Suppression of fibroblast proliferation by oral spirochetes

Challenge of Bovine Foot Skin Fibroblasts With Digital Dermatitis Treponemes Identifies Distinct Pathogenic Mechanisms

Bovine digital dermatitis (BDD) is a common infectious disease of digital skin in cattle and an important cause of lameness worldwide, with limited treatment options. It is of increasing global concern for both animal welfare and food security, imposing a large economic burden on cattle farming industries each year. A polytreponemal etiology has been consistently identified, with three key phylogroups implicated globally: Treponema medium, Treponema phagedenis, and Treponema pedis. Pathogenic mechanisms which might enable targeted treatment/therapeutic development are poorly defined. This study used RNA sequencing to determine global differential mRNA expression in primary bovine foot skin fibroblasts following challenge with three representative BDD treponemes and a commensal treponeme, Treponema ruminis. A pro-inflammatory response was elicited by the BDD treponemes, mediated through IL-8/IL-17 signaling. Unexpectedly, the three BDD treponemes elicited distinct mechanisms of pathogenesis. T. phagedenis and T. pedis increased abundance of mRNA transcripts associated with apoptosis, while T. medium and T. pedis increased transcripts involved in actin rearrangement and loss of cell adhesion, likely promoting tissue invasion. The upregulation of antimicrobial peptide precursor, DEFB123, by T. phagedenis spirochaetes may present a microbial ecological advantage to all treponemes within BDD infected tissue, explaining their dominance within lesions. A commensal, T. ruminis, significantly dysregulated over three times the number of host mRNA transcripts compared to BDD treponemes, implying BDD treponemes, akin to the syphilis pathogen (Treponema pallidum), have evolved as "stealth pathogens" which avoid triggering substantial host immune/inflammatory responses to enable persistence and tissue invasion. Immunohistochemistry demonstrated increased IL-6, IL-8, RND1, and CFB protein expression in BDD lesions, confirming in vitro fibroblast observations and highlighting the system's value in modeling BDD pathogenesis. Several unique shared gene targets were identified, particularly RGS16, GRO1, MAFF, and ZC3H12A. The three key BDD Treponema phylogroups elicited both distinct and shared pathogenic mechanisms in bovine foot skin; upregulating inflammation whilst simultaneously suppressing adaptive immunity. The novel gene targets identified here should enable future vaccine/therapeutic approaches.

Oral spirochetes: Pathogenic mechanisms in periodontal disease

Periodontitis is an infectious inflammatory disease resulting from infection of biofilm forming bacteria. Several bacterial factors regulate inflammatory response and cause to tissue damage and loss of connection between gingival and tooth. Since bacterial virulence factors and also host immune responses have role, understanding of periodontal disease is complex, in overall we can say that in this disease epithelium is deleted by bacteria. Oral spirochetes are related to periodontitis, among them, Treponema denticola, have been associated with periodontal diseases such as early-onset periodontitis, necrotizing ulcerative gingivitis, and acute pericoronitis. This review will analyse mechanisms of pathogenesis of spirochetes in periodontitis. Microorganisms cause destruction of gingival tissue by two mechanisms. In one, damage results from the direct action of bacterial enzymes and cytotoxic products of bacterial metabolism. In the other, only bacterial components have role, and tissue destruction is the inevitable side effect of a subverted and exaggerated host inflammatory response to plaque antigens.

Salivary type I collagen degradation end-products and related matrix metalloproteinases in periodontitis

AIM

Type I collagen degradation end-products and related matrix metalloproteinases (MMPs) were examined aiming to detect potential markers of periodontitis in saliva, with high sensitivity and specificity.

MATERIALS AND METHODS

The salivary concentrations of MMP-8, MMP-9 and MMP-13, tartrate-resistant acid phosphatase serum type 5b, C-terminal cross-linked telopeptide of type I collagen (CTx), N-terminal cross-linked telopeptide of type I collagen (NTx) and cross-linked carboxyterminal telopeptide of type I collagen were analysed in 230 subjects. Oral health examination included panoramic radiography.

RESULTS

The concentrations of MMP-8, MMP-9 and MMP-13 in saliva were higher in subjects with generalized periodontitis than in controls. Of the tested salivary markers, MMP-8 was the only marker capable of differentiating subjects with severe alveolar bone loss from those with slight bone loss (p < 0.001). The association between the salivary MMP-8 levels and periodontitis remained significant after the adjustment with age, gender and smoking. In addition, significant correlations were found between the tested markers and periodontal parameters.

CONCLUSION

Enzymes and end-products of type I collagen degradation have different associations with each other and with periodontal status that may reflect their roles in the cascade leading to alveolar bone loss. MMP-8 is a strong biomarker candidate for detecting alveolar bone destruction.

Treponema denticola interactions with host proteins

Oral Treponema species, most notably T. denticola, are implicated in the destructive effects of human periodontal disease. Progress in the molecular analysis of interactions between T. denticola and host proteins is reviewed here, with particular emphasis on the characterization of surface-expressed and secreted proteins of T. denticola involved in interactions with host cells, extracellular matrix components, and components of the innate immune system.

Oral bacterial extracts facilitate early osteogenic/dentinogenic differentiation in human dental pulp-derived cells

OBJECTIVES

Bacterial metabolites demineralize dental hard tissues, and soluble factors lead to tertiary dentinogenesis in the area of the dentin-pulp complex. However, it is unclear whether the oral bacteria are directly involved in the differentiation of dental pulp cells. In this study, we evaluated the effect of oral bacterial extracts on cellular differentiation in human dental pulp-derived cells (hDPC).

STUDY DESIGN

The hDPC were obtained from third molar teeth, and the cells were subcultured. The sonicated extracts were obtained from Porphyromonas gingivalis (gram-negative) and Streptococcus mutans (gram-positive). The effect of bacterial extracts on cellular growth and differentiation in hDPC were tested.

RESULTS

Alkaline phosphatase activity and bone sialoprotein (BSP) gene expression were increased in hDPC exposed to low concentrations of both sonicated extracts, whereas the activity was decreased upon exposure to high concentrations of sonicated extracts from P. gingivalis.

CONCLUSION

This is the first evidence that oral bacteria have a positive effect on cellular differentiation in hPDC.

