Dysbiotic Oral Microbiome Research Articles

Identification of temporal shifts of oral bacteria in bone regeneration following mandibular bone defect injury and therapeutic surgery in a porcine model.

Considered the second largest and most diverse microbiome after the gut, the human oral ecosystem is complex with diverse and niche-specific microorganisms. Although evidence is growing for the importance of oral microbiome in supporting a healthy immune system and preventing local and systemic infections, the influence of craniomaxillofacial (CMF) trauma and routine reconstructive surgical treatments on community structure and function of oral resident microbes remains unknown. CMF injuries affect a large number of people, needing extensive rehabilitation with lasting morbidity and loss of human productivity. Treatment efficacy can be complicated by the overgrowth of opportunistic commensals or multidrug-resistant pathogens in the oral ecosystem due to weakened host immune function and reduced colonization resistance in a dysbiotic oral microbiome. To understand the dynamics of microbiota's community structure during CMF injury and subsequent treatments, we induced supra-alveolar mandibular defect in Hanford miniature swine (n=3) and compared therapeutic approaches of immediate mandibullar reconstructive (IMR) versus delayed mandibullar reconstructive (DMR) surgeries. Using bacterial 16S ribosomal RNA gene marker sequencing, the composition and abundance of the bacterial community of the uninjured maxilla (control) and the injured left mandibula (lingual and buccal) treated by DMR were surveyed up to 70-day post-wounding. For the injured right mandibula receiving IMR treatment, the microbial composition and abundance were surveyed up to 14-day post-wounding. Moreover, we measured sera level of biochemical markers (e.g., osteocalcin) associated with bone regeneration and healing. Computed tomography was used to measure and compare mandibular bone characteristics such as trabecular thickness between sites receiving DMR and IMR therapeutic approaches until day 140, the end of study period. Independent of IMR versus DMR therapy, we observed similar dysbiosis and shifts of the mucosal bacteria residents after CMF injury and/or following treatment. There was an enrichment of Fusobacterium, Porphyromonadaceae, and Bacteroidales accompanied by a decline in Pasteurellaceae, Moraxella, and Neisseria relative abundance in days allotted for healing. We also observed a decline in species richness and abundance driven by reduction in temporal instability and inter-animal heterogeneity on days 0 and 56, with day 0 corresponding to injury in DMR group and day 56 corresponding to delayed treatment for DMR or injury and immediate treatment for the IMR group. Analysis of bone healing features showed comparable bone-healing profiles for IMR vs. DMR therapeutic approach.

Does a Dysbiotic Oral Microbiome Trigger the Risk of Chronic Inflammatory Disease?

Does a Dysbiotic Oral Microbiome Trigger the Risk of Chronic Inflammatory Disease?

High-Throughput Combined Analysis of Saliva Microbiota and Metabolomic Profile in Chinese Periodontitis Patients: A Pilot Study.

The onset and progression of periodontitis involves complicated interactions between the dysbiotic oral microbiota and disrupted host immune-inflammatory response, which can be mirrored by the changes in salivary metabolites profile. This pilot study sought to examine the saliva microbiome and metabolome in the Chinese population by the combined approach of 16s rRNA sequencing and high-throughput targeted metabolomics to discover potential cues for host-microbe metabolic interactions. Unstimulated whole saliva samples were collected from eighteen Stage III and IV periodontitis patients and thirteen healthy subjects. Full-mouth periodontal parameters were recorded. The taxonomic composition of microbiota was obtained by 16s rRNA sequencing, and the metabolites were identified and measured by ultra-high performance liquid chromatography and mass spectrometry-based metabolomic analysis. The oral microbiota composition displayed marked changes where the abundance of 93 microbial taxa differed significantly between the periodontitis and healthy group. Targeted metabolomics identified 103 differential metabolites between the patients and healthy individuals. Functional enrichment analysis demonstrated the upregulation of protein digestion and absorption, histidine metabolism, and nicotinate and nicotinamide metabolism pathways in the dysbiotic microbiota, while the ferroptosis, tryptophan metabolism, glutathione metabolism, and carbon metabolism pathways were upregulated in the patients. Correlation analysis confirmed positive relationships between the clinical parameters, pathogen abundances, and disease-related metabolite levels. The integral analysis of the saliva microbiome and metabolome yielded an accurate presentation of the dysbiotic oral microbiome and functional alterations in host-microbe metabolism. The microbial and metabolic profiling of the saliva could be a potential tool in the diagnosis, prognosis evaluation, and pathogenesis study of periodontitis.

