Prevotella intermedia stimulates expansion of Vbeta-specific CD4(+) T cells

Oral Dysbiosis and Autoimmunity: From Local Periodontal Responses to an Imbalanced Systemic Immunity. A Review

The current paradigm of onset and progression of periodontitis includes oral dysbiosis directed by inflammophilic bacteria, leading to altered resolution of inflammation and lack of regulation of the inflammatory responses. In the construction of explanatory models of the etiopathogenesis of periodontal disease, autoimmune mechanisms were among the first to be explored and historically, for more than five decades, they have been described in an isolated manner as part of the tissue damage process observed in periodontitis, however direct participation of these mechanisms in the tissue damage is still controversial. Autoimmunity is affected by genetic and environmental factors, leading to an imbalance between the effector and regulatory responses, mostly associated with failed resolution mechanisms. However, dysbiosis/infection and chronic inflammation could trigger autoimmunity by several mechanisms including bystander activation, dysregulation of toll-like receptors, amplification of autoimmunity by cytokines, epitope spreading, autoantigens complementarity, autoantigens overproduction, microbial translocation, molecular mimicry, superantigens, and activation or inhibition of receptors related to autoimmunity by microorganisms. Even though autoreactivity in periodontitis is biologically plausible, the associated mechanisms could be related to non-pathologic responses which could even explain non-recognized physiological functions. In this review we shall discuss from a descriptive point of view, the autoimmune mechanisms related to periodontitis physio-pathogenesis and the participation of oral dysbiosis on local periodontal autoimmune responses as well as on different systemic inflammatory diseases.

Superantigens: The Good, the Bad, and the Ugly

Increasing evidence suggests that superantigens play a role in Immune-mediated diseases. Superantigens are potent activators of CD4* T cells, causing rapid and massive proliferation of cells and cytokine production. This characteristic of superantigens can be exploited in diseases where strong immunologic responses are required, such as in the B16F10 animal model of melanoma. Superantigen administration is able to significantly enhance Ineffective anti-tumor Immune responses, resulting in potent and long-lived protective anti-tumor immunity. However, superantigens are more well-known for the role they play in diseases. Studies using an animal model for neurologic demy-elinatlng diseases such as multiple sclerosis show that superantigens can induce severe relapses and activate auto-reactive T cells not involved in the Initial bout of disease. This may also involve epitope spreading of disease. Superantigens have also been implicated in acute diseases such as food poisoning and TSS, and in chronic diseases such as psoriasis and rheumatoid arthritis. Viral superantigens are also involved in the disease process, including superantigens derived from human Immunodeficiency virus and mouse mammary tumor virus. Finally, immunotherapies that ameliorate the role played by superantigens in disease are discussed.

Autoimmune correlation of rheumatoid arthritis and periodontitis

Rheumatoid arthritis and periodontitis, both, chronic inflammatory diseases share certain common diagnostic, pathological, immunogenetic and therapeutic features. A recently discovered enzymatic mimicry between human and bacterial species is novel and it opens up a new terrain for therapeutic blockade in the management of rheumatoid arthritis.

Rheumatoid arthritis in the elderly and its relationship with periodontitis: a review

Periodontitis and rheumatoid arthritis are chronic inflammatory diseases commonly seen in the elderly. It has been proposed that the two conditions are interrelated and influence the severity of each other. Recently, the role of Porphyromonas gingivalis, a periodontopathogen, has been explained in the pathogenesis and progression of rheumatoid arthritis. It can be inferred from the present review that the two conditions share a common pathobiology, genetics and environmental risk factors. Furthermore, a thorough understanding of the aforementioned mechanisms might enable the development of conjoint treatment modalities beneficial in treating the geriatric population afflicted by both the disorders.

New insights into Prevotella diversity and medical microbiology

In light of recent studies based on cultivation-independent methods, it appears that the diversity of Prevotella in human microbiota is greater than was previously assumed from cultivation-based studies, and that the implication of these bacteria in several human diseases was unrecognized. While some Prevotella taxa were found during opportunistic infections, changes in Prevotella abundance and diversity were discovered during dysbiosis-associated diseases. As member of the microbiota, Prevotella may also be considered as a reservoir for resistance genes. Greater knowledge on Prevotella diversity, as well as new insights into its pathogenic potential and implication in dysbiosis are expected from the use of human microbe identification microarrays, from whole-genome sequence analyse, and from the NIH Human Microbiome Project data. New approaches, including molecular-based methods, could contribute to improve the diagnosis of Prevotella infections.

