Bacteroides gingivalis: Recognition of a 47 kDa Outer Membrane Protein by Sera from Patients with Chronic Periodontitis

Purification and characterization of Porphyromonas gingivalis outer membrane antigens

Porphyromonas gingivalis is strongly associated with periodontal disease. Significant titres of specific IgG antibodies to P. gingivalis can be found in healthy individuals and those with periodontitis. In this study, 22 outer membrane antigens ranging from 15.5 to 107.6 kDa were recognized by sera from persons with periodontitis and controls. Serum from individuals with periodontitis showed a significantly higher IgG response to a 31.4-kDa antigen (p < 0.05); serum from those with gingivitis demonstrated a significantly higher response to a 15.5-kDa antigen (p < 0.05). The response to the 15.5-kDa antigen might represent a protective immune response while that to the 31.4-kDa could serve as a marker for disease susceptibility. These two antigens were purified to homogeneity and their N-terminal amino acid sequences determined. The sequences did not correspond to any previously described P. gingivalis antigens. The role of these two antigens in the pathogenesis of periodontal disease remains to be determined.

Analysis of cultivable Porphyromonas gingivalis with trypsin-like protease enzyme activity and serum antibodies in chronic adult periodontitis

OBJECTIVE

Trypsin-like protease (TLPase) enzyme produced by Porphyromonas gingivalis has been implicated as a virulence factor in the pathogenesis of periodontal disease. The aims of this study were to investigate the relationship between cultivable P. gingivalis, TLPase enzyme activity (BANA hydrolysis) and serum antibody levels against cell sonicate and a purified TLPase antigen from P. gingivalis W50.

MATERIALS AND METHODS

Sub-gingival plaque samples were cultured for levels of P. gingivalis together with a chairside analysis of TLPase enzyme activity (Perioscan) from periodontitis and gingivitis sites of adult periodontitis patients. A TLPase from P. gingivalis was purified by gel filtration and ion exchange chromatography from the vesicle fraction for use as a test antigen.

RESULTS

Elevated levels of P. gingivalis were found at periodontitis sites, however, there was no correlation with sub-gingival plaque TLPase enzyme activity. Adult periodontitis patients had higher levels of IgG and IgA against cell sonicate and TLPase antigens than did controls. Those patients who were P. gingivalis culture-positive demonstrated an elevated immune response against both cell sonicate and TLPase when compared to P. gingivalis culture-negative patients. Treatment resulted in an improvement of clinical indices and no cultivable P. gingivalis could be recovered from the treated sites and there was a concomitant decrease in IgG levels against the TLPase. There was no significant difference in BANA hydrolysis at gingivitis sites or periodontitis sites after treatment.

CONCLUSIONS

Further longitudinal studies are suggested to investigate the role of the TLPase in the response to treatment of chronic adult periodontitis patients.

Protective immunity to Porphyromonas gingivalis infection in a murine model

The mouse abscess model has been used extensively to demonstrate protection after challenge with periodontopathic organisms. In the present study, an outer membrane (OM) preparation of P. gingivalis ATCC 33277 was used to immunize BALB/c mice prior to challenge with live P. gingivalis organisms. This OM preparation, particularly at the highest dose level of 100 micrograms/immunization, was able to induce high levels of specific antibody and subsequent protective immunity. Protection in all immunized mice was noted by the rapid healing of the primary lesions, a low incidence of secondary lesions, and, in the highest dose group, an absence of septicemia. Non-immunized animals demonstrated a slower development as well as healing of primary lesions, with higher numbers and larger sizes of secondary lesions. Weight loss and behavior patterns such as hunched bodies, ruffled hair, and stiffness of the hind legs were particularly noted in this group. Depletion of CD4 T cells in mice prior to immunization with 100 micrograms P. gingivalis OM resulted in significantly depressed serum levels of anti-P. gingivalis antibody and an increase in the physical signs of disease compared with both the immunized and control groups. Western blot analysis demonstrated three antigen bands (63.3, 50.1, and 45.1) recognized by all immunized groups and also the control non-immunized group, although the latter recognition occurred only after challenge. A further antigen band of 36.1 kDa was recognized by sera from the highest dose group only. This study has demonstrated the ability of P. gingivalis OM to provide protection against challenge with live P. gingivalis organisms. The increased physical signs of disease seen in the CD4 depleted animals compared with the control group not only illustrate the protective role of serum antibody, but also suggest a possible role for T cell mechanisms in control of the lesion locally. The ability of specific OM antigens to provide similar protective immunity remains to be ascertained.

Production and characterisation of monoclonal antibodies to the principle sonicate antigens of Porphyromonas gingivalis w50

Protein antigens from whole cell sonicates of Porphyromonas gingivalis W50, previously shown to be discriminatory antigens for patients with adult periodontitis, were purified using SDS-PAGE. Electroeluted proteins were used to immunize mice for the production of monoclonal antibodies (mAbs). A combination of enzyme-linked immunosorbent assay (ELISA) and Western blotting were used to screen hybridoma supernatants for mAbs. MAbs were successfully raised against M(r) 115,000, M(r) 55,000 and M(r) 47,000 antigens together with a second M(r) 55,000 polypeptide which was a contaminant of the M(r) 55,000 antigen. No immunological cross-reactivity was found between these four proteins. The mAbs were used to examine the distribution of these antigens among fifteen P. gingivalis strains together with related oral bacteria using immunostaining of dot blots and Western blots. The antigens were confined to P. gingivalis with the M(r) 115,000 and M(r) 47,000 antigens being present in all strains tested. The distribution of the M(r) 55,000 antigens were slightly more restricted: one M(r) 55,000 (outer membrane location) was present in nine of the fifteen P. gingivalis strains tested, while the other M(r) 55,000 (location unknown) was only absent from one strain. Whole cell ELISA demonstrated that the M(r) 115,000 and the outer membrane M(r) 55,000 antigen possess epitopes which are located on the surface of the bacterium.