The chymotrypsin-like protease complex of Treponema denticola ATCC 35405 mediates fibrinogen adherence and degradation

Treponema denticola is an anaerobic spirochete strongly associated with human periodontal disease. T. denticola bacteria interact with a range of host tissue proteins, including fibronectin, laminin, and fibrinogen. The latter localizes in the extracellular matrix where tissue damage has occurred, and interactions with fibrinogen may play a key role in T. denticola colonization of the damaged sites. T. denticola ATCC 35405 showed saturable binding of fluid-phase fibrinogen to the cell surface and saturable adherence to immobilized fibrinogen. Levels of fibrinogen binding were enhanced in the presence of the serine protease inhibitor phenylmethylsulfonyl fluoride. The Aalpha and Bbeta chains of fibrinogen, but not the gamma chains, were specifically recognized by T. denticola. Following fibrinogen affinity chromatography analysis of cell surface extracts, a major fibrinogen-binding component (polypeptide molecular mass, approximately 100 kDa), which also degraded fibrinogen, was purified. Upon heating at 100 degrees C, the polypeptide was dissociated into three components (apparent molecular masses, 80, 48, and 45 kDa) that did not individually bind or degrade fibrinogen. The native 100-kDa polypeptide complex was identified as chymotrypsin-like protease (CTLP), or dentilisin. In an isogenic CTLP(-) mutant strain, CKE, chymotrypsin-like activity was reduced >90% compared to that in the wild type and fibrinogen binding and hydrolysis were ablated. Isogenic mutant strain MHE, deficient in the production of Msp (major surface protein), showed levels of CTLP reduced 40% relative to those in the wild type and exhibited correspondingly reduced levels of fibrinogen binding and proteolysis. Thrombin clotting times in the presence of wild-type T. denticola cells, but not strain CKE (CTLP(-)) cells, were extended. These results suggest that interactions of T. denticola with fibrinogen, which may promote colonization and modulate hemostasis, are mediated principally by CTLP.

Mixed infections with Porphyromonas gingivalis and Treponema denticola cause excessive inflammatory responses in a mouse pneumonia model compared with monoinfections

Periodontopathic anaerobes such as Porphyromonas gingivalis are frequently found in aspiration pneumonia and lung abscesses. However, defense mechanisms and responses to these bacterial infections in the lung in vivo remain poorly understood. The coexistence of P. gingivalis with Treponema denticola has been found at higher levels and proportions in periodontally diseased sites. We hypothesized that mixed infections with P. gingivalis and T. denticola can cause severe respiratory disease. In the present study, inflammatory responses to mono- and mixed inoculations with P. gingivalis and T. denticola in the bronchoalveolar lavage (BAL) fluid were investigated. Acute pneumonia and lung abscesses in mice with the mixed infection resulted in a 40% mortality rate within 72 h, compared with only 10% mortality for the respective monoinfections. Pulmonary clearance of P. gingivalis was delayed in the mice with mixed infections with P. gingivalis and T. denticola. Tumor necrosis factor alpha (TNFalpha) interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) levels from BAL fluid of mice with mixed infections at 24 h after inoculation were significantly higher than those after P. gingivalis monoinfection (TNFalpha: P < 0.05, Il-1beta: P < 0.001, IL-6: P < 0.05). The chemokine KC level from BAL fluid of mice at 48 h (P < 0.05) and 72 h after mixed infection was also significantly increased when compared with that after P. gingivalis monoinfection (P < 0.001). The present study demonstrates that a mixed infection of P. gingivalis with T. denticola in mouse causes a marked bronchopneumonia and lung abscess in the mouse model.

Treponema denticola may stimulate both epithelial proliferation and apoptosis through MAP kinase signal pathways

Mitogen-activated protein kinases (MAP kinases) play a key role in the regulation of cell survival and death. Effects of Treponema denticola ATCC 35405 on ERK, p38 and JNK MAP kinases, and cell behavior was studied using non-keratinizing periodontal ligament epithelial cells (PLE) in vitro. Compared to Chinese hamster ovary cells, human cervix adenocarcinoma cells, human osteosacroma cells and human gingival fibroblasts, PLE cells were much more resistant to T. denticola-induced reduction in cell viability, assayed by tetrazolium and crystal violet assays. A low dose of 5 x 10(7) T. denticola cells/ml increased DNA synthesis ([3H]thymidine uptake) in PLE cells but at higher concentrations DNA synthesis was decreased. TUNEL staining analysis showed that about 50% of epithelial cells in onolayers died through apoptosis when exposed to a high dose of 10(11) T. denticola/ml for 24 h. Morphological light and electron microscopic analysis supported the idea that both apoptotic and necrotic cell death took place. Rounding, membrane damage, fragmentation and detachment were observed in selective cells of both mono- and multilayered PLE cultures challenged with T. denticola. Western blot analysis using MAP kinase phosphospecific antibodies showed that T. denticola strongly but transiently activated ERK1 and ERK2, signals mediating cell proliferation, and JNK and p38, kinases mediating apoptosis. While a specific inhibitor of the ERK MAP kinase pathway prevented the T. denticola stimulation of cell proliferation, inhibitor of p38 increased the cell numbers in T. denticola-treated cultures. The results suggest that T. denticola activates epithelial cell MAP kinase signal pathways controlling cell proliferation and cell survival. In addition, T. denticola exerts cytotoxic effects that appear to predominate at higher bacterial concentrations.

Role of Treponema denticola in periodontal diseases

Among periodontal anaerobic pathogens, the oral spirochetes, and especially Treponema denticola, have been associated with periodontal diseases such as early-onset periodontitis, necrotizing ulcerative gingivitis, and acute pericoronitis. Basic research as well as clinical evidence suggest that the prevalence of T denticola, together with other proteolytic gram-negative bacteria in high numbers in periodontal pockets, may play an important role in the progression of periodontal disease. The accumulation of these bacteria and their products in the pocket may render the surface lining periodontal cells highly susceptible to lysis and damage. T. denticola has been shown to adhere to fibroblasts and epithelial cells, as well as to extracellular matrix components present in periodontal tissues, and to produce several deleterious factors that may contribute to the virulence of the bacteria. These bacterial components include outer-sheath-associated peptidases, chymotrypsin-like and trypsin-like proteinases, hemolytic and hemagglutinating activities, adhesins that bind to matrix proteins and cells, and an outer-sheath protein with pore-forming properties. The effects of T. denticola whole cells and their products on a variety of host mucosal and immunological cells has been studied extensively (Fig. 1). The clinical data regarding the presence of T. denticola in periodontal health and disease, together with the basic research results involving the role of T. denticola factors and products in relation to periodontal diseases, are reviewed and discussed in this article.

