Production of monoclonal antibodies that recognize specific and cross-reactive antigens of Fusobacterium nucleatum

Quantitative analysis of periodontal pathogens by ELISA and real-time polymerase chain reaction

The development of analytical methods enabling the accurate identification and enumeration of bacterial species colonizing the oral cavity has led to the identification of a small number of bacterial pathogens that are major factors in the etiology of periodontal disease. Further, these methods also underpin more recent epidemiological analyses of the impact of periodontal disease on general health. Given the complex milieu of over 700 species of microorganisms known to exist within the complex biofilms found in the oral cavity, the identification and enumeration of oral periodontopathogens has not been an easy task. In recent years however, some of the intrinsic limitations of the more traditional microbiological analyses previously used have been overcome with the advent of immunological and molecular analytical methods. Of the plethora of methodologies reported in the literature, the enzyme-linked immunosorbent assay (ELISA), which combines the specificity of antibody with the sensitivity of simple enzyme assays and the polymerase chain reaction (PCR), has been widely utilized in both laboratory and clinical applications. Although conventional PCR does not allow quantitation of the target organism, real-time PCR (rtPCR) has the ability to detect amplicons as they accumulate in "real time" allowing subsequent quantitation. These methods enable the accurate quantitation of as few as 10(2) (using rtPCR) to 10(4) (using ELISA) periodontopathogens in dental plaque samples.

Anti-P. gingivalis response correlates with atherosclerosis

Significant associations between atherosclerosis and both Porphyromonas gingivalis, a major periodontopathogen, and the respiratory pathogen, Chlamydia pneumoniae, have been shown. Many individuals with evidence of atherosclerosis demonstrate seropositivity to these pathogens. The aim of the present study was to examine the atherogenic effect of repeated immunizations with either or both of these agents, and to determine if molecular mimicry of bacterial heat-shock protein (HSP), termed GroEL, and host (h) HSP60 was involved. Atherogenesis was examined in apolipoprotein-E-deficient (-/-) mice following intraperitoneal immunizations with P. gingivalis, C. pneumoniae, P. gingivalis, and C. pneumoniae or vehicle. Lesion area in the proximal aorta and levels of serum antibodies to P. gingivalis, C. pneumoniae, and GroEL were measured. The increased pathogen burden of P. gingivalis, but not of C. pneumoniae, enhanced atherosclerosis. hHSP60 was detected in lesions, and in P. gingivalis-immunized mice, lesion development was correlated with anti-GroEL antibody levels, supporting the involvement of molecular mimicry between GroEL and hHSP60.

Role of CD4+ and CD8+ T-cells in the induction of oral tolerance to Actinomyces viscosus in mice

Mucosal presentation of Actinomyces viscosus results in the induction of antigen specific systemic suppressor cells in mice. The aim of the present study was to determine the phenotype of the suppressor cells responsible for the induction of oral tolerance to low doses of A. viscosus. When CD8 cell-depleted DBA/2 mice were intragastrically immunized and systemically immunized with A. viscosus, the delayed type hypersensitivity response was suppressed but not the levels of antigen specific serum antibodies. Adoptive transfer of orally tolerized CD4(+) cells to CD4(+)-depleted mice resulted in suppression of delayed type hypersensitivity response but not of the levels of antigen specific serum antibodies. In contrast, adoptive transfer of orally immunized CD8(+) cells to CD8(+)-depleted mice resulted in partially suppressed delayed type hypersensitivity response but significantly inhibited the levels of antigen specific serum antibodies. When orally tolerized CD8(+) cells were cocultured with systemically immunized CD8(+) cell-depleted spleen cells, splenic specific antibodies were inhibited. However, no suppression of splenic specific antibodies could be observed in the cultures containing orally tolerized CD4(+) cells and systemically immunized CD4(+) cell-depleted spleen cells. The results of the present study suggest that oral tolerance of humoral and cellular immunity induced by low doses of A. viscosus may be mediated by CD8(+) and CD4(+) cells, respectively.

Gene expression in splenic CD4 and CD8 cells from BALB/c mice immunized with Porphyromonas gingivalis

BACKGROUND

T cells are fundamental in the pathogenesis of periodontal disease. Suppression of cell-mediated responses is associated with disease progression together with the concomitant increase in plaque pathogens including Porphyromonas gingivalis. The aim of the present study was to examine gene expression in T cells in response to P. gingivalis in mice.

METHODS

BALB/c mice were given weekly intraperitoneal injections of P. gingivalis outer-membrane antigens with Freund's incomplete adjuvant for 3 weeks, whereas control mice received phosphate buffered saline (PBS) and adjuvant only. Splenic CD4 and CD8 subpopulations were isolated by magnetic cell separation and their responses investigated using microarray analysis.

RESULTS

Most genes coded for enzymes concerned with metabolic pathways. Only five and 28 genes, respectively, were upregulated in CD4 and CD8 cells extracted from P. gingivalis-immunized mice, including immunoglobulin (Ig) heavy-chain genes for IgG1 and IgG2a in CD4 cells. In contrast, 1,141 and 1,175 genes, respectively, were downregulated. A total of 60 and 65 genes, respectively, coded for immune response proteins or those relevant to periodontal disease pathogenesis. The overlap of genes in the two subsets was 21%. One of the major effects, apart from T-cell function suppression, was the shift away from Th1 responses, although there was also a downregulation of two genes and upregulation of one Th2-response gene. Genes downregulated included those encoding cytokines, proteins involved in Ig binding, antigen presentation, innate immunity, extracellular matrix, and cell adhesion molecules that could result in dysregulation in the progressive periodontal lesion.

CONCLUSIONS

Early findings in humans demonstrated that periodontopathic bacteria induce immunosuppressive effects on T cells. The present study has shown that P. gingivalis had a predominant downregulatory effect on gene expression in CD4 and CD8 T cells in mice.

Cross-reactivity of GroEL antibodies with human heat shock protein 60 and quantification of pathogens in atherosclerosis

BACKGROUND/AIMS

Chronic infections such as those caused by Chlamydia pneumoniae and periodontopathic bacteria such as Porphyromonas gingivalis have been associated with atherosclerosis, possibly due to cross-reactivity of the immune response to bacterial GroEL with human heat shock protein (hHSP) 60.

METHODS

We examined the cross-reactivity of anti-GroEL and anti-P. gingivalis antibodies with hHSP60 in atherosclerosis patients and quantified a panel of six pathogens in atheromas.

RESULTS

After absorption of plasma samples with hHSP60, there were variable reductions in the levels of anti-GroEL and anti-P. gingivalis antibodies, suggesting that these antibodies cross-reacted with hHSP60. All of the artery specimens were positive for P. gingivalis. Fusobacterium nucleatum, Tannerella forsythia, C. pneumoniae, Helicobacter pylori, and Haemophilus influenzae were found in 84%, 48%, 28%, 4%, and 4% of arteries, respectively. The prevalence of the three periodontopathic microorganisms, P. gingivalis, F. nucleatum and T. forsythia, was significantly higher than that of the remaining three microorganisms.

CONCLUSIONS

These results support the hypothesis that in some patients, cross-reactivity of the immune response to bacterial HSPs including those of periodontal pathogens, with arterial endothelial cells expressing hHSP60 may be a possible mechanism for the association between atherosclerosis and periodontal infection.

Modulation of the antibody response by Porphyromonas gingivalis and Fusobacterium nucleatum in a mouse model

Successive immunization of mice with Fusobacterium nucleatum and Porphyromonas gingivalis has been shown to modulate the specific serum IgG responses to these organisms. The aim of this study was to investigate these antibody responses further by examining the IgG subclasses induced as well as the opsonizing properties of the specific antibodies. Serum samples from BALB/c mice immunized with F. nucleatum (gp1-F), P. gingivalis (gp2-P), P. gingivalis followed by F. nucleatum (gp3-PF) F. nucleatum followed by P. gingivalis (gp4-FP) or saline alone (gp5-S) were examined for specific IgG1 (Th2) and IgG2a (Th1) antibody levels using an ELISA and the opsonizing properties measured using a neutrophil chemiluminescence assay. While IgG1 and IgG2a subclasses were induced in all immunized groups, there was a tendency towards an IgG1 response in mice immunized with P. gingivalis alone, while immunization with F. nucleatum followed by P. gingivalis induced significantly higher anti-P. gingivalis IgG2a levels than IgG1. The maximum light output due to neutrophil phagocytosis of P. gingivalis occurred at 10 min using nonopsonized bacteria. Chemiluminescence was reduced using serum-opsonized P. gingivalis and, in particular, sera from P. gingivalis-immunized mice (gp2-P), with maximum responses occurring at 40 min. In contrast, phagocytosis of immune serum-opsonized F. nucleatum demonstrated peak light output at 10 min, while that of F. nucleatum opsonized with sera from saline injected mice (gp5-S) and control nonopsonized bacteria showed peak responses at 40 min. The lowest phagocytic response occurred using gp4-FP serum-opsonized F. nucleatum. In conclusion, the results of the present study have demonstrated a systemic Th1/Th2 response in mice immunized with P. gingivalis and/or F. nucleatum with a trend towards a Th2 response in P. gingivalis-immunized mice and a significantly increased anti-P. gingivalis IgG2a (Th1) response in mice immunized with F. nucleatum prior to P. gingivalis. Further, the inhibition of neutrophil phagocytosis of immune serum-opsonized P. gingivalis was modulated by the presence of anti-F. nucleatum antibodies, while anti-P. gingivalis antibodies induced an inhibitory effect on the phagocytic response to F. nucleatum.

