Regulation of inflammation by microbiota interactions with the host

Probiotics: Reiterating What They Are and What They Are Not

It has been over seventeen years since the scientific definition of probiotics was crafted, along with guidelines ensuring the appropriate use of the term. This definition is now used globally, yet on a consistent basis scientists, media and industry misrepresent probiotics or make generalized statements that illustrate a misunderstanding of their utility and limitations. The rate of discovery of novel organisms with potentially therapeutic benefit for both human and environmental health is progressing at an unprecedented rate. However, the term “probiotic” is often misapplied to describe any microbe with plausible therapeutic utility in the human host. It is argued that strict compliance to the scientific definition of the term “probiotic” and avoidance of generalizations to the whole field of probiotics based upon studies of one product, will help advance the development and validation of microbial therapies, and applications to improve human health.

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.

Impact of microbiota on central nervous system and neurological diseases: the gut-brain axis

Development of central nervous system (CNS) is regulated by both intrinsic and peripheral signals. Previous studies have suggested that environmental factors affect neurological activities under both physiological and pathological conditions. Although there is anatomical separation, emerging evidence has indicated the existence of bidirectional interaction between gut microbiota, i.e., (diverse microorganisms colonizing human intestine), and brain. The cross-talk between gut microbiota and brain may have crucial impact during basic neurogenerative processes, in neurodegenerative disorders and tumors of CNS. In this review, we discuss the biological interplay between gut-brain axis, and further explore how this communication may be dysregulated in neurological diseases. Further, we highlight new insights in modification of gut microbiota composition, which may emerge as a promising therapeutic approach to treat CNS disorders.

Modulation of the Immune Response to Improve Health and Reduce Foodborne Pathogens in Poultry

Salmonella and Campylobacter are the two leading causes of bacterial-induced foodborne illness in the US. Food production animals including cattle, swine, and chickens are transmission sources for both pathogens. The number of Salmonella outbreaks attributed to poultry has decreased. However, the same cannot be said for Campylobacter where 50⁻70% of human cases result from poultry products. The poultry industry selects heavily on performance traits which adversely affects immune competence. Despite increasing demand for poultry, regulations and public outcry resulted in the ban of antibiotic growth promoters, pressuring the industry to find alternatives to manage flock health. One approach is to incorporate a program that naturally enhances/modulates the bird's immune response. Immunomodulation of the immune system can be achieved using a targeted dietary supplementation and/or feed additive to alter immune function. Science-based modulation of the immune system targets ways to reduce inflammation, boost a weakened response, manage gut health, and provide an alternative approach to prevent disease and control foodborne pathogens when conventional methods are not efficacious or not available. The role of immunomodulation is just one aspect of an integrated, coordinated approach to produce healthy birds that are also safe and wholesome products for consumers.

Gut microbiome patterns correlate with higher postoperative complication rates after pancreatic surgery

Background

Postoperative complications are of great relevance in daily clinical practice, and the gut microbiome might play an important role by preventing pathogens from crossing the intestinal barrier. The two aims of this prospective clinical pilot study were: (1) to examine changes in the gut microbiome following pancreatic surgery, and (2) to correlate these changes with the postoperative course of the patient.

Results

In total, 116 stool samples of 32 patients undergoing pancreatic surgery were analysed by 16S-rRNA gene next-generation sequencing. One sample per patient was collected preoperatively in order to determine the baseline gut microbiome without exposure to surgical stress and/or antibiotic use. At least two further samples were obtained within the first 10 days following the surgical procedure to observe longitudinal changes in the gut microbiome. Whenever complications occurred, further samples were examined.

Based on the structure of the gut microbiome, the samples could be allocated into three different microbial communities (A, B and C). Community B showed an increase in Akkermansia, Enterobacteriaceae and Bacteroidales as well as a decrease in Lachnospiraceae, Prevotella and Bacteroides. Patients showing a microbial composition resembling community B at least once during the observation period were found to have a significantly higher risk for developing postoperative complications (B vs. A, odds ratio = 4.96, p < 0.01**; B vs. C, odds ratio = 2.89, p = 0.019*).

Conclusions

The structure of the gut microbiome is associated with the development of postoperative complications.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1399-5) contains supplementary material, which is available to authorized users.

Establishment of an ideal gut microbiota to boost healthy growth of neonates

For decades, supporting the optimal growth of low birth weight (LBW) infants has been considered one of the most important paediatric challenges, despite advances in neonatal intensive care technology and nutrition interventions. Since gut microbiota affects such diverse phenotypes in adults, the difference in gut microbiota composition between normal infants and LBW infants raises the possibility of gut microbiota playing an important role in different growth rates of neonates. Based on the concept that probiotics are generally beneficial to the health, numerous studies have been made on probiotics as a supplement to the diet of the LBW infants. However, clinical results on the effects of probiotics on LBW infant growth are either inconsistent or contradictory with each other, and thus the contribution of gut microbiota in neonatal growth has remained inconclusive. In this review, recent researches on neonatal gut microbiota are discussed to develop a new strategy for targeting gut microbiota as a solution to growth retardation in LBW infants. We also discuss how to establish the ideal gut microbiota to support optimal growth of LBW infants.