Fimbria-mediated coaggregation between human oral anaerobes Treponema medium and Porphyromonas gingivalis

Bacterial binding phenomena among different bacterial genera or species play an important role in bacterial colonization in a mixed microbiota such as in the human oral cavity. The coaggregation reaction between two gram-negative anaerobes, Treponema medium and Porphyromonas gingivalis, was characterized using fimbria-deficient mutants of P. gingivalis and specific antisera against purified fimbriae and bacterial whole cells. T. medium ATCC 700273 strongly coaggregated with fimbriate P. gingivalis strains ATCC 33277 and 381, but not with afimbriate strains including transposon-induced fimbria-deficient mutants and KDP98 as a fimA-disrupted mutant of P. gingivalis ATCC 33277. In the P. gingivalis-T. medium coaggregation assay, the presence of rabbit antiserum against the purified fimbriae or the whole cells of P. gingivalis ATCC 33277 produced different "aggregates" consisting predominantly of P. gingivalis cells with few spirochetes, but both preimmune serum and the antiserum against the afimbriate KDP98 cells did not inhibit the coaggregation reaction. Heated P. gingivalis cells lost their ability to bind both heated and unheated T. medium cells. This T. medium-P. gingivalis coaggregation reaction was inhibited by a cysteine proteinase inhibitor, leupeptin, and also by arginine and lysine, but not by EDTA or sugars including lactose. A binding assay on nitrocellulose membranes and immunoelectron microscopy demonstrated that a heat-stable 37 kDa surface protein on the T. medium cell attached to the P. gingivalis fimbriae.

Treponema denticola outer membrane enhances the phagocytosis of collagen-coated beads by gingival fibroblasts

Human gingival fibroblasts (HGFs) degrade collagen fibrils in physiological processes by phagocytosis. Since Treponema denticola outer membrane (OM) extract perturbs actin filaments, important structures in phagocytosis, we determined whether the OM affects collagen phagocytosis in vitro by HGFs. Phagocytosis was measured by flow cytometric assessment of internalized collagen-coated fluorescent latex beads. Confluent HGFs pretreated with T. denticola ATCC 35405 OM exhibited an increase in the percentage of collagen phagocytic cells (phagocytosis index [PI]) and in the number of beads per phagocytosing cell (phagocytic capacity [PC]) compared with untreated controls. The enhancement was swift (within 15 min) and was still evident after 1 day. PI and PC of HGFs for bovine serum albumin (BSA)-coated beads were also increased, indicating a global increase in phagocytic processes. These results contrasted those for control OM from Veillonella atypica ATCC 17744, which decreased phagocytosis. The T. denticola OM-induced increase in bead uptake was eliminated by heating the OM and by depolymerization of actin filaments by cytochalasin D treatment of HGFs. Fluid-phase accumulation of lucifer yellow was enhanced in a saturable, concentration-dependent, transient manner by the T. denticola OM. Our findings were not due to HGF detachment or cytotoxicity in response to the T. denticola OM treatment since the HGFs exhibited minimal detachment from the substratum; they did not take up propidium iodide; and there was no change in their size, granularity, or content of sub-G1 DNA. We conclude that a heat-sensitive component(s) in T. denticola OM extract stimulates collagen phagocytosis and other endocytic processes such as nonspecific phagocytosis and pinocytosis by HGFs.

Cytopathic effects of the major surface protein and the chymotrypsinlike protease of Treponema denticola

Prominent antigens of Treponema denticola have been suggested to be mediators of the cytopathic effects typically seen in periodontal disease. In the present study of the T. denticola major surface protein (Msp) and the surface-expressed chymotrypsinlike protease complex (CTLP), we characterized the ability of these proteins to adhere to and lyse epithelial cells. Msp and CTLP were closely associated in spirochete outer membranes. Purified Msp, both native and recombinant, and CTLP bound to glutaraldehyde-fixed periodontal ligament epithelial cells. Adherence of Msp was partially blocked by specific antibodies. Adherence of CTLP was partially blocked by serine protease inhibitors and was further inhibited by specific antibodies. Both native Msp and CTLP were cytotoxic toward periodontal ligament epithelial cells, and their cytotoxicity was inhibited by the same treatments that inhibited adherence. Msp, but not CTLP, lysed erythrocytes. Msp complex (partially purified outer membranes free of protease activity) was cytotoxic toward a variety of different cell types. Pore-forming activities of recombinant Msp in black lipid model membrane assays and in HeLa cell membranes were similar to those reported for the native protein, supporting the hypothesis that Msp cytotoxicity was due to its pore-forming activity.

Adherence of human oral spirochetes by collagen-binding proteins

The ability of spirochetes to adhere to collagens was compared among three species of human oral treponemes. Immunoblot analysis demonstrated that type I-, IV-, and V-collagen-binding polypeptides (CBPs) were detected in the heated and unheated preparations from both Treponema denticola ATCC 33520 and T. socranskii subsp. buccale ATCC 35534. Few CBPs, however, were detected in the heated and unheated preparations from a recently characterized isolate, T. medium strain G7201. Immunoelectron microscopy using rabbit antisera against the CBPs from the unheated preparations demonstrated that four CBPs, a 27 kDa type V-CBP of T. denticola ATCC 33520, a 95 kDa type IV-CBP and a 110 kDa type I-CBP of T. socranskii subsp. buccale ATCC 35534, and a 95 kDa type IV-CBP of T. medium strain G7201, were located on the outer envelopes of the individual cells. The adherence of T. denticola to the collagen-coated surfaces was significantly greater than that of T. medium, suggesting that the CBPs on the oral spirochetal cells play an important role in their adherence to collagen-rich connective tissues of the host.

Characterization of a methyl-accepting chemotaxis protein gene, dmcA, from the oral spirochete Treponema denticola

A gene, dmcA, expressing a methyl-accepting chemotaxis protein (MCP) from the oral spirochete Treponema denticola has been characterized. The gene was initially identified as an open reading frame immediately upstream from the previously characterized prtB protease gene of strain ATCC 35405. Nucleotide sequencing of the dmcA gene revealed a potential 57-kDa protein product with extensive homology with the signaling regions of MCPs from a variety of bacteria. The protein expressed in Escherichia coli cross-reacted with anti-Trg (E. coli MCP) serum, confirming its homology with MCPs. Northern blot and primer extension analyses identified the transcription start site of the monocistronic dmcA mRNA. By utilizing a T. denticola gene inactivation system recently developed in this laboratory, a mutant defective in the dmcA gene, HL0501, was constructed. The mutant was demonstrated to be defective in chemotaxis toward nutrients. In addition, the methylation profiles of cellular proteins indicated altered MCPs in the mutant relative to those of the parental strain. These results indicate that we have identified an MCP gene in the oral spirochete which plays a significant role in the chemotactic response of the organism.

