Colocalization of Porphyromonas gingivalis with CD4+ T cells in periodontal disease

Frankincense (Boswellia serrata) Extract Effects on Growth and Biofilm Formation of Porphyromonas gingivalis, and Its Intracellular Infection in Human Gingival Epithelial Cells

Frankincense is produced by Boswellia trees, which can be found throughout the Middle East and parts of Africa and Asia. Boswellia serrata extract has been shown to have anti-cancer, anti-inflammatory, and antimicrobial effects. Periodontitis is an oral chronic inflammatory disease that affects nearly half of the US population. We investigated the antimicrobial effects of B. serrata extract on two oral pathogens associated with periodontitis. Using the minimum inhibitory concentration and crystal violet staining methods, we demonstrated that Porphyromonas gingivalis growth and biofilm formation were impaired by treatment with B. serrata extracts. However, the effects on Fusobacterium nucleatum growth and biofilm formation were not significant. Using quantification of colony-forming units and microscopy techniques, we also showed that concentrations of B. serrata that were not toxic for host cells decreased intracellular P. gingivalis infection in human gingival epithelial cells. Our results show antimicrobial activity of a natural product extracted from Boswellia trees (B. serrata) against periodontopathogens. Thus, B. serrata has the potential for preventing and/or treating periodontal diseases. Future studies will identify the molecular components of B. serrata extracts responsible for the beneficial effects.

Hemophore-like proteins produced by periodontopathogens are recognized by the host immune system and react differentially with IgG antibodies

Aims

Hemophore-like proteins sequester heme from host hemoproteins. We aimed to determine whether the host immune system can recognize not only Porphyromonas gingivalis HmuY but also its homologs expressed by other periodontopathogens, and how periodontitis influences the production of respective antibodies.

Methods

The reactivity of total bacterial antigens and purified proteins with serum IgG antibodies of 18 individuals with periodontitis and 17 individuals without periodontitis was examined by enzyme-linked immunosorbent assay (ELISA). To compare IgG reactivity between groups with and without periodontitis and within the various dilutions of sera, statistical analysis was performed using the Mann-Whitney U-test and two-way ANOVA test with the post-hoc Bonferroni test.

Results

Individuals with periodontitis produced IgG antibodies reacting more strongly not only with total P. gingivalis antigens (P = 0.0002; 1:400) and P. gingivalis HmuY (P = 0.0016; 1:100) but also with Prevotella intermedia PinA (P = 0.0059; 1:100), and with low efficiency with P. intermedia PinO (P = 0.0021; 1:100). No increase in the reactivity of IgG antibodies with Tannerella forsythia Tfo and P. gingivalis HusA was found in individuals with periodontitis.

Conclusions

Although hemophore-like proteins are structurally related, they are differentially recognized by the host immune system. Our findings point to specific antigens, mainly P. gingivalis HmuY and P. intermedia PinA, whose immunoreactivity could be further investigated to develop markers of periodontitis.

An appraisal of the role of specific bacteria in the initial pathogenesis of periodontitis

BACKGROUND

Historically, inflammatory periodontal diseases (gingivitis and periodontitis) have been recognized as being primarily of bacterial origin. Bacteria are necessary for disease development, but the presence of specific bacteria does not guarantee progression to periodontitis. Periodontitis is a multifactorial disease; specific bacteria are associated with disease, but may not be the target of treatment. Gingivitis and periodontitis are inflammatory conditions associated with bacterial overgrowth.

AIM

To analyse evidence for established thought that specific bacteria directly participate in the pathogenesis of periodontitis and question the long-held tenet that penetration of the periodontal connective tissues by bacteria and their products is a significant phase in the initial development of periodontitis.

METHODS

The literature was searched for studies on initiation of gingivitis and periodontitis by specific pathogens. The search results were insufficient for a systematic review and have been summarized in a commentary instead.

RESULTS

There is very little evidence in the literature to support the commonly held concept that specific bacteria initiate periodontitis.

CONCLUSION

We present evidence for a paradigm supporting the central role of inflammation, rather than specific microbiota, in the early pathogenesis of periodontitis, and discuss whether controlling the inflammation can influence the character and composition of the periodontal infection.

Pharmacological correction of periodontitis using synthetic analogues of indolicidin

Introduction: The leading role of pathogenic microorganisms in the pathogenesis of periodontitis is beyond doubt. However, the use of antibiotics for periodontitis is associated with a number of problems. Indolicidins have a unique anti-microbial effect. The relevance of the search for new drugs for the treatment of acute periodontitis based on the natural indolicidin peptide becomes obvious.

