Ectopic colonization of oral bacteria in the intestine drives TH1 cell induction and inflammation

Epithelial Cells as a Transmitter of Signals From Commensal Bacteria and Host Immune Cells

Intestinal epithelial cells (IECs) are non-hematopoietic cells that form a physical barrier against external antigens. Recent studies indicate that IECs have pleiotropic functions in the regulation of luminal microbiota and the host immune system. IECs produce various immune modulatory cytokines and chemokines in response to commensal bacteria and contribute to developing the intestinal immune system. In contrast, IECs receive cytokine signals from immune cells and produce various immunological factors against luminal bacteria. This bidirectional function of IECs is critical to regulate homeostasis of microbiota and the host immune system. Disruption of the epithelial barrier leads to detrimental host diseases such as inflammatory bowel disease, colonic cancer, and pathogenic infection. This review provides an overview of the functions and physiology of IECs and highlights their bidirectional functions against luminal bacteria and immune cells, which contribute to maintaining gut homeostasis.

Microbiology and immunology: An ideal partnership for a tango at the gut surface-A tribute to Philippe Sansonetti

Over the past 20 years, the highly dynamic interactions that take place between hosts and the gut microbiota have emerged as a major determinant in health and disease. The complexity of the gut microbiota represents, however, a considerable challenge, and reductionist approaches are indispensable to define the contribution of individual bacteria to host responses and to dissect molecular mechanisms. In this tribute to Philippe Sansonetti, I would like to show how rewarding collaborations with microbiologists have guided our team of immunologists in the study of host–microbiota interactions and, thanks to the use of controlled colonisation experiments in gnotobiotic mice, toward the demonstration that segmented filamentous bacteria (SFB) are indispensable to drive the post‐natal maturation of the gut immune barrier in mice. The work led with Philippe Sansonetti to set up in vitro culture conditions has been one important milestone that laid the ground for in‐depth characterization of the molecular attributes of this unusual symbiont. Recent suggestions that SFB may be present in the human microbiota encourage further cross‐fertilising interactions between microbiologists and immunologists to define whether results from mice can be translated to humans and, if so, how SFB may be used to promote human intestinal defences against enteropathogens. Nurturing the competences to pursue this inspiring project is one legacy of Philippe Sansonetti.

Oral Bacteria and Intestinal Dysbiosis in Colorectal Cancer

The human organism coexists with its microbiota in a symbiotic relationship. These polymicrobial communities are involved in many crucial functions, such as immunity, protection against pathogens, and metabolism of dietary compounds, thus maintaining homeostasis. The oral cavity and the colon, although distant anatomic regions, are both highly colonized by distinct microbiotas. However, studies indicate that oral bacteria are able to disseminate into the colon. This is mostly evident in conditions such as periodontitis, where specific bacteria, namely Fusobacterium nucrelatum and Porphyromonas gingivalis project a pathogenic profile. In the colon these bacteria can alter the composition of the residual microbiota, in the context of complex biofilms, resulting in intestinal dysbiosis. This orally-driven disruption promotes aberrant immune and inflammatory responses, eventually leading to colorectal cancer (CRC) tumorigenesis. Understanding the exact mechanisms of these interactions will yield future opportunities regarding prevention and treatment of CRC.

Dysbiosis of the buccal mucosa microbiome in primary Sjögren's syndrome patients

Objectives

Environmental factors in the aetiology of primary Sjögren's syndrome (pSS) are largely unknown. Host-microbiome interaction at mucosal surfaces is presumed to be involved in the aetiopathogenesis of pSS. Here, we assessed whether the microbiome of the buccal mucosa is specific for pSS compared with symptom-controls.

Methods

The bacterial composition of buccal swab samples from 37 pSS patients, 86 non-SS sicca patients (with similar dryness symptoms to pSS patients, but not fulfilling the classification criteria) and 24 healthy controls (HCs) was determined with 16S rRNA sequencing. Multivariate Association with Linear Models was used to find associations between individual taxa and pSS, taking into account smoking and dental status. Associations were replicated in a general population cohort (n = 103).

Results

The buccal mucosa microbiome of pSS and non-SS sicca patients both differed from HCs. A higher Firmicutes/Proteobacteria ratio was characteristic for both pSS and non-SS sicca patients. Disease status (pSS, non-SS sicca, HCs) and salivary secretion rate contributed almost equally to the variation in bacterial composition between individuals (3.8 and 4.3%, respectively). Two taxa were associated with pSS compared with non-SS sicca patients and 19 compared with HCs. When salivary secretion rate was taken into account, no taxon was associated with pSS compared with non-SS sicca. Twelve of the 19 pSS-associated taxa were correlated with salivary secretion.

Conclusion

Dysbiosis of the buccal mucosa microbiome in pSS patients resembles that of symptom-controls. The buccal mucosa microbiome in pSS patients is determined by a combination of reduced salivary secretion and disease-specific factors.

Reprogramming of Th1 cells into regulatory T cells through rewiring of the metabolic status

T helper type 1 (Th1) cells form one of the most stable CD4 T-cell subsets, and direct conversion of fully differentiated Th1 to regulatory T (Treg) cells has been poorly investigated. Here, we established a culture method for inducing Foxp3 from Th1 cells of mice and humans. This is achieved simply by resting Th1 cells without T-cell receptor ligation before stimulation in the presence of transforming growth factor-beta (TGF-β). We named the resulting Th1-derived Foxp3+ cells Th1reg cells. Mouse Th1reg cells showed an inducible Treg-like phenotype and suppressive ability both in vitro and in vivo. Th1reg cells could also be induced from in vivo-developed mouse Th1 cells. Unexpectedly, the resting process enabled Foxp3 expression not through epigenetic changes at the locus, but through metabolic change resulting from reduced mammalian target of rapamycin complex 1 (mTORC1) activity. mTORC1 suppressed TGF-β-induced phosphorylation of Smad2/3 in Th1 cells, which was restored in rested cells. Our study warrants future research aiming at development of immunotherapy with Th1reg cells.

[Oral microbiota and inflammatory bowel disease]

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract with a high incidence but a poor therapeutic outcome. However, IBD is generally caused by complicated interactions between environmental factors and gut microflora in genetically susceptible individuals. In view of a series of oral manifestations in patients with IBD and a high detection rate of oral bacteria among this population, oral microbiota may play an important role in the development of IBD. This article reviews the relationship between oral microbiota and IBD.

Microbiomes through the Looking Glass: What Do UC?

Pediatric ulcerative colitis incidence is rapidly rising, yet improved prognostic and therapeutic strategies are needed. In this issue of Cell Host & Microbe, Schirmer et al. (2018) reveal the dynamism of pediatric patient microbiomes through initial diagnosis and treatments, providing insights into microbial targets that predict therapeutic response and disease outcomes.

