Adherence of oral treponemes and their effect on morphological damage and detachment of epithelial cells in vitro

Treponema denticola chymotrypsin-like protease as associated with HPV-negative oropharyngeal squamous cell carcinoma

BACKGROUND

An opportunistic oral pathogen, Treponema denticola (Td), has been linked to orodigestive carcinogenesis, but its role in oropharyngeal squamous cell carcinoma (OPSCC) has remained open. We evaluated the presence of Td chymotrypsin-like protease (Td-CTLP) in a series of 201 unselected consecutive OPSCC patients, and the relation of the Td-CTLP to human papillomavirus (HPV) status, to expression of toll-like receptors (TLR) 5, 7, and 9, and to clinical parameters and patient outcome.

METHODS

Clinicopathological data came from hospital registries. The expression of cell surface-bound Td-CTLP was evaluated by immunohistochemistry. Immunoexpression of TLRs 5, 7, and 9, and HPV status we studied earlier in this patient series.

RESULTS

We detected Td-CTLP in 81% of the OPSCC, and especially in HPV-negative tumours (48% of all OPSCCs). Among the HPV-positive tumours (52% of all OPSCCs), low Td-CTLP expression associated with low TLR 5 and high TLR 7 expression. Among those HPV-negative, higher TLR 5 and lower TLR 7 expression associated with high Td-CTLP expression. Strong Td-CTLP expression associated with poor disease-specific survival, but no similar association among HPV-positive and HPV-negative subgroups emerged.

CONCLUSIONS

Td-CTLP was highly expressed in OPSCC and was associated with the HPV status of tumour tissue.

Multilocus Sequence Analysis of Phylogroup 1 and 2 Oral Treponeme Strains

More than 75 "species-level" phylotypes of spirochete bacteria belonging to the genus Treponema reside within the human oral cavity. The majority of these oral treponeme phylotypes correspond to as-yet-uncultivated taxa or strains of uncertain standing in taxonomy. Here, we analyze phylogenetic and taxonomic relationships between oral treponeme strains using a multilocus sequence analysis (MLSA) scheme based on the highly conserved 16S rRNA, pyrH, recA, and flaA genes. We utilized this MLSA scheme to analyze genetic data from a curated collection of oral treponeme strains (n = 71) of diverse geographical origins. This comprises phylogroup 1 (n = 23) and phylogroup 2 (n = 48) treponeme strains, including all relevant American Type Culture Collection reference strains. The taxonomy of all strains was confirmed or inferred via the analysis of ca. 1,450-bp 16S rRNA gene sequences using a combination of bioinformatic and phylogenetic approaches. Taxonomic and phylogenetic relationships between the respective treponeme strains were further investigated by analyzing individual and concatenated flaA (1,074-nucleotide [nt]), recA (1,377-nt), and pyrH (696-nt) gene sequence data sets. Our data confirmed the species differentiation between Treponema denticola (n = 41) and Treponema putidum (n = 7) strains. Notably, our results clearly supported the differentiation of the 23 phylogroup 1 treponeme strains into five distinct "species-level" phylotypes. These respectively corresponded to "Treponema vincentii" (n = 11), Treponema medium (n = 1), "Treponema sinensis" (Treponema sp. IA; n = 4), Treponema sp. IB (n = 3), and Treponema sp. IC (n = 4). In conclusion, our MLSA-based approach can be used to effectively discriminate oral treponeme taxa, confirm taxonomic assignment, and enable the delineation of species boundaries with high confidence.

IMPORTANCE

Periodontal diseases are caused by persistent polymicrobial biofilm infections of the gums and underlying tooth-supporting structures and have a complex and variable etiology. Although Treponema denticola is strongly associated with periodontal diseases, the etiological roles of other treponeme species/phylotypes are less well defined. This is due to a paucity of formal species descriptions and a poor understanding of genetic relationships between oral treponeme taxa. Our study directly addresses these issues. It represents one of the most comprehensive analyses of oral treponeme strains performed to date, including isolates from North America, Europe, and Asia. We envisage that our results will greatly facilitate future metagenomic efforts aimed at characterizing the clinical distributions of oral treponeme species/phylotypes, helping investigators to establish a more detailed understanding of their etiological roles in periodontal diseases and other infectious diseases. Our results are also directly relevant to various polymicrobial tissue infections in animals, which also involve treponeme populations.

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.

An efficient method for enumerating oral spirochetes using flow cytometry

Spirochetes, such as Treponema denticola, are thin walled, helical, motile bacteria. They are notoriously difficult to enumerate due to their thinness and the difficulties associated with culturing them. Here we have developed a modified oral bacterial growth medium (OBGM) that significantly improves the cultivation of T. denticola compared with a previously published growth medium. Three methods for the enumeration of T. denticola, semi-solid growth medium colony-forming unit (CFU) counts, DNA analysis and flow cytometry, are described and compared. Enumeration of T. denticola using the semi-solid agar method resulted in a positive linear relationship with absorbance of the culture (R(2)=0.9423). However, the semi-solid agar method was found to consistently underestimate (by 50 fold) the T. denticola cell density compared to previously published data. DNA analysis of T. denticola cultures reliably and consistently resulted in a positive linear relationship with absorbance (R(2)=0.9360), giving a calculated cell density of 6.9 x 10(8)cells/mL at an absorbance of 0.2 at 650 nm. Flow cytometry was also found to result in a positive linear relationship with absorbance (R(2)=0.9874), giving a calculated cell density of 6.6 x 10(8)cells/mL at an absorbance of 0.2 at 650 nm. In comparing all of these enumeration methods, the flow cytometry method was found to have distinct advantages, as it is accurate, rapid, and could distinguish between live and dead bacteria. Thus flow cytometry is a recommended means for the rapid and reliable enumeration of viable spirochetes from culture.