Alterations in macrophage polarization play a key role in control and development of periodontal diseases.

Periodontitis is a chronic inflammatory disease driven by complex interplays between a dysbiotic oral microbiome and a dysregulated host inflammatory response that results in the destruction of the tooth-supporting apparatus. Among the inflammatory cells involved in the pathogenesis of periodontitis, macrophages are recruited early on to sites of periodontal infection. These cells can polarize in different phenotypes that mediate the initiation and resolution of inflammatory responses, as well as in tissue healing. Macrophage phenotypic plasticity is thought to play a critical role in the induction and resolution of inflammation and may be compromised in patients with chronic inflammatory diseases. Here, we reviewed the role of macrophage polarization in periodontal disease and therapy.

Porphyromonas gingivalis Peptidyl Arginine Deiminase (PPAD) in the Context of the Feed-Forward Loop of Inflammation in Periodontitis.

Periodontitis is a widespread chronic inflammatory disease caused by a changed dysbiotic oral microbiome. Although multiple species and risk factors are associated with periodontitis, Porphyromonas gingivalis has been identified as a keystone pathogen. The immune-modulatory function of P. gingivalis is well characterized, but the mechanism by which this bacterium secretes peptidyl arginine deiminase (PPAD), a protein/peptide citrullinating enzyme, thus contributing to the infinite feed-forward loop of inflammation, is not fully understood. To determine the functional role of citrullination in periodontitis, neutrophils were stimulated by P. gingivalis bearing wild-type PPAD and by a PPAD mutant strain lacking an active enzyme. Flow cytometry showed that PPAD contributed to prolonged neutrophil survival upon bacterial stimulation, accompanied by the secretion of aberrant IL-6 and TNF-α. To further assess the complex mechanism by which citrullination sustains a chronic inflammatory state, the ROS production and phagocytic activity of neutrophils were evaluated. Flow cytometry and colony formation assays showed that PPAD obstructs the resolution of inflammation by promoting neutrophil survival and the release of pro-inflammatory cytokines, while enhancing the resilience of the bacteria to phagocytosis.

Abstract C011: Markers of periodontitis in the setting of colon cancer in African American patients

Abstract Colorectal cancer (CRC) is the third most common cancer and the third leading cause of cancer death in the United States. Among all the racial/ethnic groups, African American (AA) patients have the highest incidence of CRC and mortality rate. Periodontitis is an oral chronic inflammatory disease that damages the soft tissue and bone that supports the tooth and is among the 10 most prevalent chronic diseases. AAs are more often diagnosed with periodontal disease than other racial or ethnic groups. A dysbiotic oral microbiome might induce local and systemic immune dysregulation that produces a pro-inflammatory environment that could lead to colon cancer. The human bacteria Fusobacterium nucleatum (Fn), which primarily inhabits the oral cavity, causes periodontal disease and also has been implicated in the development of colorectal cancer. This pro-inflammatory bacteria has been shown to be significantly higher in the colon tumors from AAs compared to Caucasian American patients. No studies have been published describing differences in levels of inflammatory proteins and bacterial communities between the right/left location of colon cancer in AA patients. This pilot study aimed to determine the feasibility of measuring serum cytokines and evaluating oral bacterium associated with periodontitis (Fn) in the setting of colon cancer. Methods: We assessed quantitative measurement of 20 human periodontal disease associated inflammatory cytokines (IL-1a, IL-1b, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, IFNg, TNFa, and CRP); matrix metalloproteinases (MMP-9, and MMP-13) and their inhibitors (MIP-1a); bone metabolism related cytokines (OPG, OPN, RANK), osteoactivin, and TGFb1. Readings were taken using the Quantibody Human Periodontal Disease Array, which is a multiplexed sandwich using an enzyme-linked immunosorbent assay (ELISA)-based quantitative array platform on a glass slide. Quantitative polymerase chain reaction (qPCR) assays was used to detect Fn DNA in colon tumor tissues and measured the levels as compared to non-tumor tissues. Results: Right-sided colon cancer patients have increased levels of cytokines associated with periodontitis. Stage III patients have significantly elevated levels of OPG (p= 0.0157) and OPN (p= 0.0033) compared with early stages I-II. Fn is present in both tumor and non-tumor tissues. Conclusion: Circulating cytokines, like OPG and OPN, and oral pathogens associated with periodontitis (Fn), could be a potential indicator for location and stage of cancer when combined with other serological markers. Next step will be to evaluate the microbiome composition in tumor and non-tumor tissues from AA colon cancer patients using 16S rRNA amplicon sequencing. Citation Format: Sofia C. Tortora, Marzia Spagnardi, Jenny Paredes, Olalekan Lanipekun, Laura Martello-Rooney. Markers of periodontitis in the setting of colon cancer in African American patients [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr C011.

