Degradation of immunoglobulins A2, A2, and G by suspected principal periodontal pathogens

Porphyromonas endodontalis HmuY differentially participates in heme acquisition compared to the Porphyromonas gingivalis and Tannerella forsythia hemophore-like proteins

Introduction

Porphyromonas gingivalis and Porphyromonas endodontalis belong to the Bacteroidota phylum. Both species inhabit the oral cavity and can be associated with periodontal diseases. To survive, they must uptake heme from the host as an iron and protoporphyrin IX source. Among the best-characterized heme acquisition systems identified in members of the Bacteroidota phylum is the P. gingivalis Hmu system, with a leading role played by the hemophore-like HmuY (HmuYPg) protein.

Methods

Theoretical analysis of selected HmuY proteins and spectrophotometric methods were employed to determine the heme-binding mode of the P. endodontalis HmuY homolog (HmuYPe) and its ability to sequester heme. Growth phenotype and gene expression analysis of P. endodontalis were employed to reveal the importance of the HmuYPe and Hmu system for this bacterium.

Results

Unlike in P. gingivalis, where HmuYPg uses two histidines for heme-iron coordination, other known HmuY homologs use two methionines in this process. P. endodontalis HmuYPe is the first characterized representative of the HmuY family that binds heme using a histidine-methionine pair. It allows HmuYPe to sequester heme directly from serum albumin and Tannerella forsythia HmuYTf, the HmuY homolog which uses two methionines for heme-iron coordination. In contrast to HmuYPg, which sequesters heme directly from methemoglobin, HmuYPe may bind heme only after the proteolytic digestion of hemoglobin.

Conclusions

We hypothesize that differences in components of the Hmu system and structure-based properties of HmuY proteins may evolved allowing different adaptations of Porphyromonas species to the changing host environment. This may add to the superior virulence potential of P. gingivalis over other members of the Bacteroidota phylum.

Prevotella: An insight into its characteristics and associated virulence factors

Prevotella species, a gram-negative obligate anaerobe, is commonly associated with human infections such as dental caries and periodontitis, as well as other conditions such as chronic osteomyelitis, bite-related infections, rheumatoid arthritis and intestinal diseases like ulcerative colitis. This generally harmless commensal possesses virulence factors such as adhesins, hemolysins, secretion systems exopolysaccharide, LPS, proteases, quorum sensing molecules and antibiotic resistance to evolve into a well-adapted pathogen capable of causing successful infection and proliferation in the host tissue. This review describes several of these virulence factors and their advantage to Prevotella spp. in causing inflammatory diseases like periodontitis. In addition, using genome analysis of Prevotella reference strains, we examined other putative virulence determinants which can provide insights as biomarkers and be the targets for effective interventions in Prevotella related diseases like periodontitis.

Classification, structural biology, and applications of mucin domain-targeting proteases

Epithelial surfaces throughout the body are coated by mucins, a class of proteins carrying domains characterized by a high density of O-glycosylated serine and threonine residues. The resulting mucosal layers form crucial host-microbe interfaces that prevent the translocation of microbes while also selecting for distinct bacteria via the presented glycan repertoire. The intricate interplay between mucus production and breakdown thus determines the composition of the microbiota maintained within these mucosal environments, which can have a large influence on the host during both homeostasis and disease. Most research to date on mucus breakdown has focused on glycosidases that trim glycan structures to release monosaccharides as a source of nutrients. More recent work has uncovered the existence of mucin-type O-glycosylation-dependent proteases that are secreted by pathogens, commensals, and mutualists to facilitate mucosal colonization and penetration. Additionally, immunoglobulin A (IgA) proteases promote bacterial colonization in the presence of neutralizing secretory IgA through selective cleavage of the heavily O-glycosylated hinge region. In this review, we summarize families of O-glycoproteases and IgA proteases, discuss known structural features, and review applications of these enzymes to glycobiology.

The oral microbiome - friend or foe?

The microbiome and the human body constitute an integrated superorganism, which is the result of millions of years of coevolution with mutual adaptation and functional integration, and confers significant benefits for both parties. This evolutionary process has resulted in a highly diverse oral microbiome, which covers the full spectrum of acidogenic, aciduric, inflammatory, and anti-inflammatory properties. The relative proportions of members of the microbiome are affected by factors associated with modern life, such as general diet patterns, sugar consumption, tobacco smoking, oral hygiene, use of antibiotics and other antimicrobials, and vaccines. A perturbed balance in the oral microbiome may result in caries, periodontal disease, or candidiasis, and oral bacteria passively transferred to normally sterile parts of the body may cause extra-oral infections. Nevertheless, it should never be our goal to eliminate the oral microbiome, but rather we have to develop ways to re-establish a harmonious coexistence that is lost because of the modern lifestyle. With regard to oral diseases, this goal can normally be achieved by optimal oral hygiene, exposure to fluoride, reduction of sucrose consumption, stimulation of our innate immune defense, smoking cessation, and control of diabetes.

Recent Advances in the Microbiology of Sinusitis and Their Relation to Persistent Ethmoidal Inflammation

The organisms that commonly cause acute sinusitis have been found to produce a number of factors which may be involved in the transition to a state of chronicity. These factors, combined with increasing ostial obstruction caused by tissue inflammation, propagate a hypoxic environment which favors pathogen survival at the expense of host defenses. Bacterial toxins and hypoxia disrupt the mucociliary clearance system. Both aerobic and anaerobic organisms produce proteases, which may act synergistically to cause immune subversion and prevent opsonization. We have studied the role of bacteria in persistent ethmoid mucosal inflammation in 13 patients undergoing endoscopic endonasal surgery for recurrent acute or chronic sinusitis and found that in 46% of samples there was no significant growth of bacteria but in 33% there was a significant growth of anaerobes. There appeared to be little evidence for synergistic activity between aerobes and anaerobes. Mucosal apposition may account for persistent inflammation in those cases without any significant growth. There is no evidence that the ethmoid sinus acts as a reservoir for reinfection, and it appears likely that acute exacerbations in chronic sinusitis are caused by viral infection. Treatment should be aimed at restoring the host's mucosal defenses either medically with topical decongestants or surgically by endoscopic endonasal surgery. Recurrent courses of antibiotic treatment are not indicated.