Differences in mouse strain influence leukocyte and immunoglobulin phenotype response to Porphyromonas gingivalis

This study examined the nature of the infiltrating cells in Porphyromonas gingivalis-induced lesions and immunoglobulins in the serum samples of BALB/c (H-2d), C57BL6 (H-2b), DBA/2J (H-2d) and CBA/CaH (H-2k) mice. Mice were immunized intraperitoneally with P. gingivalis outer membrane antigens or sham-immunized with phosphate-buffered saline followed by subcutaneous challenge with live organisms 1 week after the final immunization. The resulting skin abscesses were excised 7 days later, cryostat sections cut and an immunoperoxidase method used to detect the presence of CD4+ and CD8+ T-cell subsets, CD14+ macrophages and CD19+ B cells. Peroxidase positive neutrophils and IgG1- and IgG2a-producing plasma cells were also identified. Anti P. gingivalis IgG1 and IgG2a subclass antibodies were determined in serum obtained by cardiac puncture. Very few CD8+ T cells and CD19+ B cells were found in any of the lesions. The percentages of CD4+ cells, CD14+ cells and neutrophils were similar in lesions of immunized BALB/c and C57BL6 mice, with a trend towards a higher percentage of CD14+ cells in sham-immunized mice. The percentage of CD14+ cells was higher than that of CD4+ cells in immunized compared with sham-immunized DBA/2J mice. The percentages of CD4+ and CD14+ cells predominated in immunized CBA/CaH mice and CD4+ cells in sham-immunized CBA/CaH mice. The percentage of neutrophils in immunized CBA/CaH mice was significantly lower than that of CD14+ cells and CD4+ cells in sham-immunized mice. IgG1+ plasma cells were more dominant than IgG2a+ cells in immunized BALB/c, C57BL6 and DBA/2J mice, whereas IgG2a+ plasma cells were more obvious in sham-immunized mice. IgG2a+ plasma cells were predominant in immunized and sham-immunized CBA/CaH mice. In the serum, specific anti-P. gingivalis IgG2a antibody levels (Th1 response) were higher than IgG1 levels (Th2 response) in sham-immunized CBA/CaH and DBA/2J mice. In immunized BALB/c mice, IgG2a levels were lower than IgG1 levels, while IgG2a levels were higher in immunized C57BL6 mice. In conclusion, this study has shown differences in the proportion of infiltrating leukocytes and in the subclasses of immunoglobulin produced locally and systemically in response to P. gingivalis in different strains of mice, suggesting a degree of genetic control over the response to P. gingivalis.

Immunoglobulins in saliva of preterm and full-term infants

The aim of this longitudinal study was to determine salivary levels of total IgA, IgG and IgM in 84 preterm and 214 full-term infants, from birth to 18 months of age. Unstimulated whole saliva was collected from each infant at birth, and subsequently at 3-monthly intervals. Immunoglobulin levels were estimated using an ELISA technique. At birth, IgA was detected in 147/214 (69%) full-term infants but only 47/84 (56%) preterm infants (P < 0.01). In the case of IgG, 61% of full-term and 56% of preterm infants showed detectable levels, whereas IgM was found in 71% and 73%, respectively. Levels of IgA and IgG rose from birth to 18 months, whereas IgM levels did not change significantly. Increases in salivary levels of IgA were associated with introduction of solid foods (P < 0.001), as well as tooth eruption (P < 0.001). Our results indicate that the majority of full-term and preterm infants are orally immunocompetent at birth.

IgG subclass specific antibody response to periodontopathic organisms in HIV-positive patients

BACKGROUND

We previously reported an increased rate of progression of periodontal disease over an 18-month period in human immunodeficiency virus (HIV)-positive subjects compared to controls. The mechanism for disease progression and rapid tissue loss was unknown. Data on the microbiological studies failed to show any significant difference in the microbial characteristics of the periodontal lesions in HIV-positive patients compared to HIV-negative controls. Immunological analysis had identified neutrophils as an important component of the host defense against periodontal infection, especially against rapid tissue loss. Serum IgG reactivities to periodontal pathogens in HIV-positive patients with periodontitis were reduced. Other data provided circumstantial evidence to suggest that IgG subclass (IgG2) specific antibody might assist bacterial clearing in periodontal infection. The aim of the current study was to examine the specific IgG subclass antibody response to a panel of periodontopathic organisms: Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella Intermedia (Pi), Fusobacterium nucleatum (Fn), Campylobacter rectus (Cr), and Bacteroides forsythus (Bf) in HIV-positive patients compared to HIV-negative controls.

METHODS

Sera from 120 HIV-positive patients (40 periodontitis, 69 gingivitis, and 11 no oral diseases) were tested for IgG subclass specific antibody response to the above listed 6 organisms using enzyme-linked immunosorbent assay. Data were compared with those obtained from 40 HIV-negative control subjects (35 periodontitis, 2 gingivitis, and 3 no oral diseases).

RESULTS

In the HIV-positive group, a consistently high response rate was found in IgG1 to all the bacteria tested. In addition, high levels of IgG3 and IgG4 to Pg and IgG1 and IgG2 to Pi were also present. However, no significant difference was detected among the periodontitis, gingivitis, and no oral disease subgroups. When the periodontitis patients from the HIV-positive group were compared to the HIV-negative group, no difference in the antibody levels and response rates was noted.

CONCLUSION

We conclude that in HIV-positive patients, the specific IgG subclass antibody response to periodontopathic organisms was similar to that of HIV-negative subjects.

The role of CD4+ cells in vivo on the induction of the immune response to Porphyromonas gingivalis in mice

BACKGROUND

It has previously been suggested that CD4+ T cells play a pivotal role in regulating the immune response to periodontal pathogens. The aim of the present study therefore was to determine delayed type hypersensitivity (DTH), spleen cell proliferation, serum and splenic anti-Porphyromonas gingivalis antibody levels, and lesion sizes following challenge with viable P. gingivalis in CD4-depleted BALB/c mice immunized with P. gingivalis outer membrane proteins (OMP).

METHODS

Four groups of BALB/c mice were used. Groups 1 and 2 were injected intraperitoneally (ip) with saline for 3 consecutive days and then weekly throughout the experiment. Groups 3 and 4 were injected ip with rat immunoglobulin and a monoclonal rat anti-mouse CD4 antibody, respectively. Two days later, group 1 mice were injected ip with saline only, while all the other groups were immunized ip with P gingivalis OMP weekly for 3 weeks. One week later following the last immunization of OMP, 3 separate experiments were conducted to determine: 1) the DTH response to P gingivalis OMP by measuring footpad swelling; 2) the levels of antibodies to P gingivalis in serum samples and spleen cell cultures using an enzyme-linked immunosorbent assay, as well as spleen cell proliferation after stimulation with OMP; and 3) the lesion sizes after a subcutaneous challenge with viable P. gingivalis cells.

RESULTS

In CD4+ T-cell-depleted mice (group 4), the DTH response and antigen-stimulated cell proliferation were significantly suppressed when compared to groups 2 and 3. Similarly, the levels of serum and splenic IgM, IgG, and all IgG subclass antibodies to P. gingivalis OMP were depressed. Delayed healing of P gingivalis-induced lesions was also observed in the CD4+ T-cell-depleted group.

CONCLUSIONS

This study has shown that depletion of CD4+ T cells prior to immunization with P gingivalis OMP led to the suppression of both the humoral and cell-mediated immune response to this microorganism and that this was associated with delayed healing. These results suggest that the induction of the immune response to P. gingivalis is a CD4+ T-cell-dependent mechanism and that CD4+ T cells are important in the healing process.

Genetic dependence of the specific T-cell cytokine response to Porphyromonas gingivalis in mice

BACKGROUND

Susceptibility to periodontal infections may, in part, be genetically determined. Porphyromonas gingivalis is a major periodontopathogen, and the immune response to this organism requires T-cell help. The aim of the present study was to examine the specific T-cell cytokine responses to P. gingivalis outer membrane antigens in a mouse model and their relationship with H-2 haplotype.

METHODS

BALB/c and DBA/2J (H-2d), CBACaH (H-2k), and C57BL6 (H-2b) mice were immunized with P. gingivalis outer membrane antigens weekly for 3 weeks. One week after the final injection, the spleens were removed, and 6 T-cell lines specific for P. gingivalis were established for each mouse strain. The percentage of CD4 and CD8 cells in the P. gingivalis-specific T-cell lines staining positive for intracytoplasmic interleukin (IL)-4, interferon (IFN)-gamma, and IL-10 was determined by 2-color flow cytometry.