Oral Microbiome and Systemic Diseases

As one of the most diverse microbial communities within the human body, the oral microbiome is an important component that contributes to the maintenance of human health. The microbial composition of different sites in the oral cavity varies significantly and a dynamic equilibrium is maintained through communications with the environment and oral and distal organs of the host. It has been reported that there is significant correlation between dysbiotic oral microbiome and the occurrence or progression of a variety of systemic diseases. In this review, we summarized recent advances in research on the relationship between oral microbiome and systemic health, focusing on the interaction and pathological mechanisms between oral microbiome and systemic health and hoping to provide new avenues for the early prevention and clinical diagnosis and treatment of systemic diseases.

SAP deficiency aggravates periodontitis possibly via C5a-C5aR signaling-mediated defective macrophage phagocytosis of Porphyromonas gingivalis

IntroductionSerum amyloid P component (SAP) regulates the innate immune system and microbial diseases. Periodontitis is an inflammatory oral disease developed by the host immune system's interaction with the dysbiotic oral microbiome, thereby SAP could play a role in periodontitis pathogenicity. ObjectivesTo investigate the role of SAP in oral microbiome modulation and peridontitis pathogenicity. MethodsIn this study, wildtype and SAP-knockout (KO) mice were used. Ligature-based periodontitis was developed in mice. Oral microbiome diversity was analyzed by 16 s rRNA sequencing. Macrophages and Porphyromonas gingivalis (P. gingivalis) co-culture system analyzed the effect of SAP in macrophage phagocytosis of P. gingivalis. ResultsThe level of SAP was upregulated in the periodontitis-affected periodontium of humans and mice but not in the liver and blood circulation. Periodontal macrophages were the key source of upregulated SAP in periodontitis. SAP-KO aggravated periodontal inflammation, periodontitis, and a higher number of M1-type inflammatory macrophage infiltration in the periodontium. The oral microbiome of SAP-KO periodontitis mice was altered with a higher abundance of Porphyromonas at the genus level. SAP-KO macrophages showed compromised phagocytosis of P. gingivalis in the co-culture system. Co-culture of SAP-KO macrophages and P. gingivalis induced the C5a expression and exogenous SAP treatment nullified this effect. Exogenous recombinant SAP treatment did not affect P. gingivalis growth and opsonization. PMX205, an antagonist of C5a, treatment robustly enhanced P. gingivalis phagocytosis by SAP-KO macrophages, indicating the involvement of the C5a-C5aR signaling in the compromised P. gingivalis phagocytosis by SAP-KO macrophages. ConclusionSAP deficiency aggravates periodontitis possibly via C5a-C5aR signaling-mediated defective macrophage phagocytosis of P. gingivalis. A higher abundance of P. gingivalis during SAP deficiency could promote M1 macrophage polarization and periodontitis. This finding suggests the possible protecting role of elevated levels of periodontal SAP against periodontitis progression.

