of P. gingivalis growth in a protein-based medium. In summary, this study demonstrates that gingipain propeptides are capable of inhibiting their mature cognate proteinases.

Lactoferrin: an alternative view of its role in human biological fluids

Lactoferrin is a major component of biologically important mucosal fluids and of the specific granules of neutrophils. Understanding its biological function is essential for understanding neutrophil- and mucosal-mediated immunity. In this review, we reevaluate the in vivo functions of human lactoferrin (hLF) emphasizing in vivo studies and in vitro studies performed in biologically relevant fluids. We discuss the evidence in the literature that supports (or does not support) proposed roles for hLF in mucosal immunity and in neutrophil function. We argue that the current literature supports a microbiostatic role, but not a microbicidal role, for hLF in vivo. The literature also supports a role for hLF in inhibiting colonization and infection of epithelial surfaces by microorganisms and in protecting tissues from neutrophil-mediated damage. Using this information, we briefly discuss hLF in the context of the complex biological fluids in which it is found.

Structural requirements for recognition of essential porphyrin byPorphyromonas gingivalis

Porphyromonas gingivalis is an anaerobic Gram negative bacterium implicated in destructive infection of the tissues that support the teeth. This organism is unusual in that it cannot synthesize the porphyrin macrocycle and is therefore dependent on exogenous porphyrin for growth. Accordingly, in addition to physiologically relevant sources of heme, growth is stimulated by a number of iron-free porphyrins. Without exception, the capacity of porphyrins to support normal growth of P. gingivalis was associated with recognition by a sub-domain protein HA2 which is located within three outer-membrane proteins and which recognizes the porphyrin macrocycle in an iron-independent manner. Previous analysis in our laboratories indicated that recognition of the propanoate face of porphyrin was a distinguishing feature of the HA2 receptor. More detailed analysis indicated that derivatization of the two propionic acid substituents as their methyl esters or taurine derived N-(ethyl-2-sulfonic acid)amides abolished recognition by HA2 whereas the ethylenediamine derived N-(2-aminoethyl)amides did not affect binding by HA2 . The importance of the 2- and 4-vinyl groups of protoporphyrin IX for transport and growth was evaluated by testing compounds with hydrogen, sulfonic acid and glycol substituents at the 2- and 4-positions. While these derivatives bound HA2 with high affinity, study of protoporphyrin isomers indicated that the distribution of vinyl group substitution was important in regulating recognition by HA2 . In this report, the behaviour of mesoporphyrin IX in which the vinyl groups are replaced by ethyl groups and of chlorin E4 which contains only one propionic acid sidechain, were investigated to further define the structural requirements for recognition by HA2 . Both porphyrins were recognized by low affinity interactions. Based on these findings, a model for binding is proposed. The apparently unique mode of recognition of porphyrins by the receptor presents opportunities for specific targeting of this pathogenic organism.

Lactoferrin inhibits Porphyromonas gingivalis proteinases and has sustained biofilm inhibitory activity

Porphyromonas gingivalis is a bacterial pathogen associated with chronic periodontitis that results in destruction of the tooth's supporting tissues. The major virulence determinants of P. gingivalis are its cell surface Arg- and Lys-specific cysteine proteinases, RgpA/B and Kgp. Lactoferrin (LF), an 80-kDa iron-binding glycoprotein found in saliva and gingival crevicular fluid, is believed to play an important role in innate immunity. In this study, bovine milk LF displayed proteinase inhibitory activity against P. gingivalis whole cells, significantly inhibiting both Arg- and Lys-specific proteolytic activities. LF inhibited the Arg-specific activity of purified RgpB, which lacks adhesin domains, and also inhibited the same activity of the RgpA/Kgp proteinase-adhesin complexes in a time-dependent manner, with a first-order inactivation rate constant (k(inact)) of 0.023 min(-1) and an inhibitor affinity constant (K(I)) of 5.02 μM. LF inhibited P. gingivalis biofilm formation by >80% at concentrations above 0.625 μM. LF was relatively resistant to hydrolysis by P. gingivalis cells but was cleaved into two major polypeptides (53 and 33 kDa) at R(284) to S(285), as determined by in-source decay mass spectrometry; however, these polypeptides remained associated with each other and retained inhibitory activity. The biofilm inhibitory activity of LF against P. gingivalis was not attributed to direct antibacterial activity, as LF displayed little growth inhibitory activity against planktonic cells. As the known RgpA/B and Kgp inhibitor N-α-p-tosyl-l-lysine chloromethylketone also inhibited P. gingivalis biofilm formation, the antibiofilm effect of LF may at least in part be attributable to its antiproteinase activity.