Pathological Characteristics of Periodontal Disease in Patients with Chronic Kidney Disease and Kidney Transplantation

Chronic kidney disease (CKD) is recognized as an irreversible reduction of functional nephrons and leads to an increased risk of various pathological conditions, including cardiovascular disease and neurological disorders, such as coronary artery calcification, hypertension, and stroke. In addition, CKD patients have impaired immunity against bacteria and viruses. Conversely, kidney transplantation (KT) is performed for patients with end-stage renal disease as a renal replacement therapy. Although kidney function is almost normalized by KT, immunosuppressive therapy is essential to maintain kidney allograft function and to prevent rejection. However, these patients are more susceptible to infection due to the immunosuppressive therapy required to maintain kidney allograft function. Thus, both CKD and KT present disadvantages in terms of suppression of immune function. Periodontal disease is defined as a chronic infection and inflammation of oral and periodontal tissues. Periodontal disease is characterized by the destruction of connective tissues of the periodontium and alveolar bone, which may lead to not only local symptoms but also systemic diseases, such as cardiovascular diseases, diabetes, liver disease, chronic obstructive pulmonary disease, and several types of cancer. In addition, the prevalence and severity of periodontal disease are significantly associated with mortality. Many researchers pay special attention to the pathological roles and clinical impact of periodontal disease in patients with CKD or KT. In this review, we provide information regarding important modulators of periodontal disease to better understand the relationship between periodontal disease and CKD and/or KT. Furthermore; we evaluate the impact of periodontal disease on various pathological conditions in patients with CKD and KT. Moreover, pathogens of periodontal disease common to CKD and KT are also discussed. Finally, we examine the importance of periodontal care in these patients. Thus, this review provides a comprehensive overview of the pathological roles and clinical significance of periodontal disease in patients with CKD and KT.

Variations in Oral Microbiota Composition Are Associated With a Risk of Throat Cancer

In this study, a next-generation sequencing strategy on 16S ribosomal RNA (16S rRNA) gene was employed to analyze 70 oral samples from 32 patients with throat cancer, nine patients with vocal cord polyp, and 29 healthy individuals (normal controls). Using this strategy, we demonstrated, for the first time, that the salivary microbiota of cancer patients were significantly different from those of patients with a polyp and healthy individuals. We observed that the beta diversity of the cancer group was divergent from both the normal and polyp groups, while alpha-diversity indices such as the Chao1 estimator (P = 8.1e-05), Simpson (P = 0.0045), and Shannon (P = 0.0071) were significantly reduced in cancer patients compared with patients containing a polyp and normal healthy individuals. Linear discriminant analysis (LDA) and Kruskal–Wallis test analyses and real-time quantitative polymerase chain reaction (qPCR) verification test revealed that the genera Aggregatibacter, Pseudomonas, Bacteroides, and Ruminiclostridium were significantly enriched in the throat cancer group compared with the vocal cord polyp and normal control groups (score value >2). Finally, diagnostic models based on putatively important constituent bacteria were constructed with 87.5% accuracy [area under the curve (AUC) = 0.875, 95% confidence interval (CI): 0.695–1]. In summary, in this study we characterized, for the first time, the oral microbiota of throat cancer patients without smoking history. We speculate that these results will help in the pathogenic mechanism and early diagnosis of throat cancer.

Antibacterial activity of disodium succinoyl glycyrrhetinate, a derivative of glycyrrhetinic acid against Streptococcus mutans

Streptococcus mutans is a cariogenic bacterium that localizes in the oral cavity. Glycyrrhetinic acid (GRA) is a major component of licorice extract. GRA and several derivatives, including disodium succinoyl glycyrrhetinate (GR-SU), are known to have anti-inflammatory effects in humans. In this study, the antimicrobial effect of GRA and its derivatives against the S. mutans UA159 strain were investigated. Minimum inhibitory concentrations (MICs) of GRA and GR-SU showed antibacterial activity against the S. mutans strain, whereas other tested derivatives did not. Because GR-SU is more soluble than GRA, GR-SU was used for further experiments. The antibacterial activity of GR-SU against 100 S. mutans strains was evaluated and it was found that all strains are susceptible to GR-SU, with MIC values below 256 µg/mL. A cell viability assay showed that GR-SU has a bacteriostatic effect on S. mutans cells. As to growth kinetics, sub-MICs of GR-SU inhibited growth. The effect of GR-SU on S. mutans virulence was then investigated. GR-SU at sub-MICs suppresses biofilm formation. Additionally, GR-SU greatly suppresses the pH drop caused by the addition of glucose and glucose-induced expression of the genes responsible for acid production (ldh and pykF) and tolerance (aguD and atpD). Additionally, expression of enolase, which is responsible for the carbohydrate phosphotransferase system, was not increased in the presence of GR-SU, indicating that GR-SU suppresses incorporation of sugars into S. mutans. In conclusion, GR-SU has antibacterial activity against S. mutans and also decreases S. mutans virulence.

Distal Consequences of Oral Inflammation

Periodontitis is an incredibly prevalent chronic inflammatory disease, which results in the destruction of tooth supporting structures. However, in addition to causing tooth and alveolar bone loss, this oral inflammatory disease has been shown to contribute to disease states and inflammatory pathology at sites distant from the oral cavity. Epidemiological and experimental studies have linked periodontitis to the development and/or exacerbation of a plethora of other chronic diseases ranging from rheumatoid arthritis to Alzheimer's disease. Such studies highlight how the inflammatory status of the oral cavity can have a profound impact on systemic health. In this review we discuss the disease states impacted by periodontitis and explore potential mechanisms whereby oral inflammation could promote loss of homeostasis at distant sites.

Modulation of Saliva Microbiota through Prebiotic Intervention in HIV-Infected Individuals

Human immunodeficiency virus (HIV) infection is characterized by an early depletion of the mucosal associated T helper (CD4+) cells that impair the host immunity and impact the oral and gut microbiomes. Although, the HIV-associated gut microbiota was studied in depth, few works addressed the dysbiosis of oral microbiota in HIV infection and, to our knowledge, no studies on intervention with prebiotics were performed. We studied the effect of a six-week-long prebiotic administration on the salivary microbiota in HIV patients and healthy subjects. Also, the co-occurrence of saliva microorganisms in the fecal bacteria community was explored. We assessed salivary and feces microbiota composition using deep 16S ribosomal RNA (rRNA) gene sequencing with Illumina methodology. At baseline, the different groups shared the same most abundant genera, but the HIV status had an impact on the saliva microbiota composition and diversity parameters. After the intervention with prebiotics, we found a drastic decrease in alpha diversity parameters, as well as a change of beta diversity, without a clear directionality toward a healthy microbiota. Interestingly, we found a differential response to the prebiotics, depending on the initial microbiota. On the basis of 100% identity clustering, we detected saliva sequences in the feces datasets, suggesting a drag of microorganisms from the upper to the lower gastrointestinal tract.

