Effects of the association of conventional rats with Actinomyces viscosus Nyl and Bacteroides gingivalis W83

Induction of experimental periodontitis in mice with Porphyromonas gingivalis-adhered ligatures

BACKGROUND

Little information is available on the colonization of periodontopathic bacteria and alveolar bone loss in a mouse system, because of the difficulty in establishing bacteria in the oral cavity. The aim of this study was to establish experimental periodontitis in mice by applying a Porphyromonas gingivalis-adhered ligature onto the molars.

METHODS

Specific pathogen-free C3H/HeN mice were divided into 3 groups: 80 infected, 80 sham-infected, and 48 non-treated control mice. Sterile silk ligatures were preincubated with and without P. gingivalis 381 in vitro and then physically tied on the right maxillary first molar of infected and sham-infected mice, respectively. Ten mice from the infected and sham-infected groups and 6 from the control group were sacrificed at 2-week intervals for up to 15 weeks after infection.

RESULTS

Plaque samples were collected at the time of sacrifice and alveolar bone loss was examined. The results indicated that P. gingivalis was recovered from the plaque samples in 95% of the infected mice after 1 week and then gradually dropped to 58% after 15 weeks of infection, whereas P. gingivalis was not isolated in either sham-infected or control mice throughout the experimental period. The infected mice showed significant P. gingivalis-induced bone loss at the sites where the ligature was tied weeks 13 to 15. A linear regression analysis revealed a significant positive correlation between the number of P. gingivalis recovered and alveolar bone loss at 15 weeks after infection (P <0.01).

CONCLUSIONS

The use of a P. gingivalis-adhered ligature supported a long-lasting infection of P. gingivalis in mice, resulting in P. gingivalis-induced alveolar bone breakdown.

The relationship between colonization and haemagglutination inhibiting and B cell epitopes of Porphyromonas gingivalis

Passive immunization with the monoclonal antibody 61BG1.3 selectively prevents colonization by Porphyromonas gingivalis in humans (Booth V, Ashley FP, Lehner T. Infect Immun 1996; 64:422-7). The protective MoAb recognizes the beta component of the RI protease of P. gingivalis which is formed by proteolytic processing of a polyprotein precursor termed PrpR1. This subunit is both a haemagglutinin and an antigen which is recognized by sera from patients with periodontitis. In this study the relationship was investigated between a colonization epitope which is recognized by the MoAb 61BG1.3, a haemagglutinating and B cell epitope which are recognized by sera from patients with periodontitis. B cell epitopes were mapped by Western blotting with a series of truncated recombinant polypeptides spanning the adhesion domain within residues 784-1130 of PrpR1 and by ELISA using a panel of synthetic peptides spanning the same sequence. The epitope which is recognized by the protective MoAb was mapped within residues 907-931 of PrpR1, while serum responses of patients were directed predominantly to the adjacent carboxy-terminal sequence within residues 934-1042. The haemagglutinating epitope was mapped to residues 1073-1112. In view of our previous findings that the MoAb 61BG1.3 prevents colonization of P. gingivalis in vivo and inhibits haemagglutination, these two epitopes may be in proximity in the native protein. Active or passive immunization strategies which target the protective or haemagglutinating epitopes of the adhesion domain of PrpR1 may provide a means of preventing infection with P. gingivalis.

