Periodontal disease in free-ranging koalas (Phascolarctos cinereus) from the Mount Lofty Ranges, South Australia, and its association with koala retrovirus infection

BACKGROUND

In northern Australian koala populations (Queensland and New South Wales), periodontal disease (gingivitis and periodontitis) is common while koala retrovirus subtype A is endogenous, with other subtypes transmitted exogenously. Koala retrovirus has been hypothesised to cause immune suppression and may predispose koalas to diseases caused by concurrent infections. In southern Australia populations (Victoria and South Australia) periodontal disease has not been investigated, and koala retrovirus is presumably exogenously transmitted. This study described oral health in South Australian koalas and investigated if an association between periodontal disease and koala retrovirus exists.

METHODS

Oral health was examined for wild-caught koalas from the Mount Lofty Ranges (n = 75). Koala retrovirus provirus was detected in whole blood using nested PCR and proviral load determined with qPCR. Periodontal disease severity was recorded and used to calculate the Final Oral Health Index (0-normal, 24-severe).Results Periodontal disease was observed in 84% (63/75) of koalas; 77% had gingivitis (58/75) and 65% (49/75) had periodontitis. The average Final Oral Health Index was 5.47 (s.d 3.13). Most cases of periodontal disease were associated with the incisors. Koala retrovirus-infected koalas were more likely to present with periodontitis (p = 0.042) and the Final Oral Health Index was negatively correlated with proviral load (ρ = -0.353, p = 0.017).

CONCLUSION

South Australian koalas had a high prevalence of gingivitis and periodontitis. Periodontal disease was more prevalent in the incisors. Exogenous koala retrovirus infection may also facilitate the development of periodontitis by modulation of the immune response to concurrent oral bacterial infections.

Malocclusions in the koala (Phascolarctos cinereus)

Malocclusions are a misalignment or incorrect positioning of the teeth when the upper and lower jaws close. These are poorly described in the koala and can result in irregular mastication which can have lifelong effects on body condition and oral health. A total of 370 koalas from two populations in Queensland (295) and one in South Australia (75) were examined for malocclusions. The prevalence of malocclusions in South Australian free-ranging koalas, captive Queensland koalas and Queensland free-ranging koalas was 39% (44), 30% (29) and 22% (29) respectively. Four types of malocclusion were identified based on severity of misalignment of the incisor/canine region, types 1, 2, 3 and 4. Maxillary overbite measurements of the molariform teeth were determined and these anisognathic values were then used to describe malocclusions within familial relationships in captive colonies. Captive koalas with a malocclusion had narrower mandibular width that ranged between 0.5 and 1% less than the normal measurements. The specific malocclusions reported in this study affected individuals by leading to tooth rotation, mobility and erosion with inefficient mastication of food and vegetation compaction. These changes increased the oral cavity pathology, by placing animals at risk of periodontal disease. There was evidence of familial links to malocclusion types in captive animals. Therefore captive breeding recommendations should consider known koala malocclusion traits to minimise their effect on future generations.

Nitric oxide production by a human osteoblast cell line stimulated with Aggregatibacter actinomycetemcomitans lipopolysaccharide

BACKGROUND/AIM

Human osteoblasts induced by inflammatory stimuli express an inducible nitric oxide synthase (iNOS). The aim of the present study was to test the hypothesis that Aggregatibacter actinomycetemcomitans lipopolysaccharide stimulates the production of nitric oxide (NO) by a human osteoblast-like cell line (HOS cells).

METHODS

Cells were stimulated directly with A. actinomycetemcomitans lipopolysaccharide or pretreated with the following l-NIL (an iNOS inhibitor), anti-CD14, Toll-like receptor 2 (TLR2), or TLR4 antibody before stimulation with A. actinomycetemcomitans lipopolysaccharide. The role of the cyclic nucleotides was assessed by pretreating the cells with the following; ODQ (a guanylyl cyclase inhibitor); SQ22536 (an adenylyl cyclase inhibitor); db-cAMP (a cyclic adenosine monophosphate analog); br-cGMP (a cyclic guanosine monophosphate analog); forskolin (an adenylyl cyclase activator), IBMX [a non-specific phosphodiesterase (PDE) inhibitor], or KT5720 [a protein kinase A (PKA) inhibitor]. The cells were also preincubated with genistein [a protein tyrosine kinase (PTK) inhibitor], bisindolylmaleimide [a protein kinase C (PKC) inhibitor], BPB [a phospholipase A2 (PLA2) inhibitor], and NDGA (a lipoxygenase inhibitor). The iNOS activity and nitrite production in the cell cultures were determined spectrophotometrically.

RESULTS

The results showed that A. actinomycetemcomitans lipopolysaccharide stimulated both iNOS activity and nitrite production by HOS cells; this was reduced by l-NIL, anti-CD14, or anti-TLR4 antibody, SQ22536, KT5720, genistein, bisindolylmaleimde, BPB, and NDGA, but was enhanced by db-cAMP, IBMX, and forskolin.

CONCLUSION

These results therefore suggest that A. actinomycetemcomitans lipopolysaccharide may induce the production of NO by HOS cells via a CD14-TLR4 molecule complex, a cAMP-PKA pathway, as well as by a PTK, PKC, PLA2, and lipoxygenase-dependent mechanism.

Effect of exogenous nitric oxide on murine immune response induced by Aggregatibacter actinomycetemcomitans lipopolysaccharide

BACKGROUND AND OBJECTIVE

Elevated nitric oxide (NO) has been associated with destructive periodontal disease. The aim of the present study was to test the hypothesis that exogenous NO may inhibit a protective immune response to Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS) in a murine model.