Klebsiella and Providencia emerge as lone survivors following long-term starvation of oral microbiota

It is well-understood that many bacteria have evolved to survive catastrophic events using a variety of mechanisms, which include expression of stress-response genes, quiescence, necrotrophy, and metabolic advantages obtained through mutation. However, the dynamics of individuals leveraging these abilities to gain a competitive advantage in an ecologically complex setting remain unstudied. In this study, we observed the saliva microbiome throughout the ecological perturbation of long-term starvation, allowing only the species best equipped to access and use the limited resources to survive. During the first several days, the community underwent a death phase that resulted in a ∼50-100-fold reduction in the number of viable cells. Interestingly, after this death phase, only three species, Klebsiella pneumoniae, Klebsiella oxytoca, and Providencia alcalifaciens, all members of the family Enterobacteriaceae, appeared to be transcriptionally active and recoverable. Klebsiella are significant human pathogens, frequently resistant to multiple antibiotics, and recently, ectopic colonization of the gut by oral Klebsiella was documented to induce dysbiosis and inflammation. MetaOmics analyses provided several leads for further investigation regarding the ecological success of the Enterobacteriaceae. The isolates accumulated single nucleotide polymorphisms in known growth advantage in stationary phase alleles and produced natural products closely resembling antimicrobial cyclic depsipeptides. The results presented in this study suggest that pathogenic Enterobacteriaceae persist much longer than their more benign neighbors in the salivary microbiome when faced with starvation. This is particularly significant, given that hospital surfaces contaminated with oral fluids, especially sinks and drains, are well-established sources of outbreaks of drug-resistant Enterobacteriaceae.

Bilberry anthocyanin extract promotes intestinal barrier function and inhibits digestive enzyme activity by regulating the gut microbiota in aging rats

This study was aimed at understanding potential mechanisms regarding bilberry anthocyanin extract consumption and healthy aging and the effects on intestinal barrier function and digestive enzyme activity, through regulating the gut microbiota in aging rats. Medium-dose bilberry anthocyanin extract consumption (20 mg per kg bw per day) was the optimum amount to regulate the intestinal function of aging rats. After consumption, bacteria beneficial to the intestine (Aspergillus oryzae, Lactobacillus, Bacteroides, Clostridiaceae-1, the Bacteroidales-S24-7-group and the Lachnospiraceae_NK4A136_group) were induced to grow, and harmful bacteria (Verrucomicrobia and Euryarchaeota) were inhibited. However, high-dose bilberry anthocyanin extract consumption altered some intestinally beneficial bacteria in an adverse way. There was a correlation between changes in bacterial composition and changes in short-chain fatty acids and the intestinal mucosal barrier. Bilberry anthocyanin extract consumption also decreased the activity of digestive enzymes. Our results suggest that bilberry anthocyanin extract consumption is a potential approach for assisting healthy aging.

Specific Bacteria and Metabolites Associated With Response to Fecal Microbiota Transplantation in Patients With Ulcerative Colitis

BACKGROUND & AIMS

Fecal microbiota transplantation (FMT) can induce remission in patients with ulcerative colitis (UC). In a randomized controlled trial of FMT in patients with active UC, we aimed to identify bacterial taxonomic and functional factors associated with response to therapy.

METHODS

We performed a double-blind trial of 81 patients with active UC randomly assigned to groups that received an initial colonoscopic infusion and then intensive multidonor FMT or placebo enemas, 5 d/wk for 8 weeks. Patients in the FMT group received blended homogenized stool from 3-7 unrelated donors. Patients in the placebo group were eligible to receive open-label FMT after the double-blind study period. We collected 314 fecal samples from the patients at screening, every 4 weeks during treatment, and 8 weeks after the blinded or open-label FMT therapy. We also collected 160 large-bowel biopsy samples from the patients at study entry, at completion of 8 weeks of blinded therapy, and at the end of open-label FMT, if applicable. We analyzed 105 fecal samples from the 14 individual donors (n = 55), who in turn contributed to 21 multidonor batches (n = 50). Bacteria in colonic and fecal samples were analyzed by both 16S ribosomal RNA gene and transcript amplicon sequencing; 285 fecal samples were analyzed by shotgun metagenomics, and 60 fecal samples were analyzed for metabolome features.

RESULTS

FMT increased microbial diversity and altered composition, based on analyses of colon and fecal samples collected before vs after FMT. Diversity was greater in fecal and colon samples collected before and after FMT treatment from patients who achieved remission compared with patients who did not. Patients in remission after FMT had enrichment of Eubacterium hallii and Roseburia inulivorans compared with patients who did not achieve remission after FMT and had increased levels of short-chain fatty acid biosynthesis and secondary bile acids. Patients who did not achieve remission had enrichment of Fusobacterium gonidiaformans, Sutterella wadsworthensis, and Escherichia species and increased levels of heme and lipopolysaccharide biosynthesis. Bacteroides in donor stool were associated with remission in patients receiving FMT, and Streptococcus species in donor stool was associated with no response to FMT.

CONCLUSIONS

In an analysis of fecal and colonic mucosa samples from patients receiving FMT for active UC and stool samples from donors, we associated specific bacteria and metabolic pathways with induction of remission. These findings may be of value in the design of microbe-based therapies for UC. ClinicalTrials.gov, Number NCT01896635.

Can oral bacteria affect the microbiome of the gut?

Oral bacteria spreading through the body have been associated with a number of systemic diseases. The gut is no exception. Studies in animals and man have indicated that oral bacteria can translocate to the gut and change its microbiota and possibly immune defense. The ectopic displacement of oral bacteria particularly occurs in severe systemic diseases, but also in patients with “chronic” periodontitis. Thus, Porphyromonas gingivalis, which creates dysbiosis in the subgingival microbiota and immune defense, may also cause dysregulation in the gut. A dysbiotic gut microbiota may cause diseases elsewhere in the body. The fact that “chronic” periodontitis may affect the gut microbiota could imply that consideration might in the future be given to a coordinated approach to the treatment of periodontitis and gastrointestinal disease. This area of investigation, which is in its infancy, may represent another pathway for oral bacteria to cause systemic diseases and deserves more research.

