Distribution and immunochemical specificities of fimbriae of Porphyromonas gingivalis and related bacterial species

Porphyromonas gingivalis Virulence Factors and Clinical Significance in Periodontal Disease and Coronary Artery Diseases

Porphyromonas gingivalis is a gram-negative, anaerobic bacterium that lives in the oral cavity. It is an integral part of the oral microbiome, which includes more than 500 types of bacteria. Under certain circumstances, as a consequence of virulence factors, it can become very destructive and proliferate to many cells in periodontal lesions. It is one of the causative agents present extremely often in dental plaque and is the main etiological factor in the development of periodontal disease. During various therapeutic procedures, P. gingivalis can enter the blood and disseminate through it to distant organs. This primarily refers to the influence of periodontal agents on the development of subacute endocarditis and can facilitate the development of coronary heart disease, atherosclerosis, and ischemic infarction. The action of P. gingivalis is facilitated by numerous factors of virulence and pathogenicity such as fimbriae, hemolysin, hemagglutinin, capsules, outer membrane vesicles, lipopolysaccharides, and gingipains. A special problem is the possibility of biofilm formation. P. gingivalis in a biofilm is 500 to 1000 times less sensitive to antimicrobial drugs than planktonic cells, which represents a significant problem in the treatment of infections caused by this pathogen.

Diversity analysis of genes encoding Mfa1 fimbrial components in Porphyromonas gingivalis strains

Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is associated with the development of periodontal disease. The genetic diversity in virulence factors, such as adhesive fimbriae, among its strains affects the bacterial pathogenicity. P. gingivalis generally expresses two distinct types of fimbriae, FimA and Mfa1. Although the genetic diversity of fimA, encoding the major FimA fimbrilin protein, has been characterized, the genes encoding the Mfa1 fimbrial components, including the Mfa1 to Mfa5 proteins, have not been fully studied. We, therefore, analyzed their genotypes in 12 uncharacterized and 62 known strains of P. gingivalis (74 strains in total). The mfa1 genotype was primarily classified into two genotypes, 53 and 70. Additionally, we found that genotype 70 could be further divided into two subtypes (70A and 70B). The diversity of mfa2 to mfa4 was consistent with the mfa1 genotype, although no subtype in genotype 70 was observed. Protein structure modeling showed high homology between the genotypes in Mfa1 to Mfa4. The mfa5 gene was classified into five genotypes (A to E) independent of other genotypes. Moreover, genotype A was further divided into two subtypes (A1 and A2). Surprisingly, some strains had two mfa5 genes, and the 2^ndmfa5 exclusively occurred in genotype E. The Mfa5 protein in all genotypes showed a homologous C-terminal half, including the conserved C-terminal domain recognized by the type IX secretion system. Furthermore, the von Willebrand factor domain at the N-terminal was detected only in genotypes A to C. The mfa1 genotypes partially correlated with the ragA and ragB genotypes (located immediately downstream of the mfa gene cluster) but not with the fimA genotypes.

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.

Possible requirement of intercellular adhesion molecule-1 for invasion of gingival epithelial cells byTreponema medium

Oral treponemes are members of the spirochete family of bacteria associated with periodontal diseases. In the present study, we demonstrate that intercellular adhesion molecule-1 (ICAM-1) on human gingival epithelial cells (HGEC) contributed to the invasion of Treponema medium , a medium-sized oral Treponema, into those cells. The quantity of T. medium in HGEC was found to peak at 2 h after inoculation and then decreased gradually. Immunofluorescence microscopy findings showed that the bacteria were colocalized with ICAM-1 on HGEC. Furthermore, knockdown of ICAM-1 in HGEC resulted in inhibition of T. medium invasion by RNA interference, whereas that of Toll-like receptor 2 did not. These results suggest that ICAM-1 may be required for the invasion of T. medium into HGEC, and they indicate that the molecule plays a principal role in the primary stages of the development and progression of chronic periodontitis.

