Induction of the immune response to periodontopathic bacteria and its role in the pathogenesis of periodontitis

Advances and challenges in the development of periodontitis vaccines: A comprehensive review

Periodontitis is a prevalent polymicrobial disease. It damages soft tissues and alveolar bone, and causes a significant public-health burden. Development of an advanced therapeutic approach and exploration of vaccines against periodontitis hold promise as potential treatment avenues. Clinical trials for a periodontitis vaccine are lacking. Therefore, it is crucial to address the urgent need for developing strategies to implement vaccines at the primary level of prevention in public health. A deep understanding of the principles and mechanisms of action of vaccines plays a crucial role in the successful development of vaccines and their clinical translation. This review aims to provide a comprehensive summary of potential directions for the development of highly efficacious periodontitis vaccines. In addition, we address the limitations of these endeavors and explore future possibilities for the development of an efficacious vaccine against periodontitis.

Regulation of the Host Immune Microenvironment in Periodontitis and Periodontal Bone Remodeling

The periodontal immune microenvironment is a delicate regulatory system that involves a variety of host immune cells including neutrophils, macrophages, T cells, dendritic cells and mesenchymal stem cells. The dysfunction or overactivation of any kind of local cells, and eventually the imbalance of the entire molecular regulatory network, leads to periodontal inflammation and tissue destruction. In this review, the basic characteristics of various host cells in the periodontal immune microenvironment and the regulatory network mechanism of host cells involved in the pathogenesis of periodontitis and periodontal bone remodeling are summarized, with emphasis on the immune regulatory network that regulates the periodontal microenvironment and maintains a dynamic balance. Future strategies for the clinical treatment of periodontitis and periodontal tissue regeneration need to develop new targeted synergistic drugs and/or novel technologies to clarify the regulatory mechanism of the local microenvironment. This review aims to provide clues and a theoretical basis for future research in this field.

Stem cell microencapsulation maintains stemness in inflammatory microenvironment

Maintaining the stemness of the transplanted stem cell spheroids in an inflammatory microenvironment is challenging but important in regenerative medicine. Direct delivery of stem cells to repair periodontal defects may yield suboptimal effects due to the complexity of the periodontal inflammatory environment. Herein, stem cell spheroid is encapsulated by interfacial assembly of metal-phenolic network (MPN) nanofilm to form a stem cell microsphere capsule. Specifically, periodontal ligament stem cells (PDLSCs) spheroid was coated with Fe^III/tannic acid coordination network to obtain spheroid@[Fe^III-TA] microcapsules. The formed biodegradable MPN biointerface acted as a cytoprotective barrier and exhibited antioxidative, antibacterial and anti-inflammatory activities, effectively remodeling the inflammatory microenvironment and maintaining the stemness of PDLSCs. The stem cell microencapsulation proposed in this study can be applied to multiple stem cells with various functional metal ion/polyphenol coordination, providing a simple yet efficient delivery strategy for stem cell stemness maintenance in an inflammatory environment toward a better therapeutic outcome.

Downregulation of Matriptase Inhibits Porphyromonas gingivalis Lipopolysaccharide-Induced Matrix Metalloproteinase-1 and Proinflammatory Cytokines by Suppressing the TLR4/NF-κB Signaling Pathways in Human Gingival Fibroblasts

Matriptases are cell surface proteolytic enzymes belonging to the type II transmembrane serine protease family that mediate inflammatory skin disorders and cancer progression. Matriptases may affect the development of periodontitis via protease-activated receptor-2 activity. However, the cellular mechanism by which matriptases are involved in periodontitis is unknown. In this study, we examined the antiperiodontitis effects of matriptase on Porphyromonas gingivalis-derived lipopolysaccharide (PG-LPS)-stimulated human gingival fibroblasts (HGFs). Matriptase small interfering RNA-transfected HGFs were treated with PG-LPS. The mRNA and protein levels of proinflammatory cytokines and matrix metalloproteinase 1 (MMP-1) were evaluated using the quantitative real-time polymerase chain reaction (qRT-PCR) and an enzyme-linked immunosorbent assay (ELISA), respectively. Western blot analyses were performed to measure the levels of Toll-like receptor 4 (TLR4)/interleukin-1 (IL-1) receptor-associated kinase (IRAK)/transforming growth factor β-activated kinase 1 (TAK1), p65, and p50 in PG-LPS-stimulated HGFs. Matriptase downregulation inhibited LPS-induced proinflammatory cytokine expression, including the expression of IL-6, IL-8, tumor necrosis factor-α (TNF-α), and IL-Iβ. Moreover, matriptase downregulation inhibited PG-LPS-stimulated MMP-1 expression. Additionally, we confirmed that the mechanism underlying the effects of matriptase downregulation involves the suppression of PG-LPS-induced IRAK1/TAK1 and NF-κB. These results suggest that downregulation of matriptase PG-LPS-induced MMP-1 and proinflammatory cytokine expression via TLR4-mediated IRAK1/TAK1 and NF-κB signaling pathways in HGFs.

The Ability of a Novel Trypsin-like Peptidase Activity Assay Kit to Detect Red-Complex Species

The trypsin-like peptidase activity assay kit measures the trypsin-like protease produced by three red-complex species, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola, causing periodontitis, and detects the presence of these bacteria in samples. The purpose of this study was to investigate the relationship between the detection of TLPs by a novel TLP-AA, ADCHECK and the detection of red-complex pathogens by real-time PCR using tongue swabs from patients with periodontitis. The detection limit of trypsin-like protease activity by ADCHECK was validated using the culture supernatants of two different Porphyromonas gingivalis bacterial strains. Real-time PCR was performed to determine the number of red-complex species in the tongue coatings of patients with periodontal disease. Trypsin-like protease activity in tongue-swab samples was scored using ADCHECK. ADCHECK successfully detected trypsin-like protease activity in 103 Porphyromonas gingivalis bacterial strains. The specificity, positive predictive value, negative predictive value, and accuracy of ADCHECK for the presence of red-complex pathogens determined by real-time PCR were 90%, 97%, 98%, and 92%, respectively. ADCHECK is an effective tool for the detection of red-complex pathogens.