Impact of Oral Microbiome in Periodontal Health and Periodontitis: A Critical Review on Prevention and Treatment.

The skin, oral cavity, digestive and reproductive tracts of the human body harbor symbiotic and commensal microorganisms living harmoniously with the host. The oral cavity houses one of the most heterogeneous microbial communities found in the human organism, ranking second in terms of species diversity and complexity only to the gastrointestinal microbiota and including bacteria, archaea, fungi, and viruses. The accumulation of microbial plaque in the oral cavity may lead, in susceptible individuals, to a complex host-mediated inflammatory and immune response representing the primary etiological factor of periodontal damage that occurs in periodontitis. Periodontal disease is a chronic inflammatory condition affecting about 20–50% of people worldwide and manifesting clinically through the detection of gingival inflammation, clinical attachment loss (CAL), radiographic assessed resorption of alveolar bone, periodontal pockets, gingival bleeding upon probing, teeth mobility and their potential loss in advanced stages. This review will evaluate the changes characterizing the oral microbiota in healthy periodontal tissues and those affected by periodontal disease through the evidence present in the literature. An important focus will be placed on the immediate and future impact of these changes on the modulation of the dysbiotic oral microbiome and clinical management of periodontal disease.

Correction of postcovid anemia in pregnant women with impaired dental health status

Introduction. The novel coronavirus pandemic makes the issue of iron deficiency in pregnancy even more urgent and forces multidisciplinary clinicians to search for modern ways to correct disorders caused by this infection.Objective. To assess the features of the course of post-covid anemia associated with combination therapy, as well as the effect of therapy on the dental health status in pregnant women.Materials and methods. 30 pregnant women (treatment group 1) in the third trimester who had coronavirus infection with mild IDA during gestation were enrolled in the prospective study. Comparison group 2: included 15 patients with mild IDA who did not have coronavirus infection during gestation. Control group 3: included 15 conditionally healthy pregnant women without IDA who did not have a novel coronavirus infection during gestation.Results. Pregnant women who had COVID-19 during gestation were significantly more likely to suffer from gum bleeding, angular cheilitis, oral erosive and ulcerative lesions. Gum bleeding was significantly more common in pregnant women with IDA against the background of coronavirus infection, than in the women in the comparison and control groups (SBI index, p < 0.05). The decrease in the normal microflora suggests the presence of dysbiotic changes in all pregnant women against the background of IDA, however, the patients after the COVID-19 infection had the most significant changes in it.Conclusions. The novel coronavirus infection, which the women had during gestation, aggravates the course of IDA, reduces the quality of life of patients with characteristic complaints (gum bleeding, angular cheilitis, oral erosive and ulcerative lesions), leads to dysbiotic oral microbiome changes. The management of this group of patients requires a systemic correction of the microflora balance, the introduction of individual oral hygiene regimens and adequate treatment of IDA using high-technology medicinal products

Intermolecular latency regulates the essential C-terminal signal peptidase and sortase of the Porphyromonas gingivalis type-IX secretion system

Porphyromonas gingivalis is a keystone pathogen of the human dysbiotic oral microbiome that causes severe periodontitis. It employs a type-IX secretion system (T9SS) to shuttle proteins across the outer membrane (OM) for virulence. Uniquely, T9SS cargoes carry a C-terminal domain (CTD) as a secretion signal, which is cleaved and replaced with anionic lipopolysaccharide by transpeptidation for extracellular anchorage to the OM. Both reactions are carried out by PorU, the only known dual-function, C-terminal signal peptidase and sortase. PorU is itself secreted by the T9SS, but its CTD is not removed; instead, intact PorU combines with PorQ, PorV, and PorZ in the OM-inserted "attachment complex." Herein, we revealed that PorU transits between active monomers and latent dimers and solved the crystal structure of the ∼260-kDa dimer. PorU has an elongated shape ∼130 Å in length and consists of seven domains. The first three form an intertwined N-terminal cluster likely engaged in substrate binding. They are followed by a gingipain-type catalytic domain (CD), two immunoglobulin-like domains (IGL), and the CTD. In the first IGL, a long "latency β-hairpin" protrudes ∼30 Å from the surface to form an intermolecular β-barrel with β-strands from the symmetric CD, which is in a latent conformation. Homology modeling of the competent CD followed by in vivo validation through a cohort of mutant strains revealed that PorU is transported and functions as a monomer through a C690/H657 catalytic dyad. Thus, dimerization is an intermolecular mechanism for PorU regulation to prevent untimely activity until joining the attachment complex.