Altered Immunity and Microbial Dysbiosis in Aged Individuals With Long-Term Controlled HIV Infection

The introduction of highly active antiretroviral therapy (HAART) resulted in a significant increase in life expectancy for HIV patients. Indeed, in 2015, 45% of the HIV+ individuals in the United States were ≥55 years of age. Despite improvements in diagnosis and treatment of HIV infection, geriatric HIV+ patients suffer from higher incidence of comorbidities compared to age-matched HIV- individuals. Both chronic inflammation and dysbiosis of the gut microbiome are believed to be major contributors to this phenomenon, however carefully controlled studies investigating the impact of long-term (>10 years) controlled HIV (LTC-HIV) infection are lacking. To address this question, we profiled circulating immune cells, immune mediators, and the gut microbiome from elderly (≥55 years old) LTC-HIV+ and HIV- gay men living in the Palm Springs area. LTC-HIV+ individuals had lower frequency of circulating monocytes and CD4+ T-cells, and increased frequency CD8+ T-cells. Moreover, levels of systemic INFγ and several growth factors were increased while levels of IL-2 and several chemokines were reduced. Upon stimulation, immune cells from LTC-HIV+ individuals produced higher levels of pro-inflammatory cytokines. Last but not least, the gut microbiome of LTC-HIV+ individuals was enriched in bacterial taxa typically found in the oral cavity suggestive of loss of compartmentalization, while levels of beneficial butyrate producing taxa were reduced. Additionally, prevalence of Prevotella negatively correlated with CD4+ T-cells numbers in LTC-HIV+ individuals. These results indicate that despite long-term adherence and undetectable viral loads, LTC-HIV infection results in significant shifts in immune cell frequencies and gut microbial communities.

Microbiome Dependent Regulation of Tregs and Th17 Cells in Mucosa

Mammals co-exist with resident microbial ecosystem that is composed of an incredible number and diversity of bacteria, viruses and fungi. Owing to direct contact between resident microbes and mucosal surfaces, both parties are in continuous and complex interactions resulting in important functional consequences. These interactions govern immune homeostasis, host response to infection, vaccination and cancer, as well as predisposition to metabolic, inflammatory and neurological disorders. Here, we discuss recent studies on direct and indirect effects of resident microbiota on regulatory T cells (T_regs) and Th17 cells at the cellular and molecular level. We review mechanisms by which commensal microbes influence mucosa in the context of bioactive molecules derived from resident bacteria, immune senescence, chronic inflammation and cancer. Lastly, we discuss potential therapeutic applications of microbiota alterations and microbial derivatives, for improving resilience of mucosal immunity and combating immunopathology.

IL-36γ regulates mediators of tissue homeostasis in epithelial cells

IL-36 cytokines are critical regulators of mucosal inflammation and homeostasis. IL-36γ regulates the expression of inflammatory cytokines and antimicrobial proteins by gingival epithelial cells (e.g. TIGK cells). Here, we show that IL-36γ also regulates the expression of matrix metalloproteinase 9 (MMP9) and neutrophil gelatinase-associated lipocalin (NGAL), important mediators of antimicrobial immunity and tissue homeostasis in mucosal epithelia. MMP9 and NGAL were not similarly induced by IL-17 or IL-22, thus indicating the importance of IL-36γ in the regulation of MMP9 and NGAL. Mechanistically, MMP9 and NGAL expression was demonstrated to be induced in an IRAK1- and NF-κB-dependent manner. Furthermore, signaling by p38 MAP kinase may enable their expression to be independently regulated by IL-36γ. The stronger IL-36γ-inducible expression of MMP9 and NGAL in terminally differentiating TIGK cells suggests that control of their expression is associated with the maturation of the gingival epithelium. Although MMP9 and NGAL expression in epithelial cells can also be induced by bacteria, their expression in TIGK cells was not induced by the periodontal pathogen Porphyromonas gingivalis, most likely due to antagonism by the gingipain proteinase virulence factors. This study advances our understanding of how IL-36γ may promote oral mucosal immunity and tissue homeostasis, and how this may be dysregulated by bacterial pathogens.

Microbial Colonization Coordinates the Pathogenesis of a Klebsiella pneumoniae Infant Isolate

Enterobacteriaceae are among the first colonizers of neonate intestine. Members of this family, such as Escherichia and Klebsiella, are considered pathobionts and as such are capable of inducing local and systemic disease under specific colonization circumstances. Interplay between developing microbiota and pathogenic function of pathobionts are poorly understood. In this study, we investigate the functional interaction between various colonization patterns on an early colonizer, K. pneumoniae. K. pneumoniae 51-5 was isolated from stool of a healthy, premature infant, and found to contain the genotoxin island pks associated with development of colorectal cancer. Using intestinal epithelial cells, macrophages, and primary splenocytes, we demonstrate K. pneumoniae 51-5 upregulates expression of proinflammatory genes in vitro. Gnotobiotic experiments in Il10-/- mice demonstrate the neonate isolate induces intestinal inflammation in vivo, with increased expression of proinflammatory genes. Regulation of microbiota assembly revealed K. pneumoniae 51-5 accelerates onset of inflammation in Il10-/- mice, most significantly when microbiota is naturally acquired. Furthermore, K. pneumoniae 51-5 induces DNA damage and cell cycle arrest. Interestingly, K. pneumoniae 51-5 induced tumors in ApcMin/+; Il10-/- mice was not significantly affected by absence of colibactin activating enzyme, ClbP. These findings demonstrate pathogenicity of infant K. pneumoniae isolate is sensitive to microbial colonization status.

Insights into microbiome research 5: Mapping is first but function must come next

Several efforts identifying differential bacterial prevalence in the gut of multiple sclerosis (MS) patients have been reported and many more are underway. While these are critical first steps in determining the involvement of gut microbes in MS pathogenesis, functional assays (both in vitro and in vivo) are needed to explore the mechanisms underlying the observed changes and ultimately implementing interventional strategies to counter severity, progression or even reduce the chance that it develops in the first place.

Inverse Association Between the Skin and Oral Microbiota in Atopic Dermatitis

Previous studies have shown independently that the skin and gut microbiota are closely associated with atopic dermatitis (AD); however, the microbiota across different habitats of AD patients as an integrated community has not been characterized. In the present study, we comparatively analyzed the structure and function of the microbial communities in the skin, oral cavity, and gut of 172 AD patients and 120 healthy controls through 16S ribosomal RNA gene amplicon sequencing. The skin and oral cavity, but not the gut, of AD patients demonstrated differential reduction in the microbial diversity, and these were distinctly correlated with disease severity. Different degrees of shifts in the community structure were found among different habitats, and the lineage distance between the skin and oral microbiota of AD patients was closer than that observed in the controls. The different habitats of AD patients exhibited site-specific alterations at the genus level, and many oral-specific microbes of AD showed opposing directions of enrichment in the skin and oral cavity. Most interestingly, an inverse association in the functional pathways was found between the skin and oral microbiota of AD patients. Additionally, the alterations of the microbiota in different body sites of AD patients were differentially affected by age.