Effects of non-iron metalloporphyrins on growth and gene expression of Porphyromonas gingivalis

The oral anaerobic bacterium Porphyromonas gingivalis, which is implicated as an important pathogen for chronic periodontitis, requires heme for its growth. Non-iron metalloporphyrins, In-PPIX and Ga-PPIX, were examined for antibacterial effects on P. gingivalis. Both In-PPIX and Ga-PPIX caused retardation of P. gingivalis growth in a dose-dependent fashion. Microarray and qPCR analyses revealed that In-PPIX treatment upregulated the expression of several genes encoding proteins including ClpB and ClpC, which are members of the Clp (caseinolytic protease, Hsp100) family, and aRNR, aRNR-activating protein and thioredoxin reductase, whereas In-PPIX treatment had no effect on the expression of genes encoding proteins involved in heme uptake pathways, Hmu-mediated, Iht-mediated and Tlr-mediated pathways. P. gingivalis ihtA and ihtB mutants were more resistant to In-PPIX than was the wild-type parent, whereas hmuR and tlr mutants did not show such resistance to In-PPIX. The results suggest that In-PPIX is incorporated by the Iht-mediated heme uptake pathway and that it influences protein quality control and nucleotide metabolism and retards growth of P. gingivalis.

Effects of orally administered lactoferrin and lactoperoxidase-containing tablets on clinical and bacteriological profiles in chronic periodontitis patients

This study was undertaken to evaluate the effect of oral administration of lactoferrin (LF) and lactoperoxidase-(LPO-)containing tablet on periodontal condition. Seventy-two individuals with chronic periodontitis were randomly assigned to take either bovine LF and LPO-containing tablets (test group, n = 37) or control tablets (control group, n = 35) every day for 12 weeks. Periodontal parameters and levels of subgingival plaque bacteria, human and bovine LF, and endotoxin in gingival crevicular fluid (GCF) were evaluated at baseline, 1 week, 4 weeks, and 12 weeks. Significant differences were observed in GCF levels of bovine LF between the test and control groups throughout the study (P < .05). However, clinical and bacteriological parameter values proved comparable between the two groups at 1 week to 12 weeks. Therefore, the effect of oral administration of LF and LPO-containing tablets might be weak on periodontal and bacteriological profile in this study.

Suppressive effect of the antimicrobial peptide LL-37 on expression of IL-6, IL-8 and CXCL10 induced by Porphyromonas gingivalis cells and extracts in human gingival fibroblasts

Porphyromonas gingivalis is a major periodontogenic bacterium and possesses immunostimulatory components, such as lipopolysaccharides (LPS) and fimbriae. The host antimicrobial peptide, LL-37, suppresses proinflammatory responses of immune cells but its effect on human gingival fibroblasts (HGFs) is not known. In this study, we assessed the effect of LL-37 on the proinflammatory responses of HGFs stimulated with P. gingivalis cells and their components. Live P. gingivalis cells did not induce proinflammatory responses of HGFs, and LL-37 did not alter these responses. However, LL-37 was able to suppress the killed P. gingivalis cell-induced secretion of interleukin (IL)-6 and IL-8. LL-37 also suppressed the expression of IL6, IL8, and CXCL10 genes that was induced by P. gingivalis components, including phenol-water extracts, lipid A, and fimbriae, and the induction of phosphorylation of p38 and extracellular signal-regulated kinase (ERK) by P. gingivalis lipopolysaccharide (LPS). CAMP was found to be expressed in oral epithelial cells but not in HGFs, despite stimulation with P. gingivalis components. Therefore, LL-37 can exert a suppressive effect on P. gingivalis-induced proinflammatory responses of HGFs in a paracrine manner, suggesting that excess inflammatory responses to P. gingivalis in the gingival tissue are suppressed by LL-37 in vivo.