Elevated opsonic activity for Porphyromonas (Bacteroides) gingivalis in serum from patients with a history of destructive periodontal disease. A case: control study

We have measured the opsonic capacity of serum for the phagocytosis of Porphyromonas (Bacteroides) gingivalis by polymorphonuclear leucocytes (PMN) in 35 patients with a history of destructive periodontitis and 35 matched control subjects. The serum from cases, tested at concentrations of 8% and 0.8% opsonised P. gingivalis for phagocytosis by PMN to a level significantly greater than controls (p < 0.0001 and < 0.01 respectively). IgG antibody levels to P. gingivalis whole cells estimated by ELISA were also significantly higher in the cases (p < 0.0001). The IgG antibody levels correlated significantly with the opsonic capacity of the serum tested at 8% concentration in controls (r = 0.371, p = 0.03) but not in cases (r = 0.235, p = 0.17); in 0.8% serum, the opsonic capacity of the cases and controls were not significantly correlated. Elevated opsonisation by serum was a significant predictor that a subject was a case rather than a control, even after allowing for the effect of elevated IgG antibody in the cases. The data suggest that an elevated capacity of serum to opsonise P. gingivalis is a distinctive feature in patients with past destructive periodontal disease.

Identification of the major surface protein antigens of Porphyromonas gingivalis using IgG antibody reactivity of periodontal case-control serum

The identity of the major surface antigens of Porphyromonas gingivalis was investigated. Outer membranes of P. gingivalis strains W83, W50, 381 and NCTC 11843 were prepared following inactivation of the trypsin-like enzyme activity. Three proteins, molecular weight 115, 55 and 40 kDa, were major components of the outer membranes of strains W83 and W50 and were also present in strains 381 and NCTC 11834. Two proteins, 55 and 47 kDa, were released from the cells during the sonication step of the outer membrane preparation procedure. Immunoblots using preparations of P. gingivalis W83 and serum from a case-control study of adult periodontitis demonstrated higher mean antibody reactivity in the case population to all the major proteins except for the 115 kDa outer membrane protein, which was recognized equally well by both populations. We conclude that the 55, 47 and 40 kDa proteins are important surface antigens of P. gingivalis. Characterization of the structure and function of these components should lead to an improved understanding of the host-parasite interactions in adult periodontitis.

The immunogenicity of outer membrane proteins of haemin-depleted Porphyromonas (Bacteroides) gingivalis W50 in periodontal disease

The antigens from outer membrane protein extracts of Porphyromonas gingivalis (W50), grown under different haemin concentrations, were examined for binding with serum antibodies from patients with severe progressive periodontitis or from periodontally healthy control subjects. P. gingivalis was grown under haemin limitation (0.33 micrograms/ml) and haemin excess (2.5 micrograms/ml) conditions in a chemostat at a mean generation time of 6.9 h, at pH 7.5. Sarkosyl-insoluble fractions of outer membrane proteins from P. gingivalis were prepared, and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot techniques. The SDS-PAGE analysis of the outer membrane of haemin-limited P. gingivalis identified several new protein components, or changed expression of bands compared with cells grown under haemin excess. Immunoblot analysis showed IgG antibodies to 2 haemin deprivation-induced proteins in patients with severe progressive periodontitis, but not in the control sera. These results confirm the immunogenicity of some of the haemin-regulated outer membrane proteins of P. gingivalis in severe progressive periodontitis.

Specific antibody responses to subgingival plaque bacteria as aids to the diagnosis and prognosis of destructive periodontitis

We have reviewed the recent literature on the humoral immune responses to a variety of subgingival plaque bacterial species in patients with destructive periodontal diseases. We do not feel that the information presently available on the specific antibody responses to proposed pathogens such as Bacteroides gingivalis and Actinobacillus actinomycetemcomitans allows antibody responses to be diagnostic. All control subjects without periodontal destruction have antibodies to candidate pathogens but the generally higher levels in patients are not sufficiently elevated to be diagnostic. Nor can they be used to predict the initiation of disease or the onset of new episodes of destruction where disease had previously occurred. Successful treatment of patients may lead to lower levels of antibodies to some organisms, including possible pathogens, and thus support a given species in the aetiopathogenesis of disease. It appears that unsuccessful treatment may be accompanied by continuing high antibody levels to some organisms and further studies may enable this observation to be used to monitor therapy. There is some evidence from serological studies that each destructive episode may be induced by a different bacterial species or consortium. The start of studies using single antigens and the techniques of molecular biology will provide not only antibody-based diagnostic methods but also allow us to determine which bacterial antigens are virulence factors and thus the role of the antibody responses, whether protective or damaging, in the periodontal diseases.