The association between rheumatoid arthritis and periodontal disease

Chronic, plaque-associated inflammation of the gingiva and the periodontium are among the most common oral diseases. Periodontitis (PD) is characterized by the inflammatory destruction of the periodontal attachment and alveolar bone, and its clinical appearance can be influenced by congenital as well as acquired factors. The existence of a rheumatic or other inflammatory systemic disease may promote PD in both its emergence and progress. However, there is evidence that PD maintains systemic diseases. Nevertheless, many mechanisms in the pathogenesis have not yet been examined sufficiently, so that a final explanatory model is still under discussion, and we hereby present arguments in favor of this. In this review, we also discuss in detail the fact that oral bacterial infections and inflammation seem to be linked directly to the etiopathogenesis of rheumatoid arthritis (RA). There are findings that support the hypothesis that oral infections play a role in RA pathogenesis. Of special importance are the impact of periodontal pathogens, such as Porphyromonas gingivalis on citrullination, and the association of PD in RA patients with seropositivity toward rheumatoid factor and the anti-cyclic citrullinated peptide antibody.

Association of periodontitis with rheumatoid arthritis and atherosclerosis: Novel paradigms in etiopathogeneses and management?

There is increasing documentation of a link between inflammatory periodontal disease affecting the supporting structure of teeth, rheumatoid arthritis, and coronary artery disease. Periodontitis is initiated predominantly by Gram-negative bacteria and progresses as a consequence of the host inflammatory response to periodontal pathogens. Lipopolysaccharide, a cell wall constituent stimulates the production of inflammatory cytokines via the activation of signaling pathways perpetuating inflammatory pathogenesis in a cyclical manner in susceptible individuals; with an element of autoimmune stimulation, not dissimilar to the sequential events seen in RA. Periodontitis, also implicated as a risk factor for cardiovascular disease, promotes mechanisms for atherosclerosis by enhancing an imbalance in systemic inflammatory mediators; more direct mechanisms attributed to microbial products are also implicated in both RA and atherogenesis. Severe periodontal disease characterized by clinical and radiographic parameters has been associated with ischemic stroke risk, significant levels of C-reactive protein and serum amyloid A, amongst others common to both periodontitis and atherosclerosis. Existing data supports the hypothesis that persistent localized infection in periodontitis may influence systemic levels of inflammatory markers and pose a risk for RA and atherosclerosis. A common nucleus of activity in their pathogeneses provides novel paradigms of therapeutic targeting for reciprocal benefit.

[Pathogenesis of parodontitis in rheumatic diseases]

Inflammatory periodontal disease (PD) is a common disease worldwide that has a primarily bacterial aetiology and is characterized by dysregulation of the host inflammatory response. The degree of inflammation varies among individuals with PD independently of the degree of bacterial infection, suggesting that alteration of the immune function may substantially contribute to its extent. Factors such as smoking, education, and body mass index (BMI) are discussed as potential risk factors for PD. Most PD patients respond to bacterial invaders by mobilizing their defensive cells and releasing cytokines such as interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha, and IL-6, which ultimately causes tissue destruction by stimulating the production of collagenolytic enzymes, such matrix metalloproteinases. Recently, there has been growing evidence suggesting an association between PD and the increased risk of systemic diseases, such ateriosclerosis, diabetes mellitus, stroke, and rheumatoid arthritis (RA). PD and rheumatologic diseases such as RA share many pathological aspects and immunological findings.

Rheumatoid arthritis is linked to oral bacteria: etiological association

The purpose of this review is to evaluate the association between rheumatoid arthritis (RA) and periodontopathic bacteria. Clinical studies of RA and periodontal disease have provided evidence for a significant association between the two disorders. Patients with long-standing active RA have a substantially increased frequency of periodontal disease compared with that among healthy subjects. High levels of oral anaerobic bacterial antibodies have been found in the serum and synovial fluid of RA patients. Porphyromonas gingivalis, Tannerella forsythensis, and Prevotella intermedia have been identified in RA synovial fluid. Ornidazole, levofloxacin, and clarithromycin are used in the treatment of infections caused by anaerobic bacteria. These antibiotics have been shown to be effective against RA. The evidence in this review indicates that oral bacteria directly associate with etiopathogenesis of RA.

Gene expression profile and pathogenicity of biofilm-forming Prevotella intermedia strain 17

BACKGROUND

Prevotella intermedia (P. intermedia), a gram-negative, black-pigmented anaerobic rod, has been implicated in the development of chronic oral infection. P. intermedia strain 17 was isolated from a chronic periodontitis lesion in our laboratory and described as a viscous material producing strain. The stock cultures of this strain still maintain the ability to produce large amounts of viscous materials in the spent culture media and form biofilm-like structures. Chemical analyses of this viscous material showed that they were mainly composed of neutral sugars with mannose constituting 83% of the polysaccharides. To examine the biological effect of the extracellular viscous materials, we identified and obtained a naturally-occurring variant strain that lacked the ability to produce viscous materials in vitro from our stock culture collections of strain 17, designated as 17-2. We compared these two strains (strains 17 versus 17-2) in terms of their capacities to form biofilms and to induce abscess formation in mice as an indication of their pathogenicity. Further, gene expression profiles between these two strains in planktonic condition and gene expression patterns of strain 17 in solid and liquid cultures were also compared using microarray assays.