Black-pigmented gram-negative anaerobes in periodontitis

Black-pigmented Gram-negative anaerobes have been associated with periodontal disease and tooth loss since they were first isolated by Burdon in 1928. Porphyromonas gingivalis, which is usually not isolated from children, adolescents or adults with no periodontal breakdown, has been recognized as one of the most important periodontopathogens. Its presence is strongly correlated with deep periodontal pockets, which are assumed to be its main habitat. Correlations have been shown also with attachment loss, clinical inflammation and serum antibody levels, indicating an aetiological role in the periodontal disease. Their pathogenicity in animal models resembling periodontal disease is documented. They are frequently isolated from periodontal abscesses. The relationship between Prevotella intermedia and periodontal disease is not clear. It is frequently isolated from advanced periodontitis, often as the only black-pigmented Gram-negative anaerobic species; however, the prevalence in adults with no periodontal breakdown is high. It is found frequently in periodontal abscesses and in acute necrotizing and ulcerative gingivitis. Serogroup I is found predominantly in deep periodontal pockets, whereas all serogroups (I-III) are found in shallow pockets and gingivitis. No conclusive difference in pathogenicity between serogroups has been found. Pr. melaninogenica, Pr. denticola and Pr. loescheii are frequently found in the gingival crevice in preschool children and other age groups with gingivitis, but are seldom found in deep periodontal pockets.

Effect of LongoVital treatment on development of periodontal disease in rats

LongoVital is a herbal tablet with documented immunostimulatory effects in man. In the present study the effect of LongoVital on development of periodontal disease was investigated in a rat model. Fifty-four conventional rats, 5 wk old, were distributed into the following groups: A) untreated, uninfected; B) untreated, infected with Actinomyces viscosus and Porphyromonas gingivalis wk 8; C) treated with LongoVital 80 mg x 3/wk, wk 5-14, uninfected; D) treated with LongoVital 80 mg x 3/wk, wk 5-14, infected with A. viscosus and P. gingivalis wk 8; E) treated with LongoVital 200 mg x 1 in wk 8 and 80 mg wk 9-14, uninfected; F) infected with A. viscosus and P. gingivalis wk 8, subsequently treated with LongoVital 200 mg x 1 in wk 8 and 80 mg wk 9-14. All animals were killed when they were 15 wk old, and periodontal bone support was assessed radiographically. Statistically significant bone loss was found in untreated, infected rats, as compared with untreated, uninfected rats. In LongoVital-treated animals, no significant difference was seen in bone level between infected and uninfected rats. These results indicate that LongoVital-treated rats were protected against periodontal bone loss caused by infection with A. viscosus and P. gingivalis. Furthermore, the protection seemed effective both when LongoVital was administered prophylactically and after exposure to periodontal pathogens. The active components of LongoVital, as well as the mechanisms responsible for the protection, remain obscure.

Porphyromonas gingivalis virulence in mice: induction of immunity to bacterial components

Selected cell envelope components of Porphyromonas gingivalis were tested in a BALB/c mouse model in an attempt to elucidate further the outer membrane components of this putative oral pathogen that might be considered as virulence factors in host tissue destruction. Lipopolysaccharide (LPS), outer membrane, and outer membrane vesicles of P. gingivalis W50, ATCC 53977, and ATCC 33277 were selected to examine an immunological approach for interference with progressing tissue destruction. Mice were actively immunized with heat-killed (H-K) or Formalin-killed (F-K) whole cells or with the outer membrane fraction, LPS, or outer membrane vesicles of the invasive strain P. gingivalis W50. The induction of invasive spreading lesions with tissue destruction and lethality were compared among different immunization groups in normal, dexamethasone-treated (dexamethasone alters neutrophil function at the inflammatory site), and galactosamine-sensitized (galactosamine sensitization increases endotoxin sensitivity) mice after challenge infection with the homologous strain (W50) and heterologous strains (ATCC 53977 and ATCC 33277). Enzyme-linked immunosorbent assay analyses revealed significantly elevated immunoglobulin G and M antibody responses after immunization with H-K or F-K cells or the outer membrane fraction compared with those of nonimmunized mice. The killed whole-cell vaccines provided significantly greater protection against challenge infection in normal mice (decreased lesion size and death) than did either the outer membrane fraction or LPS immunization. The lesion development observed in dexamethasone-pretreated mice was significantly enhanced compared with that of normal mice after challenge with P. gingivalis. Immunization with P. gingivalis W50 provided less protection against heterologous challenge infection with P. gingivalis ATCC 53977; however, some species-specific antigens were recognized and induced protective immunity. Only viable P. gingivalis induced a spreading lesion in normal, dexamethasone-treated, or galactosamine-sensitized mice; F-K or H-K bacteria did not induce lesions. The F-K and outer membrane vesicle immunization offered greater protection from lesion induction than did the H-K immunogen after challenge infection simultaneous with galactosamine sensitization. The H-K cell challenge with galactosamine sensitization produced 100% mortality without lesion induction, suggesting that LPS or LPS-associated outer membrane molecules were functioning like endotoxin. Likewise, P. gingivalis W50 LPS (1 micrograms per animal) administered intravenously produced 80% mortality in galactosamine-sensitized mice. In contrast to the effects of immunization on lesion development, immunization with H-K or F-K cells or LPS provided no protection against intravenous challenge with LPS; 100% of the mice died from acute endotoxin toxicity.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of immunization with Porphyromonas gingivalis and Prevotella intermedia on progression of ligature-induced periodontitis in the nonhuman primate Macaca fascicularis