Bifidobacterium Strains Present Distinct Effects on the Control of Alveolar Bone Loss in a Periodontitis Experimental Model.

Periodontitis is an inflammatory disease induced by a dysbiotic oral microbiome. Probiotics of the genus Bifidobacterium may restore the symbiotic microbiome and modulate the immune response, leading to periodontitis control. We evaluated the effect of two strains of Bifidobacterium able to inhibit Porphyromonas gingivalis interaction with host cells and biofilm formation, but with distinct immunomodulatory properties, in a mice periodontitis model. Experimental periodontitis (P+) was induced in C57Bl/6 mice by a microbial consortium of human oral organisms. B. bifidum 1622A [B+ (1622)] and B. breve 1101A [B+ (1101)] were orally inoculated for 45 days. Alveolar bone loss and inflammatory response in gingival tissues were determined. The microbial consortium induced alveolar bone loss in positive control (P + B-), as demonstrated by microtomography analysis, although P. gingivalis was undetected in oral biofilms at the end of the experimental period. TNF-α and IL-10 serum levels, and Treg and Th17 populations in gingiva of SHAM and P + B- groups did not differ. B. bifidum 1622A, but not B. breve 1101A, controlled bone destruction in P+ mice. B. breve 1101A upregulated transcription of Il-1β, Tnf-α, Tlr2, Tlr4, and Nlrp3 in P-B+(1101), which was attenuated by the microbial consortium [P + B+(1101)]. All treatments downregulated transcription of Il-17, although treatment with B. breve 1101A did not yield such low levels of transcripts as seen for the other groups. B. breve 1101A increased Th17 population in gingival tissues [P-B+ (1101) and P + B+ (1101)] compared to SHAM and P + B-. Administration of both bifidobacteria resulted in serum IL-10 decreased levels. Our data indicated that the beneficial effect of Bifidobacterium is not a common trait of this genus, since B. breve 1101A induced an inflammatory profile in gingival tissues and did not prevent alveolar bone loss. However, the properties of B. bifidum 1622A suggest its potential to control periodontitis.

The oral microbiome of treated and untreated chronic HCV infection: A preliminary study.

Chronic hepatitis C virus (HCV) infection is a debilitating disease that is lately treated using direct-acting antivirals (DAAs). Changes in the oral microbiome were detected in other liver diseases; however, oral microbiome was never investigated in patients having chronic HCV infection, whether pre- or post-treatment. This case-control preliminary study enrolled three equal groups: Group (I): untreated HCV patients; group (II): HCV patients who achieved viral clearance after DAA administration; and group (III): healthy controls. For each participant, a buccal swab was harvested and its 16S rRNA was sequenced. The oral microbiome of chronic HCV patients had a significantly distinct bacterial community compared to healthy controls, characterized by high diversity and abundance of certain pathogenic species. These changes resemble that of oral lichen planus patients. After treatment by DAAs, the oral microbiome shifted to a community with partial similarity to both the diseased and the healthy ones. Chronic HCV is associated with dysbiotic oral microbiome having abundant pathogenic bacteria. With HCV clearance by DAAs, the oral microbiome shifts to approach the healthy composition.

Resveratrol and Its Analogs as Functional Foods in Periodontal Disease Management

Periodontitis is a common chronic inflammatory disease driven by the interaction between a dysbiotic oral microbiome and the dysregulated host immune-inflammatory response. Naturally derived nutraceuticals, such as resveratrol and its analogs, are potential adjunctive therapies in periodontal treatment due to their antimicrobial and anti-inflammatory properties. Furthermore, different analogs of resveratrol and the choice of solvents used may lead to varying effects on therapeutic properties. This review presents the current findings and gaps in our understanding on the potential utility of resveratrol and its analogs in periodontal treatment.