Extensive transmission of microbes along the gastrointestinal tract

The gastrointestinal tract is abundantly colonized by microbes, yet the translocation of oral species to the intestine is considered a rare aberrant event, and a hallmark of disease. By studying salivary and fecal microbial strain populations of 310 species in 470 individuals from five countries, we found that transmission to, and subsequent colonization of, the large intestine by oral microbes is common and extensive among healthy individuals. We found evidence for a vast majority of oral species to be transferable, with increased levels of transmission in colorectal cancer and rheumatoid arthritis patients and, more generally, for species described as opportunistic pathogens. This establishes the oral cavity as an endogenous reservoir for gut microbial strains, and oral-fecal transmission as an important process that shapes the gastrointestinal microbiome in health and disease.

The microbiome and immunodeficiencies: Lessons from rare diseases

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system, associated with a considerable increase in susceptibility to infections. PIDs can also predispose to malignancy, inflammation and autoimmunity. There is increasing awareness that some aspects of the immune dysregulation in PIDs may be linked to intestinal microbiota. Indeed, the gut microbiota and its metabolites have been shown to influence immune functions and immune homeostasis both locally and systemically. Recent studies have indicated that genetic defects causing PIDs lead to perturbations in the conventional mechanisms underlying homeostasis in the gut, resulting in poor immune surveillance at the intestinal barrier, which associates with altered intestinal permeability and bacterial translocation. Consistently, a substantial proportion of PID patients presents with clinically challenging IBD-like pathology. Here, we describe the current body of literature reporting on dysbiosis of the gut microbiota in different PIDs and how this can be either the result or cause of immune dysregulation. Further, we report how infections in PIDs enhance pathobionts colonization and speculate how, in turn, pathobionts may be responsible for increased disease susceptibility and secondary infections in these patients. The potential relationship between the microbial composition in the intestine and other sites, such as the oral cavity and skin, is also highlighted. Finally, we provide evidence, in preclinical models of PIDs, for the efficacy of microbiota manipulation to ameliorate disease complications, and suggest that the potential use of dietary intervention to correct dysbiotic flora in PID patients may hold promise.

Mycobacterial infection induces eosinophilia and production of α-defensin by eosinophils in mice

It has been well known in humans that eosinophil infiltration into the site of inflammation and eosinophilia occur in mycobacterial infections. However, the role of eosinophils against the mycobacterium is unclear. We showed in previous study that in situ mouse eosinophils infiltrated into tissues produce α-defensin, an anti-bacterial peptide. We investigated in this study whether eosinophils reacting to mycobacteria produce α-defensin in mice and whether it can be used as a model. We showed that mycobacterial infection induced blood eosinophilia and infiltration of α-defensin producing eosinophils that to surround mycobacteria at the site of infection. These findings were usually seen during human mycobacterial infection. We established a good model to study host defense mechanism against mycobacteria through α-defensin via eosinophils.

A defined commensal consortium elicits CD8 T cells and anti-cancer immunity

There is a growing appreciation for the importance of the gut microbiota as a therapeutic target in various diseases. However, there are only a handful of known commensal strains that can potentially be used to manipulate host physiological functions. Here we isolate a consortium of 11 bacterial strains from healthy human donor faeces that is capable of robustly inducing interferon-γ-producing CD8 T cells in the intestine. These 11 strains act together to mediate the induction without causing inflammation in a manner that is dependent on CD103⁺ dendritic cells and major histocompatibility (MHC) class Ia molecules. Colonization of mice with the 11-strain mixture enhances both host resistance against Listeria monocytogenes infection and the therapeutic efficacy of immune checkpoint inhibitors in syngeneic tumour models. The 11 strains primarily represent rare, low-abundance components of the human microbiome, and thus have great potential as broadly effective biotherapeutics.

Microbiotas from Humans with Inflammatory Bowel Disease Alter the Balance of Gut Th17 and RORγt+ Regulatory T Cells and Exacerbate Colitis in Mice

Microbiota are thought to influence the development and progression of inflammatory bowel disease (IBD), but determining generalizable effects of microbiota on IBD etiology requires larger-scale functional analyses. We colonized germ-free mice with intestinal microbiotas from 30 healthy and IBD donors and determined the homeostatic intestinal T cell response to each microbiota. Compared to microbiotas from healthy donors, transfer of IBD microbiotas into germ-free mice increased numbers of intestinal Th17 cells and Th2 cells and decreased numbers of RORγt+ Treg cells. Colonization with IBD microbiotas exacerbated disease in a model where colitis is induced upon transfer of naive T cells into Rag1-/- mice. The proportions of Th17 and RORγt+ Treg cells induced by each microbiota were predictive of human disease status and accounted for disease severity in the Rag1-/- colitis model. Thus, an impact on intestinal Th17 and RORγt+ Treg cell compartments emerges as a unifying feature of IBD microbiotas, suggesting a general mechanism for microbial contribution to IBD pathogenesis.

Gut pathobionts underlie intestinal barrier dysfunction and liver T helper 17 cell immune response in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disease and its frequent complication with ulcerative colitis highlights the pathogenic role of epithelial barrier dysfunction. Intestinal barrier dysfunction has been implicated in the pathogenesis of PSC, yet its underlying mechanism remains unknown. Here, we identify Klebsiella pneumonia in the microbiota of patients with PSC and demonstrate that K. pneumoniae disrupts the epithelial barrier to initiate bacterial translocation and liver inflammatory responses. Gnotobiotic mice inoculated with PSC-derived microbiota exhibited T helper 17 (T_H17) cell responses in the liver and increased susceptibility to hepatobiliary injuries. Bacterial culture of mesenteric lymph nodes in these mice isolated K. pneumoniae, Proteus mirabilis and Enterococcus gallinarum, which were prevalently detected in patients with PSC. A bacterial-organoid co-culture system visualized the epithelial-damaging effect of PSC-derived K. pneumoniae that was associated with bacterial translocation and susceptibility to T_H17-mediated hepatobiliary injuries. We also show that antibiotic treatment ameliorated the T_H17 immune response induced by PSC-derived microbiota. These results highlight the role of pathobionts in intestinal barrier dysfunction and liver inflammation, providing insights into therapeutic strategies for PSC.