In vitro effect of the Sensonic toothbrush on Treponema denticola

The purpose of this in vitro study was to compare the effects of the Sensonic. Oral-B Braun mechanical and Oral-B manual toothbrushes upon the morphology and cellular integrity of Treponema denticola. This spirochete was chosen because of its frequent isolation from active lesions of inflammatory periodontal disease and its pathogenic potential. T. denticola, strain ATCC 33421, was grown in an anaerobic nitrogen rich atmosphere in enhanced 1186 mycoplasma broth. 160, 5-ml aliquots of cultured microbes were assigned to 1 of 3 brushing treatment groups and a control group. Samples were further divided into 4 groups of 10 samples each and assigned to one of 4 brushing exposure times: 15, 30, 45, and 60 seconds. After treatment, 0.2 ml of each sample was applied to a millipore filter and examined by SEM. Intact microbes were counted from 10 non-overlapping fields at 4500x. Remaining treated samples were pelleted and examined by TEM. A statistically significant reduction of intact microbes for the Sensonic treatment group at each exposure time was found when compared to Oral-B Braun, Oral-B manual, and non-treated controls. TEM examination of Sensonic treated samples revealed separation of the outer membrane at lower exposure times and only cellular debris after exposures of 45 and 60 s. These results suggest that exposure to the sonic frequency generated by the Sensonic toothbrush is capable of severely disrupting the structural integrity of T. denticola.

Evidence for genetic control of changes in f-actin polymerization caused by pathogenic microorganisms: in vitro assessment using gingival fibroblasts from human twins

Attachment to and migration upon a substratum, as well as other functions of connective tissue cells, are regulated mainly by cytoplasmic structural proteins, particularly filamentous actin (f-actin). Pathogenic microorganisms exert negative effects on cytoskeletal proteins. In the present study, normal gingival fibroblasts from 10 sets of human twins (6 fraternal, DZ; 4 identical, MZ) were exposed to soluble extracts from Porphyromonas gingivalis or Fusobacterium nucleatum, then f-actin was stained using FITC-labeled phalloidin. Cells were examined under fluorescence, and a computer-assisted image analyzer quantitated f-actin polymerization as fluorescence intensity on a per-cell basis. Intraclass correlation coefficients for f-actin in MZ/MZ vis-a-vis DZ/DZ paired cell cultures were determined to assess the possible heritability of responses to the microorganism preparations. F-actin labeling was significantly different between control cultures and those exposed to the extracts. Both F. nucleatum and P. gingivalis effected f-actin and fibroblast morphology. When the data were adjusted for gender and age effects, and for differences in control f-actin levels, fibroblasts from MZ twin pairs were moderately similar in both absolute and relative responses to bacterial challenges; cells from DZ twins showed little similarity when response was measured on the absolute scale, and moderate similarity using the relative scale.

The major surface protein complex of Treponema denticola depolarizes and induces ion channels in HeLa cell membranes

The oral spirochete Treponema denticola is closely associated with periodontal diseases in humans. The 53-kDa major surface protein (Msp) located in the outer membrane of T. denticola serovar a (ATCC 35405) has both pore-forming activity and adhesin activity. We have used standard patch clamp recording methods to study the effects of a partially purified outer membrane complex containing Msp on HeLa cells. The Msp complex was free of the chymotrypsin-like proteinase also found in the outer membrane of T. denticola. Msp bound to several HeLa cell proteins, including a 65-kDa surface protein and a 96-kDa cytoplasmic protein. The Msp complex depolarized and increased the conductance of the HeLa cell membrane in a manner which was not strongly selective for Na+, K+, Ca2+, and Cl- ions. Cell-attached patches of HeLa cell membrane exposed to Msp complex exhibited short-lived channels with a slope conductance of 0.4 nS in physiologically normal saline. These studies show that Msp binds both a putative epithelial cell surface receptor and cytoplasmic proteins and that the Msp complex can form large conductance ion channels in the cytoplasmic membrane of epithelial cells. These properties may contribute to the cytopathic effects of T. denticola on host epithelial cells.

Proteases of Treponema denticola outer sheath and extracellular vesicles

Electron microscopical observations of the oral periodontopathogen Treponema denticola show the presence of extracellular vesicles bound to the bacterial surface or free in the surrounding medium. Extracellular vesicles from T. denticola ATCC 35404, 50 to 100 nm in diameter, were isolated and further characterized. Protein and proteolytic patterns of the vesicles were found to be very similar to those of isolated T. denticola outer sheaths. They were enriched with the major outer sheath polypeptides (molecular sizes, 113 to 234 kDa) and with outer sheath proteases of 91, 153, 173, and 228 kDa. These findings indicate that treponemal outer sheath vesicles contain the necessary adhesins and proteolytic arsenal for adherence to and damage of eucaryotic cells and mammalian matrix proteins. The major outer sheath- and vesicle-associated protease of T. denticola ATCC 35404 was purified and characterized. The purified enzyme had a molecular size of 91 kDa, and it dissociated into three polypeptides of 72, 38, and 35 kDa upon heating in the presence of sodium dodecyl sulfate with or without a reducing agent. The activity of the enzyme could be inhibited by diisopropylfluorophosphate, phenylmethylsulfonyl fluoride, and phenylboronic acid. The value of the second-order rate constant of the protease inactivation by phenylmethylsulfonyl fluoride was 0.48 x 10(4) M(-1) min-1. Inhibition of the enzyme by phenylboronic acid was rapid (< 1 min) and pH dependent. These data strongly suggest that this major surface proteolytic activity belongs to a family of serine proteases.

Effect of sonicated material from Fusobacterium nucleatum on the functional capacity of accessory cells derived from dental pulp

Fusobacterium nucleatum-derived components were studied for their effect on the ability of accessory pulpal cells to induce T-lymphocyte proliferation. In initial experiments, spleen cells were used to establish concentration ranges at which testing of the effect of the bacterial components would be suitable. At low concentrations, bacterial substances induced a stimulatory effect on the proliferation rate of spleen cells, but not when purified T-lymphocytes were incubated in the presence of concanavalin A and pulpal accessory cells. At increasing concentrations, a dose-dependent reduction was observed. Pretreatment with the bacterial products for 4 h gave a stimulatory effect in the absence of concanavalin A for both spleen cells and T-lymphocytes. Removal of low-molecular weight components (<3.5 kDa) did not influence the inhibitory effect, whereas preheating the bacterial substances to 100 degrees C eliminated the observed inhibition. Findings show that heat-sensitive, high-molecular-weight components of F. nucleatum can evoke a concentration-dependent stimulatory or suppressive effect on the proliferation rate of T-lymphocytes in the presence of accessory cells derived from the dental pulp.