Antimicrobial Activity of Roselle-capped​ Silver​ Nanochip on Aggregatibacter actinomycetemcomitans

OBJECTIVES

 This article aimed to study the effects of the​ roselle-capped​ silver​ nanochip​ ​(SNP-Ro​ chip)​ against Aggregatibacter actinomycetemcomitans, and the toxicity of this film on fibroblast cells to develop this SNP-Ro chip into a local chemical for the treatment of periodontitis in the future.

MATERIALS AND METHODS

 Using a microwave-assisted synthesis method, silver​ nanoparticles (SNPs) were prepared from a silver nitrate solution and roselle extract as a reducing and capping agent. Then, SNP-Ro chips were fabricated by mixing a solution of SNP-Ro with alginate gel. The antimicrobial effect of the synthesized SNP-Ro chips was performed by the disc diffusion technique and time kill assay. The cytotoxic effect was also determined by the MTS assay.

STATISTICAL ANALYSIS

 One-way analysis of variance (ANOVA) and Scheffe's method were used to analyze the data for this experiment.

RESULTS

 All three ratios of the SNP-Ro chip produced inhibition zones ranging between 18.75 ± 2.08 and 19.03 ± 2.25 mm. In studying the killing time, the three groups of the SNP-Ro chips completely eradicated A. actinomycetemcomitans within 180 minutes. The percentage of the viable SNP-Ro chip-treated human gingival fibroblasts (HGFs) were significantly increased when compared with the alginate chip-treated cells (p < 0.05).

CONCLUSION

 This study developed a new method for the deposition of SNPs in alginate gel to make a thin small chip for the sustained release of the SNPs in a periodontal lesion. Therefore, the SNP-Ro chip has the potential to be developed as an adjunctive locally delivered antimicrobial agent in periodontal therapy.

The Role of Alcohol, LPS Toxicity, and ALDH2 in Dental Bony Defects

It is estimated that 560 million people carry an East Asian-specific ALDH2*2 dominant-negative mutation which leads to enzyme inactivation. This common ALDH2 polymorphism has a significant association with osteoporosis. We hypothesized that the ALDH2*2 mutation in conjunction with periodontal Porphyromonas gingivalis bacterial infection and alcohol drinking had an inhibitory effect on osteoblasts and bone regeneration. We examined the prospective association of ALDH2 activity with the proliferation and mineralization potential of human osteoblasts in vitro. The ALDH2 knockdown experiments showed that the ALDH2 knockdown osteoblasts lost their proliferation and mineralization capability. To mimic dental bacterial infection, we compared the dental bony defects in wild-type mice and ALDH2*2 knockin mice after injection with purified lipopolysaccharides (LPS), derived from P. gingivalis which is a bacterial species known to cause periodontitis. Micro-computed tomography (micro-CT) scan results indicated that bone regeneration was significantly affected in the ALDH2*2 knockin mice with about 20% more dental bony defects after LPS injection than the wild-type mice. Moreover, the ALDH2*2 knockin mutant mice had decreased osteoblast growth and more dental bone loss in the upper left jaw region after LPS injection. In conclusion, these results indicated that the ALDH2*2 mutation with alcohol drinking and chronic exposure to dental bacterial-derived toxin increased the risk of dental bone loss.

The contribution of Tannerella forsythia dipeptidyl aminopeptidase IV in the breakdown of collagen

In this study, we characterized a serine protease from Tannerella forsythia that degrades gelatin, type I, and III collagen. Tannerella forsythia is associated with periodontitis progression and severity. The primary goal of this research was to understand the mechanisms by which T. forsythia contributes to periodontitis progression. One of our previous metatranscriptomic analysis revealed that during periodontitis progression T. forsythia highly expressed the bfor_1659 ORF. The N-terminal end is homologous to dipeptidyl aminopeptidase IV (DPP IV). DPP IV is a serine protease that cleaves X-Pro or X-Ala dipeptide from the N-terminal end of proteins. Collagen type I is rich in X-Pro and X-Ala sequences, and it is the primary constituent of the periodontium. This work assessed the collagenolytic and gelatinolytic properties of BFOR_1659. To that end, the complete BFOR_1659 and its domains were purified as His-tagged recombinant proteins, and their collagenolytic activity was tested on collagen-like substrates, collagen type I and III combined, and on the extracellular matrix (ECM) formed on human gingival fibroblasts culture HGF-1. BFOR_1659 was only found in T. forsythia supernatants, highlighting its potential role on the pathogenicity of T. forsythia. We also found that BFOR_1659 efficiently degrades all tested substrates but the individual domains were inactive. Given that BFOR_1659 is highly expressed in the periodontal pocket, its clinical relevance is suggested to periodontitis progression.

Humoral immune responses to periodontal pathogens in the elderly

PURPOSE

Elderly people are thought to be more susceptible to periodontal disease due to reduced immune function associated with aging. However, little information is available on the nature of immune responses against putative periodontal pathogens in geriatric patients. The purpose of this study was to evaluate the serum IgG antibody responses to six periodontal pathogens in geriatric subjects.

METHODS

The study population consisted of 85 geriatric patients and was divided into three groups: 29 mild (MCP), 27 moderate (MoCP) and 29 severe (SCP) chronic periodontitis patients. Serum levels of IgG antibody to Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum and Prevotella intermedia were measured by enzyme-linked immunosorbent assay (ELISA) and compared among the groups.

RESULTS

All three groups showed levels of serum IgG in response to P. gingivalis, A. actinomycetemcomitans, and P. intermedia that were three to four times higher than levels of IgG to T. forsythia, T. denticola, and F. nucleatum. There were no significant differences among all three groups in IgG response to P. gingivalis (P=0.065), T. forsythia (P=0.057), T. denticola (P=0.1), and P. intermedia (P=0.167), although the IgG levels tended to be higher in patients with SCP than in those with MCP or MoCP (with the exception of those for P. intermedia). In contrast, there were significant differences among the groups in IgG levels in response to F. nucleatum (P=0.001) and A. actinomycetemcomitans (P=0.003). IgG levels to A. actinomycetemcomitans were higher in patients with MCP than in those with MoCP or SCP.