MATERIAL AND METHODS

Mice of the BALB/c strain were sham immunized, immunized with A. actinomycetemcomitans LPS, treated with S-nitroso-N-acetyl penicillamine (SNAP; a NO donor) and immunized with A. actinomycetemcomitans LPS or treated with SNAP plus 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO) and immunized with A. actinomycetemcomitans LPS. All animals were then challenged subcutaneously with viable A. actinomycetemcomitans. The serum-specific immunoglobulin G (IgG) subclasses and both interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) as well as splenic inducible nitric oxide synthase (iNOS) activity before and after bacterial challenge were assessed. The diameter of skin lesions was determined. Groups of mice were treated with l-N(6)-(1-iminoethyl)-lysine (l-NIL), an iNOS inhibitor, or 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ), a guanylyl cyclase inhibitor, prior to injections with SNAP and/or A. actinomycetemcomitans LPS, and the skin lesions were assessed.

RESULTS

Treatment with SNAP increased the iNOS activity, suppressed both serum-specific IgG2a and IFN-gamma levels, and delayed the healing of the lesions. These SNAP-induced immune alterations were restored by treatment with carboxy-PTIO. Pretreatment with l-NIL resulted in partial healing, whereas pretreatment with ODQ induced a delayed healing of the lesions.

CONCLUSION

The present study suggests that exogenous NO may suppress a protective T helper 1-like murine immune response to A. actinomycetemcomitans LPS by an endogenous NO-independent but a cyclic GMP-dependent mechanism.

217. Inflammatory stimulation of human decidual cells by periodontopathic bacteria

Periodontal disease is associated with increased risk of preterm birth, although a mechanistic connection has not yet been confirmed. We hypothesised that circulating endotoxins (e.g. lipopolysaccharide, LPS) from periodontopathic organisms might possess the ability to exert highly potent immunostimulatory effects in extraplacental membranes, thereby triggering inflammatory activation sufficient to precipitate preterm labour and birth in the absence of overt intrauterine infection. We therefore tested the stimulatory effects of LPS prepared from three periodontopathic bacteria [porphyromonas gingivalis (P.g), Aggregatibacter actinomycetemcomitants (A.a), Fusobacterium nucleatum (F.n)] in comparison with ‘standard' LPS from E.Coli (O55:B5). Human decidual cells were isolated by collagenase/dispase digestion with Percoll purification from term decidual membranes delivered before the onset of labour by Caesarean section. Cells were stimulated overnight with 0.02, 0.2 and 2 mg/L LPS or equivalent doses of whole cell non-viable bacteria. As an index of inflammatory stimulation, cytokine (TNF-α) production was measured by ELISA and normalised to cellular protein. The different LPS preparations all stimulated decidual cytokine production, with ranked potencies as follows: Ec > Aa > Fn > > Pg. Maximal stimulation of TNF-α production achieved was 15-, 4.5-, 23- and 7-fold above control by Ec, Aa, Fn and Pg, respectively. Overall, the LPS preparations were more potent stimulators than whole cell bacteria, achieving greater levels of stimulation at lower doses. However, whole cell Aa was notable for its inflammatory effects, generating a >60-fold increase in TNF-α levels relative to control at the highest dose tested (2 mg/L). These data highlight wide variability in the ability of periodontopathic bacteria to stimulate an inflammatory response in the human decidua, both in terms of their potency and efficacy. The potential significance of bacterial molecular patterns other than LPS as potential triggers of inflammation-driven preterm labour warrants further investigation.

The role of cytokines in a Porphyromonas gingivalis-induced murine abscess model

INTRODUCTION

Porphyromonas gingivalis is an important periodontopathic bacterium that is strongly associated with periodontal disease and is part of human dental plaque. Periodontal disease results from the interaction of the host with bacterial products, and T-cell-derived cytokines remain critical in the immunoregulation of periodontal disease.

METHODS

The aim of this study was to examine the role of T helper type 1 [interleukin-12p40 (IL-12p40), interferon-gamma, tumour necrosis factor (TNF)] and type 2 (IL-4, IL-10) cytokines in the immune response to a subcutaneous challenge with P. gingivalis using a well-established murine abscess model, in genetically modified cytokine-specific knockout mice.

RESULTS

IL-12p40(-/-) mice exhibited more advanced tissue destruction and a reduced inflammatory cell infiltrate after subcutaneous P. gingivalis challenge. Deficiency of IL-4 or IL-10 did not result in increased susceptibility to P. gingivalis-mediated tissue destruction. Furthermore, TNF deficiency appeared to reduce local tissue destruction. Interestingly, serum-specific antibodies suggested a strong T helper type 2 response.

CONCLUSION

The results of our study indicate an important role for IL-12 in a primary P. gingivalis subcutaneous challenge.

Effect of l-N6-(1-iminoethyl)-lysine, an inducible nitric oxide synthase inhibitor, on murine immune response induced by Actinobacillus actinomycetemcomitans lipopolysaccharide

BACKGROUND AND OBJECTIVES

Inducible nitric oxide synthase (iNOS) activity is known to regulate the immune response. The present study was carried out to determine the effect of L-N6-(1-iminoethyl)-lysine (L-NIL), an iNOS inhibitor, on the induction of immune response to Actinobacillus actinomycetemcomitans lipopolysaccharide in mice.

MATERIAL AND METHODS

BALB/c mice were sham-immunized (group I), immunized with A. actinomycetemcomitans lipopolysaccharide (group II) or treated with L-NIL and immunized with A. actinomycetemcomitans lipopolysaccharide (group III). All animals were then challenged with viable A. actinomycetemcomitans. The levels of serum nitric oxide (NO), specific immunoglobulin G (IgG) isotypes and both interferon-gamma and interleukin-4, as well as spleen cell-derived iNOS activity, before and after bacterial challenge, were assessed. The diameter of skin lesions was also determined. Serum and spleen cells from the above groups were adoptively transferred to the recipients that were then subsequently challenged with live bacteria.