Materials and methods: The investigation was performed on 320 Wistar male rats, using synthetic analogues of natural indolicidin: No. 7 and No. 8, which were administered intraperitoneally at a dose of 500 µg/kg in a volume of 0.2 ml once a day for 7 days. Periodontitis was simulated in animals according to the method proposed by Volozhin A.I. and Vinogradova S.I.

Results and discussion: The correcting effect of indolicidin analogues on the periodontitis course, was manifested by a decrease in edema and in the relative area of cell infiltrates, a significant increase in the relative area of normal tissue, and a correction of the periodontal composition. The use of indolicidin analogues led to an increase in the functional activity of neutrophils and macrophages, acute phase proteins concentration, a correction of pro-oxidant-antioxidant balance and production of vasoactive substances. The effect of indolicidin analogues was higher than that of lincomycin. The greater effectiveness of peptide No.8 compared to that of No.7 was established.

Conclusion: The investigation opens up the prospects of the synthesis of new antimicrobial drugs on the basis of the synthetic analogues of indolicidin.

Host modulation therapy using anti-inflammatory and antioxidant agents in periodontitis: A review to a clinical translation

OBJECTIVE

To highlight the shifting paradigm of periodontitis, describe mechanism of periodontal bone destruction, and propose an updated host modulation therapy (HMT) strategy. To add further clinical relevance, related studies investigating the efficacy of several HMT agents in periodontitis will be discussed.

DESIGN

Literature searches were conducted from articles published in PubMed using keywords "periodontal disease AND periodontitis AND host modulation therapy AND anti-inflammatory AND antioxidant", and then the findings were comprehensively summarized and elaborated.

RESULT

Accumulating evidence indicates that periodontitis is no longer defined solely as a pathogen-induced disease; rather, it is now recognized as a consequence of uncontrolled immune response and oxidative stress leading to periodontal tissue damage. Although periodontopathic bacteria initiate the disease, inflammation and oxidative stress were reported to be the main causes for the severity of tissue destruction. Thus, since the concept of periodontitis has shifted, our approach to its management needs to be adjusted to accommodate the latest paradigm. Nowadays, the modulation of inflammation and oxidative stress is considered a target of HMT. HMT agents, such as probiotics, anti-inflammatory drugs, anti-chemokines, lipid mediators, and bio-active fatty acids, have been extensively investigated for their remarkable functions in modulating the immune response and providing antioxidant effects.

CONCLUSION

Findings from in vitro, in vivo, and human studies frequently demonstrate positive association by the administration of HMT in periodontitis. HMT strategy targeted on anti-inflammatory and antioxidant in periodontitis might serve as an excellent therapeutic approach to reach the level of clinical benefit.

Porphyromonas gingivalis PgFur Is a Member of a Novel Fur Subfamily With Non-canonical Function

Porphyromonas gingivalis, a keystone pathogen of chronic periodontitis, uses ferric uptake regulator homolog (PgFur) to regulate production of virulence factors. This study aimed to characterize PgFur protein in regard to its structure-function relationship. We experimentally identified the 5′ mRNA sequence encoding the 171-amino-acid-long PgFur protein in the A7436 strain and examined this PgFur version as a full-length protein. PgFur protein did not bind to the canonical Escherichia coli Fur box, but the wild-type phenotype of the mutant Δpgfur strain was restored partially when expression of the ecfur gene was induced from the native pgfur promoter. The full-length PgFur protein contained one zinc atom per protein monomer, but did not bind iron, manganese, or heme. Single cysteine substitutions of CXXC motifs resulted in phenotypes similar to the mutant Δpgfur strain. The modified proteins were produced in E. coli at significantly lower levels, were highly unstable, and did not bind zinc. The pgfur gene was expressed at the highest levels in bacteria cultured for 24 h in the absence of iron and heme or at higher levels in bacteria cultured for 10 h in the presence of protoporphyrin IX source. No influence of high availability of Fe²⁺, Zn²⁺, or Mn²⁺ on pgfur gene expression was observed. Two chromosomal mutant strains producing protein lacking 4 (pgfurΔ4aa) or 13 (pgfurΔ13aa) C-terminal amino acid residues were examined in regard to importance of the C-terminal lysine-rich region. The pgfurΔ13aa strain showed a phenotype typical for the mutant Δpgfur strain, but both the wild-type PgFur protein and its truncated version bound zinc with similar ability. The Δpgfur mutant strain produced higher amounts of HmuY protein compared with the wild-type strain, suggesting compromised regulation of its expression. Potential PgFur ligands, Fe²⁺, Mn²⁺, Zn²⁺, PPIX, or serum components, did not influence HmuY production in the Δpgfur mutant strain. The mutant pgfurΔ4aa and pgfurΔ13aa strains exhibited affected HmuY protein production. PgFur, regardless of the presence of the C-terminal lysine-rich region, bound to the hmu operon promoter. Our data suggest that cooperation of PgFur with partners/cofactors and/or protein/DNA modifications would be required to accomplish its role played in an in vivo multilayer regulatory network.

