Immunobiological activities of synthetic peptide segments of fimbrial protein from Porphyromonas gingivalis

Generation and functional characterization of recombinant Porphyromonas gingivalis W83 FimA

Porphyromonas gingivalis (P. gingivalis) is regarded as a keystone pathogen in destructive periodontal diseases. It expresses a variety of virulence factors, amongst them fimbriae that are involved in colonization, invasion, establishment and persistence of the bacteria inside the host cells. The fimbriae also were demonstrated to affect the host immune-response mechanisms. The major fimbriae are able to bind specifically to different host cells, amongst them peripheral blood monocytes. The interaction of these cells with fimbriae induces release of cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α). The aim of this study was to generate recombinant major FimA protein from P. gingivalis W83 fimbriae and to prove its biological activity. FimA of P. gingivalis W83 was amplified from chromosomal DNA, cloned in a vector and transferred into Listeria innocua. (L. innocua).The expressed protein was harvested and purified using FPLC via a His trap HP column. The identity and purity was demonstrated by gel-electrophoresis and mass-spectrometry. The biological activity was assessed by stimulation of human oral epithelial cells and peripheral blood monocytes with the protein and afterwards cytokines in the supernatants were quantified by enzyme linked immunosorbent assay (ELISA) and cytometric bead array. Recombinant FimA could successfully be generated and purified. Gel-electrophoresis and mass-spectrometry confirmed that the detected sequences are identical with FimA. Stimulation of human monocytes induced the release of high concentrations of IL-1β, IL-6, IL-10 and TNF-α by these cells. In conclusion, a recombinant FimA protein was established and its biological activity was proven. This protein may serve as a promising agent for further investigation of its role in periodontitis and possible new therapeutic approaches.

Periodontal bacterial supernatants modify differentiation, migration and inflammatory cytokine expression in human periodontal ligament stem cells

Periodontal ligament stem cells (PDLSC) play an important role in periodontal tissue homeostasis/turnover and could be applied in cell-based periodontal regenerative therapy. Bacterial supernatants secreted from diverse periodontal bacteria induce the production of cytokines that contribute to local periodontal tissue destruction. However, little is known about the impact of whole bacterial toxins on the biological behavior of PDLSC. Therefore this study investigated whether proliferation, migration, inflammatory cytokines expression and transcriptional profile would be affected by exposure to endotoxins from bacterial species found in the subgingival plaque. PDLSC were cultured with the following bacterial supernatants: S. mutans, S. anginosus, P. intermedia, F. nucleatum, P. gingivalis and T. denticola. These supernatants were prepared in dilutions of 1:1000, 1:500, 1:300 and 1:50. Using quantitative RT-PCR, gene expression of selected inflammatory cytokines (IL-6, IL-8 and IL-1β) and cell-surface receptors (TLR2, TLR4) showed upregulation of ≈2.0- to 3.0-fold, when exposed to P. intermedia, F. nucleatum, P. gingivalis and T. denticola. However, supernatants did not affect proliferation (MTT) and migration (wound scratch assays) of PDLSC. Next generation RNA sequencing confirmed modified lineage commitment of PDLSC by stimulating chondrogenesis, adipogenesis and inhibition of osteogenesis under P. gingivalis supernatant treatment compared to control. Taken together, this study shows stem cell immunomodulatory response to different periodontal bacteria supernatant and suggests that stem cell transcriptional capacity, migration/proliferation and osteogenesis may differ in the presence of those pathogens. These results bring into question stem cell contribution to periodontal tissue regeneration and onset of inflammation.

Detectable Dioxins in Human Saliva and Their Effects on Gingival Epithelial Cells

Dioxin, a powerful hormone-disrupting chemical, exhibits serious health effects when it reaches body fat. Here we analyzed coplanar polychlorinated biphenyls (PCBs) and polychlorinated-dibenzo- p-dioxins (PCDDs) in human saliva as compared with blood specimens, and examined their effects on human gingival epithelial cells (HGEC). High levels of tri- and tetrachlorinated PCBs were found in saliva, whereas we detected predominantly hexa- and heptachlorinated PCBs in blood. Among PCDDs, the saliva and blood specimens contained mainly 1,2,3,4,6,7,8,9-octachlorodibenzo- p-dioxin (OCDD). Among the toxic dioxins proposed by the World Health Organization (WHO) in 1998, 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118) and OCDD, which were mainly found in saliva, significantly induced IL-8 production in HGEC. Furthermore, these two dioxins markedly augmented IL-8 production stimulated with fimbriae from Porphyromonas gingivalis, which is well-known as a pathogenic factor in periodontal diseases. These results suggest that dioxins in saliva may be a risk factor for periodontal diseases.

Porphyromonas gingivalis fimbriae are pro-inflammatory but do not play a prominent role in the innate immune response to P. gingivalis

The fimA gene encodes the major fimbrial protein of Porphyromonas gingivalis. It has been shown to stimulate adhesion to salivary proteins and other bacteria. It is also thought to play a major role in invading and stimulating host cells. To determine whether the fimA gene represents one of the principal molecules of P. gingivalis that induces inflammation, we tested purified FimA protein and a mutant P. gingivalis (DPG3) that lacks the fimA gene versus wild-type (WT) P. gingivalis. When injected into connective tissue of the scalp, purified FimA protein induced TNF-α and MIP-2 expression confirming that it is pro-inflammatory. WT P. gingivalis induced TNF-α expression and recruitment of PMNs in the same model. However, DPG3 P. gingivalis stimulated TNF expression and PMN recruitment to the same extent. The latter was consistent with similar induction of the chemokine MIP-2. Similar results were obtained with diabetic mice that have a more prolonged inflammatory response to bacterial stimulation. These results indicate that FimA is a potent inducer of inflammatory cytokine expression but, in the context of P. gingivalis infection, it is not a principal stimulator of the innate host response.

Heme acquisition mechanisms of Porphyromonas gingivalis - strategies used in a polymicrobial community in a heme-limited host environment

Porphyromonas gingivalis, a main etiologic agent and key pathogen responsible for initiation and progression of chronic periodontitis requires heme as a source of iron and protoporphyrin IX for its survival and the ability to establish an infection. Porphyromonas gingivalis is able to accumulate a defensive cell-surface heme-containing pigment in the form of μ-oxo bisheme. The main sources of heme for P. gingivalis in vivo are hemoproteins present in saliva, gingival crevicular fluid, and erythrocytes. To acquire heme, P. gingivalis uses several mechanisms. Among them, the best characterized are those employing hemagglutinins, hemolysins, and gingipains (Kgp, RgpA, RgpB), TonB-dependent outer-membrane receptors (HmuR, HusB, IhtA), and hemophore-like proteins (HmuY, HusA). Proteins involved in intracellular heme transport, storage, and processing are less well characterized (e.g. PgDps). Importantly, P. gingivalis may also use the heme acquisition systems of other bacteria to fulfill its own heme requirements. Porphyromonas gingivalis displays a novel paradigm for heme acquisition from hemoglobin, whereby the Fe(II)-containing oxyhemoglobin molecule must first be oxidized to methemoglobin to facilitate heme release. This process not only involves P. gingivalis arginine- and lysine-specific gingipains, but other proteases (e.g. interpain A from Prevotella intermedia) or pyocyanin produced by Pseudomonas aeruginosa. Porphyromonas gingivalis is then able to fully proteolyze the more susceptible methemoglobin substrate to release free heme or to wrest heme from it directly through the use of the HmuY hemophore.