Biochemical properties of membrane-associated proteases of Brachyspira pilosicoli isolated from humans with intestinal disorders

A membrane-associated, subtilisin-like, serine protease activity was found in both pathogenic and non-pathogenic strains of Brachyspira species in a previous study, but the biochemical properties of the enzyme were not investigated. The purpose of the present study was to characterize further the biochemical properties, including substrate specificity, of the membrane-associated protease of Brachyspira pilosicoli isolated from humans with intestinal disorders. Protease activity of detergent-enriched membrane protein extracts of B. pilosicoli was assessed using fluorescent dye-labelled synthetic peptides as substrates and determination of electrophoretic mobility of cleavage products in agarose gels. Each activity was further confirmed with class-specific protease inhibitors and thermal denaturation. The presence of a hydrophilic membrane-associated thermolabile serine endopeptidase with specificity for Leu was confirmed. Two additional hydrophilic membrane-associated thermostable proteolytic activities were identified, one with a putative Ala specificity, and one a carboxypeptidase. Taken together, these data suggest that, in addition to a previously described membrane-associated subtilisin-like serine protease, the membrane of B. pilosicoli contains proteins with at least two other proteolytic activities.

Viability of cultured periodontal pocket epithelium cells and Porphyromonas gingivalis association

OBJECTIVES

Porphyromonas gingivalis, one of the key pathogens in the development of periodontitis, produces a number of virulence factors that might explain its pathogenicity. One of them is the ability to adhere and invade pocket epithelium. The aim of this study was to follow, over time, the association of P. gingivalis and consequent morphological changes of the pocket epithelium cells.

MATERIAL AND METHODS

The association capacity of four P. gingivalis serotypes [K1, K2, K4, K- (nonencapsulated)] with in vitro cultured mono-layers from periodontal pocket epithelial cells of patients with periodontitis, was followed by fluorescence microscopy and bacterial culture. The contact time between bacteria and epithelium cells ranged from 45 min to 8 h. The microscopic evaluation allowed differentiation between dead and living cells (bacteria as well as epithelium) and description of the morphological changes after association.

RESULTS

A highly significant difference in the number of associating bacteria was found between dead and living epithelium cells, and between non-capsulated and capsulated strains. A significant increase in the proportion of dead pocket epithelium cells was found with prolonged association time. The morphological changes (rounding of the epithelial cell, detachment from the glass cover-slip and loss of intercellular contact) occurred faster for mono-layers inoculated with the non-encapsulated P. gingivalis strain.

CONCLUSIONS

This study indicates that dead pocket epithelium cells harbor more P. gingivalis cells, and that a positive correlation exists between contact time and cell death. For the P. ginigvalis species, non-encapsulated strains associate in higher number. As a result, the damage they cause to the host cell seems to occur faster than occurs in encapsulated strains. As such, cell death can be seen as the end-result of bacterial association.

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.

Outer sheath associated proteins of the oral spirochete Treponema maltophilum

We recently cloned the major outer membrane protein of Treponema maltophilum [Heuner, K., Choi, B.K., Schade, R., Moter, A., Otto, A., Göbel, U.B., J. Bacteriol. 181, 1025-1029]. Here we report the localization of the major sheath protein (Msp)A protein in T. maltophilum by immunogold electron microscopy and its expression. Northern blot analysis revealed that mspA is expressed constitutively as a monocistronic unit. The transcription initiation site of the mspA gene was identified by primer extension analysis. A further screening of a genomic library of T. maltophilum with an anti-outer membrane fraction antibody was done. We were able to clone DNA regions of T. maltophilum encoding putative sugar transport operons and putative outer membrane proteins of this oral treponeme which has a high prevalence in periodontal lesions.

Papillomatous pastern dermatitis with spirochetes and Pelodera strongyloides in a Tennessee Walking Horse

Papillomatous digital dermatitis is a common disease in cattle. The pastern dermatitis observed in a horse shared many of the gross characteristics of papillomatous digital dermatitis in cattle. Lesions included a mixture of proliferative and erosive changes, with a verrucose appearance in some areas. Microscopic similarities included pseudoepitheliomatous and papillomatous epidermal hyperplasia with hyperkeratosis, spongiosis of the epidermis, and intraepidermal spirochetes. The horse was also concurrently infected with Pelodera strongyloides. Papillomatous digital dermatitis in cattle is associated with poor husbandry practices. The environment of the affected horse was heavily contaminated with urine, manure, and other organic debris. Verrucous pododermatitis of horses may be the same as or similar to bovine papillomatous digital dermatitis, and these conditions have similar etiologies.

A flagellar gene cluster from the oral spirochaete Treponema maltophilum

A flagellar gene cluster from the oral spirochaete Treponema maltophilum ATCC 51939T was cloned. Sequence analysis revealed six putative ORFs, two of which encode the flagellar subunit proteins FlaB2 (286 aa) and FlaB3 (285 aa). Northern blot analysis revealed two flagellin transcripts with the expected size of monocistronic mRNAs. Sequence analysis and primer extension experiments indicated that the transcription of the flaB2 gene is directed by a sigma28-like FliA factor. Using fliA and fliA+ Escherichia coli K-12 strains, it was shown that flaB2 expression in E. coli required the sigma28 factor using an initiation site identical to that in Treponema maltophilum. Primer extension analysis revealed two transcriptional start sites 5' of the flaB3 gene, a strong promoter with a sigma28-like -10 promoter element and a weak promoter with a putative sigma54 promoter consensus sequence. Downstream of flaB3, a putative fliD homologue was found, probably encoding the flagellar cap protein of Treponema maltophilum. Flagellin-gene-specific DNA probes hybridized to all 13 Treponema strains investigated, whereas a fliD-specific DNA probe only hybridized to Treponema maltophilum, other treponemal group IV isolates and Treponema brennaborense.