Oral microbiome and pregnancy: A bidirectional relationship

The oral cavity contains the second most complex microbial population within the human body, with more than 700 bacterial organisms. Recent advances in Next Generation Sequencing technology have unraveled the complexities of the oral microbiome and provided valuable insights into its role in health and disease. The human oral microbiome varies dramatically during the different stages of life, including pregnancy. The total viable microbial counts in pregnant women are known to be higher compared to non-pregnant women, especially in the first trimester of pregnancy. A balanced oral microbiome is vital for a healthy pregnancy, as perturbations in the oral microbiome composition can contribute to pregnancy complications. On the other hand, physiological changes and differences in hormonal levels during pregnancy, increase susceptibility to various oral diseases such as gingivitis and periodontitis. A growing body of evidence supports the link between the composition of the oral microbiome and adverse pregnancy outcomes such as preterm birth, preeclampsia, low birth weight among others. This review aims to summarize the dynamics of oral microbiome during pregnancy and to discuss the relationship between a dysbiotic oral microbiome and pregnancy complications.

Casein phosphopeptide–amorphous calcium phosphate fluoride treatment enriches the symbiotic dental plaque microbiome in children

ObjectivesThe dysbiotic oral microbiome plays a key role in the pathogenesis of caries in children. Topical application of casein phosphopeptide–amorphous calcium phosphate containing fluoride (CPP-ACP/F) is an effective treatment modality for children with caries (CC). Hitherto the mechanism by which CPP-ACP/F modules the oral microbiome in CC has not been investigated. The study aimed to examine the CPP–ACP/F effect on the dental plaque microbiome of children group with caries. MethodsThis preliminary prospective clinical cohort included 10 children with caries. The children received topical fluoride CPP–ACP/F once-a-week for one month. Plaque samples were collected before and after treatment and subjected to 16S rDNA-based next-generation-sequencing. Microbial composition, diversity and functional roles were analyzed in comparison to the clinical characteristics of cohort using standard bioinformatics tools. ResultsCPP-ACP/F treatment modulated dysbiotic oral microbiome towards healthier community as the higher proportion of Proteobacteria and certain microbial protective species were enriched following CPP-ACP/F treatment. Despite overall uniformity of community structure in children with caries between the groups, some bacterial species were differentially represented in a statistically significant manner between pre- and post- treatments. Three bacterial species were found to be predictive of strongly sensitive to the CPP-ACP/F treatment, marked by decreased abundance of Lautropia mirabalis and increased abundance of Gemella haemolysans and Schwartzia succinivorans. ConclusionWithin the limits of the current study, it could be concluded that the CPP-ACP/F varnish treatment modulated the microbial composition of the dental plaque microbiome towards symbiosis. These symbiotic changes may demonstrate the potential clinical significance of CPP-ACP/F varnish treatment.

Healthy mouth, healthy gut: a dysbiotic oral microbiome exacerbates colitis.

Healthy mouth, healthy gut: a dysbiotic oral microbiome exacerbates colitis.

Intracellular Porphyromonas gingivalis Promotes the Tumorigenic Behavior of Pancreatic Carcinoma Cells.

Porphyromonas gingivalis is a member of the dysbiotic oral microbiome associated with oral inflammation and periodontal disease. Intriguingly, epidemiological studies link P. gingivalis to an increased risk of pancreatic cancer. Given that oral bacteria are detected in human pancreatic cancer, and both mouse and human pancreata harbor microbiota, we explored the involvement of P. gingivalis in pancreatic tumorigenesis using cell lines and a xenograft model. Live P. gingivalis induced proliferation of pancreatic cancer cells; however, surprisingly, this effect was independent of Toll-like receptor 2, the innate immune receptor that is engaged in response to P. gingivalis on other cancer and immune cells, and is required for P. gingivalis to induce alveolar bone resorption. Instead, we found that P. gingivalis survives inside pancreatic cancer cells, a trait that can be enhanced in vitro and is increased by hypoxia, a central characteristic of pancreatic cancer. Increased tumor cell proliferation was related to the degree of intracellular persistence, and infection of tumor cells with P. gingivalis led to enhanced growth in vivo. To the best of our knowledge, this study is the first to demonstrate the direct effect of exposure to P. gingivalis on the tumorigenic behavior of pancreatic cancer cell lines. Our findings shed light on potential mechanisms underlying the pancreatic cancer–periodontitis link.