CONCLUSIONS

When IgG levels were compared among three periodontal disease groups, only IgG levels to F. nucleatum significantly increased with the severity of disease. On the contrary, IgG levels to A. actinomycetemcomitans decreased significantly in patients with SCP compared to those with MCP. There were no significant differences in the IgG levels for P. gingivalis, T. forsythia, T. denticola, and P. intermedia among geriatric patients with chronic periodontitis.

The Association Between Periodontal Inflammation and Labor Triggers (Elevated Cytokine Levels) in Preterm Birth: A Cross-Sectional Study

BACKGROUND

Periodontitis is considered to be a risk factor for preterm birth. Mechanisms have been proposed for this pathologic relation, but the exact pathologic pattern remains unclear. Therefore, the objective of the present study is to evaluate levels of four major labor triggers, prostaglandin E2 (PGE2), interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, in gingival crevicular fluid (GCF) and serum samples between women with preterm birth (PTB) and full-term birth (FTB) and correlate them with periodontal parameters.

METHODS

PGE2, IL-1β, IL-6, and TNF-α levels were estimated using enzyme-linked immunosorbent assays in GCF and serum samples collected 24 to 48 hours after labor from 120 women (60 FTB, 60 PTB).

RESULTS

Women with PTB exhibited significantly more periodontitis, worse periodontal parameters, and increased GCF levels of IL-6 and PGE2 compared with the FTB group; there were no significant differences in serum levels of measured markers. GCF levels of IL-1β, IL-6, and PGE2 and serum levels of TNF-α and PGE2 were significantly higher in women with periodontitis compared with periodontally healthy women. Serum levels of PGE2 were positively correlated with probing depth (PD) and clinical attachment level (CAL) as well as with GCF levels of TNF-α in women with PTB.

CONCLUSIONS

Women with PTB demonstrated worse periodontal parameters and significantly increased GCF levels of IL-6 and PGE2 compared with those with FTB. Based on significant correlations among serum PGE2 and PD, CAL, and GCF TNF-α in PTB, periodontitis may cause an overall increase of labor triggers and hence contribute to preterm labor onset.

Level of Interleukin-35 in Gingival Crevicular Fluid, Saliva, and Plasma in Periodontal Disease and Health

BACKGROUND

A novel member of the interleukin (IL)-12 family, IL-35 is an important inhibitory cytokine released by regulatory T cells. The aim of this study is to evaluate gingival crevicular fluid (GCF), saliva, and plasma levels of IL-35 in periodontal disease and health.

METHODS

Samples of GCF, whole saliva, and plasma were obtained from systemically healthy, non-smoking individuals with gingivitis (n = 20) or chronic periodontitis (CP) (n = 20) and periodontally healthy individuals (n = 20). Full-mouth clinical periodontal measurements, including probing depth (PD), bleeding on probing, gingival index, and plaque index (PI), were also recorded. Enzyme-linked immunosorbent assay was used to determine IL-35 levels in the samples. Data were tested statistically by analysis of variance and Pearson rank correlation test.

RESULTS

All clinical parameters were significantly higher in the CP group than the healthy and gingivitis groups (P <0.001). The GCF total amount of IL-35 was significantly higher in the CP group than the other groups (P = 0.04), whereas the GCF concentration of IL-35 was significantly higher in the healthy group than the other groups (P = 0.002). There were significant differences among the study groups in terms of salivary IL-35 level (P <0.001), with the highest level observed in the healthy group and the lowest in the CP group. There was no statistical difference between groups in plasma levels of IL-35 (P >0.05). There was a positive correlation between GCF total amount of IL-35 and PD (r = 0.338, P = 0.03) and PI (r = 0.374, P = 0.005) parameters.

CONCLUSIONS

IL-35 could have an important role in suppressing periodontal inflammation and maintaining periodontal health. Additional studies are required to evaluate its role in periodontal diseases.

IL-17 and IL-11 GCF levels in aggressive and chronic periodontitis patients: relation to PCR bacterial detection

Objectives. This study evaluated IL-17 and IL-11 in gingival crevicular fluid (GCF) of generalized chronic periodontitis (GCP) and generalized aggressive periodontitis (GAgP) patients in relation to periodontopathic bacteria. Subjects and Methods. GCF samples were collected from 65 subjects including 25 CP, 25 GAgP, and 15 controls (C) and analyzed for IL-17 and IL-11 by an enzyme-linked immunosorbent assay. Molecular detection of bacteria in the dental plaque was determined by polymerase chain reaction. Results. The total amount of IL-17 was significantly higher in GAgP group than in GCP and C groups (P < 0.001). The IL-11 concentration was significantly higher in C and GCP groups than GAgP group (P < 0.001). The IL-11/IL-17 ratio was significantly higher in the C group than in GCP and GAgP groups (P < 0.05). Moreover, GAgP group showed lower ratios of IL-11/IL-17 when compared to GCP group. The high positivity of P. gingivalis in the dental plaque was associated with significantly increased GCF levels of IL-17 in GCP and GAgP patients. Conclusions. The increased IL-17 level in GCF of GAgP suggests a potential role in the aetiopathogenesis. Meanwhile, the decreased ratio of IL-11/IL-17 might reflect an imbalance between the proinflammatory and anti-inflammatory cytokines in different periodontal diseases.

A review of C-reactive protein: A diagnostic indicator in periodontal medicine

Periodontitis is a local inflammatory process mediating the destruction of periodontal tissues, triggered by bacterial insult. Recent evidence suggests the presence of chronic inflammatory periodontal disease may significantly affect systemic health conditions such as coronary heart disease, stroke, or adverse pregnancy outcome. C-reactive protein (CRP) is an acute phase protein which reflects a measure of the acute phase response. CRP is used as one of the markers of choice in monitoring the acute phase response because it increases to a relatively high concentration compared to basal concentration. CRP has been shown to predict cardiovascular (CV) mortality in recent studies, and elevated CRP levels have been observed in middle-aged patients with periodontitis. Combination of chronic infections like periodontitis with elevated CRP is associated with higher chronic heart diseases. The recognition of the relationship between periodontal diseases and atherosclerotic events is relatively recent and mostly based on the inflammatory hypothesis of atherosclerosis. Periodontal disease is one of the risk factors for cardiovascular disease and possibly one of its causes. Hence, even associations of modest magnitude have a large impact. The cost to the society directly attributable to atherosclerotic sequelae is very large. Periodontitis is treatable; moreover, it is preventable. Experimental conformation of this shows that another widely prevalent and preventable contributor to the burden of cardiovascular disease would be added to the options available of the clinicians and public health practitioners for the control of the epidemic of cardiovascular disease.