Immunogenicity of a cholera toxin B subunit Porphyromonas gingivalis fimbrial antigen fusion protein expressed in E. coli

The gram-negative anaerobic oral bacterium Porphyromonas gingivalis initiates periodontal disease through fimbrial attachment to saliva-coated oral surfaces. To study the effects of immunomodulation on enhancement of subunit vaccination, the expression in E. coli and immunogenicity of P. gingivalis fimbrial protein (FimA) linked to the C-terminus of the cholera toxin B subunit (CTB) were investigated. Complementary DNAs encoding the P. gingivalis 381 fimbrillin protein sequence FimA1 (amino acid residues 1-200) and FimA2 (amino acid residues 201-337) were cloned into an E. coli expression vector downstream of a cDNA fragment encoding the immunostimulatory CTB. CTB-FimA1 and CTB-FimA2 fusion proteins synthesized in E. coli BL21 (DE3) cells were purified under denaturing conditions by Ni2+-NTA affinity column chromatography. Renaturation of the CTB-FimA1 and CTB-FimA2 fusion proteins, permitted identification of CTB-FimA pentamers and restored CTB binding activity to GM1-ganglioside to provide a biologically active CTB-FimA fusion protein. Mice orally inoculated with purified CTB-FimA1 or CTB-FimA2 fusion proteins generated measurable FimA1 and FimA2 IgG antibody titers, while no serum fimbrial IgG antibodies were detected when mice were inoculated with FimA1 or FimA2 proteins alone. Immunoblot analysis confirmed that sera from mice immunized with CTB linked to FimA1 or FimA2 contained antibodies specific for P. gingivalis fimbrial proteins. In addition, mice immunized with FimA2 or CTB-FimA2 generated measurable intestinal IgA titers indicating the presence of fimbrial antibody class switching. Further, mice orally immunized with CTB-FimA1 generated higher IgA antibody titers than mice inoculated with FimA1 alone. The experimental data show that the immunostimulatory molecule CTB enhances B cell-mediated immunity against linked P. gingivalis FimA fusion proteins, in comparison to immunization with FimA protein alone. Thus, linkage of CTB to P. gingivalis fimbrial antigens can increase subunit vaccine immunogenicity to provide enhanced protection against periodontal disease.

Cytokine production induced by a 67-kDa fimbrial protein from Porphyromonas gingivalis

Fimbriae have been reported to play an important role in the adherence of Porphyromonas gingivalis to oral surfaces and possibly in triggering host responses. P. gingivalis ATCC 33277 has two distinctly different fimbriae expressed on the cell surface. The 67-kDa fimbriae differ in size and antigenicity from the earlier reported FimA, a major 41-kDa fimbrial component of P. gingivalis. Expression of the 67-kDa fimbriae on the cell surface of a fimA mutant was investigated by electron microscopy. The 67-kDa fimbrial protein was purified from the fimA mutant by sonication, precipitation, and chromatography on a DEAE Sepharose CL-6B column. The N-terminal amino acid sequence of the 67-kDa fimbrillin was distinct from that of the 41-kDa fimbrillin. Moreover, we have found that the 67-kDa fimbrial protein from P. gingivalis ATCC 33277 induced IL-1alpha, IL-beta, IL-6 and TNFalpha cytokine expression in mouse peritoneal macrophages. These results suggest that P. gingivalis 67-kDa fimbriae may play a part in the inflammatory response during the development of periodontal diseases.

Fimbria-dependent activation of cell adhesion molecule expression in Porphyromonas gingivalis-infected endothelial cells

Porphyromonas gingivalis is an oral pathogen that has recently been associated with chronic inflammatory diseases such as atherosclerosis. The strength of the epidemiological associations of P. gingivalis with atherosclerosis can be increased by the demonstration that P. gingivalis can initiate and sustain growth in human vascular cells. We previously established that P. gingivalis can invade aortic, heart, and human umbilical vein endothelial cells (HUVEC), that fimbriae are required for invasion of endothelial cells, and that fimbrillin peptides can induce the expression of the chemokines interleukin 8 and monocyte chemotactic protein. In this study, we examined the expression of surface-associated cell adhesion molecules on endothelial cells in response to P. gingivalis infection by fluorescence-activated cell sorting FACS analysis and confocal microscopy. Coculture of HUVEC with P. gingivalis strain 381 or A7436 resulted in the induction in the expression of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and P- and E-selectins, which was maximal at 48 h postinfection. In contrast, we did not observe induction of ICAM-1, VCAM-1, or P- or E-selectin expression in HUVEC cultured with the noninvasive P. gingivalis fimA mutant DPG3 or when P. gingivalis was incubated with fimbrillin peptide-specific anti-sera prior to the addition to HUVEC. Furthermore, the addition of a peptide corresponding to the N-terminal domain of fimbrillin to HUVEC resulted in an increase in ICAM-1, VCAM-1, and P- and E-selectins, which was maximal at 48 h and similar to that observed for live P. gingivalis. Treatment of P. gingivalis-infected HUVEC with cytochalsin D, which prevented P. gingivalis invasion, also resulted in the inhibition of ICAM-1, VCAM-1, or P- and E-selectin expression. Taken together, these results indicate that active P. gingivalis invasion of HUVEC mediated via the major fimbriae stimulates surface-associated cell adhesion molecule expression. Stimulation of adhesion molecules involved in the recruitment of leukocytes to sites of inflammation by P. gingivalis may play a role in the pathogenesis of systemic inflammatory diseases associated with this microorganism, including atherosclerosis.

Role for fimbriae and lysine-specific cysteine proteinase gingipain K in expression of interleukin-8 and monocyte chemoattractant protein in Porphyromonas gingivalis-infected endothelial cells