Requirement for intercellular adhesion molecule 1 and caveolae in invasion of human oral epithelial cells by Porphyromonas gingivalis

Porphyromonas gingivalis, a periodontopathic bacterium, is known to invade oral epithelial cells in periodontal lesions, although the mechanism is unclear. In the present study, goat polyclonal anti-intercellular adhesion molecule 1 (anti-ICAM-1) antibody inhibited the invasion of P. gingivalis into KB cells (human oral epithelial cells). Further, the P. gingivalis fimbria, a pathogenic adhesion molecule, bound to recombinant human ICAM-1, as shown by enzyme-linked immunosorbent assay. P. gingivalis was also found to colocalize with ICAM-1 on KB cells, as seen with an immunofluorescence microscope, and the knockdown of ICAM-1 in KB cells resulted in the inhibition of P. gingivalis invasion by RNA interference. In addition, methyl-beta-cyclodextrin, a cholesterol-binding agent, inhibited the colocalization of P. gingivalis with ICAM-1 and invasion by the microorganism. The colocalization of caveolin-1, a caveolar marker protein, on KB cells with P. gingivalis was also shown, and the knockdown of caveolin-1 in KB cells caused a reduced level of P. gingivalis invasion. These results suggest that ICAM-1 and caveolae are required for the invasion of P. gingivalis into human oral epithelial cells, and these molecules appear to be associated with the primary stages of the development and progression of chronic periodontitis.

Genetic variation of a fimbrial protein from Porphyromonas gingivalis and its distribution in patients with periodontal diseases

Pg-II fim from various strains of Porphyromonas gingivalis was classified on the basis of each nucleotide sequence, while the distribution of Pg-II fim types in 141 subgingival plaque samples was analyzed using PCR assays. Pg-II fim was divided into two types as follows: strains OMZ409, HG405, 381, ATCC 33277 and BH18/10 (type 1) and strains OMZ314 and HW24D-1 (type 2). The presence of P. gingivalis was demonstrated in 2.8% of healthy subjects and 56.1% of patients with periodontal diseases, and Pg-II fim was detected in 91.8% of the P. gingivalis-positive subjects. We also analyzed the distribution of the Pg-II fim types among Pg-II fim-positive patients, with the following results: type 1 (38.2%), type 2 (56.4%) and types 1 and 2 (5.4%). These findings strongly suggest that P. gingivalis organisms possessing Pg-II fim type 2 was principally detected in patients with periodontal diseases.

Binding ofPorphyromonas gingivalisfimbriae toTreponema denticoladentilisin

Treponema denticola has been reported to coaggregate with Porphyromonas gingivalis and localize closely together in matured subgingival plaque. In this study of the interaction of T. denticola with P. gingivalis, the P. gingivalis fimbria-binding protein of T. denticola was identified by two-dimensional electrophoresis followed by a ligand overlay assay with P. gingivalis fimbriae, and was determined to be dentilisin, a chymotrypsin-like proteinase of T. denticola. The binding was further demonstrated with a ligand overlay assay using an isolated GST fusion dentilisin construct. Our results suggest that P. gingivalis fimbriae and T. denticola dentilisin are implicated in the coaggregation of these bacteria.

Purification and characterization of a novel secondary fimbrial protein from Porphyromonas gingivalis strain 381

We previously reported the existence of two different kinds of fimbriae expressed by Porphyromonas gingivalis ATCC 33277. In this study, we isolated and characterized a secondary fimbrial protein from strain FPG41, a fimA-inactivated mutant of P. gingivalis 381. FPG41 was constructed by a homologous recombination technique using a mobilizable suicide vector, and failed to express the long fimbriae (41-kDa fimbriae) that were produced on the cell surface of P. gingivalis 381. However, short fimbrial structures were observed on the cell surface of FPG41 by electron microscopy. The fimbrial protein was purified from FPG41 by DEAE-Sepharose CL-6B column chromatography. The secondary fimbrial protein was eluted at 0.15 M NaCl, and the molecular mass of this protein was approximately 53 kDa as estimated by SDS-PAGE. An antibody against the 53-kDa fimbrial protein reacted with the short fimbriae of the FPG41 and the wild-type strain. However, the 41-kDa long fimbriae of the wild-type strain and the 67-kDa fimbriae of ATCC 33277 did not react with the same antibody. Moreover, the N-terminal amino acid sequence of the 53-kDa fimbrial protein showed only 2 of 15 residues that were identical to those of the 41-kDa fimbrial protein. These results show that the properties of the 53-kDa fimbriae are different from those of the 67-kDa fimbriae of ATCC 33277 as well as those of the 41-kDa fimbriae.