Periodontitis, periodontopathic bacteria and lactoferrin

Lactoferrin (LF) is a component of saliva and is suspected to be a defense factor against oral pathogens including Streptococcus mutans and Candida albicans. Periodontitis is a very common oral disease caused by periodontopathic bacteria. Antimicrobial activities and other biological effects of LF against representative periodontopathic bacteria, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia, have been widely studied. Association of polymorphisms in LF with incidence of aggressive periodontitis and the role of LF in the gingival crevicular fluid as a marker of periodontitis severity have also been reported. Periodontopathic bacteria reside as a biofilm in supragingival and subgingival plaque. Our recent study indicated that LF exhibits antibacterial activity against planktonic forms of P. gingivalis and P. intermedia at higher concentrations, and furthermore, LF effectively inhibits biofilm formation and reduces the established biofilm of these bacteria at physiological concentrations. A small-scale clinical study indicated that oral administration of bovine LF reduces P. gingivalis and P. intermedia in the subgingival plaque of chronic periodontitis patients. LF seems to be a biofilm inhibitor of periodontopathic bacteria in vitro and in vivo.

Prevention of biofilm formation on titanium surfaces modified with conjugated molecules comprised of antimicrobial and titanium-binding peptides

Specific binding of antimicrobial peptides to titanium (Ti) surfaces may serve to prevent biofilm formation, leading to a reduction in peri-implantitis. This study evaluated the binding behavior of conjugated molecules consisting of antimicrobial and hexapeptidic Ti-binding peptides (minTBP-1) using the quartz crystal microbalance (QCM-D) technique, and investigated the effect of modification of Ti surfaces with these peptides on the bioactivity of Porphyromonas gingivalis. Four kinds of peptide were prepared: histatin 5 (DSHAKRHHGYKRKFHEKHHSHRGY), minTBP-1 + histatin 5 (RKLPDAPDSHAKRHHGYKRKFHEKHHSHRGY), lactoferricin (FQWQRNMRKVR), and minTBP-1 + lactoferricin (RKLPDAPGGFQWQRNMRKVR). The QCM-D analysis demonstrated that significantly larger increases in peptide adsorption were observed in the conjugated peptides than in antimicrobial peptides alone. In addition, ATP activity in P. gingivalis in peptide-modified specimens significantly decreased compared to that in the Ti control. These results indicate that surface modification with conjugated molecules consisting of antimicrobial and Ti-binding peptides is a promising method for reduction of biofilm formation on Ti surfaces.

Inhibitory effects of lactoferrin on growth and biofilm formation of Porphyromonas gingivalis and Prevotella intermedia

Lactoferrin (LF) is an iron-binding antimicrobial protein present in saliva and gingival crevicular fluids, and it is possibly associated with host defense against oral pathogens, including periodontopathic bacteria. In the present study, we evaluated the in vitro effects of LF-related agents on the growth and biofilm formation of two periodontopathic bacteria, Porphyromonas gingivalis and Prevotella intermedia, which reside as biofilms in the subgingival plaque. The planktonic growth of P. gingivalis and P. intermedia was suppressed for up to 5 h by incubation with >or=130 microg/ml of human LF (hLF), iron-free and iron-saturated bovine LF (apo-bLF and holo-bLF, respectively), and >or=6 microg/ml of bLF-derived antimicrobial peptide lactoferricin B (LFcin B); but those effects were weak after 8 h. The biofilm formation of P. gingivalis and P. intermedia over 24 h was effectively inhibited by lower concentrations (>or=8 microg/ml) of various iron-bound forms (the apo, native, and holo forms) of bLF and hLF but not LFcin B. A preformed biofilm of P. gingivalis and P. intermedia was also reduced by incubation with various iron-bound bLFs, hLF, and LFcin B for 5 h. In an examination of the effectiveness of native bLF when it was used in combination with four antibiotics, it was found that treatment with ciprofloxacin, clarithromycin, and minocycline in combination with native bLF for 24 h reduced the amount of a preformed biofilm of P. gingivalis compared with the level of reduction achieved with each agent alone. These results demonstrate the antibiofilm activity of LF with lower iron dependency against P. gingivalis and P. intermedia and the potential usefulness of LF for the prevention and treatment of periodontal diseases and as adjunct therapy for periodontal diseases.