Recent cross-sectional and prospective epidemiological studies have demonstrated an association between periodontal disease and atherosclerosis and human coronary heart disease. Previously, we have established that the periodontal pathogen Porphyromonas gingivalis is capable of invading aortic, heart, and human umbilical vein endothelial cells (HUVEC). Since atherosclerosis is a chronic inflammatory response initiated at the vascular wall, interactions of P. gingivalis with endothelial cells and the subsequent host cell response to infection may be important in the pathogenesis of atherosclerosis. In this study we examined the consequences of P. gingivalis infection of HUVEC on the expression of the chemokines interleukin-8 (IL-8) and monocyte chemotactic protein 1 (MCP-1). HUVEC were found to constitutively produce low levels of IL-8 and MCP-1. The addition of P. gingivalis fimbrillin-specific peptides, lipopolysaccharides (LPS), or heat-killed whole cell preparations to HUVEC stimulated modest IL-8 and MCP-1 responses. In contrast, coculture of HUVEC with live P. gingivalis strain A7436, 33277, or 381 abolished the IL-8 and MCP-1 responses. Inhibition of IL-8 and MCP-1 production was not dependent on bacterial adherence since similar results were obtained with the nonadherent P. gingivalis fimA mutant DPG3 or when P. gingivalis was preincubated with fimbrillin peptide antisera prior to the addition to HUVEC. Furthermore, treatment of P. gingivalis-infected HUVEC with cytochalsin D, which prevented P. gingivalis invasion, also abolished the constitutive IL-8 and MCP-1 responses. Treatment of HUVEC with E. coli LPS stimulated robust IL-8 and MCP-1 responses that were abolished when stimulated cells were cocultured with live P. gingivalis. Analysis of P. gingivalis-infected HUVEC cultures by an RNase protection assay revealed an increase in the IL-8 transcript relative to uninfected HUVEC. Pretreatment of P. gingivalis with protease inhibitors prior to the addition to HUVEC prevented the inhibition of IL-8 and MCP-1 production in P. gingivalis-infected HUVEC, indicating that the inhibition was proteolytically mediated. Coculture of HUVEC with a P. gingivalis mutant deficient in lysine-specific cysteine proteinase (gingipain K [Kgp]) resulted in an increase in both IL-8 transcription and protein expression relative to that observed in HUVEC cocultured with the P. gingivalis wild-type strain. These results indicate that P. gingivalis can temporally modulate the chemokine response in endothelial cells through both fimbriae and gingipain-mediated mechanisms.

Bacterial fimbriae and their peptides activate human gingival epithelial cells through Toll-like receptor 2

Gingival epithelial cells are a central component of the barrier between oral microflora and internal tissues. Host responses to periodontopathic bacteria and surface components containing fimbriae are thought to be important in the development and progression of periodontal diseases. To elucidate this mechanism, we established immortalized human gingival epithelial cells (HGEC) that were transfected with human papillomavirus. HGEC predominantly expressed Toll-like receptor (TLR) 2, but not TLR4 or CD14. They also induced interleukin-8 (IL-8) production when stimulated with Porphyromonas gingivalis fimbriae and Staphylococcus aureus peptidoglycan, but not Escherichia coli-type synthetic lipid A. Furthermore, an active synthetic peptide composed of residues 69 to 73 (ALTTE) of the fimbrial subunit protein, derived from P. gingivalis and similar to a common component of cell wall peptidoglycans in parasitic bacteria, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), significantly induced IL-8 production and NF-kappaB activation in HGEC, and these cytokine-producing activities were augmented by a complex of soluble CD14 and lipopolysaccharide-binding protein (LBP). IL-8 production in HGEC stimulated with these bacterial components was clearly inhibited by mouse monoclonal antibody to human TLR2. These findings suggest that P. gingivalis fimbrial protein and its active peptide are capable of activating HGEC through TLR2.

Immunobiological activities of a chemically synthesized lipid A of Porphyromonas gingivalis

A synthetic lipid A of Porphyromonas gingivalis strain 381 (compound PG-381), which is similar to its natural lipid A, demonstrated no or very low endotoxic activities as compared to Escherichia coli-type synthetic lipid A (compound 506). On the other hand, compound PG-381 had stronger hemagglutinating activities on rabbit erythrocytes than compound 506. Compound PG-381 also induced mitogenic responses in spleen cells from lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ mice, as well as LPS-responsive C3H/HeN mice. The addition of polymyxin B resulted in the inhibition of mitogenic activities, however, compound 506 did not show these capacities. Additionally, compound PG-381 showed a lower level of activity in inducing cytokine production in peritoneal macrophages and gingival fibroblasts from C3H/HeN mice, but not C3H/HeJ mice, in comparison to compound 506. Thus, this study demonstrates that the chemical synthesis of lipid A, mimicking the natural lipid A portion of LPS from P. gingivalis, confirms its low endotoxic potency and immunobiological activity.

Role of the amino-terminal region of Porphyromonas gingivalis fimbriae in adherence to epithelial cells

Porphyromonas gingivalis fimbriae elicit many responses in eukaryotic cells, including mitogenicity, cytokine production, epithelial cell invasion, and cellular immune response. Specific domains of the major fimbrial protein (FimA) have been shown to be important in triggering some of these functions. The goal of the present study was to identify the domain(s) of P. gingivalis FimA responsible for specific interaction with human mucosal epithelial cells. Fimbriated P. gingivalis strains have been shown to bind to buccal epithelial cells, whereas nonfimbriated strains bind at low levels or not at all. This and other studies provide evidence that FimA mediates the adherence of P. gingivalis to oral epithelial cells. To determine the specific region(s) of P. gingivalis FimA involved in epithelial cell binding, specific antipeptide antibodies were used to inhibit the binding of iodinated purified fimbriae as well as the binding of P. gingivalis cells to epithelial cells. Antibodies directed against peptides 49 to 68 (VVMANTAGAMELVGKTLAEVK) and 69 to 90 (ALTTELTAENQEAAGLIMTAEP) were found to highly inhibit both the binding of fimbriae and the binding of P. gingivalis cells to epithelial cells. The antibody against FimA peptides 69 to 90 also reacted with P. gingivalis fimbriae in immunogold labeling and immunoblot analysis, thereby indicating that this peptide domain is exposed on the surface of fimbriae. Our results suggest that the amino-terminal domain corresponding to amino acid residues 49 to 90 of the fimbrillin protein is a major epithelial cell binding domain of P. gingivalis fimbriae.

Life below the gum line: pathogenic mechanisms of Porphyromonas gingivalis

Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent in the initiation and progression of severe forms of periodontal disease. An opportunistic pathogen, P. gingivalis can also exist in commensal harmony with the host, with disease episodes ensuing from a shift in the ecological balance within the complex periodontal microenvironment. Colonization of the subgingival region is facilitated by the ability to adhere to available substrates such as adsorbed salivary molecules, matrix proteins, epithelial cells, and bacteria that are already established as a biofilm on tooth and epithelial surfaces. Binding to all of these substrates may be mediated by various regions of P. gingivalis fimbrillin, the structural subunit of the major fimbriae. P. gingivalis is an asaccharolytic organism, with a requirement for hemin (as a source of iron) and peptides for growth. At least three hemagglutinins and five proteinases are produced to satisfy these requirements. The hemagglutinin and proteinase genes contain extensive regions of highly conserved sequences, with posttranslational processing of proteinase gene products contributing to the formation of multimeric surface protein-adhesin complexes. Many of the virulence properties of P. gingivalis appear to be consequent to its adaptations to obtain hemin and peptides. Thus, hemagglutinins participate in adherence interactions with host cells, while proteinases contribute to inactivation of the effector molecules of the immune response and to tissue destruction. In addition to direct assault on the periodontal tissues, P. gingivalis can modulate eucaryotic cell signal transduction pathways, directing its uptake by gingival epithelial cells. Within this privileged site, P. gingivalis can replicate and impinge upon components of the innate host defense. Although a variety of surface molecules stimulate production of cytokines and other participants in the immune response, P. gingivalis may also undertake a stealth role whereby pivotal immune mediators are selectively inactivated. In keeping with its strict metabolic requirements, regulation of gene expression in P. gingivalis can be controlled at the transcriptional level. Finally, although periodontal disease is localized to the tissues surrounding the tooth, evidence is accumulating that infection with P. gingivalis may predispose to more serious systemic conditions such as cardiovascular disease and to delivery of preterm infants.