Immunological Pathways Triggered by Porphyromonas gingivalis and Fusobacterium nucleatum: Therapeutic Possibilities?

Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) are Gram-negative anaerobic bacteria possessing several virulence factors that make them potential pathogens associated with periodontal disease. Periodontal diseases are chronic inflammatory diseases of the oral cavity, including gingivitis and periodontitis. Periodontitis can lead to tooth loss and is considered one of the most prevalent diseases worldwide. P. gingivalis and F. nucleatum possess virulence factors that allow them to survive in hostile environments by selectively modulating the host's immune-inflammatory response, thereby creating major challenges to host cell survival. Studies have demonstrated that bacterial infection and the host immune responses are involved in the induction of periodontitis. The NLRP3 inflammasome and its effector molecules (IL-1β and caspase-1) play roles in the development of periodontitis. We and others have reported that the purinergic P2X7 receptor plays a role in the modulation of periodontal disease and intracellular pathogen control. Caspase-4/5 (in humans) and caspase-11 (in mice) are important effectors for combating bacterial pathogens via mediation of cell death and IL-1β release. The exact molecular events of the host's response to these bacteria are not fully understood. Here, we review innate and adaptive immune responses induced by P. gingivalis and F. nucleatum infections and discuss the possibility of manipulations of the immune response as therapeutic strategies. Given the global burden of periodontitis, it is important to develop therapeutic targets for the prophylaxis of periodontopathogen infections.

PgFur participates differentially in expression of virulence factors in more virulent A7436 and less virulent ATCC 33277 Porphyromonas gingivalis strains

Background

Porphyromonas gingivalis is considered a keystone pathogen responsible for chronic periodontitis. Although several virulence factors produced by this bacterium are quite well characterized, very little is known about regulatory mechanisms that allow different strains of P. gingivalis to efficiently survive in the hostile environment of the oral cavity, a typical habitat characterized by low iron and heme concentrations. The aim of this study was to characterize P. gingivalis Fur homolog (PgFur) in terms of its role in production of virulence factors in more (A7436) and less (ATCC 33277) virulent strains.

Results

Expression of a pgfur depends on the growth phase and iron/heme concentration. To better understand the role played by the PgFur protein in P. gingivalis virulence under low- and high-iron/heme conditions, a pgfur-deficient ATCC 33277 strain (TO16) was constructed and its phenotype compared with that of a pgfur A7436-derived mutant strain (TO6). In contrast to the TO6 strain, the TO16 strain did not differ in the growth rate and hemolytic activity compared with the ATCC 33277 strain. However, both mutant strains were more sensitive to oxidative stress and they demonstrated changes in the production of lysine- (Kgp) and arginine-specific (Rgp) gingipains. In contrast to the wild-type strains, TO6 and TO16 mutant strains produced larger amounts of HmuY protein under high iron/heme conditions. We also demonstrated differences in production of glycoconjugates between the A7436 and ATCC 33277 strains and we found evidence that PgFur protein might regulate glycosylation process. Moreover, we revealed that PgFur protein plays a role in interactions with other periodontopathogens and is important for P. gingivalis infection of THP-1-derived macrophages and survival inside the cells. Deletion of the pgfur gene influences expression of many transcription factors, including two not yet characterized transcription factors from the Crp/Fnr family. We also observed lower expression of the CRISPR/Cas genes.

Conclusions

We show here for the first time that inactivation of the pgfur gene exerts a different influence on the phenotype of the A7436 and ATCC 33277 strains. Our findings further support the hypothesis that PgFur regulates expression of genes encoding surface virulence factors and/or genes involved in their maturation.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1511-x) contains supplementary material, which is available to authorized users.

Gingival Perfusion and Tissue Biomarkers During Early Healing of Postextraction Regenerative Procedures: A Prospective Case Series

BACKGROUND

Postextraction alveolar bone loss, mostly affecting the buccal plate, occurs despite regenerative procedures. To better understand possible determinants, this prospective case series assesses gingival blood perfusion and tissue molecular responses in relation to postextraction regenerative outcomes.