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

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

Transformation and expression of a cloned fimA gene in Porphyromonas gingivalis

The Porphyromonas gingivalis fimbria is an important virulence factor involved in the adherence and colonization of the organism in the oral cavity. In this study, we transformed this organism with a gene, fimA381, encoding the fimbrial subunit of P. gingivalis 381 (fimbrillin) by using the host-vector system that we developed previously and examined expression of the cloned fimA381 gene. The recombinant plasmid pYHF2 was constructed by ligating a fragment containing the fimA381 gene into the plasmid vector pYH420 and transformed into the restriction-deficient P. gingivalis host YH522. pYHF2 was autonomously maintained in YH522 cells, and the fimbrillin polypeptide (recombinant fimbrillin) was fully expressed. The molecular mass of the recombinant fimbrillin was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as 41 kDa, which was identical to that of the native fimbrillin of strain 381. The amino acid sequences of the 20 amino-terminal residues of the recombinant fimbrillin and the native fimbrillin of the strain 381 were identical. In addition, characteristic long and thin fimbrial structures (recombinant fimbriae) that were distinguishable from the host's native fimbriae when examined by immunogold electron microscopy were observed around the cell surface of the transformants containing the fimA381 gene. These results suggested that transformation of fimA gene from a different strain of P. gingivalis followed by accumulation of the mature fimbrial subunit protein was sufficient for production of fimbrial structures that were observable by electron microscopy.

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.

Conservation of fimbriae and the hemagglutinating adhesin HA-Ag2 among Porphyromonas gingivalis strains and other anaerobic bacteria studied by epitope mapping analysis

Monoclonal antibodies characterized as antifimbria and anti-HA-Ag2 were used in immunoblotting to examine the antigenic distribution of fimbriae and HA-Ag2 among a collection of human and animal Porphyromonas strains and human Prevotella and Bacteroides strains. The results showed that fimbrial and HA-Ag2 antigenic structures are peculiar to the species Porphyromonas gingivalis.

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.

Levels of Porphyromonas gingivalis Fimbriae and inflammatory cytokines in gingival crevicular fluid from adult human subjects

The Porphyromonas gingivalis fimbriae level was examined in the gingival crevicular fluid (GCF) from adult human subjects using an immunoblot assay with a monoclonal antibody. The cytokines, interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6 and tumor necrosis factor-alpha (TNF-alpha) levels in the GCF were quantified by enzyme-linked immunosorbent assay (ELISA). The reactivity of the GCF samples with the monoclonal antibody against P. gingivalis fimbriae was related to the IL-2 beta, IL-6 and TNF-alpha levels. Moreover, the fimbriae content was associated with the gingival index (GI). In contrast, no significant correlation was seen between the fimbriae content and IL-1 alpha level. These results suggest that there are possible associations between P. gingivalis fimbriae and IL-1 beta, IL-6 and TNF-alpha in the gingival crevicular fluid.

Isolation and characterization of a minor fimbria from Porphyromonas gingivalis

We have discovered two distinctly different fimbriae expressed by the same Porphyromonas gingivalis strain. The construction of a fimA mutant of P. gingivalis ATCC 33277 has previously been reported by N. Hamada et al. (Infect. Immun. 62:1696-1704, 1994). Expression of fimbriae on the surface of the fimA mutant and the wild-type strain, ATCC 33277, were investigated by electron microscopy. The wild-type strain produced long fimbrial structures extending from the cell surface, whereas those structures were not observed on the fimA mutant. However, short fimbrial structures were seen on the surface of the fimA mutant. The short fimbrial protein was purified from the fimA mutant by selective protein precipitation and chromatography on DEAE Sepharose CL-6B. We have found that the second fimbrial structure of P. gingivalis ATCC 33277 is distinct from the 41-kDa (43-kDa) major fimbrial protein (FimA). We provisionally call this protein minor fimbriae. The molecular mass of the minor fimbriae is 67 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions after boiling at 100 degrees C. The component shows a ladder-like pattern at 80 degrees C under nonreducing conditions, suggesting a tendency to aggregate or polymerize. In immunoblotting analysis, anti-minor fimbria serum reacted with both the 100 degrees C- and the 80 degrees C-treated minor fimbriae. The anti-minor fimbria serum also reacts with the same-molecular-size fimbrial preparation from the wild-type strain. Immunogold electron microscopy showed that the anti-minor fimbria serum bound to the minor fimbria on the cell surface of the wild-type strain. This is the first report on the identification of the minor fimbria produced by P. gingivalis. These results suggest that the minor fimbriae appearing on the fimA mutant strain are produced together with numerous long major fimbriae on the wild-type strain. Moreover, the minor fimbriae are different in size and antigenicity from the earlier-reported FimA, a major 41-kDa fimbrial component of P. gingivalis.

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.

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.