RESULTS

Treatment with L-NIL suppressed serum NO and splenic iNOS activity, but enhanced serum-specific IgG2a antibody and interferon-gamma levels. The lesions in L-NIL-treated mice healed much more rapidly. Transfer with serum and cells from L-NIL-treated and A. actinomycetemcomitans lipopolysaccharide-immunized donors resulted in rapid healing of the lesions in the recipients.

CONCLUSION

It is suggested that treatment with L-NIL in mice immunized with A. actinomycetemcomitans lipopolysaccharide may shift the immune response towards a protective T helper 1-like immunity against A. actinomycetemcomitans-induced infection.

The role of cyclic-AMP on arginase activity by a murine macrophage cell line (RAW264.7) stimulated with lipopolysaccharide from Actinobacillus actinomycetemcomitans

AIMS

The aim of the present study was to determine the role of cyclic adenosine monophosphate (cAMP) on arginase activity in a murine macrophage cell line (RAW264.7 cells) stimulated with lipopolysaccharide (LPS) from Actinobacillus actinomycetemcomitans.

MATERIALS AND METHODS

The cells were treated with A. actinomycetemcomitans LPS for 24 h. The effects of SQ22536 (an adenylyl cyclase inhibitor), ODQ (a guanylyl cyclase inhibitor), dibutyryl cAMP (a cAMP analog), 8-bromo cyclic guanosine monophosphate (a cGMP analog), forskolin (an adenylyl cylase activator), and cycloheximide (a protein synthesis inhibitor) on arginase activity in A. actinomycetemcomitans LPS-stimulated RAW264.7 cells were also determined. Arginase activity was assessed in LPS-stimulated cells in the presence of 3-isobutyl-1-methylxanthine (IBMX), siguazodan and rolipram [phosphodiesterase (PDE) inhibitors] as well as KT5720 [a protein kinase A (PKA) inhibitor].

RESULTS

Arginase activity in A. actinomycetemcomitans LPS-stimulated RAW264.7 cells was suppressed by SQ22536 but not ODQ. Enhancement of arginase activity was observed in the presence of cAMP analog or forskolin but not cGMP analog. Cycloheximide blocked arginase activity in the cells in the presence of cAMP analog or forskolin with or without A. actinomycetemcomitans LPS. IBMX augmented arginase activity in A. actinomycetemcomitans LPS-stimulated cells. Rolipram (a PDE4 inhibitor) increased the levels of arginase activity higher than siguazodan (a PDE3 inhibitor) in the antigen-stimulated cells. The effect of cAMP analog or forskolin on arginase activity in the presence or absence of A. actinomycetemcomitans LPS was blocked by the PKA inhibitor (KT5720).

CONCLUSION

The results of the present study suggest that A. actinomycetemcomitans LPS may stimulate arginase activity in murine macrophages (RAW264.7 cells) in a cAMP-PKA-dependent pathway.

The role of CD4+and CD8+T cells on antibody production by murine Peyer's patch cells following mucosal presentation of Actinomyces viscosus

The aim of this study was to determine the role of CD4 and CD8 cells on specific antibody production by murine Peyer's patch (PP) cells after oral immunization with Actinomyces viscosus in mice. Female DBA/2 mice were orally immunized with three low doses of heat-killed A. viscosus. Sham-immunized mice served as a control group. Mice were depleted of CD4 or CD8 cells by intraperitoneal injection of anti-CD4 or anti-CD8 antibodies daily for 3 days before oral immunization. One week after the last oral immunization, PPs were removed and cell suspensions were cultured with A. viscosus. Specific antibody production in the culture supernatants was assessed by enzyme-linked immunosorbent assay. The results showed that oral immunization with A. viscosus induced a predominant specific immunoglobulin A (IgA) response by PP cells and, to a lesser extent, IgM antibodies. Depletion of CD4 but not CD8 cells suppressed the production of specific antibodies. These results suggest that oral immunization with low doses of A. viscosus may induce the production of specific antibodies by murine PP cells in a CD4-cell-dependent fashion.

The induction of oral tolerance to Actinomyces viscosus in mice

OBJECTIVES

To determine whether oral tolerance with the oral bacterium Actinomyces viscosus was inducible in mice.

MATERIALS AND METHODS

Mice were intragastrically (i.g.) and then intraperitoneally (i.p.) immunized with heat-killed A. viscosus. A control group of mice received only saline. A delayed type hypersensitivity (DTH) response and the levels of isotype specific antibodies were assessed. Spleen cells from mice that were i.g. immunized with A. viscosus were transferred to A. viscosus-primed mice in vivo and in vitro. Furthermore, mice were i.g. immunized with saline or A. viscosus and then challenged i.p. with saline, A. viscosus, or Porphyromonas gingivalis.

RESULTS

Intragastric immunization with A. viscosus suppressed both DTH and serum specific antibodies to A. viscosus. DTH suppression lasted until week 4, while serum immunoglobulin (Ig)A and both IgG and IgM specific antibody levels remained suppressed up to week 8 and 12 respectively. IgG specific antibody suppression was transferable. The DTH response and serum antibodies specific to A. viscosus were suppressed in mice after i.g. challenged with A. viscosus but not P. gingivalis.

CONCLUSION

Mucosal presentation of A. viscosus in mice led to the suppression of immune response to this bacterium in an antigen-specific fashion. Tolerance of DTH response was short lived, while suppression of antigen-specific IgG antibodies in mucosally tolerized mice was long-lasting.