Adherence to and penetration through endothelial cells by oral treponemes

Oral spirochetes were co-incubated with monolayers of endothelial cells seeded into multiwell plates or onto filters mounted in plastic chambers. Attachment was assessed using an enzyme-linked immunosorbent assay and scanning electron microscopy. Invasiveness was determined by monitoring media beneath filters within chambers for spirochetes using darkfield microscopy. Transmission electron microscopy was used to estimate intercellular and intracellular passage of spirochetes through monolayers. All tested treponemes attached to monolayers in a dose- and time-dependent manner, except Treponema phagedenis. A few treponemes were observed within host cell cytoplasm. Unidentified spirochetes obtained from dental plaque were also invasive. Results indicate that oral spirochetes possess virulence-associated characteristics shared with pathogenic spirochetes. Further studies should examine the possibility that invasive spirochetes could disseminate from within affected gingiva.

Studies on the binding of Treponema pectinovorum to HEp-2 epithelial cells

We developed a radioassay to assess the adherence of the oral treponemes Treponema denticola and Treponema pectinovorum to live HEp-2 epithelial cells. T. pectinovorum bound firmly to the epithelial cell monolayer in a concentration-dependent manner. The results indicated that a subpopulation of T. pectinovorum appeared to bind and that the binding could be influenced by environmental factors. Increasing concentrations of fetal bovine serum inhibited binding, whereas T. pectinovorum membrane vesicles and co-incubation with T. denticola ATCC 35404 increased the number of cells bound to the monolayer. Treatment of T. pectinovorum with periodic acid, but not trypsin or proteinase K, decreased the binding suggesting that a cell surface carbohydrate, such as the O-antigenic component of the lipopolysaccharide, mediates attachment of the bacteria to the epithelial cells. Co-infection of the HEp-2 cells with both T. denticola and T. pectinovorum did not interfere with each other in attachment to the epithelial cell suggesting that they do not compete for the same cellular receptor on the host cell surface. This study demonstrates that T. pectinovorum is capable, in vitro, of forming a tight association with host cells and that this binding could represent an initial step in the pathogenesis of T. pectinovorum.

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.

Virulence characteristics of oral treponemes in a murine model

This study was designed to investigate the virulence characteristics of Treponema denticola, T. socranskii, T. pectinovorum, and T. vincentii following challenge infection of mice. These microorganisms induced well-demarcated, dose-dependent, raised subcutaneous (s.c.) abscesses which were similar in time of onset, lesion progression, and duration of healing. Only viable cells were capable of inducing these characteristic s.c. abscesses. Histological examination of the skin lesion 3 and 5 days postinfection revealed abscess formation in the s.c. tissues, and abundant spiral organisms were demonstrated to be present in the abscess. Host resistance modulation by dexamethasone (neutrophil alteration) and cyclophosphamide (neutrophil depletion) pretreatment had a minimal effect on the virulence expression by any of these treponemes. The T. denticola isolates demonstrated significant trypsin-like protease (TLPase) activity, while both T. socranskii and T. vincentii were devoid of this activity. Interestingly, T. pectinovorum strains were heterogeneous with respect to TLPase as high producers, low producers, and nonproducers. However, no differences in lesion formation were noted regardless of whether the species expressed this proteolytic activity or whether treatment with N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) and dithiothreitol was performed. These results showed that (i) a murine model may be used to evaluate virulence expression by oral treponemes; (ii) while TLPase activity varies among the oral treponemes, this protease does not appear to participate in abscess induction in the mouse model; and (iii) T. pectinovorum strains show variation in TLPase activity.

Differential attachment of oral treponemes to monolayers of epithelial cells

This in vitro study describes the attachment properties of several oral treponemes to monolayers of epithelial cells and the effect of epithelial cell confluence on treponeme attachment. Four serotypes of Treponema denticola, Treponema scoliodontum, three subspecies of Treponema socranskii, and Treponema vincentii were tested with monolayers of epithelial cells of human and canine origin. Attachment of oral treponemes were compared to attachment by T. pallidum subsp. pallidum, and by the non-pathogen Treponema phagedenis. Results indicated that different serotypes of T. denticola had similar abilities to attach to epithelial cells. However, subspecies of T. socranskii differed in their ability to attach to epithelial cells. The proportion of epithelial cells susceptible to attachment by oral spirochetes was strongly related to the confluence level of the monolayer. In contrast, T. pallidum attached equally well to both epithelial cell lines at all confluence levels. T. phagedenis attached to < 1% of all epithelial cells. In general, attachment of oral treponemes to canine cells was lower than to human cells, suggesting species-specificity for adherence. Attachment of oral treponemes to epithelial cells may promote colonization of the periodontal pocket, as well as retention of treponeme colonies within plaque. The preference of oral treponemes to attach to cells of low confluence fields may translate in vivo to an increased ability to attach to cells which are actively dividing. Such cells are found in areas of repair, a common status within inflamed periodontal pockets. Furthermore, attachment of oral treponemes to epithelial cell barriers may promote or potentiate cytopathic processes.