The nonhuman primate (Nhp) has proven to be a useful model of human periodontitis. This study describes the immunological characteristics of this model and the ability of active immunization to interfere with ecological changes in the microbiota and its associated disease symptoms. Nhps were parenterally immunized with whole-cell antigens of Porphyromonas gingivalis and Prevotella intermedia. The immunization elicited an approximate 2-log increase in serum immunoglobulin G (IgG), IgM, and IgA isotype antibody that was highly specific for these immunogens. Postimmunization and postligation, there was minimal change in the levels of specific antibody. P. gingivalis immunization significantly inhibited the emergence of this species during disease progression. In contrast, induction of anti-P. intermedia antibody had a minimal effect on this species within the subgingival plaque. Plaque indices showed few changes that could be attributed to active immunization. Both bleeding on probing and loss of attachment were higher in ligated sites of immunized animals than in the placebo-treated group. A significant increase in bone density loss was observed in the ligated teeth from immunized versus control animals. These findings indicate that active immunization of Nhps can elicit a substantial systemic immune response; however, while this response may effect the emergence of an individual microorganism, it appears that other ecological considerations are critical in disease progression. It is also possible that the induction of a broad-based immune response to multiple bacterial antigens can result in increased disease, potentially associated with hypersensitivity reactions to the bacteria in the subgingival plaque.

Periodontal bone level and gingival proteinase activity in gnotobiotic rats immunized with Bacteroides gingivalis

Bacteroides gingivalis is associated with various forms of periodontal disease. To assess the role of the immune response in modulating B. gingivalis-associated periodontal disease, the effect of immunization of B. gingivalis-induced periodontal bone loss was evaluated in gnotobiotic rats. Male Sprague-Dawley rats immunized with various doses of whole cells or sham-immunized with incomplete Freund's adjuvant were monoinfected with B. gingivalis in carboxymethylcellulose by gavage. Two additional groups served as either sham-immunized or untreated germ-free controls. Forty-two days after infection, all rats were killed, periodontal bone level was assessed morphometrically and radiographically, and gingival proteinase (mammalian collagenase and acid cathepsin) activity was assessed biochemically. B. gingivalis was present in oral samples from all monoinfected rats, and no contaminating bacteria were detected in any oral or fecal sample. Animals immunized with B. gingivalis cells had elevated serum and saliva antibodies to whole cells and partially purified fimbriae from B. gingivalis. Infected sham-immunized rats had significantly more periodontal bone loss than noninfected controls, whereas the periodontal bone level in infected rats immunized with 10(10) B. gingivalis cells was similar to that of the noninfected controls. The activities of gingival collagenase and cathepsin B and L were high in sham-immunized infected rats and low in all other animal groups. In conclusion, it is possible to reduce B. gingivalis-induced periodontal tissue loss in gnotobiotic rats by immunization.