BAFF augments IgA2 and IL-10 production by TLR7/8 stimulated total peripheral blood B cells

Class‐switching of B cells to IgA can be induced via both T‐cell‐dependent and T‐cell‐independent mechanisms. IgA is most predominantly produced mucosally and is important for combating infections and allergies. In contrast to mice, humans have two forms of IgA; IgA1 and IgA2 with diverse tissue distribution. In early life, IgA levels might be sub‐optimal especially during the fall season when bacterial and viral infections are more common. Therefore, we investigated using human B cells whether T‐cell‐independent factors ‐promoting cell survival, class switching and immunoglobulin secretion‐ BAFF, APRIL, IL‐10 and retinoic acid can boost IgA production in the context of viral or bacterial infection. To this end total and naive peripheral blood B cells were stimulated with these factors for 6 days in the presence or absence of TLR7/8 agonist R848 (mimicking viral infection) or TLR9 agonist CpG‐ODN (mimicking bacterial infection). We show that BAFF significantly augments IgA2 production in TLR7/8 stimulated mature, but not naïve B cells. In addition, BAFF augments IL‐10 production and viability in TLR7/8 and TLR9 stimulated mature B cells. These data warrant further investigation of its role in immune regulation both in the periphery and mucosal tissues in early life or during disease.

Gingival crevicular fluid as a periodontal diagnostic indicator--I: Host derived enzymes and tissue breakdown products

Researchers involved in the delivery of periodontal therapy are currently investigating the possible use of oral fluids in the diagnosis of oral diseases and drug development. Substantial improvements have been made in the understanding of the mediators implicated on the initiation, pathogenesis, and progression of periodontitis. This review will analyze the mechanisms involved in the breakdown of periodontal supporting tissues during chronic periodontitis and highlights the potential array of biomarkers present in gingival crevicular fluid (GCF), which may relate to existing or predicted tissue regions undergoing metabolic change.

Inflammation and wound healing in cats with chronic gingivitis/stomatitis after extraction of all premolars and molars were not affected by feeding of two diets with different omega-6/omega-3 polyunsaturated fatty acid ratios

Feline chronic gingivitis/stomatitis (FCGS) is a painful inflammatory disease in cats. Extraction of teeth, including all premolars and molars, has been shown to be the therapy of choice in cats not responding sufficiently to home care (e.g. tooth brushing) and/or medical treatment (corticosteroids and/or antibiotics). In this study, we hypothesize that a cat food with an omega-6 polyunsaturated fatty acid (ω6 PUFA) to ω3 PUFA ratio of 10:1 reduces inflammation of the FCGS and accelerates soft tissue wound healing of the gingiva after dental extractions, compared to a cat food with a ω6:ω3 PUFA ratio of 40:1. The cats were fed diets with chicken fat and fish oil as sources of fatty acids. In one diet, part of the fish oil was replaced by safflower oil, resulting in two diets with ω6:ω3 PUFA ratios of 10:1 and 40:1. This double-blinded study in two groups of seven cats revealed that dietary fatty acids influence the composition of plasma cholesteryl esters and plasma levels of inflammatory cytokines. The diet with the 10:1 ratio lowered PGD(2) , PGE(2) and LTB(4) plasma levels significantly, compared to the diet with the 40:1 ratio (p = 0.05, p = 0.04, and p = 0.02 respectively). However, feeding diets with dietary ω6:ω3 PUFA ratios of 10:1 and 40:1, given to cats with FCGS for 4 weeks after extraction of all premolars and molars, did not alter the degree of inflammation or wound healing.

Levels of specific immunoglobulin G to the forsythia detaching factor of Tannerella forsythia in gingival crevicular fluid are related to the periodontal status

BACKGROUND AND OBJECTIVE

Forsythia detaching factor (FDF) is a putative virulence factor of Tannerella forsythia that induces detachment of adherent cells and interleukin-8 production in human fibroblasts. The objective of the present study was to clarify the relationship between anti-FDF IgG levels in gingival crevicular fluid and the clinical status in patients with periodontitis and in healthy subjects.

MATERIAL AND METHODS

Gingival crevicular fluid and subgingival plaque samples were obtained from both the diseased and healthy sites of 37 patients with periodontitis and from 30 healthy subjects. Anti-FDF IgG levels were evaluated, and both the fdf gene and T. forsythia 16S ribosomal RNA (rRNA) were detected using the PCR.

RESULTS

Anti-FDF IgG levels (of both diseased and healthy sites) of patients with periodontitis were significantly higher than those of healthy subjects. Among the patients with periodontitis, anti-FDF IgG levels of healthy sites were significantly higher than those of diseased sites and the levels showed negative correlations with probing pocket depth and clinical attachment level. Among the patients with periodontitis, T. forsythia 16S rRNA was detected in 18 of 37 diseased sites and in 5 of 29 healthy sites, and the fdf gene was detected in 19 of 37 diseased sites and in 7 of 29 healthy sites. By contrast, no healthy subjects were positive for T. forsythia 16S rRNA or the fdf gene.

CONCLUSION

These data suggest that anti-FDF IgG levels in gingival crevicular fluid are related to the periodontal status.

Interpain A, a cysteine proteinase from Prevotella intermedia, inhibits complement by degrading complement factor C3

Periodontitis is an inflammatory disease of the supporting structures of the teeth caused by, among other pathogens, Prevotella intermedia. Many strains of P. intermedia are resistant to killing by the human complement system, which is present at up to 70% of serum concentration in gingival crevicular fluid. Incubation of human serum with recombinant cysteine protease of P. intermedia (interpain A) resulted in a drastic decrease in bactericidal activity of the serum. Furthermore, a clinical strain 59 expressing interpain A was more serum-resistant than another clinical strain 57, which did not express interpain A, as determined by Western blotting. Moreover, in the presence of the cysteine protease inhibitor E64, the killing of strain 59 by human serum was enhanced. Importantly, we found that the majority of P. intermedia strains isolated from chronic and aggressive periodontitis carry and express the interpain A gene. The protective effect of interpain A against serum bactericidal activity was found to be attributable to its ability to inhibit all three complement pathways through the efficient degradation of the alpha-chain of C3 -- the major complement factor common to all three pathways. P. intermedia has been known to co-aggregate with P. gingivalis, which produce gingipains to efficiently degrade complement factors. Here, interpain A was found to have a synergistic effect with gingipains on complement degradation. In addition, interpain A was able to activate the C1 complex in serum, causing deposition of C1q on inert and bacterial surfaces, which may be important at initial stages of infection when local inflammatory reaction may be beneficial for a pathogen. Taken together, the newly characterized interpain A proteinase appears to be an important virulence factor of P. intermedia.