Inflammation, heat shock proteins and periodontal pathogens in atherosclerosis: an immunohistologic study

BACKGROUND

Inflammation is a significant component of atherosclerosis lesions. Bacteria, including periodontopathogens, have been demonstrated in atherosclerotic plaques and cross-reactivity of the immune response to bacterial GroEL with human heat shock protein 60 has been suggested as a link between infections and atherosclerosis.

METHODS

In this study, the nature of the inflammatory infiltrate and the presence of human heat shock protein 60 and GroEL were examined in 31 carotid endarterectomy specimens. Additionally, monoclonal antibodies were used to detect the presence of six bacteria, including those implicated in periodontal disease.

RESULTS

The inflammatory cell infiltrate of the lesions was dominated by CD14(+) macrophages and CD4(+) T cells. Most cells of the infiltrate as well as the endothelium were HLA-DR(+), indicating activation; however, there was an absence of CD25 expression, demonstrating that the activated T cells were not proliferating. Few CD1a(+) and CD83(+) cells were noted. Human heat shock protein 60 expression was evident on endothelial cells and cells with the appearance of smooth muscle cells and lymphocytes. GroEL and bacteria were detected within intimal cells. Chlamydia pneumoniae, Porphyromonas gingivalis, Fusobacterium nucleatum, Tannerella forsythia, Prevotella intermedia, and Actinobacillus actinomycetemcomitans were found in 21%, 52%, 34%, 34%, 41%, and 17% of arteries, respectively.

CONCLUSION

These results give evidence for a specific immune response associated with atherosclerosis. Whether bacteria initiate the observed inflammation in atherosclerotic lesions is not clear; however, the present study shows that maintenance of inflammation may be enhanced by the presence of periodontopathic bacteria.

Arginase activity in a murine macrophage cell line (RAW264.7) stimulated with lipopolysaccharide from Actinobacillus actinomycetemcomitans

AIMS

The aim of the present study was to determine whether or not lipopolysaccharide from Actinobacillus actinomycetemcomitans could stimulate arginase activity in a murine macrophage cell line (RAW264.7 cells).

METHODS

RAW264.7 cells were treated with A. actinomycetemcomitans-lipopolysaccharide or lipopolysaccharide from Escherichia coli for 24 h. The effect of polymyxin B, l-norvaline, dl-norvaline, dexamethasone and cytokines (interferon-gamma and interleukin-4) on arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells was also determined. The cells were pretreated with anti-CD14, anti -toll-like receptor 2, or anti-toll-like receptor 4 antibody prior to stimulation with A. actinomycetemcomitans-lipopolysaccharide. Arginase activity was determined by a colorimetric assay.

RESULTS

A. actinomycetemcomitans-lipopolysaccharide stimulated arginase activity in RAW264.7 cells in a dose-dependent manner, but was less potent than E. coli-lipopolysaccharide. Polymyxin B and l-norvaline, but not dl-norvaline, blocked the arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells. Dexamethasone and interleukin-4 but not interferon-gamma augmented arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells. Treatment of the cells with anti-CD14 and anti-toll-like receptor 4 but not anti-toll-like receptor 2 antibody decreased arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells.

CONCLUSION

The results of the present study suggest that lipopolysaccharide from A. actinomycetemcomitans via CD14/toll-like receptor 4 complex molecules and the regulatory control of glucocorticoid and cytokines may stimulate arginase activity in RAW264.7 cells.

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.

Immunohistological analysis of Tannerella forsythia-induced lesions in a murine model

Tannerella forsythia has been implicated as a defined periodontal pathogen. In the present study a mouse model was used to determine the phenotype of leukocytes in the lesions induced by subcutaneous injections of either live (group A) or nonviable (group B) T. forsythia. Control mice (group C) received the vehicle only. Lesions were excised at days 1, 2, 4, and 7. An avidin-biotin immunoperoxidase method was used to stain infiltrating CD4+ and CD8+ T cells, CD14+ macrophages, CD19+ B cells, and neutrophils. Hematoxylin and eosin sections demonstrated lesions with central necrotic cores surrounded by neutrophils, macrophages and lymphocytes in both group A and group B mice. Lesions from control mice exhibited no or only occasional solitary leukocytes. In both groups A and B, neutrophils were the dominant leukocyte in the lesion 1 day after injection, the numbers decreasing over the 7-day experimental period. There was a relatively low mean percent of CD4+ and CD8+ T cells in the lesions and, whereas the percent of CD8+ T cells remained constant, there was a significant increase in the percent of CD4+ T cells at day 7. This increase was more evident in group A mice. The mean percent of CD14+ macrophages and CD19+ B cells remained low over the experimental period, although there was a significantly higher mean percent of CD19+ B cells at day 1. In conclusion, the results showed that immunization of mice with live T. forsythia induced a stronger immune response than nonviable organisms. The inflammatory response presented as a nonspecific immune response with evidence of an adaptive (T-cell) response by day 7. Unlike Porphyromonas gingivalis, there was no inhibition of neutrophil migration.

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.