METHODS

Adults scheduled to receive bone grafting in maxillary, non-molar, single-tooth extraction sites were recruited. Clinical documentation included the following: 1) probing depth (PD); 2) keratinized tissue width (KT); 3) tissue biotype (TB); and 4) plaque level. Wound closure was clinically evaluated. Gingival blood perfusion was measured by laser Doppler flowmetry (LDF). Wound fluid (WF) and gingival biopsies were analyzed for protein levels and gene expression, respectively, of relevant molecular markers. Bone healing outcomes were determined radiographically (cone-beam computed tomography). Healing was followed for 4 months.

RESULTS

Data from 15 patients are reported. Postoperatively, neither complications nor changes in PD, KT, or TB were observed. LDF revealed decreased perfusion followed by hyperemia that persisted for 1 month (P ≤0.05). WF levels of angiopoietin-2, interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-α), and vascular endothelial growth factor peaked on day 6 (P ≤0.05) and decreased thereafter. Only IL-8 and TNF-α exhibited increased gene expression. Linear bone changes were negligible. Volumetric bone changes were minimal but statistically significant, with more bone loss when membrane was used (P = 0.05).

CONCLUSIONS

Gingival blood perfusion after postextraction bone regenerative procedures follows an ischemia-reperfusion model. Transient increases in angiogenic factor levels and prolonged hyperemia characterize the soft tissue response. These soft tissue responses do not determine radiographic bone changes.

Antimicrobial activity of stable hemiaminals against Porphyromonas gingivalis

Porphyromonas gingivalis is a major etiologic agent and a key pathogen responsible for the development and progression of chronic periodontitis. Controlling the number of periodontal pathogens is one of the primary actions for maintaining oral health; therefore, active compounds with a capacity to exert antimicrobial activity have received considerable attention as they may represent potential new therapeutic agents for the treatment of chronic periodontitis. Heterocyclic compounds possessing 1,2,4- or 1,2,3-triazoles are known for several biological activities, including antibacterial properties. Among them are stable hemiaminals which can be obtained in reaction between nitrobenzaldehyde derivatives and 4-amino-1,2,4-triazole or 4-amino-3,5-dimethyl-1,2,4-triazole. In this study, we selected two relatively stable hemiaminals: (2,4-dinitrophenyl)(4H-1,2,4-triazole-4-ylamino)methanol (24DNTAM) and (2,4-dinitrophenyl)(4H-3,5-dimethyl-1,2,4-triazole-4-ylamino)methanol (24DNDMTAM). Both compounds showed promising anti-P. gingivalis activity, higher against ATCC 33277 strain as compared to A7436 strain. The lowest hemiaminal concentration inhibiting visible planktonic bacterial growth under high-iron/heme conditions was ∼0.06 mg/ml, and the lowest hemiaminal concentration showing killing of bacteria was ∼0.25 mg/ml. Antimicrobial activity was also observed against P. gingivalis grown on blood agar plates. Slightly higher antimicrobial activity of both compounds was observed when P. gingivalis was grown in co-cultures with epithelial HeLa cells under low-iron/heme conditions, which mimic those occurring in vivo. 24DNTAM was more effective against P. gingivalis, but exhibited higher cytotoxic activity against epithelial and red blood cells, as compared with 24DNDMTAM. We conclude that both hemiaminals might originate a novel group of biologically important molecules.

Role of Porphyromonas gingivalis HmuY in Immunopathogenesis of Chronic Periodontitis

Periodontitis is a multifactorial disease, with participation of bacterial, environmental, and host factors. It results from synergistic and dysbiotic multispecies microorganisms, critical "keystone pathogens," affecting the whole bacterial community. The purpose of this study was to review the role of Porphyromonas gingivalis in the immunopathogenesis of chronic periodontitis, with special attention paid to HmuY. The host response during periodontitis involves the innate and adaptive immune system, leading to chronic inflammation and progressive destruction of tooth-supporting tissues. In this proinflammatory process, the ability of P. gingivalis to evade the host immune response and access nutrients in the microenvironment is directly related to its survival, proliferation, and infection. Furthermore, heme is an essential nutrient for development of these bacteria, and HmuY is responsible for its capture from host heme-binding proteins. The inflammatory potential of P. gingivalis HmuY has been shown, including induction of high levels of proinflammatory cytokines and CCL2, decreased levels of IL-8, and increased levels of anti-HmuY IgG and IgG1 antibodies in individuals with chronic periodontitis. Therefore, the HmuY protein might be a promising target for therapeutic strategies and for development of diagnostic methods in chronic periodontitis, especially in the case of patients with chronic periodontitis not responding to treatment, monitoring, and maintenance therapy.