Recovery of Bilophila wadsworthiafrom Clinical Specimens in Italy

This report is the first survey in Italy to evaluate the incidence of recovery of Bilophila wadsworthia in clinical situations. The survey was carried out at the departments of Microbiology in two Northern Italian hospitals over a one-year period. Tests for B. wadsworthia were carried out on a range of specimens from different body sites, when etiology by anaerobes was suspected. Out of a total of 350 samples examined, 67% were positive in bacteriological tests. Mixed anaerobic infections were detected in 53 specimens, corresponding to 23% of all cases. Strains of B. wadsworthia were isolated from 12 samples, equivalent to 5% and 22% of total and mixed/anaerobic infections, respectively. Bilophila wadsworthia was always isolated in mixed infections, mainly from the large intestine (67% of cases). The infectious process of B. wadsworthia was often complicated by abscess formation, regardless of body site. Interestingly, a strain was isolated from one case of bacteremia. The microorganisms most frequently isolated with B. wadsworthia were Escherichia coli for facultative species (38%), and Bacteroides fragilis, from anaerobic isolates (25%). Production of beta-lactamases by B. wadsworthia isolates was found in ten strains (83%), which appeared to be penicillin G resistant at concentration equal to or greater than the break-point (4 microg/mL). Epidemiological and clinical data from this and previous studies point to the involvement of B. wadsworthia in mixed infections. To assess the specific contribution of the species to the disease, studies of pathogenetic factors are to be considered in parallel. Nonetheless, production of beta-lactamases by most B. wadsworthia isolates could easily interfere with the therapeutical approach to infections involving the new species. The addition of a selective medium to culture specimens from the abdominal cavity should be considered in order to detect the presence of B. wadsworthia.

Bacteria and cancer: cause, coincidence or cure? A review

Research has found that certain bacteria are associated with human cancers. Their role, however, is still unclear. Convincing evidence links some species to carcinogenesis while others appear promising in the diagnosis, prevention or treatment of cancers. The complex relationship between bacteria and humans is demonstrated by Helicobacter pylori and Salmonella typhi infections. Research has shown that H. pylori can cause gastric cancer or MALT lymphoma in some individuals. In contrast, exposure to H. pylori appears to reduce the risk of esophageal cancer in others. Salmonella typhi infection has been associated with the development of gallbladder cancer; however S. typhi is a promising carrier of therapeutic agents for melanoma, colon and bladder cancers. Thus bacterial species and their roles in particular cancers appear to differ among different individuals. Many species, however, share an important characteristic: highly site-specific colonization. This critical factor may lead to the development of non-invasive diagnostic tests, innovative treatments and cancer vaccines.

Critical pathways in microbial virulence

The virulence of a microbe represents a combination of complex factors including the agent's transmissibility and the severity of the disease associated with infection and is also significantly influenced by the susceptibility of the colonized host. Virulence factors may be defined as those products of the organism which are required to complete the various stages of the life cycle leading to pathology in the host. In this review, we examine some of the approaches which have been adopted in other fields of infectious disease in order to categorically identify virulence factors using a classical genetics approach with relevant models or human subjects. The absence of an accurate experimental model for periodontal disease means that our understanding of the microbial virulence determinants and pathways in this disease remains hypothetical and based largely on observations in vitro. However, factors which enable the organism to persist in spite of the elevated immune and inflammatory pressure at sites of disease are liable to be critical. Periodontal bacterial genomics is liable to make a significant impact on the field through an increased appreciation of the role of gene acquisition and gene loss in the evolution of periodontal bacteria and of the consequences of strain variation in gene content on virulence potential.

Pathogenesis of apical periodontitis and the causes of endodontic failures

Apical periodontitis is a sequel to endodontic infection and manifests itself as the host defense response to microbial challenge emanating from the root canal system. It is viewed as a dynamic encounter between microbial factors and host defenses at the interface between infected radicular pulp and periodontal ligament that results in local inflammation, resorption of hard tissues, destruction of other periapical tissues, and eventual formation of various histopathological categories of apical periodontitis, commonly referred to as periapical lesions. The treatment of apical periodontitis, as a disease of root canal infection, consists of eradicating microbes or substantially reducing the microbial load from the root canal and preventing re-infection by orthograde root filling. The treatment has a remarkably high degree of success. Nevertheless, endodontic treatment can fail. Most failures occur when treatment procedures, mostly of a technical nature, have not reached a satisfactory standard for the control and elimination of infection. Even when the highest standards and the most careful procedures are followed, failures still occur. This is because there are root canal regions that cannot be cleaned and obturated with existing equipments, materials, and techniques, and thus, infection can persist. In very rare cases, there are also factors located within the inflamed periapical tissue that can interfere with post-treatment healing of the lesion. The data on the biological causes of endodontic failures are recent and scattered in various journals. This communication is meant to provide a comprehensive overview of the etio-pathogenesis of apical periodontitis and the causes of failed endodontic treatments that can be visualized in radiographs as asymptomatic post-treatment periapical radiolucencies.