L-arginine-dependent nitric oxide production of a murine macrophage-like RAW 264.7 cell line stimulated with Porphyromonas gingivalis lipopolysaccharide

The aim of this study was to determine nitric oxide (NO) production of a murine macrophage cell line (RAW 264.7 cells) when stimulated with Porphyromonas gingivalis lipopolysaccharides (Pg-LPS). RAW 264.7 cells were incubated with i) various concentrations of Pg-LPS or Salmonella typhosa LPS (St-LPS), ii) Pg-LPS with or without L-arginine and/or NG-monomethyl-L-arginine (NMMA), an arginine analog or iii) Pg-LPS and interferon-gamma (IFN-gamma) with or without anti-IFN-gamma antibodies or interleukin-10 (IL-10). Tissue culture supernatants were assayed for NO levels after 24 h in culture. NO was not observed in tissue culture supernatants of RAW 264.7 cells following stimulation with Pg-LPS, but was observed after stimulation with St-LPS. Exogenous L-arginine restored the ability of Pg-LPS to induce NO production; however, the increase in NO levels of cells stimulated with Pg-LPS with exogenous L-arginine was abolished by NMMA. IFN-gamma induced independent NO production by Pg-LPS-stimulated macrophages and this stimulatory effect of IFN-gamma could be completely suppressed by anti-IFN-gamma antibodies and IL-10. These results suggest that Pg-LPS is able to stimulate NO production in the RAW 264.7 macrophage cell model in an L-arginine-dependent mechanism which is itself independent of the action of IFN-gamma.

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.

Induction of suppressor cells following mucosal presentation of Actinomyces viscosus in mice

Mucosal presentation of Actinomyces viscosus results in antigen-specific systemic immune suppression, known as oral tolerance. The aim of the present study was to determine the mechanism by which this oral tolerance is induced. DBA/2 mice were gastrically immunized with A. viscosus. Serum, Peyer's patch (PP) and spleen cells were transferred to syngeneic recipients which were then systemically challenged with the sameiA. viscosus strain. To determine antigen-specificity of cells from gastrically immunized mice, recipients which received immune spleen cells were also challenged with Porphyromonas gingivalis. One week after the last systemic challenge, the delayed type hypersensitivity (DTH) response was determined by footpad swelling and the level of serum IgG, IgA and IgM antibodies to A. viscosus or P. gingivalis measured by an ELISA. No suppression of DTH response or of specific serum antibodies was found in recipients which received serum from gastrically immunized mice. Systemic immune suppression to A. viscosus was observed in recipients which had been transferred with PP cells obtained 2 days but not 4 and 6 days after gastric immunization with A. viscosus. Conversely, suppressed immune response could be seen in recipients transferred with spleen cells obtained 6 days after gastric immunization. The immune response to P. gingivalis remained unaltered in mice transferred with A. viscosus-gastrically immunized cells. The results of the present study suggest that oral tolerance induced by A. viscosus may be mediated by antigen-specific suppressor cells which originate in the PP and then migrate to the spleen.

A longitudinal study of Streptococcus mutans colonization in infants after tooth eruption

We previously reported that, before tooth eruption, over one-half of infants aged 6 mos were already infected with Streptococcus mutans. The aim of this investigation was to determine the colonization of S. mutans after tooth eruption in the same cohort of 111 infants (35 pre-term, 76 full-term). Our results showed that S. mutans colonization increased with increasing age, so that by 24 mos of age, 84% harbored the bacteria (p < 0.01). The mean and median ages of S. mutans colonization in dentate infants were 15.7 mos and 16.0 mos, respectively. Factors associated with S. mutans colonization were sweetened fluids taken to bed (p < 0.01), frequent sugar exposure (p < 0.03) and snacking (p < 0.03), sharing of foods with adults (p < 0.03), and maternal S. mutans levels of > 10(5) CFU/mL (p < 0.02). In contrast, non-colonization of S. mutans was associated with toothbrushing (p < 0.03) and multiple courses of antibiotics (p < 0.001). Analysis of our data establishes the timing of S. mutans colonization in children from birth to 24 mos of age.

The effects of chlorhexidine gel on Streptococcus mutans infection in 10-month-old infants: a longitudinal, placebo-controlled, double-blind trial

PURPOSE

This study investigated the long-term effects of 0.2% chlorhexidine gel, used as a weekly brush-on gel, on Streptoccocus mutans infection in 10-month-old infants.

METHODS

The investigation followed the criteria of a placebo-controlled, double-blind, longitudinal clinical trial. Infants were recruited at birth and oral microbiological swabs were taken at 3 monthly intervals, together with medical, dental, dietary and brushing histories. Children who were found to be colonized with S. mutans were randomly assigned to either the chlorhexidine-gel group (N = 50) or placebo gel group (N = 46), and parents were instructed to brush the gel on the teeth once per week for 12 weeks. In another control group (N = 210), infants did not use either chlorhexidine or placebo gels. Saliva samples were cultured using S. mutans-selective tryptone-yeast extract-cysteine-sucrose-bacitracin (TYCSB) agar. The mean age of the children was 10.2 +/- 2.6 months at the start of the trial and subjects were followed until the ages of 18 months.

RESULTS

In the children with initial low S. mutans counts of < 300 CFU/mL, there was a significant percentage reduction in S. mutans counts in the chlorhexidine-gel group compared to the placebo gel and no-gel control groups after 3 months of weekly gel brushing. However, no significant differences with the placebo group were observed after 15 months of follow-up. There were 39 children (41%) who achieved reduction of their S. mutans to 0 CFU/mL. Compared to those who remained infected with S. mutans, these children had higher toothbrushing frequencies (P < .001) and toothpaste use (P < .001), as well as lower frequencies of daily feeds (P < .01), and lesser weekly frequencies of sweet solids and liquids (P < .001).

CONCLUSIONS

Children with relatively low initial S. mutans counts (< 300 CFU/mL) showed a reduction in S. mutans counts in the first 3 months when 0.2% chlorhexidine gel was brushed on the teeth weekly. No differences were observed when compared with the placebo and no-treatment groups at later follow-up periods.

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.

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.