The importance of fimbriae in the virulence and ecology of some oral bacteria

Cumulative evidence indicates that bacterial adherence to mucosal and tooth surfaces as well as bacterial coaggregation are essential steps for colonization of various oral bacterial species. Bacterial fimbriae have been shown to play an important role in the interaction between bacteria and host cells or among bacterial cells. The properties of fimbriae from selected species of oral bacteria are discussed in terms of virulence traits and ecological significance. Among others, Porphyromonas gingivalis fimbriae have been most extensively studied. The fimbrial structure is composed of 41-kDa fimbrillin proteins. DNA sequencing of the fimbrillin gene (fimA) from nine strains of P. gingivalis suggests intraspecies variation in the structure of fimA, while retaining common immunochemical specificities. P. gingivalis fimbriae exhibit a wide variety of biological activities including immunogenicity, binding to various host proteins, stimulation of cytokine production and promotion of bone resorption, Actinobacillus actinomycetemcomitans also possesses fimbriae; however, little is known concerning their chemical, genetical, and biological properties. Fimbriae of Prevotella intermedia are shown to induce hemagglutination reaction, while those of Prevotella loescheii are found to cause coaggregation with other bacteria, i.e., Actinomyces viscosus and sanguis streptococci. Fimbriae from gram-positive oral bacteria such as oral Actinomyces and sanguis streptococci are described. These fimbriae may participate in coaggregation, binding to saliva-coated hydroxyapatite or glycoprotein of the surface layer of oral epithelial cells. Taken together, fimbriae are key components in cell-to-surface and cell-to-cell adherence of oral bacteria and pathogenesis of some oral and systemic diseases.

Models of invasion of enteric and periodontal pathogens into epithelial cells: a comparative analysis

Bacterial invasion of epithelial cells is associated with the initiation of infection by many bacteria. To carry out this action, bacteria have developed remarkable processes and mechanisms that co-opt host cell function and stimulate their own uptake and adaptation to the environment of the host cell. Two general types of invasion processes have been observed. In one type, the pathogens (e.g., Salmonella and Yersinia spp.) remain in the vacuole in which they are internalized and replicate within the vacuole. In the other type, the organism (e.g., Actinobacillus actinomycetemcomitans, Shigella flexneri, and Listeria monocytogenes) is able to escape from the vacuole, replicate in the host cell cytoplasm, and spread to adjacent host cells. The much-studied enteropathogenic bacteria usurp primarily host cell microfilaments for entry. Those organisms which can escape from the vacuole do so by means of hemolytic factors and C type phospholipases. The cell-to-cell spread of these organisms is mediated by microfilaments. The investigation of invasion by periodontopathogens is in its infancy in comparison with that of the enteric pathogens. However, studies to date on two invasive periodontopathogens. A actinomycetemcomitans and Porphyromonas (Bacteroides) gingivalis, reveal that these bacteria have developed invasion strategies and mechanisms similar to those of the enteropathogens. Entry of A. actinomycetemcomitans is mediated by microfilaments, whereas entry of P. gingivalis is mediated by both microfilaments and microtubules. A. actinomycetemcomitans, like Shigella and Listeria, can escape from the vacuole and spread to adjacent cells. However, the spread of A. actinomycetemcomitans is linked to host cell microtubules, not microfilaments. The paradigms presented establish that bacteria which cause chronic infections, such as periodontitis, and bacteria which cause acute diseases, such as dysentery, have developed similar invasion strategies.

Hyporesponsiveness of inflamed human gingival fibroblasts from patients with chronic periodontal diseases against cell surface components of Porphyromonas gingivalis

Inflamed human gingival fibroblasts (HGF) of patients with chronic periodontal diseases have less active interleukin-8 (IL-8) production compared with normal HGF of volunteers with healthy gingival tissues, after stimulation with Porphyromonas gingivalis surface components such as fimbriae, lipopolysaccharide (LPS) and its lipid A, but not LPS or lipid A from other bacterial species. A decrease in number of specific binding sites for P. gingivalis fimbrial molecules in inflamed HGF is also observed by Scatchard plot analysis. A short exposure (6 h) to P. gingivalis LPS resulted in significant potentiation of the LPS-dependent IL-8 production in normal HGF, whereas a long exposure (48 h) to the LPS significantly reduced IL-8 production. Tyrosine phosphorylation of proteins of 127 kDa and 186 kDa in inflamed HGF stimulated with P. gingivalis fimbriae or its LPS was observed by immunoblotting, and these two phosphoproteins were termed tolerance-induced protein, TIP. Protein bands of 45 kDa which bound to radioiodinated P. gingivalis fimbriae in the presence and absence of fetal bovine serum (FBS), and major 73-kDa and minor 30-kDa and 45-kDa bands which bound to radioiodinated P. gingivalis LPS in the presence of FBS in normal and inflamed HGF were observed by using photocrosslinking. These findings suggest that the hyporesponsiveness of HGF induced by a prolonged exposure to P. gingivalis may emerge because of HGF damage or result from host defense in chronic periodontal lesions.

Antagonistic effect of synthetic peptides corresponding to the binding regions within fimbrial subunit protein from Porphyromonas gingivalis to human gingival fibroblasts

Specific binding region within fimbrial subunit protein (fimbrilin) from Porphyromonas gingivalis strain 381 was studied in cultured human gingival fibroblasts. Fluorescent micrographs visualised FITC-labelled fimbriae of P. gingivalis specifically bound to normal human fibroblast cell line (Gin-1) along the cell surface. Flow cytometric analysis also revealed the binding of FITC-labelled fimbriae to Gin-1 cells. Synthetic peptides composed of residues 1-20 (AFGVGDDESKVAKLTVMVYN) of the fimbrilin from P. gingivalis, FP381 (1-20), FP381 (69-80; ALTTELTAENQE) and FP381 (171-181; DA-NYLTGSLTT) definitely inhibited P. gingivalis fimbria-binding to Gin-1 cells by enzyme-linked immunosorbent assay (ELISA). Furthermore, based on the Scatchard plot analysis of the binding of 125I-labelled P. gingivalis fimbriae to Gin-1 cells, the apparent dissociation constant (Kd) was calculated as 15.9 pM, and the number of binding sites (Rt) was estimated as 150 sites/cell. Binding studies of 125I-labelled FP381(171-181) also revealed the presence of a non-interacting, single class of affinity binding sites: the apparent Kd and Rt were 29.2 nM and 18440 sites/cell on Gin-1 cells, respectively. These results demonstrate that specific binding regions on P. gingivalis fimbriae to human gingival fibroblasts are present, and certain corresponding peptides clearly inhibited the binding of P. gingivalis fimbriae to human gingival fibroblasts.