Salivary and serum immunoglobulin levels in cats with chronic gingivostomatitis

The salivary and serum concentrations of immunoglobulins G, M and A (IgG, IgM and IgA), and the salivary concentrations of albumin were measured by ELISA in 30 cats with chronic gingivostomatitis and 32 healthy cats. The cats with chronic gingivostomatitis had significantly higher salivary concentrations of IgG, IgM and albumin, and higher serum concentrations of IgG, IgM and IgA, but significantly lower salivary concentrations of IgA than the healthy cats. The cats with chronic gingivostomatitis were treated with either methylprednisolone, sodium aurothiomalate, metronidazole and spiramycin, or oral hygiene products. After three months of treatment, the cats receiving methylprednisolone had a significant reduction in serum IgG levels compared to the cats treated with sodium aurothiomalate or metronidazole and spiramycin, but after six months of treatment there were no significant differences between the groups. Before the treatments, the levels of oral inflammation were not correlated significantly with any of the serum or salivary immunoglobulin levels. However, the changes in oral inflammation were correlated significantly with the changes in the salivary IgM concentration after three and six months of treatment, and with the change in the salivary IgA concentration after six months of treatment.

Salivary IgA subclasses and bacteria-reactive IgA in patients with aggressive periodontitis

The local salivary immunoglobulin A (IgA) response in patients with aggressive periodontitis to oral microorganisms and its role for the pathogenesis has not been determined. This study investigated the hypothesis that aggressive periodontitis patients have impaired oral secretory immunity. Our test group was made-up of 19 aggressive periodontitis patients and 19 age- and gender-matched periodontally healthy controls. Total IgA, IgA subclass 1, IgA subclass 2 and IgA reactive to Actinobacillus actinomycetemcomitans Y4, Treponema denticola ATCC 35404 and Candida albicans DSM 3454 were determined by enzyme-linked immunosorbent assay in whole unstimulated and stimulated saliva. A statistically significantly lower concentration and secretion rate of total salivary IgA (P < 0.01) and IgA1 (P < 0.001) was found in the aggressive periodontitis group in resting and stimulated saliva. A decrease of IgA2 (P < 0.05) was seen in resting saliva. Although only minor differences were detected in the concentration and secretion of bacteria-reactive IgA in both groups, the proportion of bacteria-reactive IgA from the total IgA was significantly higher (P < 0.01) in the aggressive periodontitis group in all three microorganisms tested. Our results indicate an inhibition of total secretory IgA. In particular an IgA subclass 1-specific decrease in aggressive periodontitis was noted, while the bacteria-reactive humoral immune system in saliva was activated. The role of the decrease of IgA1 immunoglobulins in aggressive periodontitis with respect to susceptibility for periodontal diseases has to be elucidated.

Identification and testing of Porphyromonas gingivalis virulence genes with a pPGIVET system

An in vivo expression technology (IVET) system was designed to identify previously unknown virulence genes of Porphyromonas gingivalis. Fourteen ivi (for in vivo induced) genes that are induced during infection in a mouse abscess model were identified in our study. Of these, seven had homology to genes in the NCBI database, and the rest had no homology to reported DNA sequences. In order to determine virulence-related properties of these genes, three mutant strains, deleted of ivi8 (no homology to genes in the database), ivi10 (homologous to a putative TonB-dependent outer membrane receptor protein), and ivi11 (an immunoreactive 33-kDa antigen PG125 in P. gingivalis), were created. The mutants were tested in a mouse abscess model for alterations in virulence relative to the wild type by a competition assay in BALB/c mice. After 5 days we observed the enrichment of the wild-type strain over mutant strains Deltaivi10 and Deltaivi11, which indicated that mutant strains Deltaivi10 and Deltaivi11 are less able to survive in this model than the wild-type strain, while Deltaivi8 survives as well as the wild-type strain. We propose that knockout of these ivi genes reduced the ability of the mutated P. gingivalis to survive and cause infection compared to the wild-type strain at the site of injection. Also, in separate experiments, groups of mice were challenged with subcutaneous injections of each individual mutant strain (Deltaivi8, Deltaivi10, and Deltaivi11) or with the wild-type strain alone and were then examined to assess their general health status. The results showed that knockout of these ivi genes conferred a reduction in virulence. The ability of the mutants to invade KB cells compared to the wild type was also determined. Interestingly, the CFU counts of the mutant strain Deltaivi10 recovered from KB cells were eight times lower than those of the wild type, indicating that this mutant has a lower capacity for invasion. These results demonstrate that IVET is a powerful tool in discovering virulence genes and the significant role that ivi genes play in the pathogenesis of this species.

The purification and characterization of an 88-kDa Porphyromonas endodontalis 35406 protease

A Porphyromonas endodontalis ATCC 35406 protease was purified from Triton X-114 cell extracts by preparative SDS-PAGE followed by electroelution. The purified enzyme exhibits a molecular size of 88 kDa and was dissociated into two polypeptides of 43 and 41 kDa upon heating in the presence of sodium dodecyl sulfate with or without a reducing agent. The protease (pH optimum 7.5-8.0) degraded the extracellular matrix proteins fibrinogen and fibronectin. Collagen IV was also degraded at 37 degrees C but not at 28 degrees C. The protease also cleaved the bioactive peptide angiotensin at amino acid residue phenylalanine-8 and tyrosine-4 but failed to hydrolyze bradykinin, vasopressin and synthetic chromogenic substrates with phenylalanine or tyrosine at the P1 position. In addition, two peptidases were detected in P. endodontalis cells: a proline aminopeptidase that remained associated with the cell pellet after detergent extraction and peptidase/s that partitioned into the Triton X-114 phase after phase separation and degraded the bioactive peptides bradykinin and vasopressin. These P. endodontalis peptidases and proteases may play an important role in both the nutrition and pathogenicity of these assacharolytic microorganisms. The inactivation of bioactive peptides and degradation of extracellular matrix proteins by bacterial enzymes may contribute to the damage of host tissues accompanied with endodontic infections.

Cysteine proteases of Porphyromonas gingivalis

The cysteine proteases of Porphyromonas gingivalis are extracellular products of an important etiological agent in periodontal diseases. Many of the in vitro actions of these enzymes are consistent with the observed deregulated inflammatory and immune features of the disease. They are significant targets of the immune responses of affected individuals and are viewed by some as potential molecular targets for therapeutic approaches to these diseases. Furthermore, they appear to represent a complex group of genes and protein products whose transcriptional and translational control and maturation pathways may have a broader relevance to virulence determinants of other persistent bacterial pathogens of human mucosal surfaces. As a result, the genetics, chemistry, and virulence-related properties of the cysteine proteases of P. gingivalis have been the focus of much research effort over the last ten years. In this review, we describe some of the progress in their molecular characterization and how their putative biological roles, in relation to the in vivo growth and survival strategies of P. gingivalis, may also contribute to the periodontal disease process.