Comparison of five selective media for the growth and enumeration of Streptococcus mutans

BACKGROUND

Although a few growth media are available for selective isolation of the cariogenic bacteria, Streptococcus mutans (S. mutans), it is still unclear as to which is the most efficacious. This study compared the selectivity and sensitivity of five different media for growing a laboratory strain of S. mutans (NCTC 10449), and for enumerating S. mutans from teeth of a group of young children, aged 2-10 years.

METHODS

The media tested in this study were mitis salivarius with bacitracin (MSB), mitis salivariuskanamycin-bacitracin (MSKB), glucose-sucrose-tellurite-bacitracin (GSTB), trypticase soy-sucrose-bacitracin (TYS20B) and tryptone-yeast-cysteine-sucrose-bacitracin (TYCSB) agars. These were prepared according to the respective manufacturer's instructions.

RESULTS

The results showed that at concentrations of bacteria 1 x 10(3) to 1 x 10(10)/mL, the recovery of the laboratory S. mutans strain was highest in TYCSB agar, followed by in descending order by TYS20B, MSB, GSTB, and MSKB (p<0.01). Similar results were obtained using dental plaque samples collected from swabs of the teeth of a group of children. In the clinical samples, TYCSB again showed the highest recovery rates of S. mutans compared to the other four media. Results were reproduced at dilutions of the samples at 1:20 x 10(6) to 1:2 x 10(6), and S. mutans concentrations of 1.6 to 7.7 Log 10 CFU/mL. In addition, there were highest ratios of mutans to non-mutans bacteria in TYCSB compared to the other media, suggesting high selectivity of this media for mutans species.

CONCLUSION

The results of our study suggest that TYCSB is the most sensitive and selective media for culture of S. mutans for laboratory and clinical studies.

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.

Oral colonization of Streptococcus mutans in six-month-old predentate infants

We hypothesize that S. mutans colonization occurs more frequently in pre-term children due to their relative immaturity. In this study of 172 predentate, six-month-old infants, we found that 50% of pre-term and 60% of full-term children harbored S. mutans. The colonization was confirmed by repeat sampling. Although there were minor differences, factors associated with S. mutans infection in pre-term and full-term infants were generally similar. In both groups, increased frequency of sugar was ranked the most important factor (p < 0.001), followed by breast-feeding (p < 0.001), and habits which allowed saliva transfer from mother to infant (p < 0.01). By contrast, non-colonization of S. mutans was associated with multiple courses of antibiotics (p < 0.001). Compared with pre-term children, there were higher percentages of full-term who had night feedings and consumed sugar during sleep times. Mothers with infected infants had S. mutans levels > 5 x 10(5) CFU/mL saliva (p < 0.001), poorer oral hygiene, more periodontal disease, and lower socio-economic status (p < 0.02) and snacked frequently (p < 0.001), compared with mothers with non-infected infants.

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.

The effects of interleukin-10 depletion in vivo on the immune response to Porphyromonas gingivalis in a murine model

BACKGROUND

The immune response to Porphyromonas gingivalis in the mouse abscess model is known to be dependent upon CD4 T-cell activation and the regulatory role of cytokines. The role of interleukin-10 (IL-10) in this mouse model was examined in vivo.

METHODS

One-week-old, female BALB/c mice were divided into 4 groups. Groups 1 and 2 were given intraperitoneal (i.p.) injections of phosphate buffered saline (PBS) weekly for 5 weeks. Group 3 was given an i.p. injection of rat immunoglobulin. Group 4 was injected with rat anti-IL-10 antibodies. At week 6, group 1 was sham-immunized with PBS, and groups 2, 3, and 4 were injected with P. gingivalis lipopolysaccharide (Pg-LPS) weekly for 2 weeks. One week after the final immunization, delayed-type hypersensitivity (DTH) was assessed by footpad swelling to Pg-LPS. The level of serum antibodies to Pg-LPS and IFN-gamma (IFN-gamma) was determined by enzyme-linked immunosorbent assay. Dorsal abscess formation induced by the injection of viable P. gingivalis was examined daily for 30 days.

RESULTS

The footpad swelling of the anti-IL-10-treated group (group 4) was significantly higher than that of groups 1 to 3. Similarly, the serum IFN-gamma level in group 4 was much higher than that of the other experimental groups. There was no significant difference in serum IgG antibodies to Pg-LPS in any of the experimental groups. However, the level of IgM antibodies in group 4 mice was significantly lower than that in groups 2 and 3. In addition, serum IgG1 was suppressed in group 4 mice, while IgG2a antibodies were raised. However, there was no difference observed between the levels of IgG2b and IgG3 antibodies in any group of mice. The lesions in sham-immunized mice (group 1) persisted for 30 days, and those in group 2 and 3 were undetected by day 18 and 20, respectively. In sharp contrast, lesions in group 4 had healed completely by day 13.

CONCLUSIONS

This study has shown that IL-10 depletion in vivo in P. gingivalis LPS-induced immune response in mice led to an elevated DTH response, an increase in serum IFN-gamma levels, and raised levels of IgG and IgG2a antibodies. Treatment with anti-IL-10 antibodies resulted in suppressed IgG1 and IgM responses and a more rapid healing of abscesses than in non-IL-10-depleted mice. These results suggest that IL-10 depletion in Pg-LPS-induced immune response in mice may lead to a Th1-like immune response and provide strong protection against a subsequent challenge with live P. gingivalis in an abscess model.

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.

A microbiological study of Papillon-Lefévre syndrome in two patients

AIM

To analyse the microflora of subgingival plaque from patients with Papillon-Lefévre syndrome (PLS), which is a very rare disease characterised by palmar-plantar hyperkeratosis with precocious periodontal destruction.