Induction of cytoskeletal rearrangements and loss of volume regulation in epithelial cells by Treponema denticola

The early responses of oral epithelial cells to the adhesion of the oral spirochaete Treponema denticola were studied as a model of microbial perturbation of the plasma membrane. KB cell (ATCC CCL 17) monolayers were incubated with T. denticola (ATCC 35405) in alpha-MEM (minimal essential medium) for periods of 1-4 h at 37 degrees C without serum. Control cultures were exposed to bacteria-conditioned alpha-MEM without serum or bacteria or to alpha-MEM alone. At the end of each incubation, detached and attached epithelial cells were harvested and analysed separately. Compared with controls, T. denticola induced in 25% of cells a two-fold, time-dependent increase of detachment by 4 h. Detached cells in both T. denticola-exposed and control cultures exhibited 25% reductions in modal diameter, did not exclude propidium iodide, did not readhere, and did not form colonies. In T. denticola-exposed cultures, a larger subset (75%) of cells remained attached to the substratum, demonstrated no significant reduction of colony-forming efficiency and excluded propidium iodide. However, these cells exhibited a 21% reduction in diameter (p < 0.05), a 60% decrease of F-actin (p < 0.001), and a 74% reduction in the proportion expressing desmoplakin II (p < 0.01) after exposure to T. denticola. Flow cytometry showed a small (14%) but significant (p < 0.001) reduction in mean fluorescence intensity due to keratin expression in T. denticola-treated cultures. Exposure of cells to anisosmotic media demonstrated that, in contrast to controls, cultures challenged by bacteria failed to undergo compensatory volume regulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Ribotyping on small-sized spirochetes isolated from subgingival plaque

In the present study DNA restriction patterns and corresponding ribotypes of 17 subgingival small-sized spirochetes (1:2:1 and 2:4:2 isolates), 2 Treponema socranskii strains and two Treponema denticola strains were examined. Purified chromosomal DNA was digested by BamHI, HindIII, PstI and ClaI. The DNA fragments were separated in a horizontal slab of 0.7% agarose containing ethidium bromide and transferred by nylon membranes. Hybridization was carried out with digoxigenin-labelled copy DNA of 16S and 23S ribosomal RNA from Escherichia coli. Depending on the restriction endonuclease used, up to 4 distinct bands were observed for the 2:4:2 isolates and the T. denticola strains. For each of the endonucleases used, identical band patterns were always observed for this group of isolates, and these patterns differed persistently from the T. denticola strains. For the 1:2:1 strains, up to 11 distinct bands were observed after digestion with HindIII, whereas a maximum of 6 bands were observed when PstI or ClaI was used. By using ClaI, the examined 1:2:1 isolates were separated into 8 groups, whereas PstI and HindIII separated these isolates into 5 groups. The ribotyping showed that the tested 1:2:1 spirochetes were more heterogeneous than the 2:4:2 spirochetes examined.

Immunochemical features of a macromolecule of Treponema denticola

In this study the extraction and the immunochemical features of a lipopolysaccharide-like (LPSL) macromolecule of T. denticola strains 35405, 35404, 33521 and 11 were investigated. The yield of LPSL molecule ranged between 0.5-0.9% of the cell dry weight, it possessed Limulus amebocyte lysate clotting activity, and it contained glucosamine, phosphate, heptose, glucose, small amounts of KDO, myristic and beta hydroxy myristic acid. Sera obtained from healthy individuals (ADA type I) periodontitis, from 3-8 month old infants, or the mouse monoclonal antibody, diluted 1:2, against T. pallidum did not react with the LPSL antigens of T. denticola strains 35405, 35404, 33521, and 11. Sera from patients with ADA type III-IV periodontitis were reactive with two 8-14 kDa bands even at serum dilutions of 1:2000. Sera from patients with ADA type II periodontitis showed good antibody response to the 8-14 kDa band at a dilution of 1:50, but were weekly reactive, or nonreactive at serum dilutions of 1:200. This study indicates that extraction of a lipopolysaccharide-like macromolecule is feasible from the assay spirochetes, and this macromolecule may be used as an antigen for the diagnosis of ADA types II-IV periodontitis.

An endo-acting proline-specific oligopeptidase from Treponema denticola ATCC 35405: evidence of hydrolysis of human bioactive peptides

An endo-acting proline-specific oligopeptidase (prolyl oligopeptidase [POPase], EC 3.4.21.26) was purified to homogeneity from the Triton X-100 extracts of cells of Treponema denticola ATCC 35405 (a human oral spirochete) by a procedure that comprised five successive fast protein liquid chromatography steps. The POPase is a cell-associated 75- to 77-kDa protein with an isoelectric point of ca. 6.5. The enzyme hydrolyzed (optimum pH 6.5) the Pro-pNA bond in carbobenzoxy-Gly-Pro-p-nitroanilide (Z-Gly-Pro-pNA) and bonds at the carboxyl side of proline in several human bioactive peptides, such as bradykinin, substance P, neurotensin, angiotensins, oxytocin, vasopressin, and human endothelin fragment 22-38. The minimum hydrolyzable peptide size was tetrapeptide P3P2P1P'1, while the maximum substrate size was ca. 3 kDa. An imino acid residue in position P1 was absolutely necessary. The hydrolysis of Z-Gly-Pro-pNA was potently inhibited by the following, with the Ki(app) (in micromolar) in parentheses: insulin B-chain (0.7), human endothelin-1 (0.5), neuropeptide Y (1.7), substance P (32.0), T-kinin (4.0), neurotensin (5.0), and bradykinin (16.0). Chemical modification and inhibition studies suggest that the POPase is a serine endopeptidase whose activity depends on the catalytic triad of COOH ... Ser ... His but not on a metal. The amino acid sequence around the putative active-site serine is Gly-Gly-Ser-Asn-Pro-Gly. The enzyme is suggested to contain a reactive cysteinyl residue near the active site. Amino acid residues 4 to 24 of the first 24 N-terminal residues showed a homology of 71% with the POPase precursor from Flavobacterium meningosepticum and considerable homology with the Aeromonas hydrophila POPase. The ready hydrolysis of human bioactive peptides at bonds involving an imino acid residue suggests that enzymes like POPase may contribute to the chronicity of periodontal infections by participating in the peptidolytic processing of those peptides.