Capnocytophaga granulosa and Capnocytophaga haemolytica: novel species in subgingival plaque

BACKGROUND

The oral cavity accommodates one of the most diverse microfloras in the human body. Knowledge of this microflora, and of the periodontal microflora in particular, proves crucial towards an understanding of the bacterial-host interactions which lead to the development of infectious inflammatory periodontal diseases. Capnocytophaga species have been implicated as putative periodontal pathogens. To date, only 3 members of this genus (C. gingivalis, C. ochracea and C. sputigena) have been isolated from subgingival plaque.

AIM

This communication reports the isolation of 2 recently-speciated strains, namely C. granulosa and C. haemolytica, from subgingival plaque collected from adult periodontitis patients.

MATERIAL AND METHODS

Subgingival plaque was collected from 29 patients with chronic adult periodontitis. Plaque samples were inoculated onto fastidious anaerobe agar and incubated anaerobically for 5 days. Routine identification of clinical isolates was performed by 16S rRNA PCR-RFLP analysis, using Cfo I as restriction enzyme and corroborated by 16S rRNA gene sequencing.

RESULTS

16 of 29 patients (55%) tested positive for either C. granulosa and or C. haemolytica. A total of 70 isolates (63 C. granulosa and 7 C. haemolytica) were cultivated from subgingival plaque. 15 (51%) patients tested positive for C. granulosa, and 3 (10%) patients tested positive for C. haemolytica.

CONCLUSION

This is the 1st report which recounts the presence of C. granulosa and C. haemolytica in subgingival plaque. Further research is required to establish the relative proportions of these species subgingivally in health and disease.

Inhibition of Actinobacillus actinomycetemcomitans leukotoxicity by bacteria from the subgingival flora

Actinobacillus actinomycetemcomitans produces a pore-forming leukotoxin that lyses human polymorphonuclear leukocytes and monocytes. Certain proteolytic bacteria may coexist with A. actinomycetemcomitans in periodontal pockets. We aimed therefore to examine whether oral bacteria can modify the leukotoxicity of A. actinomycetemcomitans. A total of 55 strains representing 45 bacterial species of the subgingival flora were tested. Each strain was incubated with the highly toxic strain of A. actinomycetemcomitans HK 1519 and the leukotoxic activity of the suspension against human polymorphonuclear leukocytes was determined from the activity of the lactate dehydrogenase released upon lysis of the leukocytes. Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Prevotella melaninogenica and Prevotella loeschii inhibited the leukotoxicity of A. actinomycetemcomitans cells as well as the activity of leukotoxin purified from the same strain. The bacterial strains without the ability to block leukotoxic activity also failed to destroy pure leukotoxin even after 5 h of incubation. The proteolytic degradation of leukotoxin by P. gingivalis was mainly dependent on the activity of the enzymes R- and K-gingipains. P. intermedia and P. nigrescens also degraded the leukotoxin by enzymes. The results imply a role of the periodontal microflora in modifying the virulence of A. actinomycetemcomitans by destroying its leukotoxin.

Generation of lys-gingipain protease activity in Porphyromonas gingivalis W50 is independent of Arg-gingipain protease activities

Porphyromonas gingivalis, a black-pigmenting anaerobe implicated in the aetiology of periodontal disease, contains two loci, rgpA and rgpB, encoding the extracellular Arg-X specific proteases (RGPs, Arg-gingipains), and kgp, which encodes a Lys-X specific protease (KGP, Lys-gingipain). The rgpA and kgp genes encode polyproteins comprising pro-peptide and catalytic domain with large N- and C-terminal extensions which require proteolytic processing at several Arg and Lys residues to generate mature enzymes. The product of rgpB contains only a pro-peptide and the catalytic domain which requires processing at an Arg residue to generate active enzyme. An rgpA rgpB double mutant (E8) of P. gingivalis was constructed to study the role of RGPs in the processing of KGP. A kgp mutant (K1A) was also studied to investigate the role of KGP in the generation of RGPs. E8 was stable in the absence of the antibiotics tetracycline and clindamycin (selection markers for rgpA and rgpB, respectively) and exhibited the same pigmentation, colony morphology and identical growth rates to the parent W50 strain in the absence of antibiotics, in both complex and chemically defined media. The KGP activity of E8, grown in the absence of tetracycline, in whole cultures and in culture supernatants (up to 6 d) was identical to levels in W50. However, in the presence of tetracycline in the growth medium, the level of KGP was reduced to 50% of levels present in whole cultures of W50. Since tetracycline had no effect on RGP or KGP activity when incorporated into assay buffer, this effect is most likely to be on the synthesis of Kgp polypeptide. K1A was also stable in the absence of antibiotics but was unable to pigment, and remained straw-coloured throughout growth. RGP activity in whole cultures of K1A was identical to levels in W50, but RGP activity in 6 d culture supernatants was reduced to 50% of levels present in W50. Thus, although KGP is not required for generation of RGP activity from RgpA and RgpB polypeptides, its absence affects the release/transport of RGP into culture supernatant.

Whole genomic DNA probe for detection of Porphyromonas endodontalis

The purpose of the present study was to develop a DNA probe for Porphyromonas endodontalis. Pure cultures of P. endodontalis were grown in TYP medium, in an anaerobic chamber. DNA was extracted from the P. endodontalis and labeled using the Genius System by Boehringer Mannheim. The labeled P. endodontalis DNA was used in dot-blot hybridization reactions with homologous (P. endodontalis) and unrelated bacterial samples. To determine specificity, strains of 40 other oral bacterial species (e.g. Porphyromonas gingivalis, Porphyromonas asaccharolytica, and Prevotella intermedia) were spotted and reacted with the P. endodontalis DNA probe. None of the panel of 40 oral bacteria hybridized with the P. endodontalis probe, whereas the blot of the homologous organism showed a strong positive reaction. To determine the sensitivity of the probe, dilutions of a P. endodontalis suspension of known concentration were blotted onto a nylon membrane and reacted with the probe. The results of our investigation indicate that the DNA probe that we have prepared specifically detects only P. endodontalis and can detect at least 3 x 10(4) cells.