IsdA protects Staphylococcus aureus against the bactericidal protease activity of apolactoferrin

An important facet of the Staphylococcus aureus host-pathogen interaction is the ability of the invading bacterium to evade host innate defenses, particularly the cocktail of host antimicrobial peptides. In this work, we showed that IsdA, a surface protein of S. aureus which is required for nasal colonization, binds to lactoferrin, the most abundant antistaphylococcal polypeptide in human nasal secretions. The presence of IsdA on the surface of S. aureus confers resistance to killing by lactoferrin. In addition, the bactericidal activity of lactoferrin was inhibited by addition of phenylmethylsulfonyl fluoride, implicating the serine protease activity of lactoferrin in the killing of S. aureus. Recombinant IsdA was a competitive inhibitor of lactoferrin protease activity. Reciprocally, antibody reactive to IsdA enhanced killing of S. aureus. Thus, IsdA can protect S. aureus against lactoferrin and acts as a protease inhibitor.

Microbicidal action of lactoferrin and lactoferricin and their synergistic effect with metronidazole in Entamoeba histolytica

Lactoferrin (Lf), in its iron-free form, has been shown to inhibit the growth of pathogenic microorganisms. In the light of new agents to control amoebiasis, the microbicidal activity of human and bovine Lf and bovine lactoferricin (bLfcin, fragment 4-14), and of each combined with metronidazole, the main drug used in amoebiasis, was evaluated in trophozoites of Entamoeba histolytica. Both lactoferrins and bLfcin were able to kill amoebas in a concentration-dependent manner. This killing effect was modulated according to the culture age, pH, and temperature. Parasites obtained from the stationary phase were more susceptible to Lf than those from the early exponential phase. The effect of Lf and its derived peptide, bLfcin, was prevented by both Fe2+ and Fe3+. However, the divalent cations Mg2+ and Ca2+ prevented the killing effect of Lf but not of bLfcin. A synergistic amoebicidal effect was found between metronidazole and human Lf, bovine Lf, or bLfcin. These data suggest that Lf and bLfcin might be used in amoebiasis if they are administered with a low dose of metronidazole to diminish the toxicity of this drug. Thus, Lf and bLfcin are therapeutically potential candidates for use as antiamoebics in patients.

Transvascular dissemination of Porphyromonas gingivalis from a sequestered site is dependent upon activation of the kallikrein/kinin pathway

BACKGROUND AND OBJECTIVE

Epidemiological evidence implicates a connection between human periodontitis and systemic diseases. One possible mechanism involves the direct dissemination of periodontopathogens to the target organs through the circulation. The aim of this work was to define the mechanism used by Porphyromonas gingivalis for dissemination from a sequestered infection site.

MATERIAL AND METHODS

BALB/c mice were subcutaneously infected with P. gingivalis via use of a mouse chamber model. Tissue fluids from various sites were collected and cultured to determine the presence of P. gingivalis. Evans Blue dye was used to measure the dissemination ability of P. gingivalis. Kinin-associated molecules were introduced into mice, and their effects on bacterial dissemination and mouse pathology were monitored.

RESULTS

P. gingivalis strain A7436 caused remote lesions and septicemia with severe cachexia, resulting in animal death. Intrachamber challenge with A7436 resulted in vascular permeability enhancement (VPE), as measured by the systemic infiltration of Evans Blue dye into chamber fluids. VPE was blocked by kininase and kinin receptor antagonist and enhanced by exogenous bradykinin and kininase inhibitor. Live bacteria were recovered from the subcutaneous perichamber and abdominal spaces (spreading), and from the blood (disseminating) of infected mice. Both kininase and kinin receptor antagonist reduced animal mortality as a result of infection with strain A7436 and decreased the number of bacteria recoverable from the blood, but they were not associated with bacterial spreading.

CONCLUSIONS

The results suggest that activation of the kinin system is involved in the breach of the vascular barrier that permits dissemination of P. gingivalis.