Serum cytokine levels in periodontitis patients in relation to the bacterial load

BACKGROUND

Periodontitis is a local inflammatory disease that also has some systemic effects. We investigated the levels of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and interleukin (IL)-2, -4, -5, and -10 in the serum of patients with periodontitis in relation to the bacterial load in the dental plaques.

METHODS

Serum cytokine levels in patients with generalized periodontitis and healthy control groups were determined using the cytometric bead array kit. Bacterial load in the dental plaque was determined semiquantitatively by real-time polymerase chain reaction. The proportions of different lymphocyte subsets were determined in the peripheral blood of patients with periodontitis by flow cytometry. Finally, relationships between the bacterial load in the subgingival plaques of patients with periodontitis and levels of cytokines and counts of lymphocyte subsets were established.

RESULTS

Serum levels of IFN-γ, TNF-α, and IL-10 were significantly increased, whereas those of IL-2 were significantly decreased in patients with periodontitis compared to healthy controls. Increased serum levels of IFN-γ and TNF-α in patients with periodontitis were associated with the enhanced dental plaque load with Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) and Porphyromonas gingivalis, respectively. Finally, as revealed by analysis of lymphocyte populations, the presence of A. actinomycetemcomitans and Trepomena denticola was associated with an increased population of CD3(-)/CD16(+) and CD3(+)/CD8(+) cells, respectively.

CONCLUSION

Certain periodontal pathogens could be associated with an increased level of proinflammatory cytokines in the peripheral blood and thus increased risk of systemic diseases.

Activation of the neutrophil respiratory burst by plasma from periodontitis patients is mediated by pro-inflammatory cytokines

AIM

To determine the effect of periodontitis patients' plasma on the neutrophil oxidative burst and the role of albumin, immunoglobulins (Igs) and cytokines.

MATERIALS AND METHODS

Plasma was collected from chronic periodontitis patients (n=11) and periodontally healthy controls (n=11) and used with/without depletion of albumin and Ig or antibody neutralization of IL-8, GM-CSF or IFN-α to prime/stimulate peripheral blood neutrophils, isolated from healthy volunteers. The respiratory burst was measured by lucigenin-dependent chemiluminescence. Plasma cytokine levels were determined by ELISA.

RESULTS

Plasmas from patients were significantly more effective in both directly stimulating neutrophil superoxide production and priming for subsequent formyl-met-leu-phe (fMLP)-stimulated superoxide production than plasmas from healthy controls (p<0.05). This difference was maintained after depletion of albumin and Ig. Plasma from patients contained higher mean levels of IL-8, GM-CSF and IFN-α. Individual neutralizing antibodies against IL-8, GM-CSF or IFN-α inhibited the direct stimulatory effect of patients' plasma, whereas the ability to prime for fMLP-stimulated superoxide production was only inhibited by neutralization of IFN-α. The stimulating and priming effects of control plasma were unaffected by antibody neutralization.

CONCLUSIONS

This study demonstrates that plasma cytokines may have a role in inducing the hyperactive (IL-8, GM-CSF, IFN-α) and hyper-reactive (IFN-α) neutrophil phenotype seen in periodontitis patients.

Identification of immunological parameters associated with the alveolar bone level in periodontal patients

Purpose

The present study was performed to clarify the relationship between periodontal disease severity and selected immunological parameters consisting of serum IgG titer against periodontopathogenic bacteria, the expression of the helper T-cell cytokine by gingival mononuclear cells, and patients' immunoreactivity to cross-reactive heat shock protein (HSP) epitope peptide from P. gingivalis HSP60.

Methods

Twenty-five patients with moderate periodontitis had their gingival connective tissue harvested of gingival mononuclear cells during an open flap debridement procedure and peripheral blood was drawn by venipuncture to collect serum. The mean level of interproximal alveolar bone was calculated to be used as an index for periodontal disease severity for a given patient. Each of selected immunologic parameters was subject to statistical management to seek their correlations with the severity of periodontal disease.

Results

A significant correlation could not be identified between serum IgG titers against specific bacteria (Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans, and Streptococcus mutans) and the severity of periodontal disease. Expression of interleukin (IL)-10 by gingival mononuclear cells was statistically significant in the group of patients who had higher levels of alveolar bone height. However, a similar correlation could not be demonstrated in cases for IL-4 or interferon-γ. Patients' serum reactivity to cross-reactive epitope peptide showed a significant correlation with the amount of alveolar bone.

Conclusions

It was concluded that expression of IL-10 by gingival mononuclear cells and patients' sero-reactivity to the cross-reactive HSP peptide of P. gingivalis HSP60 were significantly correlated with alveolar bone height.

Temporal association of elevated C-reactive protein and periodontal disease in men

BACKGROUND

Most studies on the relationship between serum C-reactive protein (CRP) and periodontal disease have been cross-sectional. In this study, we investigated the temporal association between CRP and periodontal disease by following a large number of subjects for 1 year.

METHODS

We studied 11,162 men in Nagoya, Japan, who had an initial dental examination as part of a complete physical examination and then underwent the same examination 1 year later. For the 4,997 men without periodontal disease at baseline, logistic regression analysis was performed to examine the relationship between baseline CRP and periodontal disease 1 year later, adjusting for age, body mass index, glycosylated hemoglobin A1c level, and smoking status. Similarly, logistic regression analysis was performed to examine the relationship between periodontal disease at baseline and CRP 1 year later for the 10,376 men with normal baseline CRP, adjusting for the same confounding factors.