Bactericidal activity of a monoclonal antibody against a recombinant 40-kDa outer membrane protein of Porphyromonas gingivalis

BACKGROUND

We have cloned the gene for a 40-kDa outer membrane protein (40-kDa OMP) from Porphyromonas gingivalis 381. The recombinant (r)40-kDa OMP has become the subject of considerable interest because of its potential role in the development of a vaccine useful for passive immunization. To develop such a vaccine, it is essential to fully understand the functions of anti-r40-kDa OMP antibody in the host defense against P. gingivalis. To that end, we developed a panel of monoclonal antibodies by immunizing mice with purified r40-kDa OMP. The objective of this study was to determine the bactericidal activity on P. gingivalis by the IgG1 monoclonal antibody Pg-ompA2.

METHODS

Bacterial growth measurement, a complement-mediated anti-P. gingivalis assay based on [3H]thymidine uptake, and a 14C-release assay were performed to test the bactericidal activity of Pg-ompA2 to P. gingivalis.

RESULTS

In the presence of complement, Pg-ompA2 was lethal to P. gingivalis 381 as well as to the more virulent P. gingivalis strains, including ATCC 53977 and W83. Using component-deficient complement, we determined that Pg-ompA2 killed P. gingivalis by activating both the classical and alternative complement pathways.

CONCLUSIONS

Pg-ompA2 has an in vitro complement-mediated bactericidal activity to P. gingivalis. Pg-ompA2 may contribute to the development of a local immunotherapy that can be applied in the gingival crevice of a patient with P. gingivalis-related periodontitis, or be a vaccine candidate.

Bait region cleavage and complex formation of human alpha2M with a Porphyromonas gingivalis W50 protease is not accompanied by enzyme inhibition

Three isoforms of extracellular Arg-specific proteases of P. gingivalis, W50, HRgpA, RgpAcat and mt-RgpAcat, which are all products of the same gene, show identical enzymatic properties toward small chromogenic substrates but have different subunit organisation and molecular size. In order to examine the potential inhibition of these proteases in vivo by host protease inhibitors, the interaction of HRgpA (approximately 110 kDa) and RgpAcat (approximately 55 kDa) with human (alpha2M and their cytotoxicity toward cultured fibroblasts were investigated. Both enzymes formed complexes with (alpha2M as shown by gel filtration chromatography and both cleaved the 'bait' region at Arg696-Leu697. However, whereas (alpha2M-RgpAcat) complex was unable to hydrolyse large substrates such as hide powder azure, (alpha2M-HRgpA) complex hydrolysed both small and large substrates. HRgpA was able to bind to alpha2M saturated with trypsin and also to methylamine-treated alpha2M. This suggested that HRgpA is able to bind to both 'slow' and 'fast' forms of alpha2M and formation of (alpha2M:HRgpA) complex does not trap HRgpA and cause inhibition of activity toward hide powder azure. However, the (alpha2M-HRgpA) complex is not able to cleave other alpha2M molecules, which suggests that the active site of HRgpA in the complex is constrained probably due to steric reasons. The (alpha2M-HRgpA) complex was cytotoxic to 3T3 cells, causing them to round up and detach from the surface with a reduction in metabolic activity.

Proteolysis and utilization of albumin by enrichment cultures of subgingival microbiota

Subgingival dental plaque consists mainly of microorganisms that derive their energy from amino acid fermentation. Their nutrient requirements are met by the subgingival proteolytic system, which includes proteases from microorganism and inflammatory cells, and substrate proteins from sulcus exudate, including albumin. To determine the selective effect of individual proteins on microbiota, we used albumin as the main substrate for growth. Eight subgingval plaque samples from untreated periodontal pockets of patients with adult periodontitis were inoculated in peptone yeast medium with bovine albumin (9 g/l). After three subculture steps, cell yields of the enrichment cultures at the medium with 0, 1.25, 2.5, 5, 10, and 20 g/l albumin were determined. Proteolytic activity (U/absorbance at 550 nm) of the enrichment cultures and different isolates derived from the cultures was estimated by the degradation of resorufin-labeled casein. It was observed that the yield of the mixed culture was albumin limited, and the proteolytic activities of the cultures in albumin broth were higher than in control (peptone broth). Among the isolates from the enrichment cultures, Peptostreptococcus micros, Prevotella melaninogenica, Prevotella buccae and Prevotella bivia demonstrated proteolysis. The frequent occurrence of Streptococcus gordonii and Streptococcus anginosus in the albumin cultures is explained by their ability to utilize arginine as an energy source for growth. Albumin in the medium was partly degraded by pure cultures but completely consumed in enrichment cultures, indicating synergy of bacterial proteinases. It is concluded that the subgingival microbiota possesses proteolytic activity and may use albumin as a substrate for their growth. Enrichment cultures on albumin may serve as a relatively simple in vitro model to evaluate the effects of proteinase inhibitors.

Changes in gingival crevicular fluid levels of immunoglobulin A following therapy: association with attachment loss

BACKGROUND

In previous studies, we demonstrated that increased levels of immunoglobulin A (IgA) in gingival crevicular fluid (GCF) may be "protective", while increased levels of the polymorphonuclear lysosomal enzyme, beta-glucuronidase, in GCF were associated with increased risk of disease activity. In this study, we examined the effect of scaling and root planing (SRP) on the levels of beta-glucuronidase, IgG, and IgA in GCF over a 24-week period and compared these to clinical attachment loss (CAL).