Release and activation of human neutrophil matrix metallo- and serine proteinases during phagocytosis of Fusobacterium nucleatum, Porphyromonas gingivalis and Treponema denticola

The phagocytic ingestion of reference strains and clinical isolates of Fusobacterium nucleatum, Porphyromonas gingivalis, and Treponema denticola by polymorphonuclear leukocytes (PMNs) and the concomitant release of PMN granule proteinases were studied by specific functional and immunological assays. PMNs were incubated with the microorganisms anaerobically at 37 degrees C for indicated time periods. The suspensions and pellets were used for phagocytic ingestion assay and electron microscopic study, respectively. The supernatants were used for the measurements of the amounts and activities of the released PMN enzymes including PMN gelatinase (MMP-9), collagenase (MMP-8), serine proteases (elastase and cathepsin G), and lactate dehydrogenase (LDH). Both fluorescence microscopy and transmission electron microscopy showed that F. nucleatum, P. gingivalis and T. denticola were ingested by the PMNs in comparable numbers. However, measurements of the enzymes released from the triggered PMNs revealed major differences among the three species. High amount of elastase was released from the PMNs triggered by F. nucleatum, but not by P. gingivalis or T. denticola. The treatment of PMNs with P. gingivalis whole cells resulted in the release of gelatinase partly in the 82 kD active form, suggesting proteolytic activation of the degranulated 92 kD proMMP-9. The 82 kD active form of gelatinase was not detected upon triggering the PMNs with F. nucleatum and T. denticola. The PMN-bacteria interaction did not result in release of LDH from triggered PMNs indicating the proteinase release was not due to the PMN cell death. The results show that the susceptibilities of the 3 potentially periodontopathogenic microorganisms, F. nucleatum, P. gingivalis and T. denticola to phagocytic ingestion are not directly related to the amounts and activities of PMN enzymes released during the bacteria-PMN interactions. As PMN degranulation is considered as one of the major pathogenic mechanisms in periodontitis, the observed differences among the microorganisms may be important virulence characteristics of these species.

Conservation of msp, the gene encoding the major outer membrane protein of oral Treponema spp

The major surface protein (Msp) of Treponema denticola has been implicated as a mediator of the interaction between the spirochete and the gingival epithelium in periodontal diseases. Previous studies showed that the Msp of T. denticola ATCC 35405 had porin activity, depolarized epithelial cell membranes, bound to extracellular matrix components of epithelial cells, and formed a regular hexagonal surface array in the treponemal outer membrane. The gene encoding Msp in ATCC 35405 was recently cloned, sequenced, and expressed in Escherichia coli (J. C. Fenno, K.-H. Müller, and B. C. McBride, J. Bacteriol. 178:2489-2496, 1996). In the present study, we identified genes encoding Msp-like proteins in several oral spirochetes. A prominent heat-modifiable Msp-like protein having an apparent molecular mass of between 43 and 64 kDa was present in all oral spirochete strains tested. Antibodies raised against the ATCC 35405 Msp reacted strongly with the Msp proteins of T. denticola ATCC 35404 and T. vincentii, reacted very weakly with the Msp protein of T. denticola ATCC 33520, and did not react with T. denticola OTK, T. socranskii, and T. pectinovorum. The msp loci of the T. denticola strains and T. vincentii were identified in analyses using PCR with oligonucleotide primers derived from the DNA sequence flanking msp in ATCC 35405. Southern blot analysis showed at least three groups of related msp DNA sequences. Comparison of DNA sequences of the 5' and 3' ends of the msp genes showed high sequence homology in the flanking regions and signal peptide coding regions, while the homologies between regions encoding the mature peptide were as low as 50%. The entire msp DNA sequences of T. denticola ATCC 33520 and OTK were determined, and the deduced Msp amino acid sequences were compared to the sequence of the previously reported Msp of ATCC 35405. The results show that the msp locus is conserved in oral treponemes but that there are significant differences between the mature Msp peptides of different strains. Further studies of the antigenic domains, functional domains, and physical structures of Msp proteins, based on these results, will enhance understanding of the role of Msp in the cytopathology associated with oral spirochetes.

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.

Membrane components of Treponema denticola trigger proteinase release from human polymorphonuclear leukocytes

Tissue destruction during periodontitis is believed to be primarily brought about by leukocyte proteinases. We postulate that oral spirochetes cause discharge of polymorphonuclear leukocyte (PMN) lysosomal enzymes. Effects of Treponema denticola 53-kDa outer membrane protein, lipopolysaccharide (LPS), and peptidoglycan on degranulation of matrix metalloproteinases (MMP)-8 (collagenase) and -9 (gelatinase), cathepsin G, and elastase by human peripheral blood PMNs were studied by specific enzyme assays and Western blot analysis. T. denticola 53-kDa kDa outer membrane protein was found to be a particularly efficient inducer of MMP-8 release. The induction was comparable with that of phorbol myristate acetate, a known inducer of PMN specific granule discharge. All of the treponemal substances, most notably the 53-kDa protein and LPS, induced release of MMP-9, a component of C-type granules. Both collagenase and gelatinase released from PMNs were mostly in active forms. Release of cathepsin G and elastase was also observed with the 53-kDa protein treatment. The other T. denticola substances did not induce release of these serine proteinases. Lactate dehydrogenase was not released from PMNs by the treatments, indicating that the degranulation was specific and not caused by toxic effects of the substances. This was confirmed by transmission electron microscopy of PMNs treated with the 53-kDa protein that showed rapid vacuole formation and cell shape changes but no disintegration of the cells. Thus, T. denticola may participate in the PMN-dependent extracellular matrix degradation during the course of periodontal inflammation by triggering the secretion and activation of matrix metalloproteinases.