Heme acquisition mechanisms of Porphyromonas gingivalis - strategies used in a polymicrobial community in a heme-limited host environment

Porphyromonas gingivalis, a main etiologic agent and key pathogen responsible for initiation and progression of chronic periodontitis requires heme as a source of iron and protoporphyrin IX for its survival and the ability to establish an infection. Porphyromonas gingivalis is able to accumulate a defensive cell-surface heme-containing pigment in the form of μ-oxo bisheme. The main sources of heme for P. gingivalis in vivo are hemoproteins present in saliva, gingival crevicular fluid, and erythrocytes. To acquire heme, P. gingivalis uses several mechanisms. Among them, the best characterized are those employing hemagglutinins, hemolysins, and gingipains (Kgp, RgpA, RgpB), TonB-dependent outer-membrane receptors (HmuR, HusB, IhtA), and hemophore-like proteins (HmuY, HusA). Proteins involved in intracellular heme transport, storage, and processing are less well characterized (e.g. PgDps). Importantly, P. gingivalis may also use the heme acquisition systems of other bacteria to fulfill its own heme requirements. Porphyromonas gingivalis displays a novel paradigm for heme acquisition from hemoglobin, whereby the Fe(II)-containing oxyhemoglobin molecule must first be oxidized to methemoglobin to facilitate heme release. This process not only involves P. gingivalis arginine- and lysine-specific gingipains, but other proteases (e.g. interpain A from Prevotella intermedia) or pyocyanin produced by Pseudomonas aeruginosa. Porphyromonas gingivalis is then able to fully proteolyze the more susceptible methemoglobin substrate to release free heme or to wrest heme from it directly through the use of the HmuY hemophore.

Relationship between invasion of the periodontium by periodontal pathogens and periodontal disease: a systematic review

Bacterial invasion of the periodontal tissues has been suggested as a relevant step in the etiopathogenesis of periodontal disease. However, its exact importance remains to be defined. The present systematic review assessed the scientific evidence concerning the relationship between the quality or quantity of periodontal microbiota in periodontal tissues and development of periodontal disease. The databases Medline-PubMed, Cochrane-CENTRAL, ISI Web of Knowledge and SCOPUS were searched, up to January 2014. Studies that reported evaluation of periodontal pathogens invasion on human tissues were selected. The screening of 440 title/abstracts elected 26 papers for full-text reading. Twenty three papers were subsequently excluded because of insufficient data or a study protocol not related to the objectives of this systematic review. All included studies were case-control studies that evaluated intracellular or adherent bacteria to epithelial cells from periodontal pockets versus healthy sulci. Study protocols presented heterogeneity regarding case and control definitions and methodological approaches for microbial identification. No consistent significant differences were found related to the presence/absence or proportion of specific periopathogens across the studies, as only one study found statistically significant differences regarding the presence of A. actinomycetemcomitans (p = 0.043), T. forsythia (P < 0.001), P. intermedia (P < 0.001), C. ochracea (P < 0.001) and C. rectus (P = 0.003) in epithelial cells from periodontal pockets vs. healthy sulci. All studies reported a larger unspecific bacterial load in or on the epithelial cells taken from a diseased site compared to a healthy sulcus. The current available data is of low to moderate quality and inconsistent mainly due to study design, poor reporting and methodological diversity. As so, there is insufficient evidence to support or exclude the invasion by periodontal pathogens as a key step in the etiopathogenesis of periodontal disease. Further research is needed.

Impact of nicotine on the interplay between human periodontal ligament cells and CD4+ T cells

Periodontitis is a common infectious disease associated with destruction of periodontal ligaments and alveolar bones. CD4(+) T cell-mediated immune response is involved in the progression of periodontitis. Tobacco consumption increases the risk of periodontal disease. However, the impact of nicotine on the interaction between human periodontal ligament (PDL) cells and CD4(+) T cells remains unrevealed. Our study aims to investigate the effect of nicotine on PDL cells and the cocultured CD4(+) T cells. The PDL cell cultures were established by explants from healthy individuals, exposed to nicotine or α-bungarotoxin (α-BTX), and incubated solely or in combination with CD4(+) T cells. Afterwards, cell viability, secreted cytokines, and matrix metalloproteinases (MMPs) were evaluated. In monoculture of PDL cells, nicotine dramatically repressed cell viability and increased apoptosis. Meanwhile, α-BTX largely reversed the nicotine-induced apoptosis and increased viability of PDL cells. Compared with the monoculture, MMP-1, MMP-3, interleukin (IL)-1β, IL-6, IL-17, and IL-21 in supernatant of cocultures were markedly elevated after treatment with nicotine. Moreover, α-BTX significantly attenuated nicotine-triggered production of these components either in mono- or co-cultures. In addition, PDL cell-derived CXCL12 following nicotine treatment recruited CD4(+) T cells. Above all, nicotine deteriorated periodontitis partially by promoting PDL cell-CD4(+) T cell-mediated inflammatory response and matrix degradation.