METHODS

Twenty-nine patients with periodontal disease were examined for attachment level, probing depth, plaque, and bleeding on probing at 6 sites per tooth. GCF was collected from the mesial aspect of all teeth excluding third molars and analyzed for beta-glucuronidase, IgG, and IgA. After baseline data were collected, each patient received SRP, and GCF was collected again at 2, 4, 6, 8, 12, and 24 weeks post-SRP while clinical data were obtained at 4, 8, 12, and 24 weeks. In addition, we analyzed whether the magnitude of the IgA response to SRP would affect the rate of periodontal disease progression by examining GCF IgA levels at 2 time intervals: 2 to 4 weeks post-SRP and 6 to 12 weeks post-SRP.

RESULTS

Seventeen patients (58.6%) exhibited at least 1 site losing > or =2.5 mm of CAL during the 24-week study. Beta-glucuronidase in GCF was significantly decreased at 2 weeks following SRP and then demonstrated a gradual increase throughout the study period. Levels of IgA in GCF significantly increased following SRP, reaching a peak at 6 weeks and then gradually decreasing throughout the study. Furthermore, we found an inverse relationship between GCF IgA levels at 6 to 12 weeks post-SRP and the occurrence of CAL.

CONCLUSIONS

These results support the hypothesis that maintenance of high levels of IgA in GCF may be "protective" against periodontal attachment loss. Furthermore, levels of beta-glucuronidase appear to be a more sensitive indicator of gingival inflammation than clinical measures.

Purification, characterization, and sequence analysis of a potential virulence factor from Porphyromonas gingivalis, peptidylarginine deiminase

The initiation and progression of adult-onset periodontitis has been associated with infection of the gingival sulcus by Porphyromonas gingivalis. This organism utilizes a multitude of virulence factors to evade host defenses as it establishes itself as one of the predominant pathogens in periodontal pockets. A feature common to many other oral pathogens is the production of ammonia due to its protective effect during acidic cleansing cycles in the mouth. Additionally, ammonia production by P. gingivalis has been proposed as a virulence factor due to its negative effects on neutrophil function. In this study, we describe the first purification of a peptidylarginine deiminase (PAD) from a prokaryote. PAD exhibits biochemical characteristics and properties that suggest that it may be a virulence agent. PAD deiminates the guanidino group of carboxyl-terminal arginine residues on a variety of peptides, including the vasoregulatory peptide-hormone bradykinin, to yield ammonia and a citrulline residue. The soluble protein has an apparent mass of 46 kDa, while the DNA sequence predicts a full-length protein of 61.7 kDa. PAD is optimally active at 55 degrees C, stable at low pH, and shows the greatest activity above pH 9.0. Interestingly, in the presence of stabilizing factors, PAD is resistant to limited proteolysis and retains significant activity after short-term boiling. We propose that PAD, acting in concert with arginine-specific proteinases from P. gingivalis, promotes the growth of the pathogen in the periodontal pocket, initially by enhancing its survivability and then by assisting the organism in its circumvention of host humoral defenses.

Opsonophagocytic effect of antibody against recombinant conserved 40-kDa outer membrane protein of Porphyromonas gingivalis

BACKGROUND

Porphyromonas gingivalis is associated with the initiation and progression of adult periodontitis. The outer membrane proteins of the bacteria are potentially important targets for interaction with host defense systems. A 40-kDa outer membrane protein (40-kDa OMP) is conserved among many strains of P. gingivalis. We have cloned the gene for 40-kDa OMP from P. gingivalis 381 and produced a recombinant protein. For the development of recombinant 40-kDa OMP as a component of a vaccine for passive immunization, the elucidation of the roles of the anti-recombinant 40-kDa OMP antibody in the host defense against P. gingivalis is essential. The objective of this study was to determine the opsonic capacity of the antibody for phagocytosis by neutrophils which play a key role in the immune response to microbial infections.

METHODS

To test the opsonic activity of a rabbit polyclonal antibody against r40-kDa OMP (r40-kDa OMP Ab) on human neutrophils to phagocytize P. gingivalis, we constructed a reproducible in vitro model of P. gingivalis-neutrophil interaction using the human promyelocytic cell line HL-60.

RESULTS

We demonstrated that r40-kDa OMP Ab in the presence of human complement successfully opsonized [3H]-thymidine-labeled P. gingivalis as a target for phagocytosis by HL-60 cells differentiated with dimethyl sulfoxide. The phagocytized bacteria were then intracellularly killed and lysed, and the radioactive degradation debris egested into the culture medium.

CONCLUSIONS

We conclude that antibody against r40-kDa OMP has opsonic activity on human neutrophil function for phagocytosis of P. gingivalis. Subgingival bacteria are coated in vivo with immunoglobulin and complement. When the antibody is specific for crevicular bacteria, immunological interactions can be expected in the crevice. Our observations suggest that the anti-recombinant 40-kDa OMP antibody in concert with the crevicular complement may prevent P. gingivalis colonization r40-kDa OMP may contribute to the development of a local immunotherapy when applied to the crevice of a patient with P. gingivalis-related periodontitis which relates to susceptibility for certain systemic diseases such as diabetes mellitus, cardiovascular disease, and preterm labor.

Modulation of major histocompatibility complex protein expression by human gamma interferon mediated by cysteine proteinase-adhesin polyproteins of Porphyromonas gingivalis

Cysteine proteinases have been emphasized in the virulence of Porphyromonas gingivalis in chronic periodontitis. These hydrolases may promote the degradation of extracellular matrix proteins and disrupt components of the immune system. In this study it was shown that purified Arg-gingipain and Lys-gingipain inhibited expression of class II major histocompatibility complex (MHC) proteins in response to the stimulation of endothelial cells with human gamma interferon (IFN-gamma). Treatment with the cysteine proteinases resulted in a rapid shift in the apparent molecular size of IFN-gamma from 17 to 15 kDa, as shown by Western blot analysis, a response which also occurred in the presence of serum. Further, glycosylated natural IFN-gamma from human leukocytes and unglycosylated recombinant IFN-gamma from Escherichia coli were both digested by the cysteine proteinases. Immunoblot analysis indicated that cleavage within the carboxyl terminus of recombinant IFN-gamma correlated with the loss of induction of MHC class II expression as monitored by analytical flow cytometry. No hydrolysis of MHC class II molecules or human IFN-gamma receptor by these proteinases was detected by Western blot analysis. These findings suggest that P. gingivalis cysteine proteinases may alter the cytokine network at the point of infection through the cleavage of IFN-gamma. Degradation of IFN-gamma could have important consequences for the recruitment and activation of leukocytes and therefore may contribute significantly to the destruction of the periodontal attachment.