RESULTS

Among men without high CRP at baseline, periodontal disease at baseline correlated to CRP 1 year later. The odds ratio was 1.336 (95% confidence interval [CI]: 1.115 to 1.674). However, in the men without periodontal disease, no significant correlations were seen with baseline CRP or periodontal disease 1 year later. The odds ratio was 1.163 (95% CI: 0.894 to 1.513).

CONCLUSION

Periodontal disease increased the risk for high serum CRP levels in men after 1 year of follow-up.

Microarray analysis of nicotine-induced changes in gene expression in a macrophage-like human cell line

BACKGROUND AND OBJECTIVE

Cigarette smoking has been suggested as a risk factor for periodontitis. Thousands of components are present in cigarette smoke, including nicotine, which may play an important role in the observed effects of smoking on cell metabolism. However, the mechanisms underlying these effects are unclear. Using DNA microarrays, we monitored differentially expressed genes, responsive to nicotine, in a macrophage-like human cell line.

MATERIAL AND METHODS

Human U937 cells were treated for 1 h, with or without 1.0 microg/ml of nicotine. For differentiation, cultures were incubated with 10 nm phorbol myristate acetate for 48 h. Analysis of gene expression was performed using a DNA microarray of 8500 genes.

RESULTS

The expression of 4914 genes was detected. Screening was carried out on those genes whose expression in three separate experiments showed an average change of twofold or greater, and 118 up-regulated genes and 97 down-regulated genes were identified. Among these were genes related to inflammation and other immune responses, such as phospholipase A2 and interferon. Consistent with the array findings, we found similar changes in mRNA expression after analysis using the real-time polymerase chain reaction.

CONCLUSION

The results suggest that nicotine causes excess inflammation and disturbs host defense mechanisms against pathogens.

Porphyromonas gingivalis antagonises Campylobacter rectus induced cytokine production by human monocytes

Porphyromonas gingivalis and Campylobacter rectus are two major bacterial species implicated in the pathogenesis of periodontitis. P. gingivalis can antagonise the inflammatory response to other periodontal pathogens, a property commonly attributed to its lipopolysaccharide (LPS). The aim of this study was to investigate the capacity of P. gingivalis to antagonise C. rectus induced cytokine stimulation from human monocytes, and to investigate the involvement of its LPS. Primary human monocytes and Monomac-6 cells were challenged with culture supernatants from P. gingivalis and C. rectus, and levels of IL-1beta, IL-6 and IL-8 produced were measured by ELISA after 6h incubation. Purified P. gingivalis LPS was also added alone or in combination with C. rectus culture supernatant. Both species significantly stimulated the production of all three cytokines from the two cell lines, but P. gingivalis was considerably weaker inducer. Co-stimulation of the cells with P. gingivalis and C. rectus suppressed the cytokine-stimulatory capacity of the latter. P. gingivalis LPS alone was sufficient to antagonise IL-6 and IL-8, but not IL-1beta stimulation by C. rectus. In conclusion, mixed infections may impair host immune responses by reducing pro-inflammatory cytokine levels, which may be of relevance to the pathogenesis of periodontitis.

Destructive periodontitis lesions are determined by the nature of the lymphocytic response

It is now 35 years since Brandtzaeg and Kraus (1965) published their seminal work entitled "Autoimmunity and periodontal disease". Initially, this work led to the concept that destructive periodontitis was a localized hypersensitivity reaction involving immune complex formation within the tissues. In 1970, Ivanyi and Lehner highlighted a possible role for cell-mediated immunity, which stimulated a flurry of activity centered on the role of lymphokines such as osteoclast-activating factor (OAF), macrophage-activating factor (MAF), macrophage migration inhibition factor (MIF), and myriad others. In the late 1970s and early 1980s, attention focused on the role of polymorphonuclear neutrophils, and it was thought that periodontal destruction occurred as a series of acute exacerbations. As well, at this stage doubt was being cast on the concept that there was a neutrophil chemotactic defect in periodontitis patients. Once it was realized that neutrophils were primarily protective and that severe periodontal destruction occurred in the absence of these cells, attention swung back to the role of lymphocytes and in particular the regulatory role of T-cells. By this time in the early 1990s, while the roles of interleukin (IL)-1, prostaglandin (PG) E(2), and metalloproteinases as the destructive mediators in periodontal disease were largely understood, the control and regulation of these cytokines remained controversial. With the widespread acceptance of the Th1/Th2 paradigm, the regulatory role of T-cells became the main focus of attention. Two apparently conflicting theories have emerged. One is based on direct observations of human lesions, while the other is based on animal model experiments and the inability to demonstrate IL-4 mRNA in gingival extracts. As part of the "Controversy" series, this review is intended to stimulate debate and hence may appear in some places provocative. In this context, this review will present the case that destructive periodontitis is due to the nature of the lymphocytic infiltrate and is not due to periodic acute exacerbations, nor is it due to the so-called virulence factors of putative periodontal pathogens.

The RgpB C-terminal domain has a role in attachment of RgpB to the outer membrane and belongs to a novel C-terminal-domain family found in Porphyromonas gingivalis

Porphyromonas gingivalis produces outer membrane-attached proteins that include the virulence-associated proteinases RgpA and RgpB (Arg-gingipains) and Kgp (Lys-gingipain). We analyzed the P. gingivalis outer membrane proteome and identified numerous proteins with C-terminal domains similar in sequence to those of RgpB, RgpA, and Kgp, indicating that these domains may have a common function. Using RgpB as a model to investigate the role of the C-terminal domain, we expressed RgpB as a full-length zymogen (recombinant RgpB [rRgpB]), with a catalytic Cys244Ala mutation [rRgpB(C244A)], or with the C-terminal 72 amino acids deleted (rRgpB435) in an Arg-gingipain P. gingivalis mutant (YH522AB) and an Arg- and Lys-gingipain mutant (YH522KAB). rRgpB was catalytically active and located predominantly attached to the outer membrane of both background strains. rRgpB(C244A) was inactive and outer membrane attached, with a typical attachment profile for both background strains according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but in YH522KAB, the prodomain was not removed. Thus, in vivo, RgpB export and membrane attachment are independent of the proteolytic activity of RgpA, RgpB, or Kgp. However, for maturation involving proteolytic processing of RgpB, the proteolytic activity of RgpB, RgpA, or Kgp is required. The C-terminally-truncated rRgpB435 was not attached to the outer membrane and was located as largely inactive, discrete 71-kDa and 48-kDa isoforms in the culture supernatant and the periplasm. These results suggest that the C-terminal domain is essential for outer membrane attachment and may be involved in a coordinated process of export and attachment to the cell surface.