RESULTS

The cytokine profiles of T-cell lines from BALB/c and DBA/2J mice showed no significant differences. Significantly fewer IL-4+, IFN-gamma+, and IL-10+ CD4 cells than IL-4+, IFN-gamma+, and IL-10+ CD8 cells, respectively, were demonstrated for both strains. P. gingivalis-specific T-cell lines generated from CBACaH mice were similar to those generated from BALB/c and DBA/2J mice; however, the mean percentage of IL-4+ CD4 cells in CBACaH mice was lower than the percentage of IFN-gamma+ CD4 cells. Also, the mean percentage of IFN-gamma+ CD4 cells in CBACaH mice was significantly increased compared to DBA/2J mice. Unlike the other 3 strains, T-cell lines established from C57BL6 mice contained similar percentages of cytokine-positive cells, although the percentage of IL-4+ CD4 cells was reduced in comparison to the percentage of CD8 cells. However, comparisons with the other 3 strains demonstrated a higher percentage of IL-4+ CD4 cells than in lines established from the spleens of DBA/2J mice, IFN-gamma+ CD4 cells than in lines established from BALB/c and CBACaH mice, and IL-10+ CD4 cells than in lines established from all 3 other strains. No significant differences in the percentage of positive CD8 cells were demonstrated between lines in the 4 strains of mice.

CONCLUSION

The specific T-cell response to P. gingivalis in mice may, in the case of the CD4 response, depend on MHC genes. These findings are consistent with the concept that patient susceptibility is important to the outcome of periodontal infection and may, in part, be genetically determined.

Effect of Fusobacterium nucleatum on the T and B cell responses to Porphyromonas gingivalis in a mouse model

T cell cytokine profiles and specific serum antibody levels in five groups of BALB/c mice immunized with saline alone, viable Fusobacterium nucleatum ATCC 25586, viable Porphyromonas gingivalis ATCC 33277, F. nucleatum followed by P. gingivalis and P. gingivalis followed by F. nucleatum were determined. Splenic CD4 and CD8 cells were examined for intracytoplasmic interleukin (IL)-4, interferon (IFN)-gamma and IL-10 by dual colour flow cytometry and the levels of serum anti-F. nucleatum and anti-P. gingivalis antibodies determined by an ELISA. Both Th1 and Th2 responses were demonstrated by all groups, and while there were slightly lower percentages of cytokine positive T cells in mice injected with F. nucleatum alone compared with the other groups immunized with bacteria, F. nucleatum had no effect on the T cell production of cytokines induced by P. gingivalis in the two groups immunized with both organisms. However, the percentages of cytokine positive CD8 cells were generally significantly higher than those of the CD4 cells. Mice immunized with F. nucleatum alone had high levels of serum anti-F. nucleatum antibodies with very low levels of P. gingivalis antibodies, whereas mice injected with P. gingivalis alone produced anti-P. gingivalis antibodies predominantly. Although the levels of anti-F. nucleatum antibodies in mice injected with F. nucleatum followed by P. gingivalis were the same as in mice immunized with F. nucleatum alone, antibody levels to P. gingivalis were very low. In contrast, mice injected with P. gingivalis followed by F. nucleatum produced equal levels of both anti-P. gingivalis and anti-F. nucleatum antibodies, although at lower levels than the other three groups immunized with bacteria, respectively. Anti-Actinobacillus actinomycetemcomitans, Bacteroides forsythus and Prevotella intermedia serum antibody levels were also determined and found to be negligible. In conclusion, F. nucleatum immunization does not affect the splenic T cell cytokine response to P. gingivalis. However, F. nucleatum immunization prior to that of P. gingivalis almost completely inhibited the production of anti-P. gingivalis antibodies while P. gingivalis injection before F. nucleatum demonstrated a partial inhibitory effect by P. gingivalis on antibody production to F. nucleatum. The significance of these results with respect to human periodontal disease is difficult to determine. However, they may explain in part differing responses to P. gingivalis in different individuals who may or may not have had prior exposure to F. nucleatum. Finally, the results suggested that P. gingivalis and F. nucleatum do not induce the production of cross-reactive antibodies to other oral microorganisms.

Genetic variation in the recognition of Porphyromonas gingivalis antigens in mice

T-cell cytokine profiles, anti-Porphyromonas gingivalis antibodies and Western blot analysis of antibody responses were examined in BALB/c, CBA/CaH, C57BL6 and DBA/2J mice immunized intraperitoneally with different doses of P. gingivalis outer membrane antigens. Splenic CD4 and CD8 cells were examined for intracytoplasmic interleukin (IL)-4, interferon (IFN)-gamma and IL-10 by FACS analysis and levels of anti-P. gingivalis antibodies in the serum samples determined by enzyme-linked immunosorbent assay. Western blot analysis was performed on the sera from mice immunized with 100 microg of P. gingivalis antigens. The four strains of mice demonstrated varying degrees of T-cell immunity, although the T-cell cytokine profiles exhibited by each strain were not affected by different immunizing doses. While BALB/c and DBA/2J mice exhibited responses that peaked at immunizing doses of 100-200 microg of P. gingivalis antigens, CBA/CaH and C57BL6 demonstrated weak T-cell responsiveness compared with control mice. Like the T-cell responses, serum antibody levels were not dose dependent. DBA/2J exhibited the lowest levels of anti-P. gingivalis antibodies followed by BALB/c with CBA/CaH and C57BL6 mice demonstrating the highest levels. Western blot analysis showed that there were differences in reactivity between the strains to a group of 13 antigens ranging in molecular weight from 15 to 43 kDa. Antibody responses to a number of these bands in BALB/c mice were of low density, whereas CBA/CaH and C57BL6 mice demonstrated high-density bands and DBA/2J mice showed medium to high responses. In conclusion, different immunizing doses of P. gingivalis outer membrane antigens had little effect on the T-cell cytokine responses and serum anti-P. gingivalis antibody levels. Western blot analysis, however, indicated that the four strains of mice exhibited different reactivity to some lower-molecular-weight antigens. Future studies are required to determine the significance of these differences, which may affect the outcome of P. gingivalis infection.

Distribution of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in an Australian population

BACKGROUND/AIM

The present study describes (i) the natural distribution of the three putative periodontopathogens Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans in an Australian population and (ii) the relationship between these organisms, pocket depths and supragingival plaque scores.

METHODS

Subgingival plaque was collected from the shallowest and deepest probing site in each sextant of the dentition. In total, 6030 subgingival plaque samples were collected from 504 subjects. An ELISA utilising pathogen-specific monoclonal antibodies was used to quantitate bacterial numbers.

RESULTS

: A. actinomycetemcomitans was the most frequently detected organism (22.8% of subjects) followed by P. gingivalis and P. intermedia (14.7% and 9.5% of subjects respectively). The majority of infected subjects (83%) were colonised by a single species of organism. A. actinomycetemcomitans presence was over-represented in the youngest age group but under-represented in the older age groups. Conversely, P. gingivalis and P. intermedia presence was under-represented in the youngest age group but over-represented in the older age groups. Differing trends in the distribution of these bacteria were observed between subjects depending upon the site of the infection or whether a single or mixed infection was present; however, these differences did not reach significance. Bacterial presence was strongly associated with pocket depth for both A. actinomycetemcomitans and P. gingivalis. For A. actinomycetemcomitans, the odds of a site containing this bacterium decrease with deeper pockets. In contrast, for P. gingivalis the odds of a site being positive are almost six times greater for pockets >3 mm than for pockets < or =3 mm. These odds increase further to 15.3 for pockets deeper than 5 mm. The odds of a site being P. intermedia positive were marginally greater (1.16) for pockets deeper than 3 mm.

CONCLUSIONS

This cross-sectional study in a volunteer Australian population, demonstrated recognised periodontal pathogens occur as part of the flora of the subgingival plaque. Prospective longitudinal studies are needed to examine the positive relationship between pocket depth and pathogen presence with periodontal disease initiation and/or progression.

A longitudinal study of interleukin-1 gene polymorphisms and periodontal disease in a general adult population

BACKGROUND

Cross-sectional studies have demonstrated that a specific polymorphism (allele 2 of both IL-1A +4845 and IL-1B +3954) in the IL-1 gene cluster has been associated with an increased susceptibility to severe periodontal disease and to an increased bleeding tendency during periodontal maintenance. The aim of the present study was to investigate the relationship between IL-1 genotype and periodontitis in a prospective longitudinal study in an adult population of essentially European heritage.

METHODS

From an ongoing study of the Oral Care Research Programme of The University of Queensland, 295 subjects consented to genotyping for IL-1 allele 2 polymorphisms. Probing depths and relative attachment levels were recorded at baseline, 6, 12, 24, 36, 48 and 60 months using the Florida probe. Periodontitis progression at a given site was defined as attachment loss > or =2 mm at any observation period during the 5 years of the study and the extent of disease progression determined by the number of sites showing attachment loss. Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans and Prevotella intermedia were detected using ELISA.