Development of a gene transfer system in Treponema denticola by electroporation

Treponema denticola is strongly implicated in the etiology of periodontal diseases. However, genetic transformation of this organism has not been reported. We now demonstrate a gene transfer system in T. denticola by electroporation using a broad host plasmid pKT210 as a shuttle vector. Plasmid extraction, Southern blot hybridization as well as the polymerase chain reaction indicated the presence of the plasmid in T. denticola transformants. The restriction patterns of plasmid pKT210 rescued from the T. denticola transformants in Escherichea coli suggested that some of the rescued plasmids were identical to the original pKT210, but some of them had been modified. This transformation system could be a potentially useful tool for genetic manipulation of oral spirochetes.

Sequence analysis, expression, and binding activity of recombinant major outer sheath protein (Msp) of Treponema denticola

The gene encoding the major outer sheath protein (Msp) of the oral spirochete Treponema denticola ATCC 35405 was cloned, sequenced, and expressed in Escherichia coli. Preliminary sequence analysis showed that the 5' end of the msp gene was not present on the 5.5-kb cloned fragment described in a recent study (M. Haapasalo, K. H. Müller, V. J. Uitto, W. K. Leung, and B. C. McBride, Infect. Immun. 60:2058-2065,1992). The 5' end of msp was obtained by PCR amplification from a T. denticola genomic library, and an open reading frame of 1,629 bp was identified as the coding region for Msp by combining overlapping sequences. The deduced peptide consisted of 543 amino acids and had a molecular mass of 58,233 Da. The peptide had a typical prokaryotic signal sequence with a potential cleavage site for signal peptidase 1. Northern (RNA) blot analysis showing the msp transcript to be approximately 1.7 kb was consistent with the identification of a promoter consensus sequence located optimally upstream of msp and a transcription termination signal found downstream of the stop codon. The entire msp sequence was amplified from T. denticola genomic DNA and cloned in E. coli by using a tightly regulated T7 RNA polymerase vector system. Expression of Msp was toxic to E. coli when the entire msp gene was present. High levels of Msp were produced as inclusion bodies when the putative signal peptide sequence was deleted and replaced by a vector-encoded T7 peptide sequence. Recombinant Msp purified to homogeneity from a clone containing the full-length msp gene adhered to immobilized laminin and fibronectin but not to bovine serum albumin. Attachment of recombinant Msp was decreased in the presence of soluble substrate. Attachment of T. denticola to immobilized laminin and fibronectin was increased by pretreatment of the substrate with recombinant Msp. These studies lend further support to the hypothesis that Msp mediates the extracellular matrix binding activity of T. denticola.

Aspects of adherence of oral spirochetes

Oral spirochetes are present in the oral cavity in various numbers and forms and have been strongly implicated as playing a role in the etiology of periodontal disease. Because adherence to host tissues is a critical first step in establishing a bacterial infection, reports on the attachment of oral spirochetes to host tissues and matrix components were reviewed. The great bulk of the literature concerns Treponema denticola; however, where there is information regarding other oral spirochete species, it will be noted.

Intergeneric coaggregation of oral Treponema spp. with Fusobacterium spp. and intrageneric coaggregation among Fusobacterium spp

A total of 22 strains of Treponema spp. including members of all four named human oral species were tested for coaggregation with 7 strains of oral fusobacteria, 2 strains of nonoral fusobacteria, and 45 strains of other oral bacteria, which included actinobacilli, actinomyces, capnocytophagae, eubacteria, porphyromonads, prevotellae, selenomonads, streptococci, and veillonellae. None of the treponemes coaggregated with any of the latter 45 oral strains or with the two nonoral fusobacteria. All treponemes, eight Treponema denticola strains, eight T. socranskii strains, four oral pectinolytic treponemes, one T. pectinovorum strain, and one T. vincentii strain coaggregated with at least one strain of the fusobacteria tested as partners. The partners consisted of one strain of Fusobacterium periodonticum, five F. nucleatum strains including all four subspecies of F. nucleatum, and a strain of F. simiae obtained from the dental plaque of a monkey. In the more than 100 coaggregations observed, the fusobacterial partner was heat inactivated (85 degrees C for 30 min), while the treponemes were unaffected by the heat treatment. Furthermore, the fusobacteria were usually inactivated by proteinase K treatment, and the treponemes were not affected. Only the T. denticola coaggregations were inhibited by lactose and D-galactosamine. None were inhibited by any of 23 other different sugars or L-arginine. Intragenic coaggregations were seen among the subspecies of F. nucleatum and with F. periodonticum, and none were inhibited by any of the sugars tested or by L-arginine. No intrageneric coaggregations were observed among the treponemes. These data indicate that the human oral treponemes show a specificity for oral fusobacteria as coaggregation partners. Such cell-to cell contact may facilitate efficient metabolic communication and enhance the proliferation of each cell in the progressively more severe stages of periodontal disease.

Distribution of Porphyromonas gingivalis and Treponema denticola in human subgingival plaque at different periodontal pocket depths examined by immunohistochemical methods

Localization of Porphyromonas gingivalis and Treponema denticola in different areas of subgingival plaque from advanced adult periodontitis patients was studied immunohistochemically using sensitive immunogold-silver staining and immunoelectron microscopy. Fourteen periodontally diseased teeth were extracted without damaging the subgingival plaque, fixed, and embedded. The subgingival plaque samples were sectioned according to four different pocket depths (0-2 mm, 2-4 mm, 4-6 mm and > or = 6 mm). Serial thin sections were stained using specific antisera to P. gingivalis or T. denticola and then with secondary antibody labelled with colloidal-gold. Cells of both P. gingivalis and T. denticola were predominantly found in subgingival plaque located at depths of more than 4 mm in periodontal pockets. T. denticola cells were found in the surface layers of subgingival plaque, and P. gingivalis were predominant beneath them. However, in the deeper subgingival plaque, the coexistence of P. gingivalis and T. denticola was observed. The present findings suggest that P. gingivalis and T. denticola play important roles in the pathogenicity of periodontal disease and provide the useful information for elucidating the pattern of colonization of microorganisms in the periodontal pocket.