Sequence and product analyses of the four genes downstream from the fimbrilin gene (fimA) of the oral anaerobe Porphyromonas gingivalis

The downstream DNA region of the fimbrilin gene (fimA), which encodes the major subunit protein of Porphyromonas gingivalis fimbriae, was fully sequenced. Gene products, expressed from this region in Escherichia coli, were purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their partial amino acid sequences were determined to verify open reading frames (ORFs) found in the region by DNA sequencing. Four ORFs, designated ORF1, ORF2, ORF3 and ORF4, were found in the 5.8-kb PstI fragment downstream from fimA, which was previously cloned and partially characterized by Yoshimura, Takahashi, Hibi, Takasawa, Kato, and Dickinson (Infect. Immun. 61: 5181-5189, 1993). The direction of transcription of all the ORFs was the same as that of fimA. The 50 and 80 kDa encoded proteins, ORF2 and ORF3, respectively, have been reported to be minor components associated with fimbriae. The 15 and 19 kDa proteins, ORF1 and ORF4, respectively, have been expressed in E. coli but not identified in P. gingivalis. However, all the gene products of the ORFs, expressed in E. coli, appeared to contain intact signal peptides based on their N-terminal amino acid sequences.

Cytokine-inducing components of periodontopathogenic bacteria

Pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8 and tumour necrosis factor (TNF) are believed to be the major pathological mediators of inflammatory diseases ranging from arthritis to the periodontal diseases. The stimuli inducing proinflammatory cytokine induction in the former disease is unclear but in the periodontal diseases it is obvious that the stimulus is the accumulation of bacteria in the subgingival region. As these bacteria do not invade the lesional tissues in large numbers, it is believed that their soluble components or products interact with host tissues to induce cytokine gene transcription. The paradigm is that lipopolysaccharide is the key bacterial component inducing pro-inflammatory cytokine gene expression. However, over the past decade a growing number of reports on non-oral bacteria have established that many other bacterial components, as well as secretory products, have the capacity to induce cytokine synthesis. Some of these, such as the protein pneumolysin from Streptococcus pneumoniae, are incredibly potent (in this case inducing cytokine synthesis at femtomolar concentrations). This review surveys the range of bacterial components and products which have been shown to stimulate cytokine synthesis with particular emphasis on the hypothesis that these components play a role in the pathology of the periodontal diseases.

Human monocyte response to cementum extracts from periodontally diseased teeth: effect of conditioning with tetracycline

Monocyte inflammatory cytokines, such as TNF alpha and IL-1 beta, have been implicated in the pathogenesis of periodontal destruction. The present study was designed to test the ability of extracts of cementum from periodontally diseased teeth to induce the secretion of these mediators by monocytes, to evaluate the role of adsorbed endotoxin in this process, and to test the effect of cementum conditioning with tetracycline on the monocyte response. Human monocytes were incubated with varying concentrations of cementum extracts, and TNF alpha and IL-1 beta levels in the media were measured. The results showed that while extracts of healthy cementum had no effect on monocyte secretion, concentration as low as 0.5 mg/ml of cementum from diseased sites raised the levels of TNF alpha and IL-1 beta secretion 10-fold. This response was dose-dependent. Diseased cementum were found to contain 1.5 ng/mg endotoxin, while endotoxin was not detectable in the extracts of the healthy cementum. However, neutralization of the endotoxin by polymyxin B only partially reduced the monocyte secretory response by 50 to 70%, suggesting that other factors in the extracts are also involved in monocyte stimulation. To simulate the effect of root conditioning, cementum was first agitated in a tetracycline or control solution prior to its extraction in media. Pretreatment of diseased cementum with tetracycline (50 mg/ml) was found to block the secretion of TNF alpha from cementum-stimulated monocytes. Pretreatment of the diseased cementum with 10 mg/ml tetracycline was not more effective than saline and HCI controls, with all treatments reducing cytokine secretion by approximately 80%. The direct addition of tetracycline to cementum-stimulated monocyte culture was found to block TNF alpha secretion in a dose dependent manner. The results suggest that extracts from diseased cementum are potent stimulators of monocyte secretion, and that endotoxin as well as other factor(s) appear to be involved. These factors are partially extracted by washing and a 10 mg/ml tetracycline solution is not more effective than saline in achieving this goal. In addition, tetracycline was found to be a potent inhibitor of TNF alpha secretion by cementum-stimulated monocytes, suggesting a novel mechanism for this drug in periodontal therapy.

Bacterial modulins: a novel class of virulence factors which cause host tissue pathology by inducing cytokine synthesis

Cytokines are a diverse group of proteins and glycoproteins which have potent and wide-ranging effects on eukaryotic cell function and are now recognized as important mediators of tissue pathology in infectious diseases. It is increasingly recognized that for many bacterial species, cytokine induction is a major virulence mechanism. Until recent years, the only bacterial component known to stimulate cytokine synthesis was lipopolysaccharide (LPS). It is only within the past decade that it has been clearly shown that many components associated with the bacterial cell wall, including proteins, glycoproteins, lipoproteins, carbohydrates, and lipids, have the capacity to stimulate mammalian cells to produce a diverse array of cytokines. It has been established that many of these cytokine-inducing molecules act by mechanisms distinct from that of LPS, and thus their activities are not due to LPS contamination. Bacteria produce a wide range of virulence factors which cause host tissue pathology, and these diverse factors have been grouped into four families: adhesins, aggressins, impedins, and invasins. We suggest that the array of bacterial cytokine-inducing molecules represents a new class of bacterial virulence factor, and, by analogy with the known virulence families, we suggest the term "modulin" to describe these molecules, because the action of cytokines is to modulate eukaryotic cell behavior. This review summarizes our current understanding of cytokine biology in relation to tissue homeostasis and disease and concisely reviews the current literature on the cytokine-inducing molecules produced by gram-negative and gram-positive bacteria, with an emphasis on the cellular mechanisms responsible for cytokine induction. We propose that modulins, by controlling the host immune and inflammatory responses, maintain the large commensal flora that all multicellular organisms support.