Microbiological and immunological aspects of experimental periodontal disease in rats: a review article

Animal models in which microbiological and immunological aspects of periodontal disease can be studied prospectively seem well warranted. The rat bears much resemblance to man with respect to periodontal anatomy, development and composition of dental plaque, histopathology of periodontal lesions, and basic immunobiology. Furthermore, reproducible methods are available for assessment of periodontal disease in rats, and detectable periodontal destruction can be induced in a few weeks in these animals without traumatizing periodontal tissues with ligatures. Experimental periodontitis studies in germ-free rats have confirmed the pathogenicity of several suspected periodontal pathogens (Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Capnocytophaga sputigena, Eikenella corrodens, and Fusobacterium nucleatum). The studies also suggest that the number of periodontal pathogens may be higher than generally believed, since species like Streptococcus sobrinus and Actinomyces viscosus are associated with periodontal bone loss in rats. Studies in rats with congenital or induced immune defects indicate that generalized or selective immunosuppression at the time of infection with periodontal pathogens may aggravate periodontal disease. Studies in immunized rats indicate that periodontal disease can be prevented by immunization against periodontal pathogens. However, it is also possible by immunization to induce periodontal destruction; i.e., the immune system has a destructive potential which should not be overlooked. In the future, the rat model may prove valuable for initial screening of antigen preparations and immunization regimens in the search for a periodontitis vaccine.

Increased periodontal bone loss in temporarily B lymphocyte-deficient rats

In order to study the role of T lymphocytes and B lymphocytes in the development of marginal periodontitis, experiments were performed on specific-pathogen-free (SPF) rats with various immunologic profiles. The study comprised nude (congenitally T lymphocyte-deficient), thymus-grafted nude (T-lymphocyte reconstituted), anti-mu treated (temporarily B lymphocyte-deficient), and normal rats. When they were 5 to 9 weeks old, some of the rats were inoculated with Actinomyces viscosus. Bacteroides gingivalis and a strain of oral spirochetes; 90 days later they were killed. A. viscosus and B. gingivalis colonized readily, but the spirochete strain could not be established permanently in the oral cavity of the rats, 95% of the inoculated rats raised serum IgG or IgM antibody against one or more of the microorganisms; nude rats tended to raise less antibody than the three other experimental groups. Inoculated rats had significantly less periodontal bone support than controls. Anti-mu treated inoculated rats had significantly less periodontal bone support than nude and normal rats, whereas no difference was found between normal, nude, and thymus-grafted rats. It is concluded that permanent T-lymphocyte deficiency did not interfere with the development of periodontal disease in this model, whereas a temporary and moderate reduction in B-lymphocyte numbers seemed to predispose for aggravation of periodontal bone loss.

Influence of age and immunization on development of gingivitis in rats

To study the effect of age and antigenic priming on the development of gingivitis, 33 healthy rats were placed in contact with Streptococcus mutans, Actinomyces viscosus, Fusobacterium nucleatum, and Bacteroides gingivalis. On days 0, 3, 7, and 14 after inoculation, the gingival condition was judged clinically and histologically, and serum antibody titers against the bacteria were measured. The rats were divided into three groups: 1 month old, 3 months old, and 3 months old immunized. None of the young rats developed gingivitis during the experiment, whereas half of the adult and all of the adult immunized rats bled on probing on days 7 and 14. In general, antibody titers against the bacteria were low in young rats, moderate in adult rats, and high in adult immunized rats. These results indicate that adult rats react stronger to plaque antigens than young rats and that previous contact with the antigens increases the reaction.

Implantation of Bacteroides gingivalis in nonhuman primates initiates progression of periodontitis

Although periodontitis is a bacterial disease, its multidimensional nature and its bacterial complexity have made it difficult to definitively prove that specific microorganisms initiate the disease process. The successful implantation of a rifampin-resistant strain of the putative periodontal pathogen Bacteroides gingivalis into the periodontal microbiota of monkeys (Macaca fascicularis) resulted in an increase in the systemic levels of antibody to the microorganism and rapid and significant bone loss.