Transient Expression of IL-17A in Foxp3 Fate-Tracked Cells in Porphyromonas gingivalis-Mediated Oral Dysbiosis.

In periodontitis Porphyromonas gingivalis contributes to the development of a dysbiotic oral microbiome. This altered ecosystem elicits a diverse innate and adaptive immune response that simultaneously involves Th1, Th17, and Treg cells. It has been shown that Th17 cells can alter their gene expression to produce interferon-gamma (IFN-γ). Forkhead box P3 (Foxp3) is considered the master regulator of Treg cells that produce inhibitory cytokines like IL-10. Differentiation pathways that lead to Th17 and Treg cells from naïve progenitors are considered antagonistic. However, it has been reported that Treg cells expressing IL-17A as well as IFN-γ producing Th17 cells have been observed in several inflammatory conditions. Each scenario appears plausible with T cell transdifferentiation resulting from persistent microbial challenge and consequent inflammation. We established that oral colonization with P. gingivalis drives an initial IL-17A dominated Th17 response in the oral mucosa that is dependent on intraepithelial Langerhans cells (LCs). We hypothesized that Treg cells contribute to this initial IL-17A response through transient expression of IL-17A and that persistent mucosal colonization with P. gingivalis drives Th17 cells toward an IFN-γ phenotype at later stages of infection. We utilized fate-tracking mice where IL-17A- or Foxp3-promoter activity drives the permanent expression of red fluorescent protein tdTomato to test our hypothesis. At day 28 of infection timeline, Th17 cells dominated in the oral mucosa, outnumbering Th1 cells by 3:1. By day 48 this dominance was inverted with Th1 cells outnumbering Th17 cells by nearly 2:1. Tracking tdTomato+ Th17 cells revealed only sporadic transdifferentiation to an IFN-γ-producing phenotype by day 48; the appearance of Th1 cells at day 48 was due to a late de novo Th1 response. tdTomato+ Foxp3+ T cells were 35% of the total live CD4+T cells in the oral mucosa and 3.9% of them developed a transient IL-17A-producing phenotype by day 28. Interestingly, by day 48 these IL-17A-producing Foxp3+ T cells had disappeared. Therefore, persistent oral P. gingivalis infection stimulates an initial IL-17A-biased response led by Th17 cells and a small but significant number of IL-17A-expressing Treg cells that changes into a late de novo Th1 response with only sporadic transdifferentiation of Th17 cells.

Shifts in the bacterial community of saliva give insights on the relationship between obesity and oral microbiota in adolescents.

The current study aimed at the determination of the impact of obesity on the salivary microbiome in adolescents. Sixty subjects ranging 14-17years old were enrolled (obese: n = 30-50% females, and normal weight: n = 30-50% females). Stimulated saliva was collected for denaturing gradient gel electrophoresis (DGGE) band patterns and massive 16S rRNA gene sequencing using the Ion Torrent platform. Overall, data analysis revealed that male subjects harbored a higher diverse salivary microbiome, defined by a significant higher richness (32.48 versus 26.74) and diversity (3.36 versus 3.20), higher Simpson values (0.96 versus 0.95) and distinct bacterial community structure considering either sex or condition (p < 0.05). Bacterial community fingerprinting analysis in human saliva showed a positive correlation with increased body mass index (BMI) in adolescents. Veillonella, Haemophilus and Prevotella occurrence was found to be affected by BMI, whereas Neisseria and Rothia occurrence was significantly impacted by sex in obese subjects. Our findings suggest that male and female adolescents may harbor a naturally distinct salivary microbiota and that obesity may specifically have an impact on their oral bacterial community. The potential dysbiotic oral microbiome in obese adolescents raises new insights on the etiology and prevention of future conditions in these populations.