METHODS

Bacterial isolates were identified using a combination of commercial identification kits, traditional laboratory tests, and gas liquid chromatography. Some isolates were also subjected to partial 16S rDNA sequencing. Plaque samples were also assayed for the presence of Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans in a quantitative enzyme linked immunosorbent assay (ELISA) using monoclonal antibodies.

RESULTS

The culture results showed that most isolates were capnophilic and facultatively anaerobic species-mainly Capnocytophaga spp and Streptococcus spp. The latter included S. constellatus, S. oralis, and S. sanguis. Other facultative bacteria belonged to the genera gemella, kingella, leuconostoc, and stomatococcus. The aerobic bacteria isolated were species of neisseria and bacillus. Anaerobic species included Prevotella intermedia, P. melaninogenica, and P. nigrescens, as well as Peptostreptococcus spp. ELISA detected P gingivalis in one patient in all sites sampled, whereas A. actinomycetemcomitans was detected in only one site from the other patient. Prevotella intermedia was present in low numbers.

CONCLUSIONS

Patients with PLS have a very complex subgingival flora including recognised periodontal pathogens. However, no particular periodontopathogen is invariably associated with PLS.

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.

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.

Immunohistological study of lesions induced by Porphyromonas gingivalis in a murine model

A previous study used a mouse model to demonstrate protection after challenge with Porphyromonas gingivalis ATCC 33277. In the present study, this same model was used to determine the phenotype of cells recruited into the lesions during the course of the protective immune response after immunization with this periodontal pathogen. BALB/c mice were immunized with 100 micrograms of P. gingivalis outer membrane antigens per mouse weekly for 3 weeks followed by challenge with live organisms 3 weeks after the final immunization. Hematoxylin and eosin-stained sections showed inflammatory infiltrates in all lesions from control (immunized with adjuvant only) and immunized mice. The lesions developed central necrotic cores surrounded by neutrophils, phagocytic macrophages and lymphocytes. Neutrophils were the predominant cells in the lesions 1 day after challenge with significantly more in immunized than control mice. Acid phosphatase and nonspecific esterase-positive macrophages were detected at day 4 and became the predominant cells in the healing lesions. CD4- and CD8-positive T-cells were present from day 1, and while numbers increased over time, there were no significant differences in control or immunized mice. When mice were depleted of CD4 or CD8 cells prior to immunization with P. gingivalis, fewer neutrophils were found in the lesions 1 day after challenge compared with undepleted immunized mice. Acid phosphatase and nonspecific esterase-positive macrophages were not affected by T-cell depletion. The results suggest that the P. gingivalis-induced lesion in immunized BALB/c mice is consistent with a strong innate immune response involving the recruitment of neutrophils in the first instance which may be under the control of T cells. This is followed by the infiltration of phagocytic macrophages which are involved in the healing process and do not appear to be regulated by T cells.

The detection of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia using an ELISA in an adolescent population with early periodontitis

The aim of the study was to compare the occurrence and levels of A. actinomycetemcomitans, P. gingivalis, and P. intermedia in the subgingival plaque from sites with and without early periodontitis in adolescents using an ELISA. 47, 15- to 16-year-old adolescents (39 Indo-Pakistani, 8 white Caucasian) were examined for clinical attachment level, probing depth, supragingival plaque, subgingival calculus and bleeding on probing on the mesio-buccal and disto-buccal aspects of the 1st molars and the incisors. Based on the clinical data, 2 sites per subject were selected for subgingival plaque sampling 3 weeks later: in 32 subjects with loss of attachment > or = 1 mm, a diseased site (D) and a healthy comparison control site (C) were sampled; in 15 subjects in whom loss of attachment had not yet developed, 1 of the upper molar sites was selected, called the at-risk site (R), together with a C site. The presence and levels of A. actinomycetemcomitans, P. gingivalis, and P. intermedia were determined using an ELISA. The loss of attachment subgroup had significantly more pockets > or = 4 mm, subgingival calculus and bleeding on probing (p < 0.05). Significantly more of the D than C sites had P. gingivalis both at detectable and at measurable levels (p < 0.05). In subjects who had no loss in clinical attachment levels, fewer sampled sites harboured any of the suspected periodontopathogens investigated, and no significant differences were found between the R or C sites (p > 0.05). Although there was a significantly higher prevalence and extent of loss of attachment > or = 1 mm in the Indo-Pakistani subjects compared with the Caucasians (p < 0.05), no differences could be identified in the distribution of the bacteria. It is concluded that monitoring of the subgingival plaque may be useful in studies of early periodontitis in adolescents, and the role of P. gingivalis needs to be elucidated in prospective longitudinal investigations.

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.

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.

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.

Disinfection of dental stone casts: antimicrobial effects and physical property alterations

OBJECTIVES

The purpose of this study was to evaluate the effectiveness of disinfecting solutions incorporated into dental stone casts against a standard and representative group of microorganisms and to note changes in the physical properties of the casts.

METHODS

Irreversible hydrocolloid impressions were contaminated individually with Escherichia coli, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa, Klebsiella pneumoniae, Actinobacter calcoaceticus, Bacillus subtilis, Mycobacterium phlei and Candida albicans. Four readily available disinfecting solutions (glutaraldehyde, povidone-iodine, chlorhexidine and sodium hypochlorite) were added to the die stone mix used to pour up the impressions. The set cast surfaces were swabbed at 1 h and 24 h, the samples plated on agar and incubated at 37 degrees C for 24 h and 3 d for M. phlei. Subsequently, colony forming units were counted. The physical properties assessed were setting time, setting expansion, compressive strength, detail reproduction and delayed expansion of the stone.