Induction of systemic murine B-cell responses by Fusobacterium nucleatum and Porphyromonas gingivalis

The purpose of this study was to examine the antigenic abilities of Fusobacterium nucleatum strain ATCC 25586 and Porphyromonas gingivalis strain W50 black inbred BALB/cABom mice immunized subcutaneously. Furthermore, we aimed to analyze whether the outer membranes (OM) and whole cells (WC) of F. nucleatum or P. gingivalis had an effect on the levels of antibody response and whether a combination of both could either enhance or suppress the B-cell response. A single-cell assay, solid-phase enzyme-linked immunospot (ELISPOT), was used to analyze the splenic B-cell response (immunoglobulin A (IgA), IgG and IgM). Enzyme-linked immunosorbent assay (ELISA) and immunoblotting were used to verify the specific antibody response in the sera. A statistically significant lower level of spontaneous antibody production was observed in the group immunized with P. gingivalis OM compared with groups immunized with F. nucleatum and saline. The specific antibody titers measured by ELISA indicated that the bacterial preparations were able to induce IgG and IgM response. The preparations containing P. gingivalis OM induced higher humoral response than the preparations containing P. gingivalis WC, but for F. nucleatum such a difference was not observed. The prominent proteins revealed had apparent molecular masses of 40 kDa for F. nucleatum and 115, 55-56 and 43 kDa for P. gingivalis; whereas the immunoreactive proteins were 70, 65 and 40 kDa for mice immunized with F. nucleatum and 115, 55-56, 43 and 33-34 kDa for mice immunized with P. gingivalis. Quantitative analysis of B-cell response at the single cell level with ELISPOT revealed that some component(s) of P. gingivalis OM may have a suppressive ability on splenocytes incubated for a short time.

Identification of murine protective epitopes on the Porphyromonas gingivalis fimbrillin molecule

Fimbriae from Porphyromonas gingivalis are believed to play an important role in the pathogenesis of periodontal diseases. The aim of the present study was to identify the fimbrial protective T-cell epitopes in CBA/J mice. A truncated protein corresponding to amino acids 1 to 198, PgF1-198, was generated and allowed us to demonstrate that the N terminus of the protein contains T-cell epitopes. With synthetic peptides, an immunodominant sequence was identified between amino acids 103 and 122. The corresponding peptide, PgF-P8, induced T-cell proliferation after in vitro restimulation of in vivo-primed cells, giving a stimulation index comparable to the one obtained with r-fimbrillin, and induced production of both Th1 and Th2 cytokines. Growth supernatant contained significant levels of interleukin 2 (IL-2), gamma interferon, IL-4 (28 pg/ml), and tumor necrosis factor alpha. Immunization of mice with r-fimbrillin, PgF1-198, and PgF-P8 induced production of antibodies specific to r-fimbrillin and PgF-P8. In addition, by using the mouse chamber model we found that mice immunized with PgF-P8 were dramatically protected against a normally lethal injection of P. gingivalis. Animals immunized with PgF-P8 40 days prior to challenge showed a 60% survival rate when challenged with P. gingivalis, compared with just 25% survival in control animals and just 5% survival in mice immunized with PgF-P8 only 21 days prior to challenge. Although the protection depended on the time of immunization before the bacterial challenge, it did not correlate with in vivo local cytokine production (IL-2, IL-4, IL-6, tumor necrosis factor alpha, and gamma interferon), specific antibody levels, or the isotype of anti-PgF-P8 antibodies produced.

Inductive effect of Porphyromonas gingivalis fimbriae on differentiation of human monocytic tumor cell line U937

This study used the human monocytic tumor cell line U937 to examine whether Porphyromonas gingivalis fimbriae induce differentiation of monocyte/macrophage progenitors. When the progenitor cells were incubated with P. gingivalis fimbriae, the incubation resulted in increased Fc rosette formation and increased CD11b production by the cells. The presence of a protein kinase C inhibitor, H7 or calphostin C, in the medium eliminated the stimulatory effects of P. gingivalis fimbriae on Fc rosette formation. Furthermore, CD11b expression was inhibited by calphostin C. In contrast, HA1004 , an inhibitor of cyclic nucleotide-dependent protein kinase, had no effect on P. gingivalis fimbriae-induced Fc rosette formation or CD11b expression. These results demonstrate that P. gingivalis fimbriae are a potent inducer of the differentiation of the monocyte/macrophage tumor cell line U937, most probably via cyclic nucleotide-independent protein kinase C.

Antigenic, structural, and functional relationships between fimbriae and the hemagglutinating adhesin HA-Ag2 of Porphyromonas gingivalis

While the adhesive properties of Porphyromonas gingivalis are known to allow colonization of the subgingival tissues, the roles of fimbriae and adhesin molecules in hemagglutination remain unclear. The purpose of this study was to analyze the antigenic, structural, and functional relationships of these two components. Five populations of monoclonal antibodies were produced against (i) the hemagglutinating adhesin HA-Ag2 resolved by crossed immunoelectrophoresis (CIE), (ii) native fimbriae, and (iii) each of the three immunoprecipitates, Ag8a, Ag8b, and Ag8c, that define fimbriae by CIE. The tests used for characterization of the monoclonal antibodies included immunoblot reactivity, inhibition of hemagglutination, capacity to dissociate immunoprecipitates by CIE, localization of recognized epitopes by immunoelectron microscopy, and epitope mapping by competition enzyme-linked immunosorbent assay. The results from the different immunochemical tests clearly showed a close antigenic relationship between fimbriae and the hemagglutinating adhesin HA-Ag2. We were able to establish that the epitopic domain H1 of HA-Ag2 is hemagglutinin specific and that domain F2 is fimbria specific. Our data indicate that the polymeric structural unit of fimbriae must be complexed to HA-Ag2, the adhesin, to confer hemagglutination activity to the bacterial cells.

Identification of Porphyromonas gingivalis prefimbrilin possessing a long leader peptide: possible involvement of trypsin-like protease in fimbrilin maturation

Fimbriae of Porphyromonas gingivalis have been shown to be important as one of the virulence factors for colonization on mucosal surfaces. The gene (fimA) encoding the fimbrial subunit (fimbrilin) was overexpressed in Escherichia coli by using a bacteriophage T7 promoter-polymerase expression vector system. Analysis of the resulting fimA gene product revealed that the prefimbrilin had a 46 amino acid leader peptide. This extremely long leader peptide was cleaved from the prefimbrilin by treatment with trypsin or P. gingivalis extracts containing trypsin-like protease activity, resulting in production of a mature fimbrilin. We also found that some transposon-induced trypsin-like protease deficient mutants of P. gingivalis exhibited deficiency in fimbriation and that one of the mutants accumulated a fimbrilin precursor possessing a 25 amino acid leader peptide in the cell. The presence of an extremely long leader peptide and the requirement for a leader peptidase with a substrate specificity similar to that of P. gingivalis trypsin-like protease for fimbrilin maturation indicate that P. gingivalis fimbrilin is a novel type that is different from fimbrilins of type I and IV families.

Porphyromonas gingivalis fimbria-stimulated bone resorption in vitro is inhibited by a tyrosine kinase inhibitor

Our previous study (Y. Kawata, S. Hanazawa, S. Amano, Y. Murakami, T. Matsumoto, K. Nishida, and S. Kitano, Infect. Immun. 62:3012-3016, 1994) showed that Porphyromonas gingivalis fimbriae stimulate bone resorption in vitro. Since it has recently been demonstrated that tyrosine kinase encoded by the c-src gene plays an important role in osteoclastic bone resorption, in the present study we examined the effect of a tyrosine kinase inhibitor on the fimbria-stimulated bone resorption. Genistein, a potent inhibitor of tyrosine kinase, markedly inhibited bone resorption stimulated by the fimbriae. Genistein also inhibited induction of several tyrosine-phosphorylated proteins in the fimbria-treated calvarial bone cells from mouse embryos.