Perspectives on interactions between lactoferrin and bacteriaThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process

Lactoferrin has long been recognized for its antimicrobial properties, initially attributed primarily to iron sequestration. It has since become apparent that interaction between the host and bacteria is modulated by a complex series of interactions between lactoferrin and bacteria, lactoferrin and bacterial products, and lactoferrin and host cells. The primary focus of this review is the interaction between lactoferrin and bacteria, but interactions with the lactoferrin-derived cationic peptide lactoferricin will also be discussed. We will summarize what is currently known about the interaction between lactoferrin (or lactoferricin) and surface or secreted bacterial components, comment on the potential physiological relevance of the findings, and identify key questions that remain unanswered.

Porphyromonas gingivalis-induced platelet aggregation in plasma depends on Hgp44 adhesin but not Rgp proteinase

Evidence from recent epidemiological studies suggests a link between periodontal infections and increased risk of atherosclerosis and related cardiovascular and cerebrovascular events in human subjects. One of the major pathogens of periodontitis, Porphyromonas gingivalis, has the ability to aggregate human platelets in platelet-rich plasma (PRP). Mechanism of P. gingivalis-induced platelet aggregation in PRP was investigated. Proteinase inhibitors toward Arg-gingipain (Rgp) and Lys-gingipain (Kgp) did not suppress P. gingivalis-induced platelet aggregation in PRP, whereas the Rgp inhibitor markedly inhibited P. gingivalis-induced platelet aggregation using washed platelets. Mutant analysis revealed that P. gingivalis-induced platelet aggregation in PRP depended on Rgp-, Kgp- and haemagglutinin A (HagA)-encoding genes that intragenically coded for adhesins such as Hgp44. Hgp44 adhesin on the bacterial cell surface, which was processed by Rgp and Kgp proteinases, was essential for P. gingivalis-induced platelet aggregation in PRP. P. gingivalis cell-reactive IgG in plasma, and FcgammaRIIa receptor and to a lesser extent GPIbalpha receptor on platelets were found to be a prerequisite for P. gingivalis-induced platelet aggregation in PRP. These results reveal a novel mechanism of platelet aggregation by P. gingivalis.

A non-conservative, coding single-nucleotide polymorphism in the N-terminal region of lactoferrin is associated with aggressive periodontitis in an African-American, but not a Caucasian population

Lactoferrin is an antimicrobial protein which plays an important role in regulating bacteria that are associated with aggressive periodontitis. Lactoferrin kills directly (via its strongly cationic N-terminal region) and indirectly, through sequestering the iron that bacteria require for growth. As aggressive periodontitis has a strong heritable component, we hypothesized that genetic variation within the lactoferrin gene may play a role in susceptibility to this condition. We have identified and examined a novel, functional, single-point A/G nucleotide mutation causing a threonine/alanine substitution at position 11 (T11A) of the secreted lactoferrin protein. In a pilot case-controlled study of aggressive periodontitis, analysis of 46 African-American patients and 78 controls showed that patients were twice as likely to express the G nucleotide (alanine) allele over controls (60.3 vs 30.4%; P=0.0007, odds ratio=2.564, 95% CI=1.475-4.459). A Caucasian population of 77 patients and 131 controls showed no such association (P=0.5201, odds ratio=0.862, 95% CI=0.548-1.356). The data presented provide a new insight into the genetic susceptibility to aggressive periodontitis.

Iron and heme utilization in Porphyromonas gingivalis

Porphyromonas gingivalis is a Gram-negative anaerobic bacterium associated with the initiation and progression of adult periodontal disease. Iron is utilized by this pathogen in the form of heme and has been shown to play an essential role in its growth and virulence. Recently, considerable attention has been given to the characterization of various secreted and surface-associated proteins of P. gingivalis and their contribution to virulence. In particular, the properties of proteins involved in the uptake of iron and heme have been extensively studied. Unlike other Gram-negative bacteria, P. gingivalis does not produce siderophores. Instead it employs specific outer membrane receptors, proteases (particularly gingipains), and lipoproteins to acquire iron/heme. In this review, we will focus on the diverse mechanisms of iron and heme acquisition in P. gingivalis. Specific proteins involved in iron and heme capture will be described. In addition, we will discuss new genes for iron/heme utilization identified by nucleotide sequencing of the P. gingivalis W83 genome. Putative iron- and heme-responsive gene regulation in P. gingivalis will be discussed. We will also examine the significance of heme/hemoglobin acquisition for the virulence of this pathogen.