HmuY is an important virulence factor for Porphyromonas gingivalis growth in the heme-limited host environment and infection of macrophages

Porphyromonas gingivalis, the main etiologic agent and key pathogen responsible for initiation and progression of chronic periodontitis, is a haem auxotroph, and the uptake of this compound is essential for its survival and the ability to establish an infection. The aim of this study was to examine the role of a hemophore-like HmuY protein in P. gingivalis growth and infection of macrophages. Inactivation of the hmuY gene caused reduced P. gingivalis growth in vitro in the presence of serum as a heme sole source, as well as in vivo co-cultures with THP-1-derived macrophages. This resulted in diminished invasion efficiency of macrophages by live bacteria lacking functional hmuY gene. Both features were partially restored after addition of the purified HmuY protein, which was internalized when added either together with the hmuY mutant strain or alone to macrophage cultures. We conclude that HmuY is an important virulence factor of P. gingivalis for infection of macrophages in a heme-limited host environment.

Anti-HmuY antibodies specifically recognize Porphyromonas gingivalis HmuY protein but not homologous proteins in other periodontopathogens

Given the emerging evidence of an association between periodontal infections and systemic conditions, the search for specific methods to detect the presence of P. gingivalis, a principal etiologic agent in chronic periodontitis, is of high importance. The aim of this study was to characterize antibodies raised against purified P. gingivalis HmuY protein and selected epitopes of the HmuY molecule. Since other periodontopathogens produce homologs of HmuY, we also aimed to characterize responses of antibodies raised against the HmuY protein or its epitopes to the closest homologous proteins from Prevotella intermedia and Tannerella forsythia. Rabbits were immunized with purified HmuY protein or three synthetic, KLH-conjugated peptides, derived from the P. gingivalis HmuY protein. The reactivity of anti-HmuY antibodies with purified proteins or bacteria was determined using Western blotting and ELISA assay. First, we found homologs of P. gingivalis HmuY in P. intermedia (PinO and PinA proteins) and T. forsythia (Tfo protein) and identified corrected nucleotide and amino acid sequences of Tfo. All proteins were overexpressed in E. coli and purified using ion-exchange chromatography, hydrophobic chromatography and gel filtration. We demonstrated that antibodies raised against P. gingivalis HmuY are highly specific to purified HmuY protein and HmuY attached to P. gingivalis cells. No reactivity between P. intermedia and T. forsythia or between purified HmuY homologs from these bacteria and anti-HmuY antibodies was detected. The results obtained in this study demonstrate that P. gingivalis HmuY protein may serve as an antigen for specific determination of serum antibodies raised against this bacterium.

Subcutaneous vaccination with Porphyromonas gingivalis ameliorates periodontitis by modulating Th17/Treg imbalance in a murine model

To date, Porphyromonas gingivalis (P. gingivalis) vaccination has been studied only in animals, and no effective prophylactic human periodontal vaccine has been developed, with the reason for the failure of prophylactic human periodontal vaccines unknown. T helper 17 cell (Th17)/regulatory T (Treg) cell responses play an important role in the development of periodontitis, and a Th17/Treg imbalance causes the pathogenesis of periodontitis. However, whether vaccination with P. gingivalis can prevent periodontitis through modulation of the Th17/Treg imbalance remains unknown. In this study, mice were subcutaneously vaccinated with formalin-killed P. gingivalis and then orally challenged with P. gingivalis. The vaccination protected the mice from alveolar bone resorption and inflammation. These protective effects might be ascribed to downregulation of Th17 cells and interleukin (IL)-17A production, upregulation of Treg and receptor activator of nuclear factor-kappa B ligand (RANKL)(+)CD4(+)T cells, and IL-10 and transforming growth factor-β1 production, and inhibition of lymphocyte proliferation. Our findings may provide a direction for the development of a vaccine or therapy against periodontitis by alteration of the Th17/Treg imbalance.