Innate immune signaling and Porphyromonas gingivalis-accelerated atherosclerosis

Periodontal diseases are a group of diseases that lead to erosion of the hard and soft tissues of the periodontium, which, in severe cases, can result in tooth loss. Anecdotal clinical observations have suggested that poor oral health may be associated with poor systemic health; however, only recently have appropriate epidemiological studies been initiated, with defined clinical endpoints of periodontal disease, to address the association of periodontal disease with increased risk for cardiovascular and cerebrovascular disease. Although conflicting reports exist, these epidemiological studies support this connection. Paralleling these epidemiological studies, emerging basic scientific studies also support that infection may represent a risk factor for atherosclerosis. With P. gingivalis as a model pathogen, in vitro studies support that this organism can activate host innate immune responses associated with atherosclerosis, and in vivo studies demonstrate that this organism can accelerate atheroma deposition in animal models. In this review, we focus primarily on the basic scientific studies performed to date which support that infection with bacteria, most notably P. gingivalis, accelerates atherosclerosis. Furthermore, we attempt to bring together these studies to provide an up-to-date framework of emerging theories into the mechanisms underlying periodontal disease and increased risk for atherosclerosis, as well as identify intervention strategies to reduce the incidence of periodontal disease in humans, in an attempt to decrease risk for systemic complications of periodontal disease such as atherosclerotic cardiovascular disease.

Clinical effects of scaling and root planing on untreated teeth

OBJECTIVE

The aim of this report is to examine whether scaling and root planing (SRP) in one area of the mouth may affect periodontal improvement in untreated areas in the same patient, possibly through systemic effects of treatment.

MATERIAL AND METHODS

Twenty patients diagnosed with generalized aggressive periodontitis were randomized into treatment (n=11) and no treatment (n=9) groups. Within the treatment group, three quadrants were treated by SRP at week 0, 3, 12, and 24, while a single experimental quadrant remained untreated throughout the study. The outcome for all teeth was assessed using clinical parameters, subtraction radiography, and pathogenic bacteria levels in the subgingival flora over the 24-week study period.

RESULTS

Compared with sites in no treatment patients, the treated sites in the treated patients showed a 1 mm decrease in probing depth (PD) (p<0.01) and a 0.5 mm increase in bone height (p<0.01) by 24 weeks. In untreated sites within treated subjects, however, PDs tended to improve (p=0.09) but at a reduced rate compared with treated sites. The levels of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis (Bacteroides forsythus) remained unchanged in untreated sites while levels of Prevetolla intermedia and Treponema denticola tended to decrease as compared with controls but did not reach significance.

CONCLUSIONS

This study indicates that untreated sites in treated periodontitis patients show a trend towards clinical improvement and exhibit reductions in some but not all periodontopathic bacterial species tested.

Levels of Cytokine Receptor Activator of Nuclear Factor κB Ligand in Gingival Crevicular Fluid in Untreated Chronic Periodontitis Patients

BACKGROUND

Receptor activator of nuclear factor kappaB ligand (RANK-L) is a cytokine involved in the regulation of osteoclastogenesis in bone remodeling and inflammatory osteolysis. One of the major causes of tooth loss in humans is bone destruction. The aim of our study was to determine the presence of RANK-L in gingival crevicular fluid (GCF) samples from adult patients with untreated chronic periodontitis and in healthy controls. We also identified the RANK-L present in lesions undergoing episodic attachment loss from GCF.

METHODS

GCF samples were collected from two periodontally affected sites (probing depth > or = 5 mm, attachment loss > or = 3 mm) in 20 patients (N = 40). After monitoring for 4 months, seven patients showed active periodontal disease, and GCF samples were collected from one active and one inactive site (N = 14 samples). The comparison with healthy controls was carried out by collecting GCF samples from 12 healthy volunteers (N = 24 samples). GCF was collected using a paper strip, and enzyme-linked immunosorbent assay (ELISA) was performed to determine the total amount of RANK-L.

RESULTS

RANK-L was found in a higher proportion (85%) of samples from patients than from controls (46%). The total amount of RANK-L was significantly higher in patients (115.53 +/- 78.18 picograms [pg]) than in healthy subjects (63.08 +/- 55.08 pg) (P = 0.003). Active sites, presumably associated with tissue destruction, had significantly higher levels of RANK-L than their inactive counterparts (125.95 pg versus 91.80 pg, P = 0.007).

CONCLUSION

GCF total amount of RANK-L is significantly increased in periodontal disease, supporting its role in the alveolar bone loss developed in this disease.

Lasers for initial periodontal therapy

With a greater understanding of the components that initiate the host into the downward spiral of periodontal disease, the clinician must look for better treatment and therapy options. Clinical observations and studies show good results, making incorporation of the laser into the first phase of nonsurgical periodontal therapy an excellent choice.

Lipopolysaccharide from the periodontal pathogen Porphyromonas gingivalis prevents apoptosis of HL60-derived neutrophils in vitro

Lipopolysaccharide (LPS) from Porphyromonas gingivalis prevented apoptosis of HL60-derived neutrophils, which could not be restored upon the addition of interleukin-10. Signaling of P. gingivalis LPS through Toll-like receptor 2 (TLR2), not TLR4, may account for the inhibiting effect of P. gingivalis LPS on apoptosis and provide a mechanism for the development of destructive periodontal inflammation.