Cloning and sequence analysis of a chymotrypsinlike protease from Treponema denticola

A clone expressing a Treponema denticola chymotrypsinlike protease from recombinant plasmid pSA2 was identified in a genomic library of T. denticola ATCC 35405. Nucleotide sequencing of the insert identified an open reading frame, designated the prtB gene, which codes for the protease. Two potential inverted repeat sequences are present both upstream and downstream from the prtB gene. The prtB gene would code for a putative protein of 273 amino acids with a calculated molecular mass of 30.4 kDa and an estimated pI of 7.0. The G+C content of the gene is 40.3%. The results of maxicell analysis are consistent with the expression of a 30-kDa protease from the prtB gene. Preliminary characterization of the protease indicated that it was inhibited by the protease inhibitors phenylmethylsulfonyl fluoride, diisopropylfluorophosphate, and N-tosyl-L-phenylalanine chloromethyl ketone but not by N alpha-p-tosyl-L-lysine chloromethyl ketone. Purification of the protease was accomplished with the PinPoint protein purification system following construction of site-directed mutagenized plasmid pXa-3:2. The purified protease degraded human and bovine serum albumins as well as casein. Furthermore, hemolysis of sheep erythrocytes by the protease was observed. Northern (RNA) blot analysis of mRNA extracted from strain 35405 indicated a single 1.9-kb mRNA species containing the prtB transcript. In addition, the results of primer extension analysis indicated that transcription was initiated primarily at a T residue. However, no corresponding -10 and -35 sequences related to Escherichia coli promoter sequences were identified. The availability of the purified protein and its gene will aid in evaluating the potential role of the protease in the physiology and virulence of T. denticola since proteases may play a key role in oral treponemal pathogenicity.

Pathogenic mechanisms in periodontal disease

Periodontal diseases have been considered as "infections" in which micro-organisms initiate and maintain the destructive inflammatory response. Host-mediated tissue destruction occurs via complement activation and the release of lysosomal enzymes, and connective tissue matrix metalloproteinases. Microbial enzymes may damage connective tissues directly, and, together with toxic metabolites and structural materials, are thought to disrupt the reparative activities of fibroblasts and cells of the immune defenses. The significance and relative contributions of host and microbial factors to the disease process remain unresolved. Environmental changes in the gingival sulcus and periodontal pocket and tissues, the degree of the host response and nutrient availability, concomitant with disease progression, compromise tissue metabolism and repair, and allow for enhanced or de novo expression of microbial virulence factors, such as proteases, which alter microbial pathogenicity. Proteolytic destruction of specific antibodies and complement by both viable and non-viable bacterial cells may retard phagocytic killing and removal of pathogens, thus prolonging the inflammatory response. Bacterial products may indirectly mediate tissue destruction by stimulating release of matrix metalloproteinases or by proteolytically inactivating the specific inhibitors of these enzymes.

Degradation of endogenous plasma membrane fibronectin concomitant with Treponema denticola 35405 adhesion to gingival fibroblasts

Treponema denticola adhesion and degradation of fibronectin (Fn) on human gingival fibroblasts (HGF) were studied by immunofluorescence and enzyme-linked immunosorbent assays. The number of adherent bacteria increased and the amount of immunoreactive Fn decreased as a function of increasing T. denticola concentration. The distribution of cell-bound Fn was punctate in micrographs. Anti-human Fn impaired bacterial adhesion to HGF. Phenylmethylsulfonyl fluoride inhibited Fn degradation but not adhesion. Sonicated extracts and diluted spent growth medium degraded HGF Fn but, unlike intact T. denticola cells, they hardly stimulated F-actin rearrangements.

Clustering of fibronectin adhesins toward Treponema denticola tips upon contact with immobilized fibronectin

Treponema denticola has been shown to bind to immobilized fibronectin (Fn) by its tips. Yet labeling of cells in suspension with an Fn-gold conjugate to localize the Fn adhesins shows that they are distributed in patches along the entire cell length. Subsequent experiments have shown that the number and proportion of tip-oriented cells increase with time, suggesting that Fn contact stimulates T. denticola to rearrange adhesins toward its tips. To test this hypothesis, T. denticola cells were allowed to migrate in a 2% methylcellulose column toward nitrocellulose filters coated with Fn, laminin, bovine serum albumin, or phosphate-buffered saline. Cells close to and distant from the filters were collected, labeled with Fn-gold probes, and examined by transmission electron microscopy. The number of gold particles on each of 20 cells was counted, dividing each cell into thirds along its length: the end third with the most label (end 1), the middle third, and the end with the least label (end 2). The mean number (+/- standard deviation) of gold probes per third was calculated. Fn-gold probes clustered toward one end of T. denticola cells when in contact with Fn-coated nitrocellulose, with > 55% of probes in end 1. In contrast, no clustering toward T. denticola ends occurred with laminin-, bovine serum albumin, or phosphate-buffered saline-coated filters or in the absence of a filter. Blocking access of the T. denticola cells to the Fn-coated nitrocellulose filter by placing an uncoated filter between them prevented clustering of Fn-gold. Removal of T. denticola cells from direct contact with the Fn-coated filter did not promote redistribution of clustered probes. These data suggest that T. denticola is stimulated to cluster Fn adhesins irreversibly toward its tips when it migrates into contact with immobilized Fn. This might be significant for establishing multiple adhesive interactions with host cells and ligands.

Isolation and characterization of a 53 kDa major cell envelope protein antigen from Treponema denticola ATCC 35405

A major cell envelope protein was purified from the cell envelope fraction of Treponema denticola ATCC 35405 by ion exchange chromatography after extraction with Zwittergent 3-14. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a relative molecular mass of 53 kDa for this protein with a pI of 6.3-6.8. Amino acid analysis revealed that this protein contained high proportions of hydrophobic amino acids (40.4%), and no cysteine could be detected. The N-terminus of the protein was blocked to Edman degradation. Rabbit antiserum raised against the purified 53 kDa protein reacted with the outer envelope of the T. denticola cell surface as confirmed by immunoelectron microscopy. This rabbit antiserum reacted with 4 of the 11 strains of treponemes tested in this study. Sera from 9 to 18 periodontitis patients reacted strongly with this 53 kDa cell envelope protein of T. denticola as determined by immunoblotting analysis.

Common and specific antigens of several treponemes detected by polyclonal antisera against major cellular proteins

Thirteen polypeptide antigens with molecular weights ranging from 34 kDa to 83 kDa were selected and their antigenic behaviors and distribution were examined in 12 strains of microorganisms including Treponema, Borrelia, Leptospira and Leptonema. Immunoblot analysis demonstrated that 45 kDa and 83 kDa polypeptides of Treponema socranskii subsp. buccale ATCC 35534, 53 kDa antigen of Treponema denticola ATCC 33520 and 44 kDa polypeptide of the strain G7201 were strain-specific. The 34, 62, 66 and 84 kDa polypeptide antigens were detected in all 8 treponemal strains examined. T. denticola ATCC 33520 and ATCC 35404 possessed 38 kDa, 48 kDa, 52 kDa and 72 kDa common polypeptide antigens. All 12 strains possessed the 84 kDa polypeptide antigen. Immunoelectron microscopy demonstrated that the 34 kDa and 38 kDa polypeptide antigens were located on the axial flagella and that other polypeptide antigens were located on the outer envelopes or wall-membrane complexes.