RESULTS

38.9% of the subjects were positive for the composite IL-1 genotype. A relationship between the IL-1 positive genotype and increased mean probing pocket depth in non-smokers greater than 50 years of age was found. Further, IL-1 genotype positive smokers and genotype positive subjects with P. gingivalis in their plaque had an increase in the number of probing depths > or =3.5 mm. There was a consistent trend for IL-1 genotype positive subjects to experience attachment loss when compared with IL-1 genotype negative subjects.

CONCLUSION

The results of this study have shown an interaction of the IL-1 positive genotype with age, smoking and P. gingivalis which suggests that IL-1 genotype is a contributory but non-essential risk factor for periodontal disease progression in this population.

Immune response to Bacteroides forsythus in a murine model

A murine skin abscess model was used to study the immune response to an acute infection with Bacteroides forsythus. BALB/c mice were given subcutaneous injections of either viable or heat-killed B. forsythus, while a third sham-immunized control group received phosphate-buffered saline. Weights and lesion sizes were measured. Blood was collected from the heart and specific antibodies to B. forsythus measured by an ELISA. Swabs taken from the lesions and also from pooled blood were cultured anaerobically for viable B. forsythus. Viable B. forsythus-induced lesions reached maximum size at day 7. B. forsythus cells were recovered from lesions up to day 4 although none were cultured from blood samples. Heat-killed bacteria induced much smaller lesions. Serum antibody levels increased during the 9-day study period, being significantly higher in mice injected with viable compared with heat-killed B. forsythus. Antibody levels in sham control mice were significantly lower than those seen in the other two groups. These results showed that a subcutaneous injection of viable cells of B. forsythus elicited a pronounced abscess formation and induce higher levels of specific antibodies compared with that produced by an injection of dead bacteria. This suggests that, as with other periodontopathic organisms, this mouse model can be used to study the immune response to B. forsythus.

The influence of genetic variation on the splenic T cell cytokine and specific serum antibody responses to Porphyromonas gingivalis in mice

BACKGROUND

T cell cytokine profiles in the spleens and anti-Porphyromonas gingivalis antibodies in the sera of P. gingivalis-immunized BALB/c (H-2d), CBA/CaH (H-2k), C57BL6 (H-2b), and DBA/2J (H-2d, C5 deficient) mice were examined.

METHODS

Mice were immunized either by intraperitoneal injections of P. gingivalis outer membrane antigens and Freund's incomplete adjuvant weekly for 3 weeks or sham-immunized with PBS and adjuvant, followed by subcutaneous challenge with live organisms 1 week after the final immunization. Spleens were excised and blood samples collected by heart puncture at 0 and 7 days after challenge. Splenic CD4 and CD8 cells were stained for intracytoplasmic interleukin (IL)-4, interferon (IF)-gamma, and IL-10 and levels of anti-P. gingivalis antibodies in the serum samples determined by ELISA.

RESULTS

Lesion sizes in immunized BALB/c mice remained stable for the 7-day experimental period. Immunized CBA/CaH and C57BL6 mice exhibited large lesions at day 1 reducing by day 7 particularly in the latter strain. Lesions in immunized DBA/2J mice were still larger than the other strains at day 7. With the exception of DBA/2J mice, sham-immunized mice demonstrated lesions which did not show signs of healing by day 7. T cell cytokine responses in sham-immunized mice at day 0 were low, increasing to a variable degree by day 7 after challenge in the 4 strains. Immunized BALB/c mice demonstrated intermediate T cell responses while generally exhibiting a stronger IFN-gamma response than IL-4 or IL-10. Immunized CBA/CaH and C57BL6 mice showed weak T cell cytokine responses while immunized DBA/2J displayed the strongest T cell responses particularly in regard to IL-4 positive cells. Sham-immunized mice had low levels of serum anti-P. gingivalis antibody levels at day 0 with levels increasing significantly by day 7 after challenge. Antibody levels in immunized mice seemed to correlate with lesion sizes. Immunized C57BL6 mice had the highest antibody levels followed by CBA/CaH, BALB/c with DBA/2J exhibiting low levels. The T cell and B cell antibody responses in each strain appeared to exhibit an inverse relationship.

CONCLUSIONS

This study has shown that genetic differences at the level of H-2 haplotype induce variations in the local and T and B cell responses to P. gingivalis antigens. The responses of DBA/2J mice which have the same haplotype as BALB/c mice suggest that factors other than H-2 haplotype such as the C5 deficiency may influence this immune response. The significance of the specific antibody and T cell responses and of their inverse relationship to susceptibility to periodontal disease remains to be determined.

Chemokine expression in Porphyromonas gingivalis-specific T-cell lines

Autologous non-T cells (monocytes and B cells) were added to Porphyromonas gingivalis-specific T cell lines established from 9 healthy adults together with P. gingivalis outer membrane antigens for 4-6, 16-18, 24 and 48 h. Flow cytometry was employed to analyze the CD4 and CD8 cells, monocytes and B cells for intracytoplasmic IP-10 (interferon-gamma inducible protein 10), MCP-1 (monocyte chemoattractant protein 1), MIP-1 alpha (macrophage inflammatory protein 1 alpha) and RANTES (regulated on activation normal T cell expressed and secreted) at the four time periods. All cell types were positive for each chemokine throughout the 48-h time period. There were significantly fewer MCP-1-positive cells compared with the other 3 chemokines. However, the percentages of MCP-1, MIP-1 alpha- and RANTES-positive CD8 cells were significantly higher than the percentages of positive CD4 cells in all cultures. IP-10-positive CD4, CD14-positive monocytes and CD19-positive B cells were predominant compared with MIP-1 alpha- and RANTES-positive cells at 24 h. In conclusion, the present study has shown that P. gingivalis-specific T cells, monocytes and B cells produce chemokines in response to P. gingivalis outer membrane antigens, IP-10 being predominant, with MCP-1 being significantly reduced in comparison with IP-10, MIP-1 alpha and RANTES. Increased percentages of CD8 cells were induced to produce chemokines in comparison with CD4 cells, indicating a more preferential action on CD8 rather than CD4 cells.

T-cell antigen specificity in humans following stimulation with Porphyromonas gingivalis

The effects of Porphyromonas gingivalis stimulation on T-cell clonality and cytokine mRNA expression in peripheral blood mononuclear cells from individuals with gingivitis and periodontitis were investigated. Clonality of T cells was investigated by reverse transcription-polymerase chain reaction (RT-PCR) and single-strand conformation polymorphism analysis. Cytokine mRNA expression was investigated by RT-PCR. Whereas unstimulated mononuclear cells did not demonstrate obvious clonality, clonal expansion was found in most Vbeta families after stimulation. However, there was no relation between clonal change and disease category or the presence of P. gingivalis infection. Messenger RNA for interferon-gamma and interleukin-13 was upregulated whereas interleukin-4 and -10 were downregulated following P. gingivalis stimulation. Interleukin-12p35 demonstrated no consistent pattern. This study supports the concept that P. gingivalis stimulates T cells in an antigen-specific fashion. It further suggests that peripheral blood T cells may preferentially produce interferon-gamma and interleukin-13 in response to P. gingivalis stimulation irrespective of disease or P. gingivalis status.

Apoptosis in Porphyromonas gingivalis-specific T-cell lines

Fluorescence-activated cell sorter analysis and transmission electron microscopy were used to determine the presence of apoptotic cells in Porphyromonas gingivalis-specific T-cell lines established from the peripheral blood of 10 P. gingivalis-infected individuals. P. gingivalis outer membrane antigens were presented to the T cells by autologous Epstein-Barr virus-transformed B cells for 6, 24, 48 and 72 h. Transmission electron microscopy demonstrated the presence of typical apoptotic cells in all cultures. Annexin V-positive cells were present at low concentrations at all 4 four periods. A mean of approximately 2-3% of the CD4 cells and 1-3.5% of the CD8 cells were annexin V-positive, with an increase to around 5.5% positive CD4 cells at 6 h in wells containing P. gingivalis compared with cultures not containing antigen. This difference was not, however, significant at the 0.05 level (P = 0.073). The mean (+/- standard error) CD4:CD8 ratios of the T-cell lines when first established using peripheral blood mononuclear cells as antigen-presenting cells was significantly higher (5.2 +/- 1.1) than when transformed B cells were used as antigen-presenting cell (1.2 +/- 0.5). While this study has shown apoptosis occurring in the T-cell lines, it has not shown definitively that the reversion in the CD4:CD8 ratio in the P. gingivalis-specific T cells following antigen presentation by autologous Epstein-Barr virus-transformed B cells is due to apoptosis of a CD4 population. Alternatively, the reversion in the CD4:CD8 ratio could be due to a selective proliferation of the CD8 population which, in turn, could be relevant to the immunopathology of periodontal disease induced by P. gingivalis.