Identification of Specific Oral and Gut Pathogens in Full Thickness Colon of Colitis Patients: Implications for Colon Motility

Impaired colon motility is one of the leading problems associated with inflammatory bowel disease (IBD). An expanding body of evidence supports the role of microbiome in normal gut function and in progression of IBD. The objective of this work is to determine whether diseased full thickness colon specimens, including the neuromuscular region (critical for colon motility function), contain specific oral and gut pathogens. In addition, we compared the differences in colon microbiome between Caucasians (CA) and African Americans (AA). Thirty-nine human full thickness colon (diseased colon and adjacent healthy colon) specimens were collected from Crohn's Colitis (CC) or Ulcerative Colitis (UC) patients while they underwent elective colon surgeries. We isolated and analyzed bacterial ribosomal RNA (rRNA) from colon specimens by amplicon sequencing of the 16S rRNA gene region. The microbiome proportions were quantified into Operational Taxonomic Units (OTUs) by analysis with Quantitative Insights Into Microbial ecology (QIIME) platform. Two hundred twenty-eight different bacterial species were identified by QIIME analysis. However, we could only decipher the species name of fifty-three bacteria. Our results show that proportion of non-detrimental bacteria in CC or UC colon samples were altered compared to adjacent healthy colon specimens. We further show, for the first time in full thickness colon specimens, that microbiome of CC and UC diseased specimens is dominated by putative oral pathogens belonging to the Phyla Firmicutes (Streptococcus, Staphylococcus, Peptostreptococcus), and Fusobacteria (Fusobacterium). In addition, we have identified patterns of differences in microbiome levels between CA and AA specimens with potential implications for health disparities research. Overall, our results suggest a significant association between oral and gut microbes in the modulation of colon motility in colitis patients.

Gastric Microbiota Alteration in Klebsiella pneumoniae-Caused Liver Abscesses Mice

Gastric microbiota provides a biological barrier against the invasion of foreign pathogens from the oral cavity, playing a vital role in maintaining gastrointestinal health. Klebsiella spp. of oral origin causes various infections not only in gastrointestinal tract but also in other organs, with Klebsiella pneumoniae serotype K1 resulting in a liver abscess (KLA) through oral inoculation in mice. However, the relationship between gastric microbiota and the extra-gastrointestinal KLA infection is not clear. In our study, a 454 pyrosequencing analysis of the bacterial 16S rRNA gene shows that the composition of gastric mucosal microbiota in mice with or without KLA infection varies greatly after oral inoculation with K. pneumoniae serotype K1 isolate. Interestingly, only several bacteria taxa show a significant change in gastric mucosal microbiota of KLA mice, including the decreased abundance of Bacteroides, Alisptipes and increased abundance of Streptococcus. It is worth noting that the abundance of Klebsiella exhibits an obvious increase in KLA mice, which might be closely related to KLA infection. At the same time, the endogenous antibiotics, defensins, involved in the regulation of the bacterial microbiota also show an increase in stomach and intestine. All these findings indicate that liver abscess caused by K. pneumoniae oral inoculation has a close relationship with gastric microbiota, which might provide important information for future clinical treatment. Gastric microbiota provides a biological barrier against the invasion of foreign pathogens from the oral cavity, playing a vital role in maintaining gastrointestinal health. Klebsiella spp. of oral origin causes various infections not only in gastrointestinal tract but also in other organs, with Klebsiella pneumoniae serotype K1 resulting in a liver abscess (KLA) through oral inoculation in mice. However, the relationship between gastric microbiota and the extra-gastrointestinal KLA infection is not clear. In our study, a 454 pyrosequencing analysis of the bacterial 16S rRNA gene shows that the composition of gastric mucosal microbiota in mice with or without KLA infection varies greatly after oral inoculation with K. pneumoniae serotype K1 isolate. Interestingly, only several bacteria taxa show a significant change in gastric mucosal microbiota of KLA mice, including the decreased abundance of Bacteroides, Alisptipes and increased abundance of Streptococcus. It is worth noting that the abundance of Klebsiella exhibits an obvious increase in KLA mice, which might be closely related to KLA infection. At the same time, the endogenous antibiotics, defensins, involved in the regulation of the bacterial microbiota also show an increase in stomach and intestine. All these findings indicate that liver abscess caused by K. pneumoniae oral inoculation has a close relationship with gastric microbiota, which might provide important information for future clinical treatment.

A severe case of refractory esophageal stenosis induced by nivolumab and responding to tocilizumab therapy

BACKGROUND

The prevalence of esophageal stenosis caused by immune checkpoint inhibitors in the context of induced immune mucositis and esophagitis is extremely rare.

CASE PRESENTATION

We report the case of a patient with stage IV pulmonary adenocarcinoma treated for 6 months with nivolumab who developed bilateral sterile conjunctivitis followed by oropharyngeal mucositis and esophagitis complicated by a severe esophageal stenosis. The laryngeal margin and hypopharyngeal mucosa appeared highly inflammatory with fibrinous deposits. Esophagogastroduodenoscopy revealed mucositis with a scar-like structure immediately below the upper esophageal sphincter with nonulcerative mucosa and an inflammatory aspect of the entire esophagus. No involvement of the stomach was observed. Oropharynx biopsies displayed marked lymphocytic T cell-infiltration with several foci of monocellular necrosis in the squamous epithelium. No morphologic evidence of adenocarcinoma and no signs of mycotic, bacterial or viral infection were noted. A blood sample revealed a discrete increase in the erythrocyte sedimentation rate (ESR) with no eosinophilia or leukocytosis. Liver and kidney function panel tests were normal. A thoracoabdominal CT scan reported no evidence of disease recurrence. Despite multiple boluses of methylprednisolone and high doses of prednisone continued for several months, the patient experienced very rapid symptomatological reappearance during three steroid tapering attempts and aggravation of his esophageal stenosis to an aphagic stage, requiring a nasogastric tube. This long course of high-dose corticosteroid treatment was complicated with osteoporosis-induced fractures with several spontaneous compressions of thoracolumbar vertebrae requiring an enlarged T10 to L5 cementoplasty. Anti-IL-6 blockade therapy with tocilizumab resulted in excellent clinical response, allowing the total resolution of the immune-related adverse events (irAEs) and leading to successful steroid tapering.

CONCLUSIONS

Herein, we describe the first case of a patient who developed autoimmune mucositis and esophagitis complicated by a severe refractory esophageal stenosis induced during treatment by nivolumab, which completely resolved after personalized treatment with tocilizumab, suggesting a role of IL-6 blockade in the management of severe steroid refractory esophageal stenosis and more broadly in refractory immune-related adverse events.

Signatures within the esophageal microbiome are associated with host genetics, age, and disease

BACKGROUND

The esophageal microbiome has been proposed to be involved in a range of diseases including the esophageal adenocarcinoma cascade; however, little is currently known about its function and relationship to the host. Here, the esophageal microbiomes of 106 prospectively recruited patients were assessed using 16S rRNA and 18S rRNA amplicon sequencing as well as shotgun sequencing, and associations with age, gender, proton pump inhibitor use, host genetics, and disease were tested.

RESULTS

The esophageal microbiome was found to cluster into functionally distinct community types (esotypes) defined by the relative abundances of Streptococcus and Prevotella. While age was found to be a significant factor driving microbiome composition, bacterial signatures and functions such as enrichment with Gram-negative oral-associated bacteria and microbial lactic acid production were associated with the early stages of the esophageal adenocarcinoma cascade. Non-bacterial microbes such as archaea, Candida spp., and bacteriophages were also identified in low abundance in the esophageal microbiome. Specific host SNPs in NOTCH2, STEAP2-AS1, and NREP were associated with the composition of the esophageal microbiome in our cohort.