[Expression markers of innate and adaptive immunity in gingival biopsies of patients with chronic generalized periodontitis during treatment]

Objective was to evaluate changes in expression of TLR, CD4, CD8 and CD20 in the mucosa of the gums occurring under the influence of basic treatment in patients with periodontitis. Fifty-seven periodontitis patients that received basic treatment were included in the study, gingival mucosa biopsies were obtained and immunohistochemical evaluation of the expression of TLR-2, TLR-4, CD4, CD8 and CD2 and the severity of acanthosis were assessemd in course of treatment. It is shown that one month of therapy significantly reduces the amount of TLR-2 and TLR-4 in gingival epithelial cells, populations of CD4 and CD8 lymphocytes in the inflammatory infiltrates, whereas no significant differences in the quantitative distribution of CD20-lymphocytes have been identified. Marked regression of inflammatory changes in therapy and decrease the severity of acanthosis. Therapy aimed at reducing the bacterial load in the mouth was associated with good clinical effect, as evidenced by the periodontal index and the innate immune system suppression to reduce susceptibility to periodontal patogens combined with the suppression of acquired immunity cells level in the gingival mucosa during treatment. At the same time, the protective ability of pathogens supported by the persistence of populations CD20-lymphocytes with the ability to activate humoral adaptive immunity was also seen.

Periodontitis: a host-mediated disruption of microbial homeostasis. Unlearning learned concepts

New concepts evolve when existing ones fail to address known factors adequately or are invalidated by new evidence. For decades periodontitis has been considered to be caused by specific bacteria or groups of bacteria and, accordingly, treatment protocols have largely been based on anti-infective therapies. However, close inspection of current data leads one to question whether these bacteria are the cause or the result of periodontitis. Good evidence is emerging to suggest that it is indeed the host response to oral bacteria that leads to the tissue changes noted in gingivitis. These changes lead to an altered subgingival environment that favors the emergence of 'periodontal pathogens' and the subsequent development of periodontitis if the genetic and external environmental conditions are favorable for disease development. Thus, it seems that it is indeed the initial early host-inflammatory and immune responses occurring during the development of gingivitis, and not specific bacteria or their so-called virulence factors, which determine whether periodontitis develops and progresses. In this review we consider these concepts and their potential to change the way in which we view and manage the inflammatory periodontal diseases.

T helper cells from aggressive periodontitis patients produce higher levels of interleukin-1 beta and interleukin-6 in interaction with Porphyromonas gingivalis

OBJECTIVE

In this study, we analyzed the production of Interleukin-1 beta (IL-1β) and IL-6 by activated CD4+ cells obtained from aggressive periodontitis (AgP) patients in comparison with healthy subjects (HC).

MATERIALS AND METHODS

CD4+ cells were automatically separated from lymphocytes obtained from peripheral blood of patients with AgP and healthy controls. Cells were activated for 4, 8, and 24 h with three different stimuli: anti-CD3/anti-CD28, phytohemagglutinin (PHA), and Porphyromonas gingivalis (P. gingivalis) outer membrane protein (OMP). Protein levels were measured in supernatants of activated CD4+ cells by a bead-based immunoassay (CBA). In addition, serum antibodies against P. gingivalis were determined. Data were analyzed using U test (p < 0.05).

RESULTS

T helper cells of AgP patients activated with P. gingivalis OMP produced higher levels of IL-1β and IL-6 in comparison with healthy controls (p < 0.05). Neither the activation with anti-CD3/anti-CD28 nor the activation with PHA showed significantly different production of IL-1β and IL-6 by the cells 25 % of patients and 17 % of controls presented with high serum reactivity to P. gingivalis.

CONCLUSION

In view of these results, it is possible to conclude that P. gingivalis contributes to the pathogenesis of AgP by inducing high levels of pro-inflammatory cytokines such as IL-1β and IL-6 by peripheral CD4+ T helper cells.

CLINICAL RELEVANCE

In accordance with the clinical parameters and the immunological data, we suggest that full-mouth disinfection with adjunctive systemic antibiotics might be the anti-infectious non-surgical periodontal treatment of choice in this type of patients. Microbiological analyses at the beginning and at the end of the periodontal treatment are recommended. However, it is necessary to verify these data in longitudinal clinical studies.