The proportion of interleukin-4, interferon-gamma and interleukin-10-positive cells in Porphyromonas gingivalis--specific T-cell lines established from P. gingivalis-positive subjects

T-cell cytokine profiles in ten adult periodontitis and seven age-matched healthy or gingivitis subjects were determined. Porphyromonas gingivalis-specific T-cell lines were established from the peripheral blood of these individuals all of whom had past or present evidence of P. gingivalis infection. FACS analysis was used to determine the percentage of CD4- and CD8-positive cells in each line staining for cytoplasmic interleukin (IL)-4, interferon-gamma and IL-10. There were no differences in the mean percentage of IL-4-, interferon-gamma- or IL-10-positive T cells between the two groups. However, the individual profiles showed that the CD4 cells in five of the seven healthy or gingivitis lines had a higher proportion of interferon-gamma-positive cells, with two lines demonstrating higher percentages of IL-10- and/or IL-4-positive CD4 cells. Five of the ten adult periodontitis lines demonstrated either equal or higher percentages of IL-4-positive and/or IL-10-positive CD4 cells. With respect to the CD8 cells, two of the seven lines established from the healthy or gingivitis subjects and six of the ten adult periodontitis lines showed profiles with a higher percentage IL-4- and/or IL-10-positive cells. When the total T-cell contribution (CD4 plus CD8) for each T-cell line was determined from the individual CD4:CD8 ratios, only one of the healthy or gingivitis lines showed a profile with a higher proportion of IL-10-positive cells, while the results for the adult periodontitis lines were the same as indicated for the CD4 cell profiles, with five lines showing a higher percentage of IL-4- and/or IL-10-positive cells. In conclusion, this study has shown that in P. gingivalis-responsive T-cell lines established from adult periodontitis and healthy or gingivitis subjects, there was a predominant trend towards a higher percentage of interferon-gamma positive cells than either IL-4- or IL-10-positive cells. However, there were variations from this trend, although whether these variations indicate true susceptibility to progressive disease has yet to be determined.

Antigen-specific T-cell receptor V beta expression in Porphyromonas gingivalis-specific T-cell lines

FACS analysis was used to determine the expression of 15 T-cell receptor V beta families on CD4 and CD8 cells in Porphyromonas gingivalis specific T-cell lines established from eight P. gingivalis-positive adult periodontitis and seven P. gingivalis-positive healthy or gingivitis subjects. All 15 T-cell receptor V beta families were expressed by the T-cell lines, although a significantly higher proportion of the CD4 cells expressed the 5.2-3 V beta region compared with the other 14 families, including the 5.3 region, suggesting that it is the 5.2 family which is overexpressed. This was also true for the CD8 cells, with the exception of the 3.1 region in adult periodontitis T-cell lines and the 3.1, 13.1/13.3 and 21.3 regions in healthy or gingivitis lines. Between the two clinical groups, a significantly lower percentage of 13.1/13.3-positive CD8 cells was noted in the adult periodontitis lines compared with the healthy or gingivitis lines. There was a significant reduction in DNA synthesis by the lines in the presence of P. gingivalis outer membrane antigens and fixed irradiated lymphoblastoid cell lines compared with cultures containing untreated irradiated lymphoblastoid cell lines and in cultures containing anti-class II major histocompatibility complex antibody in comparison with all other cultures. The results of this study have shown that P. gingivalis preferentially induces the T-cell receptor V beta 5.2 family on CD4 and CD8 cells in P. gingivalis-specific T-cell lines and that activation of T cells by P. gingivalis outer membrane antigens may be by antigen-specific rather than superantigen activity.

Cytokine profiles of lesional and splenic T cells in Porphyromonas gingivalis infection in a murine model

T cell cytokine profiles in the spleens and Porphyromonas gingivalis-induced lesions of P. gingivalis-immunized mice were examined. BALB/c mice were immunized with P. gingivalis outer membrane (OM) antigens/mouse weekly for 3 weeks followed by challenge with live organisms 2 weeks after the final immunization. Control mice were immunized with PBS. Spleens were excised at 0 and 4 days and lesions at 1, 4, and 7 days after challenge. Splenic and lesional CD4 and CD8 cells were stained for intracytoplasmic interleukin (IL)-4, interferon (IFN)-gamma, and IL-10. More than 50% of the T cells in the spleens of immunized mice were IFN-gamma positive at day 0 which was significantly higher than for IL-4 or IL-10, these levels decreasing significantly 4 days after challenge. Less than 6% of the T cells in sham immunized mice were cytokine positive at day 0, although at day 4, there was a significant increase in the percent IL-10 positive CD4 cells and IL-4 and IL-10 positive CD8 cells. There were no differences in the percent IL-4, IFN-gamma, or IL-10 positive T cells in the lesions of immunized mice, but there was a dramatic decrease at day 7 to very low levels in control mice. In conclusion, the results of the present study show a predominant Th1 response in the spleens of BALB/c mice after immunization with P. gingivalis OM antigens, suggesting that a protective immune response to P. gingivalis may involve a strong IFN-gamma response.

Detection of clonotypic changes of T cells after stimulation with Porphyromonas gingivalis

The aim of this study was to investigate whether Porphyromonas gingivalis stimulation would induce a selective activation and expansion of a limited T-cell receptor V beta repertoire or T-cell clonotype. Using samples from patients with chronic inflammatory periodontal diseases, we examined TCRBV gene usage and T-cell clonotypes of peripheral blood mononuclear cells incubated in the presence or absence of P. gingivalis outer membrane through a combination of reverse transcription polymerase chain reaction (RT-PCR) and subsequent single strand conformation polymorphism (SSCP) analysis. There was no difference in the mean expression for most BV families with or without P. gingivalis outer membrane in the culture. However, in individual cases, a few BV gene families did become overexpressed or underexpressed following stimulation, although a consistent pattern did not emerge. SSCP analysis showed that several new distinct bands appeared after stimulation, indicating distinct clonal accumulations, although the number of distinct bands decreased in most cases. These data suggest that clonotypic change occurred following stimulation with P. gingivalis outer membrane. Furthermore, the possibility of superantigen stimulation by P. gingivalis is unlikely to be due to the small change in BV gene usage and clonal T-cell accumulations with P. gingivalis outer membrane stimulation, as evidenced by SSCP. Thus, RT-PCR and SSCP analysis is useful in evaluating the host response to periodontopathic antigens.

Characterization of serum antibodies to Porphyromonas gingivalis in individuals with and without periodontitis

Although Porphyromonas gingivalis is a defined pathogen in periodontal disease, many subjects control the infection without experiencing loss of attachment. Differences in host susceptibility to the disease may be reflected in the pattern of humoral antibodies against specific P. gingivalis antigens. The aim of this study was to determine the presence of antibodies against immunodominant P. gingivalis antigens as well as the isotype and subclass of anti-P. gingivalis antibodies against outer membrane antigens in four groups of patients: P. gingivalis-positive, 1) with and 2) without periodontitis, and P. gingivalis-negative, 3) with and 4) without periodontitis. Antigens of molecular weight 92, 63, and 32 kDa and lipopolysaccharide were found to be immunodominant. Group 1 subjects showed a significantly higher response to the 92 and 63 kDa antigens compared with other groups. The response to lipopolysaccharide was significantly higher in group 1, and lower in group 4 than in groups 2, 3. Immunoglobulin G1 (IgG1), IgG2 and IgM antibodies against P. gingivalis outer membrane were present in all subjects, while only some subjects were seropositive for IgG3, IgG4 and IgA. There were no differences in concentrations for IgG1, IgG3 and IgM. The IgG2 concentration in group 4 was significantly higher than in groups 1 and 2, while the IgG4 concentration in group 4 was significantly lower than in other groups. The frequency of seropositivity for IgG4 and IgA was lowest in group 4, while IgG3 seropositivity was almost exclusively seen in healthy patients in groups 2, 4. These findings suggest that the presence of IgG3 may reflect non-susceptibility to the disease, while lack of IgG4 may be indicative of periodontal health and lack of infection.