RESULTS

Strain 17 induced greater abscess formation in mice as compared to that of the variant. Strain 17, but not 17-2 showed an ability to interfere with the phagocytic activity of human neutrophils. Expression of several genes which including those for heat shock proteins (DnaJ, DnaK, ClpB, GroEL and GroES) were up-regulated two to four-fold with statistical significance in biofilm-forming strain 17 as compared to the variant strain 17-2. Strain 17 in solid culture condition exhibited more than eight-fold up-regulated expression levels of several genes which including those for levanase, extracytoplasmic function-subfamily sigma factor (sigmaE; putative) and polysialic acid transport protein (KpsD), as compared to those of strain 17 in liquid culture media.

CONCLUSION

These results demonstrate that the capacity to form biofilm in P. intermedia contribute to their resistance against host innate defence responses.

Anti-Neutrophil Cytoplasmic Autoantibodies: A Renewed Paradigm in Periodontal Disease Pathogenesis?

In the past, various models including the autoimmunity model have been proposed to explain the pathogenesis of periodontal diseases. The aim of this review is to introduce the pathogenic role of anti-neutrophil cytoplasmic autoantibodies (ANCAs) in various autoimmune diseases and compare these conditions with periodontal disease to elucidate common pathogenic mechanisms. Also, a novel model to explain the pathogenesis of periodontal disease based on the concept of ANCA-associated autoimmunity is proposed. This encompasses a wide array of biochemical mediators that range from direct and indirect initiators of ANCA production and eventual release of proinflammatory mediators and free radicals, all of which have been implicated in periodontal tissue destruction in the past. In addition, specific links between the typical ANCA-associated diseases and periodontal disease are discussed. Finally, a new paradigm in the periodontal disease-associated destruction is proposed that includes the currently accepted mechanism, namely, the genetic-microbial-host interactions.

Serum antibodies to oral anaerobic bacteria in patients with rheumatoid arthritis

BACKGROUND

This study was conducted to determine the component that causes the disease in rheumatoid arthritis (RA), which shows great resemblance to periodontitis in a pathologic context.

MATERIALS AND METHODS

Within this study, the pathogen-specific IgG levels formed against Porphyromonas gingivalis FDC 381, Prevotella melaninogenica ATCC 25845, Actinobacillus actinomycetemcomitans Y4, Bacteroides forsythus ATCC 43047, and Prevotella intermedia 25611 oral bacteria were researched from the blood serum samples of 30 RA patients and 20 healthy controls with the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The IgG levels of P gingivalis, P intermedia, P melaninogenica, and B forsythus were found to be significantly higher in RA patients when compared with those of the controls. Of the other bacteria antibodies, A actinomycetemcomitans was not found at greater levels in RA serum samples in comparison with the healthy samples.

CONCLUSION

The antibodies formed against P gingivalis, P intermedia, P melaninogenica, and B forsythus could be important to the etiopathogenesis of RA.

Detection of heat shock proteins but not superantigen by isolated oral bacteria from patients with Behcet's disease

We isolated bacteria from periodontal sites and mixed saliva in eight patients with Behcet's disease and surveyed them to determine whether they produced heat shock proteins (HSPs) and superantigen. Cultivable bacterial compositions from periodontal sites and saliva were examined by anaerobic culture using blood agar plates. Gram-negative anaerobic rods such as Prevotella intermedia, Fusobacterium nucleatum, and Capnocytophaga species were predominant in the isolates from the subgingival plaque samples. The Streptococcus mitis group was the most common type isolated from the saliva samples. To detect the production of HSPs, Western blot analyses were performed using a polyclonal rabbit antibody to Escherichia coli DnaK and a monoclonal antibody to Helicobacter pylori Gro-EL. Sonic extracts of 27 of the strains (79.4%) reacted with the antibody against E. coli DnaK. Nine of these 34 strains (26.5%) were found to produce HSPs that reacted with antibody to H. pylori Gro-EL. A total of 54 isolates were examined for superantigen activity against human peripheral leukocytes. Twenty-five gram-negative clinical strains isolated from chronic periodontitis lesions and 20 ATCC strains of microorganisms were also examined. We could not detect any superantigen activity in 500x diluted supernatant of the strains isolated from the eight patients with Behcet's disease. The present study indicates that the anaerobic strains isolated from the oral cavity of these patients produce HSPs, the production being related to Bechet's disease.

Prevotella intermedia native plasmid can be mobilized by an Escherichia coli conjugal IncP plasmid

We have determined the nucleotide sequence of a small Prevotella intermedia cryptic plasmid, pYHBi1, which consisted of sequences that were highly homologous to the amino acid sequence of the replication and mobilization proteins found in related organisms. We have also demonstrated that chimeric plasmids derived from this P. intermedia native plasmid can be mobilized between Escherichia coli strains by using a broad-host-range E. coli conjugative plasmid, IncP plasmid RP4. The results suggest that pYHBi1 possesses gene(s) responsible for conjugal transfer.