A peptide, ALTTE, within the fimbrial subunit protein from Porphyromonas gingivalis, induces production of interleukin 6, gene expression and protein phosphorylation in human peripheral blood mononuclear cells

Porphyromonas gingivalis 381 fimbriae and a synthetic peptide composed of residues 69-73 (ALTTE) of the fimbrial subunit protein, FP381(69-73), function in the induction of interleukin 6 (IL-6) production, IL-6 mRNA expression, and tyrosine and serine/threonine phosphorylation of several proteins in human peripheral blood mononuclear cells (PBMC). Herbimycin A and H-7, inhibitors of tyrosine kinases and protein kinase C (PKC), markedly inhibited IL-6 production, gene expression, and tyrosine and serine/threonine phosphorylation of proteins. An inactive analog of synthetic peptide replaced alanine to glycine at position 69 in FP381(69-73), GLTTE, exhibited an antagonistic effect on the IL-6 production induced by the fimbriae. These results suggest that the peptide ALTTE functions as an agent in inflammatory reactions and immune responses in the inflamed gingival and periodontal tissues, in which the participation of protein phosphorylation by tyrosine kinases and PKC in signal transduction may be considered.

Immunochemical characterisation and epitope mapping of a novel fimbrial protein (Pg-II fimbria) of Porphyromonas gingivalis

Mouse monoclonal antibody (mAb) Pgf-II specific for a 72-kDa major cell-surface protein (72K-CSP) derived from Porphyromonas gingivalis OMZ 409 was prepared. Immunoblotting analysis revealed that mAb Pgf-II reacted with 72K-CSP but not with 41-kDa fimbrial subunit protein (41K-fimbrilin) derived from P. gingivalis 381. Electron microscopic observation revealed that P. gingivalis OMZ 409 possessed peritrichous, thin fimbriae on their surface. Immunogold electron microscopy also demonstrated that mAb Pgf-II bound to the 72K-CSP examined with the gold particles arranged along the fibril array originating from the cell surface of the bacteria. These findings suggested that P. gingivalis 72K-CSP was identifiable as another fimbriae (termed Pg-II fimbriae) different from the fimbriae (termed Pg-I fimbriae) composed of a 41K-fimbrilin. Using multipin peptide synthesis technology, 102 sequential overlapping peptides covering the entire 514 amino-acid stretch of Pg-II fimbriae were synthesised. Seven immunodominant regions within Pg-II fimbrial protein molecule, which definitely reacted with the serum of patients with periodontal diseases, were detected.

Oral infection with Porphyromonas gingivalis and induced alveolar bone loss in immunocompetent and severe combined immunodeficient mice

The suitability of a mouse model for host response in the induction of alveolar bone loss by Porphyromonas gingivalis was explored. The mouths of immunocompetent and severe combined immunodeficient (SCID) mice were infected with P. gingivalis ATCC 53977. P. gingivalis was not isolated from the mouths of these mice before infection, but was present at least 42 days after infection. P. gingivalis-specific IgG was present in sera from the infected, immunocompetent mice at the end of these experiments (42 days). Specific IgG was not present in sham-infected or uninfected immunocompetent mice, nor in any immunodeficient mice. Specific IgM was not present in any sera at 42 days. Infected, immunocompetent mice of two strains showed significant bone loss in comparison to sham-infected or uninfected immunocompetent mice (p < 0.05). Infected SCID mice, which are genetically lacking both B and T lymphocytes, also showed significant bone loss compared with sham-infected or uninfected SCID mice (p < 0.05). However, the degree of bone loss was greater in immunocompetent than immunodeficient mice: the relative amount of bone in infected mice was 77% of that in sham-infected immunocompetent mice, and 86% of sham values in SCID mice (p = 0.025). Thus oral infection of mice is a feasible model for studying the effects of host response on P. gingivalis-induced alveolar bone loss. Because bone loss was induced both in immunocompetent and SCID mice but was greater in immunocompetent mice, it appears that neither B nor T cells are absolutely necessary for bone resorption in response to P. gingivalis infection but they may significantly modulate the degree of resorption.

Porphyromonas gingivalis fimbriae induce a 68-kilodalton phosphorylated protein in macrophages

The present study was performed to examine whether Porphyromonas gingivalis fimbriae induce specifically a protein kinase-mediated phosphorylated protein that is involved in the mechanism of signal transduction. The fimbriae induced a 68-kDa phosphorylated protein (pp68) in a dose-dependent manner in mouse peritoneal macrophages. A marked appearance of pp68 was observed 20 min after the initiation of fimbrial treatment. The fimbria-induced pp68 was inhibited dramatically by staurosporine, a potent inhibitor of protein kinase C. pp68 induction was also inhibited by H-7, a potent inhibitor of several types of protein kinase. However, the induction was not inhibited by HA-1004 and H-8, relatively high-affinity inhibitors of protein kinase A. Phorbol myristate acetate and 1-oleoyl-2-acetyl-sn-glycerol, activators of protein kinase C, were able to induce pp68 in mouse peritoneal macrophages. This protein was localized in the cytosolic fraction of fimbria-treated macrophages. pp68 also was induced in fimbria-treated human monocyte-like cells. Finally, we observed that gene expression of the fimbria-induced neutrophil chemoattractant KC was inhibited markedly by staurosporine.

Chemotaxis of human monocytes by synthetic peptides that mimic segments of Porphyromonas gingivalis fimbrial protein

Porphyromonas gingivalis strain 381 fimbriae and their synthetic peptide segments were assessed for migration-stimulating activity on human peripheral blood monocytes by multiwell chemotaxis assay. P. gingivalis 381 fimbrial protein was found to markedly enhance migration of human monocytes. The observed increase in monocyte migration occurred mainly directed toward a positive stimulus (chemotaxis). Furthermore, lipopolysaccharides extracted from P. gingivalis 381 were shown to induce chemotaxis and chemokinesis. It was also revealed that the migration of monocytes was increased by specific synthetic peptide segments, FP381(61-80) and FP381(171-185), that correspond to GKTLAEVKALTTELTAENQE and DANYLTGSLTTFNGA, respectively, based on the amino acid sequence of the fimbrial subunit protein proposed by Dickinson et al., and the migration stimulation was ascribed to chemotaxis. Furthermore, within the amino acid sequences, the LTXXLTXXN sequence may play an important role in binding the organisms to monocytes and macrophages and in the induction of migration-stimulating activity.