Cytokine profiles of cells extracted from humans with periodontal diseases

FACS analysis was used to determine the percent interferon (IFN)-gamma-, interleukin (IL)-4-, IL-10-, and CD30-positive T-cells extracted from adult periodontitis (AP) and healthy/gingivitis (H/G) subjects. Additionally, the percentages of IL-1 beta-, IL-10- and IL-12-producing B-cells and macrophages were ascertained. The percent IL-10+ CD8 cells extracted from AP lesions was decreased compared with H/G tissues (p = 0.033), and the percent CD30+ CD4 (p = 0.001) and CD30+ CD8 (p = 0.028) cells was higher in AP than in H/G tissues. The percentages of IL-1 beta + macrophages (p = 0.003) and IL-12+ B-cells (p = 0.034) were both higher in AP lesions than in H/G tissues. The specific effect of Porphyromonas gingivalis on the cytokine profiles of peripheral blood mononuclear cells isolated from P. gingivalis-infected AP and H/G patients was also determined. While there were no significant differences in the percent cytokine-positive T-cells after stimulation with P. gingivalis outer membrane antigens (OM) for 6 days compared with cells incubated in medium only, the percent CD30+ CD4 cells increased significantly (p = 0.047 and p = 0.063 for AP and H/G groups, respectively). There was also an increase in the percent IL-1 beta + B-cells from AP patients (p = 0.029), and the percent IL-12+ monocytes from AP and H/G subjects was higher than the percent IL-12+ B-cells, both after stimulation with P. gingivalis OM (p = 0.005 for the AP group and p = 0.058 and therefore not quite significant for the H/G group) and when incubated in medium alone (p = 0.016 and p = 0.015 for AP and H/G groups, respectively). This study has shown that IL-10+ CD8 cells may be significant in gingival lesions, and that CD30+ T-cells indicative of Th2 or Th0 cells may play a role in progressive periodontal disease. This study has also shown that B-cells produce IL-1 in the gingival lesion and that P. gingivalis may be significant in the induction of B-cell-induced IL-1.

Expression of receptor beta-chain variable region by T cells in human periodontal disease

T cells play a major part in the immune response in periodontal diseases. In order to determine any selective T-cell receptor (TCR) beta-chain variable region (V beta) usage in the infiltrates of healthy/ gingivitis (H/G) and adult periodontitis (AP), cells were extracted from gingival biopsies, the CD4 and CD8 cells stained with antibodies to eight V beta regions, and two-colour flow cytometry used to analyse the data. The frequencies of CD4 and CD8 cells expressing each of the TCR-V beta families varied from 0 to 46% between individuals. A high percentage of CD4 and CD8 cells expressed the V beta 13 family in several AP biopsies, but, in a number of H/G tissues, a high percentage of T cells expressed up to three families including the V beta 13 region, these varying from individual to individual. The mean results showed a significantly greater percentage of V beta 5.2-3-positive CD4 cells (p = 0.003) and V beta 5.1- and 5.2-3-positive CD8 cells (p = 0.003 and 0.025, respectively) isolated from H/G than AP tissues. The percentage of V beta 3.1-positive CD4 cells extracted from H/G tissues was also higher but not quite significant at the 0.05 level (p = 0.051). Sections of gingival tissue in biopsies from H/G and AP were stained in situ; there were no significant differences in the mean expression of V beta 3.1-, 5.1- or 5.2-3-positive cells. A second aim was to determine the effect of Porphyromonas gingivalis on the TCR repertoire. There were no differences in the mean percentage of CD4 or CD8 cells expressing the eight TCR-V beta regions between the two groups after stimulation in vitro with P. gingivalis outer-membrane antigens. There was, however, a trend towards a decrease in the percentage of positive CD4 and CD8 T cells after culture with the antigen. This was significant for CD4 cells from H/G expressing the V beta 5.1 and 5.3 TCRs (p = 0.032 and p = 0.038, respectively). This trend was not evident for V beta 5.2-3-positive CD4 cells or V beta 5.1-positive CD8 cells isolated from both H/G and AP nor for V beta 3.1-positive CD8 cells from AP. The results show that there may be restricted V beta usage in gingival tissues, particularly in H/G tissues. The V beta 5 and 3.1 families may be selected for in the gingival tissues and may also be involved in P. gingivalis activation.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Establishment of peripheral blood and gingival T lymphocyte clones responsive to Porphyromonas gingivalis

T cells are central to the immune response to infection and studies have indicated a local immunoregulatory imbalance may exist in human periodontal disease. Since Porphyromonas gingivalis is generally recognized as a major periodontopathogen, the aim of this study was to establish T cell lines and clones specific to P. gingivalis from the gingival tissues and peripheral blood of P. gingivalis--infected subjects. Two subjects were selected from two groups of individuals (one from each group) established on the basis of P. gingivalis in their plaque and the presence of serum antibodies which react with P. gingivalis antigens. The two groups differed however in their clinical susceptibility (adult periodontitis) or resistance (gingivitis) to periodontal breakdown. The mean ages +/- standard error of the mean of the two groups were 47.9 +/- 2.2 and 49.6 +/- 3.7, respectively, so that resistance in the gingivitis group was related to the age of the subjects. T cell lines and clones were established from the peripheral blood of one patient from each of the two groups and also from the gingival tissues of the same periodontitis subject. This study has demonstrated the capability of establishing P. gingivalis-specific T cell lines and clones from P. gingivalis-infected subjects and FACS analysis of the T cell receptor variable regions demonstrated that the clones were indeed monoclonal. The CD4:CD8 ratios of the peripheral blood-derived T cell lines were 1.2 and 0.4 for the gingivitis-derived line and the periodontitis-derived line, respectively, thus supporting the clinical differences displayed by the two subjects.

Microbiological and serological investigations of oral lesions in Papillon-Lefèvre syndrome

Microbiological and serological (enzyme linked immunosorbent assay) investigations were carried out, including karyotyping, on two Asian children with Papillon-Lefèvre syndrome. In case 1, a girl aged four years, the most prevalent putative periodontopathogens were Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia (deciduous dentition) and Bacteroides gracilis, E corrodens and F nucleatum (permanent dentition). In case 2, a boy aged nine years, they were F nucleatum, P intermedia and P loeschii and E corrodens. Serum from case 2 showed a raised specific IgG antibody response to Actinomyces actino-mycetemcomitans serotype b. Thus, a wider range of species than hitherto reported may be associated with Papillon-Lefèvre syndrome, including A actino-mycetemcomitans and F nucleatum.

Characterization of T lymphocyte clones derived from Porphyromonas gingivalis infected subjects

Porphyromonas gingivalis plays a major role in the pathogenesis of periodontal disease, however some individuals with P. gingivalis infection do not experience periodontal breakdown. The aim of this study was to investigate the proliferative responses of two highly defined groups of subjects and to establish and characterize peripheral blood and gingival cell T cell lines and clones from subjects from these groups. The two groups were selected on the basis of P. gingivalis in their plaque and the presence of serum anti-P. gingivalis antibodies. Both groups therefore were seen to have P. gingivalis and to have responded to it. They however differed only in their clinical susceptibility (adult periodontitis) or resistance (gingivitis) to periodontal breakdown. Dose responses of peripheral blood mononuclear cells extracted from the subjects showed a trend towards a lower response by the adult periodontitis group to P. gingivalis outer membrane (OM) antigens. Peripheral blood T cell lines and clones responsive to P. gingivalis OM were established from a high responding gingivitis subject and a low responding adult periodontitis subject. Gingival T cell lines and clones were also derived from cells extracted from the periodontal tissues of the same periodontitis subject. The majority of T cells in the peripheral blood T cell line from the gingivitis subject were CD4 while those from the adult periodontitis subject were CD8. The gingival T cell line was CD3+ve CD4-ve and CD8-ve. All lines and clones proliferated slowly to P. gingivalis OM but phytohaemagglutinin (PHA) induced an increase in DNA synthesis in those derived from the gingivitis subject with little to no effect on those established from the adult periodontitis subject. Furthermore, PHA inhibited the proliferative response of the CD8 clone derived from the adult periodontitis subject. Phenotypic analysis demonstrated that all the peripheral blood clones expressed the alpha beta TCR while the gingival T cell clones expressed the gamma-delta TCR. All clones had the memory/primed CD45RO+ve phenotype and at least 80% of cells in each clone were HLA-DR+ve. A lower percent of gingival cells expressed CD45RA than the CD4 peripheral blood clones and the two CD8 clones also had a decreased CD45RA expression. The gingival T cell clones also expressed a low percent CD25 as did the CD8 clone derived from the adult periodontitis subject. The results suggest that clones derived from the gingivitis and adult periodontitis subject may be functionally different. The presence of gamma-delta T cells in adult periodontitis remains to be confirmed and their function determined.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

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.

Cytokine profiles of Porphyromonas gingivalis-reactive T lymphocyte line and clones derived from P. gingivalis-infected subjects

Porphyromonas gingivalis is generally recognized as a major periodontopathogen such that a study of T cell responses to this organism may help to elucidate immune regulation in periodontal disease.

OBJECTIVE

The aim of this study was to examine interleukin (IL)-4, interferon (IFN)-gamma and IL-10 production by P. gingivalis-responsive T cell lines and clones derived from the peripheral blood of two P. gingivalis-infected subjects with different disease expression and from the gingival tissues of one of the P. gingivalis-infected subjects.

MATERIALS AND METHODS

FACS analysis was used to determine the percentage of T cells staining positive for cytoplasmic IL-4, IFN-gamma and IL-10 and reverse transcriptase polymerase chain reaction (RT-PCR) was performed to determine the presence of mRNA for IL-4 and IFN-gamma in the T cell lines and clones.