Specific immune response to the 40-kDa outer-membrane protein of Porphyromonas gingivalis in mice

Whether B-cell activation to Porphyromonas gingivalis in periodontal diseases is the consequence of a specific immune response or is due to non-specific polyclonal activation is still not clear. Here the immune response of mice to a purified 40-kDa recombinant protein antigen, a major outer-membrane protein specific to P. gingivalis, was investigated. Patients' sera strongly reacted to this recombinant antigen. Purified splenic T and B cells from mice immunized with 40-kDa antigen or from normal mice were reconstituted in vitro and cultured in the presence or absence of the P. gingivalis 40-kDa protein antigen and antigen-presenting cells (APCs). In vitro antibody production to this particular antigen was analysed with respect to the requirement of helper T cells and APCs by enzyme-linked immunosorbent assay. The results clearly showed that an effective secondary response required the presence of B cells, T cells and APCs. In the absence of CD4+ helper T cells, an antibody response to the 40-kDa protein was not observed. In addition, the requirement of H-2 restricted, Ia-positive APCs was evident for an adequate response to the 40-kDa protein of P. gingivalis. Thus the antibody response to the 40-kDa protein of P. gingivalis was generated in an immunologically antigen-specific manner and was not simply the result of polyclonal B-cell activation. This in vitro system could be used in the detection of antigen-specific memory B or T cells in patients with periodontal diseases.

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.

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.

Correlation between cell-adherent activity and surface structure in Porphyromonas gingivalis

The cell-adherent ability of 6 strains of Porphyromonas gingivalis (381, ATCC 33277, SU63, KD1, W50 and W83) was compared by using radiolabeled bacterial cells and human gingival fibroblasts (Gin 1), human periodontal ligament fibroblasts (HPLF) and human epithelial cells (Ca9-22) that had been grown on collagen beads. The cell-adherent activity of these organisms varied among strains; P. gingivalis strains 381, ATCC 33277 and SU63 bound to the target cells at a range of 14% to 72%, but the other 3 strains (KD1, W50 and W83) were scarcely bound (0.6% to 3.5%). On the other hand, whole bacterial cells and culture supernatants of all strains showed distinct hemagglutinating activity. The 3 strains showing high cell-adherent activity were hydrophobic and the other strains showing less activity were relatively hydrophilic. Furthermore, a number of peritrichous fimbriae were found on the surface of P. gingivalis strains 381, ATCC 33277 and SU63, which showed high adherent activity, whereas, fimbriae on the other 3 strains showing low adherent ability were barely apparent. Therefore, it was assumed that the cell-adherent activity of P. gingivalis was related to the hydrophobicity of the cell surface, which was related to the number of fimbriae.

Induction of mucosal and serum immune responses to a specific antigen of periodontal bacteria

The dynamics of the host immune response to periodontal bacteria not only may be informative from the standpoint of specific mucosal protection to these pathogens, but also may reveal the capacity of the mucosal immune response to provide protection of the host. To this end, we have examined the immune response to chromatographically purified fimbriae of P. gingivalis administered orally or systemically with liposomes and adjuvant in BALB/c mice, high responders to this antigen. Oral administration of P. gingivalis fimbriae clearly enhanced the fimbriae-specific salivary IgA response. ELISPOT analysis revealed that significant numbers of fimbriae-specific IgA SFC were seen in lamina propria and mesenteric lymph nodes but not in Peyer's patches of mice immunized orally. In contrast, antigen-specific IgM and IgG SFC were seen mainly in the circulating blood mononuclear cells. On the other hand, subcutaneous injection of fimbriae with GM-53 also raised the fimbriae-specific IgG followed by IgM and IgA responses in serum, and both IgA and IgG responses in saliva. Oral immunization was less effective than subcutaneous injection in terms of the serum antibody response. However, the salivary antibody level of mice injected subcutaneously was similar to that of mice immunized orally. In the subcutaneously immunized mice, fimbriae-specific SFC were detected in the spleen, blood, and brachial lymph nodes by ELISPOT assay. Fimbriae-specific IgM SFC appeared earlier and antigen-specific IgG SFC were seen later. These results show that the combined use of fimbriae together with the adjuvant results in sharply increased IgA responses in saliva and IgG responses in serum. In summary, it is clear that the nature of the host's antibody response in serum and mucosal secretions is distinct, and depends on the route of antigen administration, the use of adjuvant and/or liposomes, and the temporal phase of the humoral immune response following various immunization regimes.