Cytopathic effects of Treponema denticola chymotrypsin-like proteinase on migrating and stratified epithelial cells

The effects of Treponema denticola and its outer membrane-bound chymotrypsin-like proteinase on periodontal ligament epithelial cell cultures at different stages of maturity were studied. In sparse cultures with migrating epithelial cells, large intracellular vacuoles were formed rapidly following exposure to live T. denticola. Treponemes showing structural damage were seen occasionally inside membrane-bound vesicles. Intensive membrane blebbing occurred in infected cells and continued for up to 48 h before the cell died. Blebbing could also be induced by a purified chymotrypsin-like proteinase of T. denticola. Cortical actin and alpha-actinin of the bacterium-treated cells showed disorganization, and pericellular fibronectin was degraded by both whole T. denticola and the isolated proteinase. Epithelial cells with well-formed lateral cell contacts appeared to be more resistant to the effects of T. denticola than migrating isolated cells. In multilayer epithelial cultures, adhesion of T. denticola and membrane blebbing were observed infrequently. There was no evidence of invasion of T. denticola into epithelial multilayers. However, immunogold electron microscopy showed rapid transport of T. denticola chymotrypsin-like proteinase into newly formed large intracellular vacuoles within the epithelial layers. These vacuoles were lined by membranes studded with ribosomes. T. denticola-treated epithelial multilayers had loose cell contacts, collapsed intercellular spaces, and increased permeability. Through its capacity to cause these unique cytopathic effects, the chymotrypsin-like proteinase of T. denticola has the potential to contribute to the initiation of periodontal disease.

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)

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.

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.

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.

Attachment of T. denticola strains ATCC 33520, ATCC 35405, B11 and Ny541 to a morphologically distinct population of rat palatal epithelial cells

In the present study an assay for the attachment of T. denticola to epithelial cells is described. An indirect immunohistochemical staining method, using two native polyclonal antisera, revealed dark-brown coloured spirochetes attached to rat palatal epithelial cell (RPE) monolayers. In addition, two morphologically distinct populations of RPE cells could be distinguished in the monolayers when using phase contrast microscopy. One minor population consisted of isolated rounded RPE cells that were lying on top of a confluent monolayer of flattened RPE cells. The rounded RPE cells were more receptive for the attachment of T. denticola than the flattened cells. The rounded RPE cells were evenly distributed over the monolayer, but the attachment of spirochetes to the rounded cells was greater at the edge than in the centre of the monolayers. The percentage of rounded RPE cells with attached spirochetes depended on the incubation time (optimum 6 h), temperature (optimum 37 degrees C) and pH (optimum 7.0). It is speculated that the attachment of T. denticola is a physical/chemical process of yet unknown nature and that differences in the number of microvilli and/or the amount of available receptors, between the two morphologically distinct cell types, accounts for the differences in the numbers of attached spirochetes.

Spirochaetes in oral infections

Oral spirochaetes, which are small-, medium- or large-sized, include species of the genus Treponema, many of which have not yet been cultured. They are found in root canal infections, pericoronitis, gingivitis and periodontitis, constituting up to 10% of the flora in endodontic abscesses, 30% in acute necrotizing ulcerative gingivitis, and 56% in advanced marginal periodontitis. The strong proteolytic activity of these organisms probably make them causes of infection rather than consequences. Being able to penetrate tissue, they bring their enzymes, metabolic products, and endotoxins, in direct contact with target cells. This may perturb essential functions of host cells and immunoglobulins. Enzyme activities may also help fulfil the complex growth requirements of spirochaetes in vivo. Reaction between infected periodontal tissue and monoclonal antibodies to Treponema pallidum has suggested that uncharacterized pathogen-related oral spirochaetes have surface structures and functions analogue to this well recognized pathogen. This warrants a more intensified search for the role of spirochaetes in oral infections.

Attachment of Treponema denticola strains to monolayers of epithelial cells of different origin

The attachment of 10 different Treponema denticola strains to monolayers of 4 types of epithelial cells derived from rat palatal epithelium, guinea pig ear, human buccal epithelium and human corneal epithelium was screened microscopically. Most T. denticola strains were able to attach to all four types of epithelial cells. The T. denticola strains seemed to attach better to epithelial cells derived from primary cultured material. The T. denticola strains showed different degrees of attachment. Scanning electron microscopy studies revealed that the attachment of T. denticola was not only tip-associated but occurred also at random points in close contact with microvilli of the epithelial cells. Attached spirochetes were non-uniformly distributed over the monolayers, indicating the presence of receptive subpopulations of epithelial cells in the monolayers.

Demonstration of a bimodal coaggregation reaction between Porphyromonas gingivalis and Treponema denticola

This study demonstrates a strong coaggregation reaction between 2 suspected periodontopathogens: Porphyromonas gingivalis and Treponema denticola. Other black-pigmented oral bacterial species tested did not coaggregate with T. denticola. This specific interbacterial aggregation was bimodal, since heating of both cell types was required to completely eliminate the reaction. The coaggregation reaction occurred between pH 4 and 9. Under some conditions, arginine and D-galactosamine were effective in preventing the coaggregation. The heat-sensitive receptor on P. gingivalis was found to be loosely bound and could be released by a light ultrasonic treatment of the cells. It is suggested that the bacterial interaction described may participate in the establishment of a potentially pathogenic subgingival plaque.