RESULTS

FACS analysis showed that virtually all the T cell lines and clones contained IL-4- and IFN-gamma-producing T cells. The RT-PCR results generally supported this trend. However, a higher percentage of cells in the clones derived from one subject produced IL-4 while a lower percentage produced IFN-gamma compared with the clones derived from the other subject. FACS analysis also demonstrated that the lines and clones derived from the two subjects showed differences in IL-10 production.

CONCLUSION

This study has demonstrated that there may be differences in IL-4 and IL-10 production by the P. gingivalis responsive lines and clones derived from P. gingivalis-infected subjects with different disease expression. Any relationship to disease however, remains to be determined.

Antibody responses of Porphyromonas gingivalis infected gingivitis and periodontitis subjects

Porphyromonas gingivalis demonstrates a strong association with adult periodontitis although some individuals with the infection do not experience attachment loss. Therefore differences in the immune response to this organism may be of importance to the outcome of the disease.

OBJECTIVE

The aim of this study was to determine whether P. gingivalis positive subjects with and without periodontal breakdown, reacted differently to P. gingivalis antigens as assessed by the pattern of serum antibody reactivity.

MATERIALS AND METHODS

Two highly defined groups of subjects were chosen for this study. Both demonstrated P. gingivalis in their plaque and both had responded to P. gingivalis as shown by the presence of serum antibodies. The two groups differed only in their apparent clinical susceptibility to periodontal breakdown. Western blots of P. gingivalis membrane antigens were probed with sera from the two groups to determine their reactivity to specific antigens.

RESULTS

Analysis of the immunoblots showed that there were no differences in either the total numbers of bands, or bands recognized by the majority of subjects in the gingivitis and adult periodontitis groups. There were however, four bands recognized by the majority of the gingivitis group and not by the majority of the adult periodontitis group, there being a significant difference (P = 0.03) in the recognition of the 91.4-kDa antigen band. A further five antigens of lower molecular weight were seen by the majority of the adult periodontitis group and not by the majority of the gingivitis group. When sera were tested against purified P. gingivalis LPS, the results indicated that the five antigens seen by the majority of the adult periodontitis group had molecular weights which were in the range exhibited by the LPS antigens.

CONCLUSION

These results suggest that gingivitis and adult periodontitis subjects with P. gingivalis infection, may recognize different P. gingivalis antigens.

IgG antibody subclass response to Porphyromonas gingivalis outer membrane antigens in gingivitis and adult periodontitis

Porphyromonas gingivalis is an important oral pathogen with a strong association with adult periodontitis. Significant titers of specific IgG antibodies to P. gingivalis can be found in the sera of both gingivitis and periodontitis patients. Since IgG subclasses have different biological characteristics, the present study dealt with the serum IgG subclass response to outer membrane antigens of P. gingivalis. Western blot analysis of P. gingivalis outer membrane was carried out using 20 adult periodontitis and 20 age- and sex-matched gingivitis patients. Antibodies in sera of both adult periodontitis and gingivitis patients recognized 38 antigen bands, ranging in molecular mass from 11.1 to 161 kDa. IgG2 was the predominant antibody subclass response in both patient groups in terms of the numbers of outer membrane antigens recognized, followed by IgG3, IgG1, and IgG4. More antigens in all IgG subclasses except IgG4 were recognized in adult periodontitis cases. Of the 23 antigens identified by IgG2 antibodies, 9 were recognized predominantly in adult periodontitis and 3 in the gingivitis group. In the IgG1 subclass, 4 antigens were recognized predominantly in the adult periodontitis group while only 1 antigen was recognized significantly more in the gingivitis group. The IgG3 response identified 14 antigens ranging in molecular mass from 11.1 to 61.2 kDa in both groups. Ten antigens were recognized significantly by the adult periodontitis group. The lowest response was seen by IgG4 antibodies, with only 3 antigens of molecular mass 61.2, 52.3, and 38.8 kDa recognized, the latter two significantly in the adult periodontitis group.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Cellular adhesion molecules on periodontal lymphocytes

T cell induced differentiation of B cells has been shown to be dependent on the CD2/LFA-3 and LFA-1/ICAM-1 pathways. Flow cytometric analysis was used to examine these adhesion molecules on T and B cells extracted from gingival tissues before and after stimulation with the putative periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. Adhesion molecule expression on peripheral blood cells from healthy adults was used as a control. Approximately 50 per cent of B cells extracted from gingival tissues expressed LFA-3 and ICAM-1 compared with 30 per cent positive peripheral blood B cells. Around 50 per cent of gingival T cells expressed CD2 relative to 76 per cent positive peripheral blood T cells. However, 40-50 per cent of both gingival and peripheral blood T cells expressed LFA-1. There was no difference in the expression of adhesion molecules on T and B cells extracted from health/marginal gingivitis or adult periodontitis lesions. After stimulation of gingival cells in vitro, the per cent CD2 positive T cells and LFA-3 and ICAM-1 positive B cells remained relatively stable over the six-day culture period, although P. gingivalis and F. nucleatum appeared to induce an increase in the percentage of gingival T cells expressing LFA-1. In contrast to the gingival lymphocytes, stimulation of peripheral blood cells resulted in an increase in the per cent CD2 positive T cells, LFA-3 and ICAM-1 positive B cells, with a decrease in LFA-1 positive T cells. The results therefore demonstrated that gingival T and B cells express adhesion molecules in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesion molecule expression in chronic inflammatory periodontal disease tissue

Differences in lymphocyte populations have been demonstrated in gingivitis and periodontitis lesions. A differential expression of adhesion molecules may play a role in lymphocyte trafficking in these tissues. An indirect avidin biotin immunoperoxidase technique was used to stain a range of adhesion molecules in tissue sections of 21 gingival biopsies from both gingivitis and periodontitis subjects. These specimens were placed into three groups according to the size of the infiltrate. ICAM-1, PECAM-1 and LECAM-1 expression on mononuclear cells in the inflammatory infiltrates increased significantly with increasing size of infiltrate. Approximately 50% of these mononuclear cells were LFA-1+ and CD29+. When specimens were grouped according to their putative disease status there were no significant differences between mononuclear cell adhesion molecule expression in small infiltrates from either gingivitis or adult periodontitis subjects. This was also the case with larger lesions from both clinical groups. Therefore there does not appear to be a differential expression of adhesion molecules on lymphocytes in gingivitis and periodontitis tissue. Endothelial cells were positive for ICAM-1, PECAM-1, CD29, GMP-140 but negative for ELAM-1. Keratinocyte expression of ICAM-1 increased with increasing size of infiltrate although in heavy infiltrates, cells in the region of the junctional epithelium which were positive in small lesions, became ICAM-1 negative. The upper layers of the oral epithelium were positive for LECAM-1 in small infiltrates and with increasing size of infiltrate, the lower layers and many of the sulcular and junctional epithelium keratinocytes were positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased salivary immunoglobulin A secretion rate after intense interval exercise in elite kayakers

Endurance athletes have been shown to suffer a high incidence of upper respiratory tract infection (URTI; e.g. colds, sore throat) during intense training and after competition. Previous studies have shown that concentrations of secretory immunoglobulin A (IgA), the major effector of host defense against micro-organisms causing URTI, decrease after intense endurance exercise. Many athletes perform intense interval exercise as part of their normal training. The purpose of this study was to determine whether salivary IgA concentrations also decrease after intense interval exercise during the normal training regime in elite athletes. Timed saliva samples were obtained from eight elite male kayakers immediately before and after three on-water training sessions during a 3-week period. The concentrations of IgA, IgG and IgM were determined separately by enzyme-linked immunosorbent assay, and secretion rates calculated for each Ig. The IgA secretion rate (micrograms.min-1) decreased 27%-38% after all three training sessions (P = 0.007); the largest decrease (38%) was noted after the most intense session at the end of an especially intense week of training. The IgA concentration relative to total protein (micrograms.mg protein-1) was significantly lower (P < 0.05) on this training day compared with the other 2 days. Concentrations and secretion rates of IgG and IgM did not change after exercise, indicating a specific effect on IgA. These data would suggest that, in elite athletes, IgA concentration and secretion rate are reduced by intense interval exercise, and that exercise-induced changes in IgA output may be one mechanism contributing to URTI in elite athletes.