The unique hmuY gene sequence as a specific marker of Porphyromonas gingivalis

Porphyromonas gingivalis, a major etiological agent of chronic periodontitis, acquires heme from host hemoproteins using the HmuY hemophore. The aim of this study was to develop a specific P. gingivalis marker based on a hmuY gene sequence. Subgingival samples were collected from 66 patients with chronic periodontitis and 40 healthy subjects and the entire hmuY gene was analyzed in positive samples. Phylogenetic analyses demonstrated that both the amino acid sequence of the HmuY protein and the nucleotide sequence of the hmuY gene are unique among P. gingivalis strains/isolates and show low identity to sequences found in other species (below 50 and 56%, respectively). In agreement with these findings, a set of hmuY gene-based primers and standard/real-time PCR with SYBR Green chemistry allowed us to specifically detect P. gingivalis in patients with chronic periodontitis (77.3%) and healthy subjects (20%), the latter possessing lower number of P. gingivalis cells and total bacterial cells. Isolates from healthy subjects possess the hmuY gene-based nucleotide sequence pattern occurring in W83/W50/A7436 (n = 4), 381/ATCC 33277 (n = 3) or TDC60 (n = 1) strains, whereas those from patients typically have TDC60 (n = 21), W83/W50/A7436 (n = 17) and 381/ATCC 33277 (n = 13) strains. We observed a significant correlation between periodontal index of risk of infectiousness (PIRI) and the presence/absence of P. gingivalis (regardless of the hmuY gene-based sequence pattern of the isolate identified [r = 0.43; P = 0.0002] and considering particular isolate pattern [r = 0.38; P = 0.0012]). In conclusion, we demonstrated that the hmuY gene sequence or its fragments may be used as one of the molecular markers of P. gingivalis.

Role of TLR2-dependent IL-10 production in the inhibition of the initial IFN-γ T cell response to Porphyromonas gingivalis

P.g., a Gram-negative bacterium, is one of the main etiological agents of the chronic inflammatory disease, periodontitis. Disease progression is thought to occur as a result of an inadequate immune response, which although happens locally, can also occur distally as a result of the dissemination of P.g. into the circulation. As IL-10 and TLR2 are pivotal molecules in the immune response that P.g. elicits, we hypothesized that TLR2-mediated IL-10 production, following the initial systemic exposure to P.g., inhibits the IFN-γ T cell response. To address this hypothesis, mice were primed with P.g., and the types of cells producing IL-10 and the capacity of T cells to produce IFN-γ following blocking or neutralization of IL-10 were assessed. Our results showed that upon initial encounter with P.g., splenic T cells and CD11b(+) cells produce IL-10, which when neutralized, resulted in a substantial increase in IFN-γ production by T cells. Furthermore, IL-10 production was dependent on TLR2/1 signaling, partly in response to the major surface protein, FimA of P.g. In addition, P.g. stimulation resulted in the up-regulation of PD-1 and its ligand PD-L1 on CD4 T cells and CD11b(+) cells, respectively. Up-regulation of PD-1 was partially dependent on IL-10 but independent of TLR2 or FimA. These results highlight the role of IL-10 in inhibiting T cell responses to the initial systemic P.g. exposure and suggest multiple inhibitory mechanisms potentially used by P.g. to evade the host's immune response, thus allowing its persistence in the host.

Expression of peptidylarginine deiminase-2 and -4, citrullinated proteins and anti-citrullinated protein antibodies in human gingiva

BACKGROUND AND OBJECTIVE

The presence of citrullinated proteins, and peptidylarginine deiminase types -2 (PAD-2) and -4 (PAD-4) in periodontal tissues, determine the presence of anti-cyclic citrullinated protein antibodies (anti-CCP) in gingival crevicular fluid (GCF) and compare the expression of these proteins between inflamed and non-inflamed sites.

MATERIAL AND METHODS

Tissue sections were stained using antibodies against citrullinated proteins, PAD-2 and PAD-4. RT-PCR was performed to investigate PAD-2 and PAD-4 mRNA in inflamed and non-inflamed gingival tissues. Anti-CCP antibodies in gingival crevicular fluid were detected by ELISA.

RESULTS

Citrullinated proteins, PAD-2 and PAD-4 were detected in gingiva. There was a correlation between inflammation and expression of these proteins. mRNAs for PAD-2 and PAD-4 were detected in both inflamed and non-inflamed gingival tissues. Antibodies to CCP were found mostly in the GCF of individuals with periodontitis.

CONCLUSION

PAD-2 and PAD-4 (protein and mRNA) as well as citrullinated proteins are present in inflamed gingiva, and anti-CCP antibodies can be detected in the GCF of some patients. Tissue expression of citrullinated proteins and PAD increased with the severity of inflammation. The presence of anti-CCP antibodies in GCF was almost exclusive to a subset of patients with periodontitis. Increased expression of these proteins in inflamed gingiva lends support to the notion that periodontal inflammation contributes to the inflammatory burden in a similar way to rheumatoid arthritis.