Black-pigmented anaerobic rods in closed periapical lesions

AIM

This study determined the frequency of Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens in 20 closed periapical lesions associated with symptomatic and asymptomatic refractory endodontic disease.

METHODOLOGY

To deliniate possible oral sources of P. endodontalis, the presence of the organism was assessed in selected subgingival sites and saliva in the same study patients. Periapical samples were obtained by paper points during surgical endodontic procedures using methods designed to minimize contamination by non-endodontic microorganisms. Subgingival plaque samples were obtained by paper points from three periodontal pockets and from the pocket of the tooth associated with the closed periapical lesion. Unstimulated saliva was collected from the surface of the soft palate. Bacterial identification was performed using a species-specific polymerase chain reaction (PCR) detection method.

RESULTS

P. endodontalis was not identified in any periapical lesion, even though subgingival samples from eight patients (40%) revealed the P. endodontalis-specific amplicon. P. gingivalis occurred in one periapical lesion that was associated with moderate pain. P. nigrescens, P. endodontalis and P. intermedia were not detected in any periapical lesion studied.

CONCLUSIONS

Black-pigmented anaerobic rods appear to be infrequent inhabitants of the closed periapical lesion.

Growth and hydrolytic enzyme production of Capnocytophaga gingivalis on different protein substrates

Capnocytophaga gingivalis was grown with proteins (albumin, collagen, mucin and hemoglobin) as carbon and energy sources in chemostat culture. The mu max (0.34 h-1) and biomass yield (0.96 g.l-1) were as high with hemoglobin (3 g.l-1) as with glucose (3 g.l-1) (20). Albumin, collagen and mucin also supported an increased mu max, or yield or both, in comparison with basal (tryptone/thiamine) medium. In steady-state, trypsin-like protease specific activity increased 3- to 5-fold in the presence of albumin, collagen and hemoglobin: whereas the greatest increase (21-fold) in alpha-glucoside activity was in the presence of mucin. There were significant, but less substantial changes in other hydrolytic enzymes (aminopeptidase, acid and alkaline phosphatases). The bulk of the detected hydrolytic activity (> 66%) was associated with the cells. The data indicate that C. gingivalis regulates its production of hydrolytic enzymes in response to environmental conditions.

Evaluation of immunoglobulin A1 (IgA1) protease and IgA1 protease-inhibitory activity in human female genital infection with Neisseria gonorrhoeae

Immunoglobulin A1 (IgA1) protease, an enzyme that selectively cleaves human IgA1, may be a virulence factor for pathogenic organisms such as Neisseria gonorrhoeae. Host protection from the effects of IgA1 protease includes antibody-mediated inhibition of IgA1 protease activity, and it is believed that the relative balance between IgA1 protease and inhibitory antibodies contributes to the pathogenesis of disease caused by IgA1 protease-producing organisms. We have examined the levels of these two opposing factors in genital tract secretions and sera from women with uncomplicated infection with N. gonorrhoeae. When IgA1 in cervical mucus was examined by Western blotting, no evidence of cleavage fragments characteristic of IgA1 protease activity was seen in gonococcus-infected or control patients. Cleavage fragments typical of IgA1 protease were detected, however, after the addition of exogenous IgA1 protease to cervical mucus. Degraded IgA1 was detected in some vaginal wash samples, but the fragment pattern was not typical of IgA1 protease activity. All N. gonorrhoeae isolates from the infected patients produced IgA1 protease in vitro. All but two serum samples and 16 of 65 cervical mucus samples displayed inhibitory activity against gonococcal IgA1 protease, but there was no significant difference in the level of inhibitory activity between gonococcus-infected and noninfected patients in either cervical mucus or serum. There was no difference in the levels of IgA1 protease-inhibitory activity in serum or cervical mucus collected from patients at recruitment and 2 weeks later. These results suggest that cleavage of IgA1 by gonococcal IgA1 protease within the lumen of the female lower genital tract is unlikely to be a significant factor in the pathogenesis of infections by N. gonorrhoeae.

Proteases of Porphyromonas gingivalis: what don't they do?

The gram-negative anaerobic bacterium Porphyromonas gingivalis has been strongly associated with the causation of human periodontal diseases. One distinguishing property of these organisms that has been implicated in periodontal destruction is the expression of potent protease activity. Recent biochemical and genetic approaches have clearly demonstrated that at least five distinct proteases are elaborated by these organisms. The utilization of monospecific mutants defective in individual proteases has demonstrated that protease activity is important in virulence but also has suggested the complexity of the functions of the enzymes in the physiology of these microorganisms. This review summarizes current progress in assessing the role of these enzymes in periodontal inflammation and discusses some unresolved issues relevant to the significance of P. gingivalis proteases in virulence.

Circulating antibody secreting cell response to parenteral pneumococcal vaccines as an indicator of a salivary IgA antibody response

This study assessed the mucosal immune response in healthy adult volunteers immunized parenterally with either pneumococcal polysaccharide (N = 8) or pneumococcal polysaccharide-protein conjugate (N = 10) vaccine with an aim to evaluate the relevance of antibody secreting cell (ASC) response after parenteral vaccination. An ASC response to the four types of capsular polysaccharide tested was observed in all vaccinees 7-9 days after immunization. IgA was the predominant class in the ASC response, and IgG the next common, with very few IgM ASCs. The IgA/IgG ratio in the ASC response was higher after immunization with the polysaccharide than the conjugate vaccine. Antibodies of the IgA class were frequently seen in the saliva already before immunization; especially to serotypes 14 and 19F. A twofold increase of the type specific secretory IgA antibodies in saliva was found in eight of the 16 instances in which the specific IgA ASC response was > 100 ASC per 10(6) cells and in only one of the 52 instances with fewer ASCs. We conclude that the ASC response in the peripheral blood is a useful parameter of the antibody response to pneumococcal vaccines and a good indicator of a secretory IgA response in the saliva.