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.

Characterization, cloning, and binding properties of the major 53-kilodalton Treponema denticola surface antigen

Treponema denticola surface proteins were studied for their biochemical and biological characteristics. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of detergent extracts of whole cells revealed a major protein of 53 kDa and a number of minor proteins. Antiserum raised against whole cells of T. denticola ATCC 35405 reacted with the 53-kDa protein and a 72-kDa protein but not with the other proteins. Immunoelectron microscopy with anti-53-kDa-protein antibodies showed that the 53-kDa protein is located on the surface of the cell. SDS-PAGE analysis of unheated samples indicated that the 53-kDa protein is the major component of oligomers with molecular masses ranging from 130 to 300 kDa. Western blot (immunoblot) analysis showed that the high-molecular-mass oligomers reacted with whole-cell antiserum and anti-53-kDa-protein antibody. The aggregates dissociated into their subunits after heating to 70 degrees C. Isoelectric focusing followed by SDS-PAGE indicated that the 53-kDa protein was separated into several forms with apparent pI values ranging from 8.0 to 5.5. The oligomeric forms were highly resistant to proteolysis by trypsin and proteinase K, whereas the monomeric proteins were readily digested. A clone expressing a 53-kDa antigen in Escherichia coli was isolated from a lambda ZAP II DNA library of T. denticola ATCC 35405. The recombinant protein had exactly the same molecular mass as the major 53-kDa T. denticola surface protein and reacted with antisera raised against this protein. The role of T. denticola ATCC 35405 surface proteins in attachment to laminin, fibronectin, gelatin, fibrinogen, and bovine serum albumin (BSA) was studied by a modified Western blot binding assay. Fibronectin, laminin, and fibrinogen attached to the 53-kDa surface protein of T. denticola as well as to a 72-kDa protein, whereas no attachment to gelatin or BSA was observed. Attachment could be inhibited by pretreating the blots with fibrinogen but not with gelatin or BSA. Our results suggest that the 53-kDa major surface protein of T. denticola may play a role in the attachment to host proteins and may thus be an important virulence determinant of this species.

Hemagglutination activity of Treponema denticola grown in serum-free medium in continuous culture

Hemagglutination by different Treponema denticola strains was observed for erythrocytes of human, horse, bovine, and rabbit origin. The growth of T. denticola ATCC 33520 in serum-free medium in continuous culture enabled us to study the hemagglutinating activity of freshly harvested spirochetes of a defined physiological status. The hemagglutinating activity was cell bound and not related to motility or appendages, such as fimbriae. The activity was destroyed by proteolytic enzymes, heat, and alkylation, indicating that the agglutinin is of a proteinaceous nature. In addition, periodate oxidation of the spirochetes indicated the involvement of carbohydrate groups. Microscopic inspection of the hemagglutination mixtures at the titration endpoints revealed that only a part of the spirochete population was involved in the hemagglutination process. The hemagglutinating activity was found to be growth phase related. The activity was blocked by serum, while of all tested amino acids and carbohydrates, only sialic acid blocked the activity at low concentrations. In conclusion, we found a hemagglutinating activity in T. denticola which was cell bound and growth phase related. The agglutinin may be a glycoprotein, like lectin, that recognizes sialic acid as a receptor.

The apical border plaque in chronic adult periodontitis. An ultrastructural study. I. Morphology, structure, and cell content

THIS STUDY CONCERNS THE APICAL BORDER (AB) plaque in relation to chronic adult periodontitis (AP). Fifty-six teeth from 24 patients with AP were examined by transmission electron microscopy (TEM). The AB was not discrete with islands of bacteria in the so-called plaque-free zone (PFZ). Coronal to the AB, the established plaque commonly consisted of three to four layers of Gram-positive and Gram-negative cocci, rods, filaments, and spirochetes and a superficial layer, mainly of spirochetes, but including filaments, "test tube brush," and "corn-cob" formations. The most apical apparently intact organisms in the PFZ were in bacterial islands or in isolation and were predominantly Gram-negative cocci and rods, with occasional other morphotypes. The most apical microorganisms were invariably ghost cells. A cuticle of varying thickness and structure was present at the plaque/tooth interface. It was concluded that there was a limited range of intact bacterial morphotypes in the apical border plaque in chronic periodontitis.

Chemical and biological activities of a 64-kilodalton outer sheath protein from Treponema denticola strains

This study examined the distribution of the major outer sheath proteins (MOSP) in several Treponema denticola strains and reports the isolation of a 64-kDa protein from the outer sheath of human clinical isolate T. denticola GM-1. The outer sheath was isolated by freeze-thaw procedures, and the distribution of outer sheath proteins was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). T. denticola GM-1, MS25, SR-5, and three low-passage clinical isolates possessed an MOSP with a relative molecular mass of 60 to 64 kDa. This MOSP was absent in T. denticola ATCC 35404 (TD-4) and clinical isolate SR-4. The latter possessed an MOSP of 58 kDa. 125I labeling revealed both MOSP to be dissociated forms of higher-molecular-mass oligomeric units between 116 and 162 kDa. Two-dimensional SDS-PAGE confirmed the modifiability of these MOSP. Isoelectric focusing of the 64-kDa MOSP indicated a pI of 6.7. Immunoblots with antiserum to GM-1 whole cells revealed the 64-kDa protein to be immunogenic and not cross-reactive with the MOSP of TD-4 or SR-4, and monospecific antibody to the 64-kDa protein recognized common epitopes on the high-molecular-weight oligomeric protein. These antibodies did not react with any component of TD-4 whole cells in immunoblots or in immunogold electron microscopy. Fab fragments inhibited the adherence of T. denticola GM-1 to human gingival fibroblasts by 78% (1:1,600; 0.72 micrograms of protein per ml), while TD-4 adherence was not inhibited. Amino acid analysis revealed a slightly acidic protein, devoid of cysteine, with 36% hydrophobic residues. Cyanogen bromide fragmentation of the 64-kDa protein revealed that a 42-kDa fragment contained a T-L-D-L-A-L-D segment which was 100% homologous with an integrin alpha subunit of a human leukocyte adhesion glycoprotein p 150,95.