Position Paper: Diagnosis of Periodontal Diseases

At the present time, the diagnosis and classification of periodontal diseases are almost entirely based on traditional clinical assessments. Supplemental quantitative and qualitative assessments of the gingival crevicular fluid and subgingival microflora can potentially provide useful information about the patient's periodontal disease. In certain situations, these supplemental risk-assessment tests may be particularly valuable in establishing the endpoint of therapy prior to placing patients on a periodontal maintenance program. Although the clinical utility of none of these tests has been validated, their further development is warranted. A genetic test for susceptibility to periodontitis has become commercially available. How best to use this and future host-based tests in clinical practice remains to be determined. Probing depth and clinical attachment loss measurements obtained with periodontal probes are practical and valid methods for assessing periodontal status. Computer-linked, controlled-force electronic periodontal probes are commercially available and are currently in use by some practitioners. Many of the logistical problems associated with subtraction radiography are being overcome and this powerful diagnostic tool may soon come into widespread use. Future developments in this and other imaging techniques are likely to have a profound effect on our approach to the diagnosis of periodontal diseases.

Porphyromonas gingivalis lipopolysaccharide signaling in gingival fibroblasts-CD14 and Toll-like receptors

Periodontal disease is the major cause of adult tooth loss and is commonly characterized by a chronic inflammation caused by infection of oral bacteria. Porphyromonas gingivalis (P. gingivalis) is one of the suspected periodontopathic bacteria and is frequently isolated from the periodontal pockets of patients with chronic periodontal disease. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Gingival fibroblasts, which are the major constituents of gingival connective tissue, may directly interact with bacteria and bacterial products, including LPS, in periodontitis lesions. It is suggested that gingival fibroblasts play an important role in the host responses to LPS in periodontal disease. P. gingivalis LPS enhances the production of inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) in gingival fibroblasts. However, the receptor that binds with P. gingivalis LPS on gingival fibroblasts remained unknown for many years. Recently, it was demonstrated that P. gingivalis LPS binds to gingival fibroblasts. It was also found that gingival fibroblasts express CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation primary response gene 88 (MyD88). P. gingivalis LPS treatment of gingival fibroblasts activates several intracellular proteins, including protein tyrosine kinases, and up-regulates the expression of monocyte chemoattractant protein-1 (MCP-1), extracellular signal-regulated kinase 1 (ERK1), and signal-regulated kinase 2 (ERK2), IL-1 receptor-associated kinase (IRAK), nuclear factor-kappaB (NF-kappaB), and activating protein-1 (AP-1). These results suggest that the binding of P. gingivalis LPS to CD14 and TLR4 on gingival fibroblasts activates various second-messenger systems. In this article, we review recent findings on the signaling pathways induced by the binding of P. gingivalis LPS to CD14 and Toll-like receptors (TLRs) in gingival fibroblasts.

Serum antibody reactivity against recombinant PrtC of Porphyromonas gingivalis following periodontal therapy

OBJECTIVES

In 34 patients with chronic periodontitis, the presence of IgA, IgG, and IgG subclass serum antibodies against recombinant PrtC (rPrtC) of Porphyromonas gingivalis was assessed by immunoblot analysis 24 months after therapy.

METHODS

rPrtC was produced from P. gingivalis ATTC 33277 using the plasmid pGEX-2T. In addition, intraoral colonization with P. gingivalis was detected by PCR in subgingival plaque and swab samples from buccal mucosae, tonsils and tongue at baseline, 10 d, and 3, 6, 9, 12, 18, and 24 months.

RESULTS

All patients were found to harbor P. gingivalis in the oral cavity at least once during the observation period. The identified antibody responses against the rPrtC of P. gingivalis were IgA (97%, i.e. 33/34 patients) and IgG (100%, i.e. 34/34), with an IgG subclass distribution of IgG2 (65%, i.e. 22/34 patients) > IgG3 (47%, i.e. 16/34) > IgG1 (38%, i.e. 13/34) > IgG4 (29%, i.e. 10/34). Anti-rPrtC IgA and IgG antibody reactivity was found in all but one patients (anti-rPrtC IgA negative), who tested negative for P. gingivalis at all of the assessed intraoral sites for at least 6 months before sera collection. There was no association between IgG subclass reactivity against the rPrtC of P. gingivalis and progression of periodontal attachment loss.

CONCLUSION

The results indicated that anti-rPrtC IgA and IgG antibodies may serve as an indicator for past or present intraoral colonization with P. gingivalis.

Expression cloning of a periodontitis-associated apoptotic effector, cagE homologue, in Actinobacillus actinomycetemcomitans

To study anti-bacterial immunity and to identify critical bacterial antigens associated with specific periodontal infection, we screened the genomic library of Actinobacillus actinomycetemcomitans, a major Gram(-) anaerobe causing human periodontitis, by expression cloning using disease-associated periodontal CD4(+)T cells derived from HuPBL-engrafted NOD/SCID mice. Here, we report one of the novel genes identified and designated, cagE homologue (in short: cagE) of A. actinomycetemcomitans, which encodes a putative bacterial type IV secretion system with significant homology to Helicobacter pylori CagE and Agrobacterium tumefaciens VirB4. All serum samples from A. actinomycetemcomitans-infected periodontitis patients, but not from the healthy controls, readily recognized CagE by ELISA and Western blot, suggesting its biological and clinical significance. The CagE protein, upon secretion, elicited significant apoptosis on primary human epithelia, endothelia, osteoblasts, and T cells by 4-12h in vitro. Importantly, both cagE(-) mutant strain and N-terminus truncated CagE protein drastically reduced (p<0.001) the induction of apoptosis on human epithelia in vitro. These data strongly suggest that a novel effector protein, CagE in A. actinomycetemcomitans, induces apoptosis of human cells and destructive immunity, thereby it may play an important role in the pathogenesis of A. actinomycetemcomitans-mediated infections.