Involvement of treponemal surface-located protein and carbohydrate moieties in the attachment of Treponema denticola ATCC 33520 to cultured rat palatal epithelial cells

We studied the nature of attachment of Treponema denticola ATCC 33520 to a microscopically distinct population of rounded rat palatal epithelial cells. The motility of the freshly harvested spirochetes appeared not be a prerequisite for attachment. Treatment of T. denticola ATCC 3350 with proteinase-K, heat, glutaraldehyde, formaldehyde and periodate oxidation decreased the attachment to the rounded rat palatal epithelial cells, indicating the involvement of protein and carbohydrate moieties. Trypsin treatment had no effect on the attachment. The attachment of T. denticola ATCC 33520 was decreased after treatment with native non-immune rabbit serum, native polyclonal rabbit serum, D-mannose, N-acetyl-D-galactosamine and sialic acid. The results indicate that the attachment of T. denticola ATCC 33520 to rounded rat palatal epithelial cells is mediated by trypsin-resistant adhesin(s) of protein and carbohydrate nature, with affinity for D-mannose, N-acetyl-D-galactosamine and sialic acid.

Biological activities of surface-associated material from Porphyromonas gingivalis

Surface-associated material (SAM) from Porphyromonas gingivalis was tested for in vitro biological activities that may be relevant to the pathogenesis of chronic periodontitis. SAM was found to stimulate bone resorption at a concentration of 1.0 microgram/ml and this was inhibited by indomethacin, interleukin-1 receptor antagonist protein and anti-tumour necrosis factor antibody. At a concentration of 10 ng/ml, the SAM inhibited DNA and collagen synthesis in osteoblasts and murine calvaria and DNA synthesis in fibroblasts, monocytes and epidermal cells. Therefore, easily solubilised surface components from P. gingivalis could play a role in the pathogenesis of chronic periodontitis if these activities operate in vivo.

Cloning and expression of the aspartate carbamoyltransferase gene from Treponema denticola

Treponema denticola seems to play a central role in the etiology of human periodontal disease. We have cloned an antigenic protein-coding sequence from T. denticola ATCC 33520. The protein-coding region was found to be a 3-kbp HindIII-HindIII fragment. The open reading frame consists of 1,426 bp and codes for a protein with an M(r) of 54,919. The deduced amino acid sequence showed 33.8% homology with that of the aspartate carbamoyltransferase of Escherichia coli. The gene products showed aspartate carbamoyltransferase activity.

Anti-proliferative and cytotoxic activity of surface-associated material from periodontopathogenic bacteria

The easily solubilized surface-associated material from three bacterial species associated with periodontal diseases, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Eikenella corrodens, produced dose-dependent inhibition of thymidine incorporation by human fibroblasts, the human monocytic cell line U937 and guinea pig epidermal cells. In contrast, lipopolysaccharides from A. actinomycetemcomitans and P. gingivalis were either inactive or substantially less active over the dose range tested. One of the constituents of surface-associated material from a 'non-leucotoxic' strain of A. actinomycetemcomitans was highly cytotoxic to human peripheral blood polymorphonuclear cells, with 50% killing from less than 1 ng/ml. A constituent of the surface-associated material from P. gingivalis was approximately one log order less active. The lipopolysaccharides from these bacteria were at least three log orders less active in neutrophil killing. These findings add weight to the hypothesis that easily solubilized exopolymers from periodontopathogens play a major part in the pathology of periodontal diseases.

Treponema denticola induces actin rearrangement and detachment of human gingival fibroblasts

Spirochetes are associated with destructive periodontal diseases, and one cultivatable oral species, Treponema denticola, binds to mammalian cells and perturbs metabolism. To evaluate the cytoskeletal responses and attachment functions of human gingival fibroblasts (HGF) exposed to T. denticola, monolayers of HGF were incubated with T. denticola strains ATCC 35405, e, and e' in serum-free medium. HGF retracted pseudopods, rounded up, and ultimately detached from the substratum. Scanning electron microscopy showed spirochetes in close contact with HGF surfaces; occasionally, bacteria were partially submerged between folds in the HGF membrane. Blebbing and numerous microvilli formed on the cell surface as the HGF retracted. By confocal microscopy, spirochetes were detected in contact with the HGF surface but were never found on the ventral surface of fibroblasts between the substratum and cell. Morphological alterations were associated with and preceded by actin assembly, as measured by microscopic fluorimetry: there was a 263% increase in actin fluorescence over controls within 30 min. Detachment of fibroblasts from the substratum was related to incubation time and was dependent on the concentration of T. denticola. Detachment was observed for all strains tested and was also dependent on the viability of T. denticola: UV light, heat, and metronidazole treatment markedly reduced the HGF detachment response. Detachment was also significantly reduced by the protease inhibitor phenylmethylsulfonyl fluoride. HGF viability was not significantly affected by coincubation with spirochetes, as measured by lactate dehydrogenase release. Thus, T. denticola induces rapid cytoskeletal remodelling followed by cell detachment, which might be stimulated by a bacterially associated protease but is not likely directly mediated by proteolytic degradation at the cell-substratum adhesive contact points.

Extrachromosomal elements of spirochetes

The spirochetes include some important pathogenic bacteria, Treponema, Borrelia and Leptospira. The pathogeneses of these spirochetes are very diverse. In an attempt to learn more about the virulence factors among the spirochetes, their genetic organization and capacity have been studied. Structural analysis of the genome in Borrelia has shown that the genome is composed of one linear maxi-chromosome with additional linear minichromosomes as well as several supercoiled circular plasmids. Moreover, the molecular analysis of the terminal ends of one of the linear minichromosomes has revealed that this unique replicon has sequence similarities with poxviruses and particularly the viral agent of African swine fever. The presence of nucleic-acid-containing vesicles and its possible role in mediating DNA transfer between borreliae is an additional, very interesting feature of these organisms. Treponema does not contain any linear DNA, chromosomal or extrachromosomal, however molecular characterization of a 2.6-kb plasmid of Treponema denticola has been performed with the aim of establishing cloning vehicles to study the virulence properties of the genus Treponema.

