Implantation of Bacteroides gingivalis in nonhuman primates initiates progression of periodontitis

Modulation of colonization by black-pigmented Bacteroides species in squirrel monkeys by immunization with Bacteroides gingivalis

Periodontal diseases are inflammatory responses thought to be triggered by specific microorganisms colonizing in the gingival crevice. Theoretically, periodontal diseases could be prevented if the etiologic organisms were not allowed to colonize the subgingival area. The humoral immune response is one mechanism which may modulate bacterial colonization in the gingival crevice. To test the effect of systemic humoral immunity on subgingival colonization by bacteria, squirrel monkeys (Saimiri sciureus) were immunized with Bacteroides gingivalis, a black-pigmented Bacteroides sp. and putative periodontal pathogen. Immunized and sham-immunized monkeys were orally inoculated with 10(10) viable B. gingivalis during ligation of five teeth in one quadrant with bacterium-soaked suture material and distribution over the entire dentogingival margin. Immunization resulted in an increased level of immunoglobulin G anti-B. gingivalis in serum and was associated with a strong trend toward a statistically significant reduction in colonization of the gingival crevice by black-pigmented bacteroides.

The effect of lipopolysaccharide from bacteroides gingivalis and muramyl dipeptide on osteoblast collagenase release

In order to determine whether the bacterial bone resorbing agents lipopolysaccharide (LPS) and muramyl dipeptide (MDP) interact with osteoblasts, their effect on the synthesis of collagenase and tissue inhibitor or metalloproteinases (TIMP) from monolayer cultures of mouse osteoblast-like cells was investigated. All concentrations of LPS (0.1, 1.0 and 10.0 micrograms/ml) significantly stimulated collagenase levels compared to unstimulated controls. This suggests that LPS, like hormonal stimulators of bone resorption, interacts with osteoblasts. In contrast, MDP (0.01, 0.1 and 1 microM) did not significantly stimulate collagenase or TIMP levels, indicating that MDP may not interact with osteoblasts. Possible alternative mechanisms of MDP-mediated bone resorption are discussed.

Periodontitis in sheep: a model for human periodontal disease

The use of sheep as a suitable animal model of destructive forms of human periodontal disease has been assessed from comparative radiological, histological, and serological investigations of sheep with and without periodontal disease. The results showed that, in sheep with periodontitis, bone resorption, collagen breakdown, degradation of blood capillary vessel walls, cellular infiltration of plasma cells, lymphocytes, and epithelial infiltration were significantly greater than in sheep without periodontitis, and the features are similar to those in rapidly destructive forms of periodontal disease in man. The levels of serum IgG antibody reactive against B. gingivalis antigens (measured by ELISA) were significantly higher in sheep with periodontitis than those without, similar to the association reported in some types of human periodontal diseases. These findings suggest that periodontitis in sheep could represent a suitable animal experimental model for certain types of rapidly destructive human periodontal diseases.

Experimental infections by Bacteroides gingivalis in non-immunized and immunized rabbits

The interactions between Bacteroides gingivalis and systemic antibodies were studied in tissue cages implanted in the backs of New Zealand white rabbits. Infectivity was evaluated according to clinical signs and to leukocyte and bacterial counts in material aspirated from the tissue cages. Pre- and post-inoculation antibody levels to sonicated whole bacterial cells were determined by enzyme-linked immunosorbent and agar immunodiffusion assays. Rabbits immunized against B. gingivalis and then challenged with pure cultures of B. gingivalis revealed complete elimination or markedly lower postinoculation bacterial counts and considerably weaker tissue reactions than non-immunized animals. B. gingivalis co-inoculated with Actinobacillus actinomycetemcomitans caused significantly more severe infections than observed in monoinfected animals. The present results suggest that the immune system acting through systemic antibodies and/or cellular mechanisms may modulate the pathogenic potential of infecting periodontal pathogens.

A protease of Bacteroides gingivalis degrades cell surface and matrix glycoproteins of cultured gingival fibroblasts and induces secretion of collagenase and plasminogen activator

To assess the direct effects of Bacteroides gingivalis on periodontal cells, human gingival fibroblasts were cultured in the presence of B. gingivalis extracts or a trypsinlike enzyme partially purified from the bacteria by chromatography on benzamidine-Sepharose and Sephacryl S-200. Analysis of cell surface glycoproteins by the periodate-[3H]borohydride labeling technique combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)-fluorography demonstrated that fibronectin and some other high-molecular-weight cell surface glycoproteins were degraded by a 35,000-Mr(35K) B. gingivalis protease. Immunostaining of the fibroblast cultures showed degradation of intercellular matrix fibronectin by the 35K protease. The pattern of fibronectin degradation was monitored by examining the reaction products with the SDS-PAGE-immunoblotting technique. The protease degraded fibronectin rapidly and more extensively than did corresponding amounts of pancreatic trypsin. Collagenase secretion by the fibroblasts was assayed by incubating cell culture medium with soluble type I [3H]collagen at 25 degrees C followed by SDS-PAGE-fluorography analysis of the reaction products. The medium was also assayed for plasminogen activator activity by using a casein-agarose diffusion plate assay. The fibroblasts cultured with the 35K protease secreted increased amounts of collagenase and plasminogen activator into the medium. The results suggest that periodontal infection by B. gingivalis causes proteolytic damage of the host cell surface structures. Concomitantly, B. gingivalis may induce the cells to degrade their pericellular matrix.

The modulation of polymorphonuclear leukocyte function by Bacteroides gingivalis

B acteroides gingivalis has been recognized as a pathogen causing adult periodontal disease. In this study, we examined the culture supernatants of B. gingival is for their ability to alter the function of polymorphonuclear leukocytes (PMNs). After a 60-minute incubation with the culture supernatants of B. gingivalis, it was found that there was a significant reduction of f-methionyl-leucyl-phenylalanine (FMLP) receptor in human and guinea pig PMNs. Superoxide anion (O- 2) production of PMNs stimulated by FMLP was also suppressed when cells were pre-incubated with the culture supernatants of B. gingivalis. A similar suppression was observed when these cells were stimulated by phorbol myristate acetate. An exohemagglutinin fraction of the culture supernatants showed suppressive activity at a low dose (10 μg/mL). The data presented in this paper suggest that B. gingivalis releases substances which suppress the functions of PMNs via the modulation of cell surface receptors and internal cellular events. These suppressive effects may be important in the pathogenesis of this micro-organism.

Autoimmunity to collagen in adult periodontal disease

Although it has been documented that exogenous antigens of microbial origin are involved in the induction of the local inflammatory responses in human adult periodontitis (AP), endogenous antigens may contribute to the chronicity of this common disease. In this study, we used the enzyme-linked immunospot (ELISPOT) test to enumerate antibody-secreting cells to human collagen Types I-VI by cells isolated from the gingivae and peripheral blood of AP patients. Analyses of dissociated cells from gingivae of 39 AP patients revealed the presence of high numbers of cells that secrete antibodies to Type I collagen, and to a lesser extent, Type III. Although the majority of such cells produced specific antibodies of the IgG class, IgA- and IgM- anti-collagen -secreting cells were also detected. When compared to the total antibody-producing cells, the numbers of cells forming specific antibodies to collagen Type I were surprisingly high. In contrast, anti-collagen antibody-producing cells were rarely detected in the peripheral blood of patients with adult periodontal disease and only low levels of anti-collagen antibodies were present in the serum. The finding of local production of anti-collagen antibodies in AP suggests that autoimmunity may contribute to the pathogenesis of this common disease.