Serum IgG to heat shock proteins and Porphyromonas gingivalis antigens in diabetic patients with periodontitis

BACKGROUND

Past studies have reported a correlation between the presence and severity of periodontitis and serum antibody titers to species-specific antigens of Porphyromonas gingivalis or to cross-reactive antigens, such as lipopolysaccharide (LPS) and heat shock proteins (HSP), shared between P. gingivalis and other bacteria. Our recent study of periodontal treatment outcome in insulin-dependent (type 1) diabetes mellitus patients with severe periodontitis (IDDMI/periodontitis) resulted in two key findings: 1. serum glutamic acid decarboxylase autoantibody (GAD65 Ab) levels were significantly associated with periodontal pocket depth change (PDC) and 2. serum IgG titers to P. gingivalis cells were positively associated with GAD65 Ab level in seropositive (GAD65 Ab +) patients. We have therefore hypothesized that profiles of serum autoantibody levels and IgG titers, to P. gingivalis-specific antigens may be useful in assessing risk for refractory periodontitis in such patients.

AIM

To determine whether PDC resulting from non-surgical periodontal treatment can be predicted using profiles of baseline IgG titers to P. gingivalis-specific antigens, human HSP, and GAD65.

METHODS

PDC was assessed two months after non-surgical periodontal treatment of 7 GAD65 Ab + and 11 GAD65 AbIDDM/periodontitis patients. Pretreatment titers to GAD65, recombinant human heat shock proteins (HSP90, HSP70, and HSP60), and various P. gingivalis antigens were measured using radioligand precipitation or enzyme-linked immunosorbent (ELISA) assays and compared to the same measurements for 154 recent-onset IDDM patients and 46 non-diabetic controls.

RESULTS

Median titers (ELISA units) to HSP90 and HSP70 were significantly higher than non-diabetic controls for GAD65 Ab + (p degrees = 0.002) and GAD65 Ab- (p = 0.034) IDDM/periodontitis patients, respectively. Multivariate regression analysis indicated significant partial correlation of PDC with log-transformed titers to HSP90 (r = - 0.62, p = 0.008), HSP70 (r = + 0.62, p = 0.009), GAD65 (r = - 0.60, p = 0.01) and P. gingivalis LPS (r = - 0.5 1, p = 0.04). Furthermore, hierarchical clustering of baseline profiles of log-transformed HSP90, HSP70, and GAD65 Ab titers sorted patients into two distinct clusters with significantly different median PDC (1.45 min, n = 10 vs. 0.65 min, n = 8; p = 0.016, Mann-Whitney).

CONCLUSION

Pretreatment profiles of serum antibody titers to HSP90, HSP70, GAD65, and P. gingivalis LPS may be useful for predicting which patients with IDDM/periodontitis will have a poor response to non-surgical periodontal therapy.

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.

Upregulation of co-stimulatory molecule expression and dendritic cell marker (CD83) on B cells in periodontal disease

T cells and their cytokines are well known for their important role in the pathogenesis of periodontitis. To date, the role of antigen presenting cells (APCs), which are known to be critical in the regulation of T cell response, has been poorly investigated in periodontitis. In this study, we analyzed the expression of co-stimulatory molecules (CD80 and CD86) and CD83, which is a marker of mature dendritic cells, on gingival cells that were isolated from severe periodontitis tissues, with the use of flow cytometry. Significant upregulation of CD86 and CD83 expression was detected in periodontitis lesions, and most of this occurred on B cells. In vitro peripheral blood mononuclear cell cultures showed that stimulation with different periodontopathic bacteria, that included Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Actinomyces viscosus, upregulated both CD86 and CD83 expression on B cells. Therefore, the presence of plaque bacteria may be responsible for the enhanced expression seen in vivo on gingival B cells. APC function by bacterial-activated B cells was further investigated using allogeneic mixed leukocyte reactions. After 24 h culture with either A. actinomycetemcomitans or P. gingivalis, these activated B cells performed as potent APCs in mixed leukocyte reactions, and they stimulated T cells to produce high levels of gamma interferon and minimal interleukin-5. In conclusion, periodontopathic bacterial-induced B cell activation with upregulation of CD86 and CD83 may be associated with enhanced APC function. The results of this study suggest, therefore, that infiltrated gingival B cells have a possible role as APCs in the regulation and maintenance of local T cell response in periodontitis.

Modulation of the host response in periodontal therapy

This paper was prepared by the Research, Science, and Therapy Committee of the American Academy of Periodontology to provide the dental profession an overview of current and potential methods to modulate the host response in the treatment of periodontal diseases. Specifically, it discusses components of periodontal disease pathogenesis (i.e., immune and inflammatory responses, excessive production of matrix metalloproteinases and arachidonic acid metabolites, and regulation of bone metabolism) and their modulation.

Multiserotype enzyme-linked immunosorbent assay as a diagnostic aid for periodontitis in large-scale studies

Periodontitis is a common chronic oral infection caused by gram-negative bacteria, including Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. Periodontitis evokes inflammatory host response locally in the periodontium but also systemically. The systemic humoral antibody response against oral pathogens can conveniently be measured by an immunoassay. The aim of the study was to measure serum immunoglobulin G class antibodies against A. actinomycetemcomitans and P. gingivalis by an enzyme-linked immunosorbent assay (ELISA) in which mixtures of several serotypes of the pathogens were used as antigens to avoid biasing of the results in favor of a particular strain. For A. actinomycetemcomitans the antigen consisted of six strains representing serotypes a, b, c, d, and e and one nonserotypeable strain. In the P. gingivalis ELISA, antigens representing serotypes a, b, and c were used. Serum samples from 90 subjects, including 35 samples from patients with diagnosed periodontitis, 10 samples from periodontally healthy controls, and 45 samples from randomly selected apparently healthy volunteers (referred to as "healthy subjects"), were tested. For both pathogens the antibody levels (means +/- standard deviations) of the patients--xpressed as area under the dilution curve--were significantly higher than those for healthy controls or healthy subjects, with values for A. actinomycetemcomitans and P. gingivalis, respectively, as follows: patients, 22.60 +/- 9.94 mm(2) and 26.72 +/- 11.13 mm(2); healthy controls, 9.99 +/- 3.92 mm(2) and 6.90 +/- 3.38 mm(2); and healthy subjects, 16.85 +/- 6.67 mm(2) and 8.51 +/- 4.23 mm(2). The serotype mixture ELISA is suitable for measuring antibodies against periodontal pathogens in large epidemiological studies in order to evaluate the role of periodontitis as a risk factor for other diseases.