Toxicity of sonicated extracts of Bacteroides gingivalis on human pulpal cells and L929 cells in vitro

Human pulpal fibroblasts and L929 cells were treated with sonicated extracts of two strains of Bacteroides gingivalis (W83 and ATCC 33277). The cell reaction was evaluated by monitoring cell growth and DNA synthesis. Light and scanning electron microscopic analysis were used to evaluate morphological changes of the cells. Extracts from both bacterial strains exerted a growth inhibitory effect on the cells. The pulpal cells were more sensitive than L929 cells. The ATCC 33277 strain of B. gingivalis was more cytotoxic than the W83 strain. Pulpal cells appeared to be markedly affected on the microscopic level. The diffusion of these toxic bacterial by-products, through dentin to the pulp, may account for pulpal cell damage that contributes to the initiation of pulpal pathosis.

Cloning and expression of protease genes from Treponema denticola in Escherichia coli

A gene bank of random fragments of chromosomal DNA from Treponema denticola ATCC 33520 was constructed in the bacteriophage vector lambda L47.1. The gene bank was plated on Escherichia coli C600 and screened for the presence of plaques in which enzyme activity was expressed, using overlays of fluorogenic synthetic substrates and a two-step procedure in which immunological screening was followed by enzyme assays of immunopositive lysates. Recombinants expressing trypsin-like, chymotrypsin-like and proline iminopeptidase activities were found. The gene for the trypsin-like activity was subcloned into plasmid pJDC9 and maintained in E. coli.

Characteristics of hemolytic and hemagglutinating activities of Treponema denticola

Treponema denticola, a suspected periodontal pathogen, was shown to agglutinate and lyse human red blood cells. Both activities were cell-associated, heat-labile, and produced during the exponential growth phase. Hemolytic activity was time-dependent and required incubation at 37 degrees C; further incubation at 4 degrees C increased the hemolysis. Hemagglutination was reduced in the presence of D-glucosamine, EDTA or sodium salicylate, whereas hemolytic activity was affected by calcium chloride, magnesium chloride, EDTA or sodium salicylate. These biological activities may favor a higher concentration of hemin-containing compounds in periodontal sites, and therefore represent additional potential virulence mechanisms.

Biochemical properties of the outer membrane of Treponema denticola

The outer membranes (OMs) from serovars a, b, and c of Treponema denticola, originally isolated from periodontal patients, were prepared. Dialysis of the OMs against 20 mM MgCl2 yielded the aggregable (A) and the nonaggregable (NA) moieties of the OMs. The absence of muramic acid, adenosine triphosphatase, hexokinase, and nucleic acid as well as electron microscopy indicated that the OM preparations were homogeneous. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the A and NA moieties of the OMs showed approximately 25 Coomassie brilliant blue R-250 stain-positive bands or 47 silver-stained polypeptides. The relative molecular masses ranged between 14 and 97 kDa. The electrophoretic polypeptide profiles of the A and NA moieties shared many similarities among serovars a, b, and c. However, they exhibited variation in the overall pattern, intensity, or location of the polypeptide stained zones. This was especially true for serovar b. Two-dimensional electrophoretic studies showed an excess of 100 silver-stained spots with isoelectric points of 4.6 to 7.0 and relative molecular masses in the 14- to 97-kDa range. The OMs contained simple proteins, glycoproteins, and lipoproteins. The NA moieties of the OMs contained 4 to 6, 10 to 12, and 4 to 6 glycopeptides as well as two, seven, and two lipoprotein bands for serovars a, b, and c, respectively. The A moieties of the OMs showed 7 to 9, 11 to 13 and 5 to 6 glycopeptides as well as four, five, and three lipoprotein bands for serovars a, b, and c, respectively. Lipopolysaccharide was detected in the OMs of the three serovars following removal of proteins with proteinase K, pronase and silver staining of sodium dodecyl sulfate-polyacrylamide gels, or removal of lipopolysaccharide from the OMs by hot phenol extraction. The 66- and 53-kDa bands were present in serovars b and c, while a band with a relative molecular mass of 45 kDa was present only in serovar c. Endotoxin-like activity was also shown in the OMs of the three serovars by the Limulus amebocyte clotting assay and the chick embryo lethality test. This is the first report on selected biochemical properties of the OM macromolecules of three known serovars of T. denticola.

Identification of components in Fusobacterium nucleatum chemostat-culture supernatants that are potent inhibitors of human gingival fibroblast proliferation

The present investigation concerned the effect of chemostat-culture cell-free supernatants of Fusobacterium nucleatum on the growth and synthetic activity of human gingival fibroblasts in vitro. Human gingival fibroblasts were cultured in fetal calf serum supplemented Dulbecco-Vogt medium containing various dilutions of conditioned or unconditioned bacterial culture medium. Cell proliferation was monitored by assessing cell growth over 5 days or incorporation of [3H]-thymidine into DNA. Protein and proteoglycan synthesis were monitored by the incorporation of [3H]-proline and [35S]-sulfate, respectively, into macromolecules. While the conditioned culture medium caused a complete inhibition of cell growth and incorporation of [3H]-thymidine DNA, there was no discernible effect on protein or proteoglycan synthesis. This indicated that the cells remained viable yet unable to divide. Such a view was supported by the observation that the inhibitory effect was reversible upon removal of the conditioned medium. This activity had a molecular size less than 30,000, was heat-stable and nonvolatile. Chemical analysis of the conditioned bacterial culture supernatants indicated that high proportions of butyrate, ammonium, and acetate were present. When these components were added to unconditioned medium and tested, most of the inhibitory activity could be attributed to ammonium and butyrate. Since many bacteria which constitute the subgingival microflora release ammonium and butyrate, a very high concentration of these metabolites may well accumulate. Clearly, the potential for inhibition of fibroblast proliferation has ramifications related to diminished tissue repair following bacterially-induced periodontal destruction.

Molecular cloning and sequence analysis of antigen gene tdpA of Treponema denticola

We isolated and characterized an immunogenic protein of an oral spirochete, Treponema denticola Johnson. A genomic DNA library constructed with bacteriophage lambda EMBL3 as a vector was immunologically screened with a rabbit antiserum against the whole cells. Using Western immunoblot analysis, we found a particular clone encoding an antigen with a molecular weight of 53,000; we designated the antigen as T. denticola protein A (TdpA). Complete sequence determination revealed an open reading frame of 1,419 bp and a signal peptide sequence that was homologous to that of bacterial lipoprotein. Southern hybridization analysis revealed that the tdpA gene is highly conserved in six tested strains of T. denticola species. Furthermore, we found that sera from some periodontitis patients contained antibody against the TdpA protein, although the reactivities of the antibodies varied among individuals.