The major structural components of two cell surface filaments of Porphyromonas gingivalis are matured through lipoprotein precursors

Bacterial cell surface filaments play significant roles in adherence to and invasion of host cells. They are generated by the chaperone/usher pathway system (class I fimbriae), the type II secretion system (type IV pili) and the nucleation-dependent polymerization system (Curli filaments) that are categorized by their modes of expression and assembly. In this study, we found that the periodontal pathogen Porphyromonas gingivalis expressed the major structural components of two cell surface filaments (fimbrilin and the 75 kDa protein) that had extremely long prosequences in their primary gene products. N-terminal amino acid sequencing of the prosequences, treatment of P. gingivalis cells with globomycin, an inhibitor for lipoprotein-specific signal peptidase, amino acid substitution of the cysteine residue of the prosequence of fimbrilin and [(3)H]-palmitic acid labelling implied that fimbrilin and the 75 kDa protein were matured through their lipoprotein precursor forms. Accumulation of precursor forms of fimbrilin and the 75 kDa protein on the cell surface of the gingipain-null mutant revealed that Arg-gingipain processed these precursors on the surface to yield their mature forms, which subsequently assembled into the filamentous structures, suggesting that the transport and assembly of the major component proteins appear to be novel.

Porphyrin-mediated cell surface heme capture from hemoglobin by Porphyromonas gingivalis

The porphyrin requirements for growth recovery of Porphyromonas gingivalis in heme-depleted cultures are investigated. In addition to physiologically relevant sources of heme, growth recovery is stimulated by a number of noniron porphyrins. These data demonstrate that, as for Haemophilus influenzae, reliance on captured iron and on exogenous porphyrin is manifest as an absolute growth requirement for heme. A number of outer membrane proteins including some gingipains contain the hemoglobin receptor (HA2) domain. In cell surface extracts, polypeptides derived from HA2-containing proteins predominated in hemoglobin binding. The in vitro porphyrin-binding properties of a recombinant HA2 domain were investigated and found to be iron independent. Porphyrins that differ from protoporphyrin IX in only the vinyl aspect of the tetrapyrrole ring show comparable effects in competing with hemoglobin for HA2 and facilitate growth recovery. For some porphyrins which differ from protoporphyrin IX at both propionic acid side chains, the modification is detrimental in both these assays. Correlations of porphyrin competition and growth recovery imply that the HA2 domain acts as a high-affinity hemophore at the cell surface to capture porphyrin from hemoglobin. While some proteins involved with heme capture bind directly to the iron center, the HA2 domain of P. gingivalis recognizes heme by a mechanism that is solely porphyrin mediated.

Construction and characterization of a nonpigmented mutant of Porphyromonas gingivalis: cell surface polysaccharide as an anchorage for gingipains

A nonpigmented mutant of Porphyromonas gingivalis was constructed by using transposon mutagenesis. The mutant possessed the transposon DNA at the novel gene porR. Gene targeted mutagenesis revealed that porR was responsible for pigmentation. The porR gene shared similarities with genes of the degT family, the products of which are now considered to be transaminases involved in biosynthesis of sugar portions of cell-surface polysaccharides and aminoglycosides. The porR mutant showed a pleiotropic phenotype: delayed maturation of fimbrillin, preferential presence of Rgp and Kgp proteinases in culture supernatants, and no haemagglutination. The porR mutant had altered phenol extractable polysaccharide compared to the porR(+) sibling strain. A mAb, 1B5, that reacts with sugar portions of P. gingivalis cell surface polysaccharide and membrane-type Rgp proteinase showed no reaction with the cell lysates of the porR mutant. These results indicate that porR is involved in biosynthesis of cell surface polysaccharide that may function as an anchorage for Rgp, Kgp, haemagglutinins and the haemoglobin receptor protein.

Survey of the year 2000 commercial optical biosensor literature

We have compiled a comprehensive list of the articles published in the year 2000 that describe work employing commercial optical biosensors. Selected reviews of interest for the general biosensor user are highlighted. Emerging applications in areas of drug discovery, clinical support, food and environment monitoring, and cell membrane biology are emphasized. In addition, the experimental design and data processing steps necessary to achieve high-quality biosensor data are described and examples of well-performed kinetic analysis are provided.