Sulfhydryl-dependent attachment of Treponema denticola to laminin and other proteins

Attachment of Treponema denticola ATCC 35405 to laminin, a major basement membrane protein, and to other proteins was studied. Microdilution plates were coated with the proteins, and the attachment of T. denticola was measured by the enzyme-linked immunosorbent assay technique. Compared with bovine serum albumin (BSA), T. denticola had a high affinity to laminin, fibronectin, fibrinogen, and gelatin, as well as to type I and type IV collagens. Attachment to RGD peptide (Gly-Arg-Gly-Asp-Ser, the integrin recognition sequence) was only about 30% of that to laminin and was comparable to attachment to BSA. Tests with laminin fragments obtained through elastase digestion showed that the spirochetes attached well to an A-chain 140-kDa fragment involved in eukaryote cell attachment but did not attach to a 50-kDa fragment that includes the heparin binding site. Pretreatment of T. denticola with soluble laminin, fibronectin, gelatin, BSA, or fibrinogen had no effect on the attachment of the bacteria to laminin or fibronectin. A wide variety of compounds were tested for their possible inhibitory actions on the attachment. While most treatments of T. denticola ATCC 35405 had little or no effect on the attachment to proteins, sulfhydryl reagents p-chloromercuribenzoic acid (pCMBA) and oxidized glutathione inhibited the attachment by 70 to 99%, depending on the protein. When T. denticola was first allowed to attach to proteins, addition of pCMBA or oxidized glutathione could no longer reverse the attachment. Heat treatment of the spirochetes also markedly reduced the attachment to laminin, gelatin, and fibrinogen but not to BSA. Mixed glycosidase treatment of the spirochetes inhibited the attachment by 20 to 80%. None of the above treatments of the substrate proteins had any marked effect on the spirochete attachment. The results indicate that T. denticola has the capacity to bind to many different kinds of proteins by utilizing specific attachment mechanisms. The binding appears to involve protein SH groups and/or carbohydrate residues on the surface of T. denticola.

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.

Pathogen-related oral spirochetes from dental plaque are invasive

Spirochetes that share pathogen-restricted antigens with Treponema pallidum subsp. pallidum have been identified in dental plaque and diseased gingival tissues, but it is not known whether these spirochetes possess virulence characteristics. In this study, plaque spirochetes were able to transmigrate a tissue barrier in vitro and were identified on the other side by using monoclonal antibodies specific for pathogen-restricted determinants from T. pallidum subsp. pallidum. This invasive capability is shared with T. pallidum subsp. pallidum, but cultured oral and intestinal treponemes did not perforate the tissue barrier. Cocultures indicated that invasive treponemes do not create opportunities for cultivable oral treponemes to cross the barrier. These findings indicate that gingival tissues may be a port of entry for previously unrecognized invasive spirochetes in humans.

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.

Factors in virulence expression and their role in periodontal disease pathogenesis

The classic progression of the development of periodontitis with its associated formation of an inflammatory lesion is characterized by a highly reproducible microbiological progression of a Gram-positive microbiota to a highly pathogenic Gram-negative one. While this Gram-negative microbiota is estimated to consist of at least 300 different microbial species, it appears to consist of a very limited number of microbial species that are involved in the destruction of periodontal diseases. Among these "putative periodontopathic species" are members of the genera Porphyromonas, Bacteroides, Fusobacterium, Wolinella, Actinobacillus, Capnocytophaga, and Eikenella. While members of the genera Actinomyces and Streptococcus may not be directly involved in the microbial progression, these species do appear to be essential to the construction of the network of microbial species that comprise both the subgingival plaque matrix. The temporal fluctuation (emergence/disappearance) of members of this microbiota from the developing lesion appears to depend upon the physical interaction of the periodontal pocket inhabitants, as well as the utilization of the metabolic end-products of the respective species intimately involved in the disease progression. A concerted action of the end-products of prokaryotic metabolism and the destruction of host tissues through the action of a large number of excreted proteolytic enzymes from several of these periodontopathogens contribute directly to the periodontal disease process.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of complement by Treponema denticola

Oral spirochetes have been shown to be associated with periodontal diseases and are present in increased numbers in lesions of greater severity. In this study, the interaction of Treponema denticola with human complement, a major antibacterial defense system, was examined. For each of two strains of T. denticola, it was found that both the classical and alternative pathways of human complement were activated in human serum upon incubation at 37 degrees C. C3 fragments were deposited on the surface of this organism following complement activation; the fragments bound included both of the major C3-derived opsonic fragments C3b and iC3b. Under incubation conditions identical to those carried out for complement activation in serum, T. denticola failed to degrade purified, hemolytically-active C3, although it readily degraded inactivated C3. Thus, despite the documented proteolytic activity of this organism, complement activation and deposition of complement-derived opsonins may be important defense mechanisms in the control of infections with T. denticola.