CONCLUSIONS

This study provides the most comprehensive assessment of the esophageal microbiome to date and identifies novel signatures and host markers that can be investigated further in the context of esophageal adenocarcinoma development.

The microbiome and HLA-B27-associated acute anterior uveitis

Acute anterior uveitis (AAU) and the spondyloarthritis (SpA) subtypes ankylosing spondylitis, reactive arthritis and psoriatic arthritis are among the inflammatory diseases affected by the biology of the intestinal microbiome. In this Review, the relationship between AAU, SpA and the microbiome is discussed, with a focus on the major SpA risk gene HLA-B*27 and how it is associated with both intestinal tolerance and the loss of ocular immune privilege that can accompany AAU. We provide four potential mechanisms to account for how dysbiosis, barrier function and immune response contribute to the development of ocular inflammation and the pathogenesis of AAU. Finally, potential therapeutic avenues to target the microbiota for the clinical management of AAU and SpA are outlined.

Qualitative and Quantitative DNA- and RNA-Based Analysis of the Bacterial Stomach Microbiota in Humans, Mice, and Gerbils

Clinical stomach interventions, such as acid inhibition or bypass surgery, have been linked to fecal microbiota alterations. We demonstrate that the stomach microbiota largely overlaps those of adjacent gastrointestinal locations and identify gradual decreases and increases in the relative abundances of specific bacteria within the stomach, suggesting selective enrichment and depletion. Moreover, similarities between stomach and esophagus samples are proportional to the concentrations of Streptococcus (Firmicutes) in the stomach. The relative abundance of Firmicutes in the stomach, compared to that of Bacteroidetes, is increased in RNA relative to DNA, indicating higher transcriptional activity. Moreover, increased absolute bacterial loads are associated with decreased relative abundance of Firmicutes and higher relative abundance of Bacteroidetes. Our findings characterize the stomach microbiota as influenced by Bacteroidetes influx against a background of transcriptionally more active Firmicutes. Human, mouse, and gerbil stomach microbiotas differ at lower taxonomic levels, which might affect the utility of these model organisms.

Clinical interventions in the stomach have been linked to fecal microbiota alterations, suggesting a function of the stomach in gastrointestinal (GI) homeostasis. We sought to determine the taxonomic bacterial biogeography of the upper GI tract, including different sites within the human stomach (cardia, corpus, and antrum), adjacent upstream (esophagus) and downstream (duodenum) locations, and luminal contents (aspirate), as well as whole-stomach samples from mice and gerbils. Qualitative and quantitative DNA- and RNA-based taxonomic microbiota analyses were combined to study the relationship of relative and absolute bacterial abundances and transcriptionally active bacterial microbiota components in the stomach of humans and mice. Stomach microbiota compositions resembled those of esophagus and duodenum. However, along the descending GI tract, the relative abundances of specific oropharyngeal commensals decreased (Streptococcus) or increased (Rothia mucilaginosa, Porphyromonas, and Lachnospiraceae). Furthermore, the compositional similarity (weighted UniFrac) between stomach aspirates and esophageal biopsy samples increased with gastric Streptococcus relative abundance. In both human aspirate and mouse stomach samples, Firmicutes were more abundant among transcriptionally active bacteria than Bacteroidetes. The relative abundance of Firmicutes in the stomach was negatively correlated and that of Bacteroidetes was positively correlated with absolute bacterial abundance, suggesting a disproportionate increase of Bacteroidetes over Firmicutes at higher bacterial densities. Human, mouse, and gerbil stomach samples showed similarities at higher taxonomic levels but differences at lower taxonomic levels. Our findings suggest selective enrichment and depletion of specific bacterial taxa in the stomach and Firmicutes being transcriptionally more active than Bacteroidetes that increase in relative abundance with total bacterial load.

IMPORTANCE Clinical stomach interventions, such as acid inhibition or bypass surgery, have been linked to fecal microbiota alterations. We demonstrate that the stomach microbiota largely overlaps those of adjacent gastrointestinal locations and identify gradual decreases and increases in the relative abundances of specific bacteria within the stomach, suggesting selective enrichment and depletion. Moreover, similarities between stomach and esophagus samples are proportional to the concentrations of Streptococcus (Firmicutes) in the stomach. The relative abundance of Firmicutes in the stomach, compared to that of Bacteroidetes, is increased in RNA relative to DNA, indicating higher transcriptional activity. Moreover, increased absolute bacterial loads are associated with decreased relative abundance of Firmicutes and higher relative abundance of Bacteroidetes. Our findings characterize the stomach microbiota as influenced by Bacteroidetes influx against a background of transcriptionally more active Firmicutes. Human, mouse, and gerbil stomach microbiotas differ at lower taxonomic levels, which might affect the utility of these model organisms.

Commensal Bacteria-Specific CD4+ T Cell Responses in Health and Disease

Over the course of evolution, mammalian body surfaces have adapted their complex immune system to allow a harmless coexistence with the commensal microbiota. The adaptive immune response, in particular CD4+ T cell-mediated, is crucial to maintain intestinal immune homeostasis by discriminating between harmless (e.g., dietary compounds and intestinal microbes) and harmful stimuli (e.g., pathogens). To tolerate food molecules and microbial components, CD4+ T cells establish a finely tuned crosstalk with the environment whereas breakdown of these mechanisms might lead to chronic disease associated with mucosal barriers and beyond. How commensal-specific immune responses are regulated and how these molecular and cellular mechanisms can be manipulated to treat chronic disorders is yet poorly understood. In this review, we discuss current knowledge of the regulation of commensal bacteria-specific CD4+ T cells. We place particular focus on the key role of commensal-specific CD4+ T cells in maintaining tolerance while efficiently eradicating local and systemic infections, with a focus on factors that trigger their aberrant activation.

Oral administration of antibiotics results in fecal occult bleeding due to metabolic disorders and defective proliferation of the gut epithelial cell in mice

Antibiotics sometimes exert adverse effects on the pathogenesis of colitis due to the dysbiosis resulting from the disruption of gut homeostasis. However, the precise mechanisms underlying colitogenic effects of antibiotic-induced colitis are largely unknown. Here, we show a novel murine fecal occult bleeding model induced by the combinatorial treatment of ampicillin and vancomycin, which is accompanied by an enlarged cecum, upregulation of pro-inflammatory cytokines IL-6 and IL-12, a reduction in Ki-67-positive epithelial cell number and an increase in the apoptotic cell number in the colon. Moreover, gas chromatography-tandem mass analysis showed that various kinds of metabolites, including glutamic acid and butyric acid, were significantly decreased in the cecal contents. In addition, abundance of butyric acid producer Clostridiales was dramatically reduced in the enlarged cecum. Interestingly, supplementation of monosodium glutamate or its precursor glutamine suppressed colonic IL-6 and IL-12, protected from cell apoptosis and prevented fecal occult blood indicating that the reduced level of glutamic acid is a possible mechanism of antibiotic-induced fecal occult bleeding. Our data showed a novel mechanism of antibiotic-induced fecal occult bleeding providing a new insight into the clinical application of glutamic acid for the treatment of antibiotic-induced colitis.