Interleukin 1, interleukin 6 and transforming growth factor-beta production by human gingival mononuclear cells following stimulation with Porphyromonas gingivalis and Fusobacterium nucleatum

Gingival mononuclear cell production of interleukin 1 (IL-1), interleukin 6 (IL-6) and transforming growth factor-beta (TGF-beta) after stimulation with the putative periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum was investigated. Using an ELISA method, gingival mononuclear cells extracted from 18 adult periodontitis subjects were found to be producing IL-1. However, IL-1 activity could only be detected in 5 out of these 18 cases when tested using a thymocyte proliferation bio-assay, suggesting the presence of IL-1 inhibitors. Depletion of monocytes from peripheral blood cultures resulted in a significant decrease in IL-1 activity following P. gingivalis stimulation while there was no effect in the level of IL-1 activity following stimulation with F. nucleatum. This suggests that P. gingivalis and F. nucleatum stimulate different cell types to produce IL-1. Like IL-1, IL-6 production by gingival mononuclear cells was significantly greater than that produced by the control peripheral blood mononuclear cells. Following P. gingivalis and F. nucleatum stimulation, higher levels of IL-6 could be detected; however, both organisms stimulated similar levels. Intracytoplasmic immunofluorescence staining demonstrated a lower percent TGF-beta+ cells in bacterial stimulated peripheral blood mononuclear cell cultures compared with cells in medium alone. In the gingival mononuclear cell cultures, the percentage TGF-beta+ cells peaked at day 1 in F. nucleatum-stimulated, whereas in P. gingivalis-stimulated cultures the peak TGF-beta+ cells occurred at day 3, again suggesting stimulation of different cell subsets. These results illustrate that different periodontopathic bacteria may stimulate different cell types to produce cytokines which may have synergistic or antagonistic effects.

Different responses in B cells induced by Porphyromonas gingivalis and Fusobacterium nucleatum

A phenotypic study had shown that gingival B cells respond differently to two periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. Further investigation now shows a reduction in the percentage of Ki-67 + T cells in cultures of gingival and peripheral blood mononuclear cells stimulated with P. gingivalis for 3 and 6 days, respectively, but no suppression of Ki-67 expression in B cells in response to either P. gingivalis or F. nucleatum. Depletion studies of cultures of peripheral blood mononuclear cells showed that in the absence of CD4 cells, the percentage of CD19+ and CD20+ B cells stimulated with P. gingivalis increased after 6 days whereas depletion of CD8 cells resulted in a rise in the percentage of F. nucleatum- and P. gingivalis-stimulated B cells, although this was not significant in the case of P. gingivalis. Specific antibody to P. gingivalis and F. nucleatum was found in culture supernatants of gingival but not of peripheral blood mononuclear cells, indicating a possible higher frequency of antigen-specific B cells in periodontal lesions. IgG was the predominant isotype in both gingival and control peripheral blood cultures, followed closely by IgA in gingival cultures. F. nucleatum stimulated higher levels of Ig in cultures of peripheral blood mononuclear cells than P. gingivalis or cells cultured in medium only, whereas in gingival cell cultures, stimulation by P. gingivalis appeared to result in higher levels of IgG. Also Ig was present at day 3 in gingival cultures, whereas in the blood cell cultures, Ig was only detected at day 6, further suggesting a degree of activation of of gingival B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The establishment of human T cell lines reactive with specific periodontal bacteria

Human T cell lines (TCLs) were obtained by stimulation of peripheral blood mononuclear cells (PBMCs) with the 2 periodontopathic bacteria, Porphyromonas gingivalis FDC-381 and Fusobacterium nucleatum FDC-263. After the first round of stimulation and rest, the cells responded specifically to the bacteria originally used to establish each line. Throughout the culture period, the responsiveness of each of the TCLs to their specific bacteria increased. Phenotypic analysis of the TCLs revealed heterogeneity of cell types. In both TCLs approximately 80% of the cells were T cells, all of which bore the alpha beta T cell receptor. The P. gingivalis-reactive TCL (PG-TCL) showed approximately equal proportions of CD4+ and CD8+ cells, whereas the F. nucleatum-reactive TCL (FN-TCL) was predominantly CD4+. The expression of CD25, HLA-DR, CD45RA and CD29 on these CD4+ cells varied throughout the culture period of 45 days. These results demonstrate that it is possible to establish long-term T cell lines reacting to specific periodontopathic bacteria.

CD45RA and CD45RO positive CD4 cells in human peripheral blood and periodontal disease tissue before and after stimulation with periodontopathic bacteria

Flow cytometric analysis was used to examine naive and primed or memory CD4 cells extracted from periodontal lesions compared with cells from peripheral blood of healthy subjects before and after stimulation with the periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. In peripheral blood, approximately 60% and 40% of CD4 cells were CD45RO+ and CD45RA+ respectively at day 0. Phytohaemagglutinin (PHA) induced CD45RO expression on almost 100% of CD4 cells. However, P. gingivalis and F. nucleatum stimulation did not cause any significant change in percentage of CD45RO+ CD4 cells except for a loss of antigen at day 6 together with re-expression at day 7, which also occurred on cells cultured in medium only. CD45RA expression on PHA and bacterial-stimulated peripheral blood CD4 cells remained fairly stable for the 10-d culture period. Greater than 90% CD4 cells extracted from healthy or marginal gingivitis (H/MG) and adult periodontitis (AP) lesions were CD45RO+ and this was maintained on AP cells throughout the 6-d culture period, except for a small decrease in the percentage of positive cells induced by P. gingivalis at day 3. Approximately 9% CD4 cells from H/MG tissue were CD45RA+, but about 22% AP cells expressed this antigen, and this increased again in P. gingivalis- and F. nucleatum-stimulated cultures after 3 d. Therefore, in peripheral blood P. gingivalis and F. nucleatum do not act as nonspecific T-cell mitogens and, in AP cells, these bacteria induce changes in phenotype, supporting previous data that although they may be polyclonal B-cell activators, they activate antigen specific T-cells.

Effect of initial treatment of chronic inflammatory periodontal disease on the frequency of peripheral blood T-lymphocytes specific to periodontopathic bacteria

Limit dilution analysis (LDA) was used to determine the effect of initial treatment of chronic inflammatory periodontal disease on the frequency of periodontopathic bacteria-specific T-cells in peripheral blood. Eleven marginal gingivitis (MG) and 8 adult periodontitis (AP) subjects took part in the study. The proliferative T-lymphocyte precursor (PTL-P) frequencies to Porphyromonas gingivalis and Actinomyces viscosus were determined using LDA and Poisson statistics both before and after treatment. Tetanus toxoid was used as a control antigen. Treatment resulted in a significant reduction in clinical disease parameters in both groups. The median peak PTL-P frequency for P. gingivalis was significantly higher in the AP group compared with the MG group before treatment. This was not the case after treatment nor with A. viscosus. In the MG group the median peak PTL-P frequency with both P. gingivalis and A. viscosus declined as a result of treatment. Although this decline was not statistically significant it may indicate an antigen-specific response in this group. In the AP group the median peak PTL-P frequency with P. gingivalis before treatment was 83.76 x 10(-6) (approximately 1 in 12,000) and after treatment it was 36.17 x 10(-6) (approximately 1 in 28,000). Dose-response relationships showed at each concentration of organisms/well this trend for a decline in PTL-P frequency after treatment, suggesting that any increased responsiveness to this organism in this group may be largely antigen-specific. However, there was no difference in this group in the median peak PTL-P frequency with A. viscosus before and after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Monoclonal antibodies for the detection of 'periodontopathic' bacteria

The development of indirect immunofluorescence assays using MAbs as specific probes has made it possible to detect a variety of suspected periodontal pathogens in subgingival plaque, with exquisite sensitivity. The studies demonstrate high reproducibility of the results if different MAbs are used to assess the same bacterial species. Bacteroides forsythus, Bact. gingivalis, Bact. intermedius and Wolinella recta, but not Actinobacillus actinomycetemcomitans were found in sites of adult periodontitis with high prevalence but quite distinct degrees of colonization. The colonization levels of Bact. forsythus and Bact. gingivalis were significantly associated with the probing depth of the lesions. The investigations demonstrate the usefulness of serological analysis of plaque and indicate that several of the organisms implicated in the aetiology of periodontal diseases may be tolerated in high numbers in subgingival lesions, without periodontal destruction.

Effects of periodontopathic bacteria on IL-1 and IL-1 inhibitor production by human polymorphonuclear neutrophils

The effect of heat-killed periodontopathic bacteria on the production of interleukin-1 (IL-1) and an IL-1 inhibitor by human polymorphonuclear neutrophils (PMN's) was examined. Peripheral blood was obtained from 18 healthy volunteers and the PMN's were separated using dextran sedimentation and Ficoll-Paque density gradient centrifugation. The PMN's (5 x 10(5) cells/well) were cultured in serum-free media with or without heat-killed periodontopathic bacteria. Four gram-negative periodontopathic bacteria were used; Bacteroides gingivalis FDC 381, Bacteroides forsythus FDC 338, Actinobacillus actinomycetemcomitans Y4 and Fusobacterium nucleatum FDC 263. The non-oral Fusobacterium mortiferum ATCC 25557 was used as a control organism. IL-1 activity was assayed using thymocyte proliferation. The non-oral organism F. mortiferum stimulated IL-1 production by PMN's, in contrast none of the periodontopathic bacteria stimulated IL-1 release although the bacteria themselves had an IL-1 enhancing effect. Following fractionation of the periodontopathic bacteria stimulated PMN supernatants, an IL-1 inhibitory fraction was identified. These results may illustrate a further mechanism by which periodontopathic bacteria may evade the protective effect of PMN's and may also suggest a regulatory role for PMN's in chronic inflammatory periodontal disease.