Hemagglutinating and chemotactic properties of synthetic peptide segments of fimbrial protein from Porphyromonas gingivalis

Porphyromonas gingivalis 381 fimbriae, their synthetic peptide segments, and lipopolysaccharide (LPS) were examined for hemagglutinating and migration-stimulating activities. P. gingivalis 381 fimbriae clearly caused hemagglutination, and several oligopeptide segments such as FP381(61-80), FP381(171-185), and FP381(302-321), corresponding to the amino acid residue numbers based on the amino acid sequence of fimbrillin proposed by Dickinson et al. (D. P. Dickinson, M. A. Kubiniec, F. Yoshimura, and R. J. Genco, J. Bacteriol. 170:1658-1665, 1988), were also demonstrated to agglutinate erythrocytes although less effectively than the native fimbriae. Furthermore, P. gingivalis 381 LPS but not Escherichia coli O55:B5 LPS definitely exhibited hemagglutination. P. gingivalis fimbriae as well as their synthetic peptides possessing hemagglutinating activity enhanced the chemotaxically induced migration of human peripheral blood monocytes. The results of the analyses using synthetic peptide FP381(61-80), its related compounds, and an analog suggested that the amino acid sequence XLTXXLTXXNXX within fimbrial protein molecules may play an important role structurally in the attachment of the protein to host cells such as erythrocytes and monocytes.

Porphyromonas gingivalis fimbriae stimulate bone resorption in vitro

Our previous study demonstrated that Porphyromonas gingivalis fimbriae induce the expression of interleukin-1, a potent bone-resorbing cytokine, in macrophages. This demonstration suggested to use the possibility that the fimbriae may stimulate bone resorption via the generation of an inflammatory cytokine(s). The present study was performed to test this suggestion. The bone-resorbing activity was evaluated by measuring the area of resorption lacunae on bone slices incubated with calvarial bone cells taken from 14-day-old mouse embryos. Fimbriae at 0.5 micrograms of protein per ml stimulated the bone-resorbing activity significantly, and the effect was dose and treatment time dependent. Since it is well known that interleukin-1 and granulocyte macrophage colony-stimulating factor induce differentiation of osteoclast lineage cells, we examined the involvement of these cytokines in fimbria-stimulated bone resorption. Fimbria-stimulated bone resorption was abolished significantly by antisera against both cytokines. We observed by Northern (RNA) blot assay that both cytokine genes were markedly expressed in the fimbria-treated calvarial bone cells. Our present data demonstrate that P. gingivalis fimbriae stimulate bone resorption in vitro.

Molecular cloning and characterization of the genes encoding the immunoreactive major cell-surface proteins of Porphyromonas gingivalis

A 72-kDa major cell-surface protein (72K-CSP) was purified from the wash fluid of Porphyromonas gingivalis OMZ409. Using the synthetic oligonucleotide probes corresponding to the determined amino-terminal amino acid sequence of 72K-CSP, recombinant plasmid clones carrying approx. 3.4-kb KpnI-XhoI fragments in XL1-Blue libraries of P. gingivalis OMZ409 and 381 were obtained. The premature form proteins of 558 and 563 amino acids led by putative signal sequences were thought to be processed to form the mature proteins of a predicted size of 55,655 Da for strain OMZ409 and of 55,654 for strain 381. Both proteins had unusual proline-rich regions in their carboxyl-terminal regions. No homologous sequences could be found in protein databases. Examination of antigen-specific antibody responses in the serum of patients with adult periodontitis by ELISA revealed that 72K-CSP had a different immunoreactivity from that of P. gingivalis 381 fimbriae.

Immunobiological activities of a 55-kilodalton cell surface protein of Prevotella intermedia ATCC 25611

A protein was extracted from whole cells of Prevotella intermedia ATCC 25611 with sodium lauroylsarcosine and purified by chromatography on a DEAE-Sepharose fast-flow column. The The apparent molecular weight of the protein was 55,000. A mouse polyclonal antibody specific for the protein recognized the cell surface structure of P. intermedia and also reacted with proteins in lysates of other black-pigmented anaerobic bacteria, such as Porphyromonas endodontalis and Prevotella melaninogenica, but not with those in lysates of Porphyromonas gingivalis or with the purified fimbriae of P. gingivalis 381. The N-terminal sequence of the 55-kDa protein showed only low homology with the cell surface proteins of any black-pigmented bacteria reported to date. The level of immunoglobulin G antibody to the antigen was higher in the sera of patients with periodontitis than in the sera of healthy volunteers. The protein induced interleukin-1 alpha, -1 beta, -6, and -8 and tumor necrosis factor alpha in human peripheral blood mononuclear cell cultures and interleukin-1 beta and -6 in human umbilical vascular endothelial cell and gingival fibroblast cultures. The protein induced interleukin-6 and tumor necrosis factor alpha activities in peritoneal macrophages from C3H/HeJ as well as from C3H/HeN mice and also induced cytokine activities in the sera of both strains of mice primed with muramyldipeptide.

Porphyromonas gingivalis fimbriae and their synthetic peptides induce proinflammatory cytokines in human peripheral blood monocyte cultures

Porphyromonas gingivalis fimbriae as well as synthetic peptides that mimic the fimbrial subunit protein, which includes the amino acid sequence XLTXXLTXXNXX, induced high production of proinflammatory cytokines such as interleukin-1 beta, interleukin-6, interleukin-8, tumor necrosis factor-alpha in human peripheral blood monocyte/macrophage cultures. Responses induced by some peptide segments were comparable to those induced by Escherichia coli lipopolysaccharides. A chemically modified peptide analogous to an active peptide segment was found to be antagonistic with regard to interleukin-6 production induced by the native fimbriae. It may be suggested that P. gingivalis fimbriae and their degraded peptides function as proinflammatory agents in vivo, while certain analog peptides inhibited the process.

Immunobiological properties of chemically defined lipid A from lipopolysaccharide of Porphyromonas (Bacteroides) gingivalis

Porphyromonas gingivalis 381 lipid A, characterized by beta-(1-6)-linked glucosamine disaccharide 1-phosphate, with one hydroxyacyl group and one acyloxyacl group, i.e., 3-hydroxy-15-methyl-hexadecanoyl and 3-hexadecanoyloxy-15-methylhexadecanoyl groups at the 2 and 2' positions, respectively, was less endotoxically active than the synthetic Escherichia-coli-type lipid A (compound 506), which possesses beta-(1-6)-linked glucosamine disaccharide 1,4'-bisphosphate, with two acyloxyacyl groups at the 2' and 3' positions and two 3-hydroxytetradecanoyl group at the 2 and 3 positions and the synthetic Salmonella-type lipid A (compound 516), which has three acyloxyacyl groups at the 2,2' and 3' positions and one hydroxyacyl group at the 3 position. P. gingivalis lipid A exhibited no or very low endotoxic activities, i.e., lethal toxicity in galactosamine-loaded mice, preparative ability for local Shwartzman reaction, pyrogenicity and Limulus test as compared with compounds 506 and 516. However, polyclonal B-cell activation of BALB/c mouse splenocytes was as strong as that of compound 506. Furthermore, P. gingivalis lipid A had stronger immunoadjuvant and hemagglutinating activities than compound 506. The absence of ester-linked phosphate at the 4' position and ester-linked fatty acids, and the presence and positions of fatty acids possessing considerable lengths of acyl chains are unique features of P. gingivalis lipid A, and they differentiate this lipid A from enterobacterial and other lipids A. The good balance between endotoxic properties and beneficial immunobiological activities of P. gingivalis lipid A may be attributable to these features.