Detection of α-defensin in eosinophils in helminth-infected mouse model

α-defensin is a potent antimicrobial peptide secreted from intestinal mucosal epithelial cells, such as Paneth cells, and affects not only bacteria but also parasites and fungi. Recently, human eosinophils have also been shown to produce α-defensin, but no studies have been done on other animals. In this study, we attempted to detect α-defensin protein in mouse eosinophils infiltrating the intestinal mucosa during a helminth infection using Zamboni fixation and immunohistochemistry. Most of the eosinophils infiltrating the intestinal mucosa during helminth infection were positive for α-defensin. The expression level of α-defensin mRNA was 50 fold that in the control. Meanwhile, the number of Paneth cells was doubled, and their α-defensin fluorescence intensity was increased. These results suggested that eosinophils are also important producers of α-defensin, such as Paneth cells in mice, and that α-defensin produced from eosinophils might be involved in defensive mechanisms against helminths. Moreover, the experimental system used in this study is a good model to study the generation of α-defensin by eosinophils.

Macrophage interactions with fungi and bacteria in inflammatory bowel disease

PURPOSE OF REVIEW

In this review, we discuss recent advances into delineating the dual role of intestinal phagocytes in health and during intestinal disease. We further discuss the key role of gut-resident macrophages in recognition of bacterial and fungal microbiota in the gut.

RECENT FINDINGS

Inflammatory bowel disease (IBD) commonly manifests with pathologic changes in the composition of gut bacterial and fungal microbiota. Intestinal macrophages are key regulators of the balance between tolerogenic immunity and inflammation. Recent studies have highlighted the role of resident intestinal macrophages in the control of commensal fungi and bacteria in the steady state and during dysbiosis. The dual role of these cells in maintaining intestinal homeostasis and responding to microbiota dysbiosis during inflammation is being increasingly studied.

SUMMARY

It is becoming increasingly clear that an aberrant proinflammatory response to microbiota by infiltrating monocytes plays a role in the development of intestinal inflammation. Intestinal mononuclear phagocytes with characteristics of macrophages play an important role in limiting fungal and bacterial overgrowth under these conditions, but can be influenced by the inflammatory environment to further propel inflammation. Better understanding of the interaction of intestinal macrophages with host microbiota including commensal fungi and bacteria, provides an opportunity for the development of more targeted therapies for IBD.

Compositional and Temporal Changes in the Gut Microbiome of Pediatric Ulcerative Colitis Patients Are Linked to Disease Course

Evaluating progression risk and determining optimal therapy for ulcerative colitis (UC) is challenging as many patients exhibit incomplete responses to treatment. As part of the PROTECT (Predicting Response to Standardized Colitis Therapy) Study, we evaluated the role of the gut microbiome in disease course for 405 pediatric, new-onset, treatment-naive UC patients. Patients were monitored for 1 year upon treatment initiation, and microbial taxonomic composition was analyzed from fecal samples and rectal biopsies. Depletion of core gut microbes and expansion of bacteria typical of the oral cavity were associated with baseline disease severity. Remission and refractory disease were linked to species-specific temporal changes that may be implicative of therapy efficacy, and a pronounced increase in microbiome variability was observed prior to colectomy. Finally, microbial associations with disease-associated serological markers suggest host-microbial interactions in UC. These insights will help improve existing treatments and develop therapeutic approaches guiding optimal medical care.

Amphiregulin-producing γδ T cells are vital for safeguarding oral barrier immune homeostasis

Loss of oral barrier homeostasis leads to the development of periodontitis, the most common chronic inflammatory condition of mankind. Therefore, it is important to better understand the immune mediators acting at this unique barrier to safeguard tissue integrity. Here we identify a vital role for γδ T cells in constraining pathological inflammation at the oral barrier, as the absence of γδ T cells resulted in enhanced pathology during periodontitis. We show that oral barrier γδ T cells produce the reparative cytokine Amphiregulin, administration of which rescued the elevated oral pathology of tcrδ^−/− mice. Collectively, we identify a pathway controlling oral immunity mediated by barrier-resident γδ T cells, highlighting that these cells are crucial guards of oral barrier immune homeostasis.

γδ T cells are enriched at barrier sites such as the gut, skin, and lung, where their roles in maintaining barrier integrity are well established. However, how these cells contribute to homeostasis at the gingiva, a key oral barrier and site of the common chronic inflammatory disease periodontitis, has not been explored. Here we demonstrate that the gingiva is policed by γδ T cells with a T cell receptor (TCR) repertoire that diversifies during development. Gingival γδ T cells accumulated rapidly after birth in response to barrier damage, and strikingly, their absence resulted in enhanced pathology in murine models of the oral inflammatory disease periodontitis. Alterations in bacterial communities could not account for the increased disease severity seen in γδ T cell-deficient mice. Instead, gingival γδ T cells produced the wound healing associated cytokine amphiregulin, administration of which rescued the elevated oral pathology of tcrδ^−/− mice. Collectively, our results identify γδ T cells as critical constituents of the immuno-surveillance network that safeguard gingival tissue homeostasis.

The intestinal microbiota in the pathogenesis of inflammatory bowel diseases: new insights into complex disease

Inflammatory bowel diseases (IBD) are a group of chronic diseases of increasing worldwide prevalence characterized by gastrointestinal (GI) inflammation leading to debilitating symptoms and complications. The contribution of the intestinal microbiota to the pathogenesis and etiology of these diseases is an area of active research interest. Here, we discuss key mechanisms underlying the chronic inflammation seen in IBD as well as evidence implicating the intestinal microbiota in the development and potentiation of that inflammation. We also discuss recently published work in areas of interest within the field of microbial involvement in IBD pathogenesis - the importance of proper microecology within the GI tract, the evidence that the intestinal microbiota transduces environmental and genetic risk factors for IBD, and the mechanisms by which microbial products contribute to communication between microbe and host. There is an extensive body of published research on the evidence for microbial involvement in IBD; the goal of this review is to highlight the growing edges of the field where exciting and innovative research is pushing the boundaries of the conceptual framework of the role of the intestinal microbiota in IBD pathogenesis.