RESULTS

Only glutaraldehyde and povidone-iodine killed all contaminating microorganisms within 1 h, while the 1:5 dilution of sodium hypochlorite solution was equally effective after 24 h. Two percent glutaraldehyde was the most effective disinfectant with the least adverse effects on the physical properties of the set cast. Although povidone-iodine caused a decrease in the compressive strength of the set cast, it can be considered to be a sound alternative.

SIGNIFICANCE

This study supports the concept of incorporating disinfectants into model stone as a standard operating procedure for impressions of unknown history and, most sensibly, all dental impressions.

Australian Dental Research Fund Trebitsch Scholarship. Immunohistological analysis of an in vivo Porphyromonas gingivalis-induced lesion in mice

Animal models have been used to study the pathogenic ability of putative periodontopathic bacteria. Injection of mice with live Porphyromonas gingivalis extracts has been shown to induce primary lesions which develop at the site of injection within one day and secondary lesions which develop at a distant site some 3-5 days later. These lesions are primarily polymorphonuclear cell (PMN) infiltrates. Recently, extensive data have shown that PMN activity may in part be controlled by T cells. Hence the aim of this report was to use the mouse model to determine the presence of T cells and macrophages in primary lesions in order to describe a baseline to be used for comparison in future studies.

Microbiological Studies of the Intestinal Microflora of the Koala, Phascolarctos-Cinereus .1. Colonization of the Cecal Wall by Tannin-Protein-Complex-Degrading Enterobacteria

The tannin-protein-complex-degrading enterobacterium (T-PCDE), which specifically colonises the caecal wall of the koala, was investigated immunohistologically. Polyclonal antisera were raised against three strains of T-PCDE. Tissue from six koalas was subjected to immunogold staining using a pooled, absorbed antiserum. Numerous T-PCDE cells were observed in the bacterial layer attached to the caecal wall of five of the animals. The distribution pattern of T-PCDE varied: cells were either scattered throughout the bacterial layer or congregated in areas that apparently contained debris of digesta. The sixth animal, which had been treated with oxytetracycline and showed severe loss of body weight, did not have any bacterial layer attached to the caecal wall and did not stain positive for T-PCDE. The evidence suggests a symbiotic association between T-PCDE and the koala; the caecal wall and the wall of the proximal colon were 'strategically' colonised by the bacterium, which may facilitate access, although it is likely to be indirect, for the host animal to the nitrogen moiety liberated from breakdown of tannin-protein complexes.

Modulation of human neutrophil adherence by oral bacteria

Polymorphonuclear neutrophils (PMNs) comprise over 90 per cent of leukocytes in the oral cavity. Although these phagocytic cells have primary defence roles in the gingiva, their stimulation by micro-organisms may also cause substantial tissue damage due to the release of lysosomal enzymes and oxygen radicals. Adherence of PMNs to the endothelium and their subsequent diapedesis and egress to areas of infection are considered early vital events in the inflammatory process. In this study, oral bacteria were screened to determine their direct effects on PMN activation using an in vitro method of measuring PMN adherence to Dacron fibres. Most of the bacteria investigated increased PMN adherence, indicating their potential to cause tissue damage through the release of PMN lysosomal enzymes and other products. In contrast, Bacteroides species suppressed PMNs, indicating their ability to circumvent the phagocytic cells, thus gaining a potential advantage in dental colonization. The modulatory effects of oral bacteria on PMN activation may have significant roles in the immunopathogenesis of oral disease.

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.

Modulation of human neutrophil adherence by periodontopathic bacteria: reversal by specific monoclonal antibodies

Previous investigations by us have shown that direct interaction of Fusobacterium nucleatum with polymorphonuclear neutrophils (PMNs) results in the stimulation of PMN adherence whereas direct interaction with Bacteroides gingivalis results in PMN suppression. In the present study, panels of monoclonal antibodies (MAbs) raised against cell wall antigens of F. nucleatum and B. gingivalis were tested to determine their ability to block the modulatory effects of the bacteria in their interactions with PMNs. While no activity was demonstrated for any of the 9 MAbs raised against F. nucleatum, it was found that 2 of 16 MAbs raised against B. gingivalis were able to reverse the suppression of PMN adherence induced by the bacteria. Further studies on these 2 reactive MAbs showed that the effect of MAbs were abrogated by heat treatment as well as by trypsin proteolysis. Investigations into the nature of the reactive epitopes on the bacterial surface showed that they probably contain protein components susceptible to proteolytic attack by subtilisin. In addition, beta-galactose may be a component of the reactive epitopes for one of the MAbs, but sialic acid residues on the bacterial surface are probably not involved as their elimination by neuraminidase did not affect the binding of both MAbs. The results of the present study strongly validate our previous observations that direct specific interaction of B. gingivalis with human PMNs occurs, resulting in the suppression of PMNs.

Interleukin-1 and interleukin-1 inhibitor production by human adherent cells stimulated with periodontopathic bacteria

This study examined the effect of the putative periodontopathic bacteria Bacteroides gingivalis and Fusobacterium nucleatum on the production of interleukin-1 (IL-1) and IL-1 inhibitors by human plastic-adherent mononuclear cells from normal donors. Fusobacterium mortiferum was used as a non-oral, non-pathogenic control organism. Unstimulated adherent cells spontaneously secreted an IL-1 inhibitor, whereas stimulation with B. gingivalis induced the synthesis and secretion of IL-1. With both fusobacteria IL-1 was present in the intracellular environment, whereas the predominant secretory product was either IL-1 or an IL-1 inhibitor. These results suggest that bacteria are capable of modulating cytokine production by monocytes and may thereby alter the local immune response.