High dietary fat intake induces a microbiota signature that promotes food allergy

BACKGROUND

Diet-induced obesity and food allergies increase in tandem, but a potential cause-and-effect relationship between these diseases of affluence remains to be tested.

OBJECTIVE

We sought to test the role of high dietary fat intake, diet-induced obesity, and associated changes in gut microbial community structure on food allergy pathogenesis.

METHODS

Mice were fed a high-fat diet (HFD) for 12 weeks before food allergen sensitization on an atopic dermatitis-like skin lesion, followed by intragastric allergen challenge to induce experimental food allergy. Germ-free animals were colonized with a signature HFD or lean microbiota for 8 weeks before induction of food allergy. Food-induced allergic responses were quantified by using a clinical allergy score, serum IgE levels, serum mouse mast cell protease 1 concentrations, and type 2 cytokine responses. Accumulation of intestinal mast cells was examined by using flow cytometry and chloroacetate esterase tissue staining. Changes in the gut microbial community structure were assessed by using high-throughput 16S ribosomal DNA gene sequencing.

RESULTS

HFD-induced obesity potentiates food-induced allergic responses associated with dysregulated intestinal effector mast cell responses, increased intestinal permeability, and gut dysbiosis. An HFD-associated microbiome was transmissible to germ-free mice, with the gut microbial community structure of recipients segregating according to the microbiota input source. Independent of an obese state, an HFD-associated gut microbiome was sufficient to confer enhanced susceptibility to food allergy.

CONCLUSION

These findings identify HFD-induced microbial alterations as risk factors for experimental food allergy and uncouple a pathogenic role of an HFD-associated microbiome from obesity. Postdieting microbiome alterations caused by overindulgence of dietary fat might increase susceptibility to food allergy.

Gut microbiome structure and metabolic activity in inflammatory bowel disease

The inflammatory bowel diseases (IBDs), which include Crohn's disease (CD) and ulcerative colitis (UC), are multifactorial chronic conditions of the gastrointestinal tract. While IBD has been associated with dramatic changes in the gut microbiota, changes in the gut metabolome-the molecular interface between host and microbiota-are less well understood. To address this gap, we performed untargeted metabolomic and shotgun metagenomic profiling of cross-sectional stool samples from discovery (n = 155) and validation (n = 65) cohorts of CD, UC and non-IBD control patients. Metabolomic and metagenomic profiles were broadly correlated with faecal calprotectin levels (a measure of gut inflammation). Across >8,000 measured metabolite features, we identified chemicals and chemical classes that were differentially abundant in IBD, including enrichments for sphingolipids and bile acids, and depletions for triacylglycerols and tetrapyrroles. While > 50% of differentially abundant metabolite features were uncharacterized, many could be assigned putative roles through metabolomic 'guilt by association' (covariation with known metabolites). Differentially abundant species and functions from the metagenomic profiles reflected adaptation to oxidative stress in the IBD gut, and were individually consistent with previous findings. Integrating these data, however, we identified 122 robust associations between differentially abundant species and well-characterized differentially abundant metabolites, indicating possible mechanistic relationships that are perturbed in IBD. Finally, we found that metabolome- and metagenome-based classifiers of IBD status were highly accurate and, like the vast majority of individual trends, generalized well to the independent validation cohort. Our findings thus provide an improved understanding of perturbations of the microbiome-metabolome interface in IBD, including identification of many potential diagnostic and therapeutic targets.

In silico prediction reveals the existence of potential bioactive neuropeptides produced by the human gut microbiota

This work reports on a large-scale potential neuropeptide activity screening in human gut microbiomes deposited in public databases. In our experimental approach, the sequences of the bioactive peptides collected in the MAHMI database, mainly predicted as immunomodulatory or antitumoral, were crossed with those of the neuroactive/digestive peptides. From 91,325,790 potential bioactive peptides, only 581 returned a match when crossed against the 5949 neuroactive peptides from the NeuroPep database and the 15 digestive hormones. Relevant bacterial taxa, such as Ruminococcus sp., Clostridium sp. were found among the main producers of the matching sequences, and many of the matches corresponded to adiponectin and the hormone produced by adipocites, which is involved in glucose homeostasis. These results show, for the first time, the presence of potentially bioactive peptides produced by gut microbiota members over the nervous cells, most notably, peptides with already predicted immunomodulatory or anti-inflammatory activity. Classical (Lactobacillus sp.) and next-generation (Faecalibacterium sp.) probiotics are shown to produce these peptides, which are proposed as a potential mechanism of action of psychobiotics. Our previous experimental results showed that many of these peptides were active when incubated with immune cells, such as dendritic cells, so their effect over the nervous system innervating the gut mucosa holds significant potential and should be explored.

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.

Antibiotic Perturbation of Gut Microbiota Dysregulates Osteoimmune Cross Talk in Postpubertal Skeletal Development

Commensal gut microbiota-host immune responses are experimentally delineated via gnotobiotic animal models or alternatively by antibiotic perturbation of gut microbiota. Osteoimmunology investigations in germ-free mice, revealing that gut microbiota immunomodulatory actions critically regulate physiologic skeletal development, highlight that antibiotic perturbation of gut microbiota may dysregulate normal osteoimmunological processes. We investigated the impact of antibiotic disruption of gut microbiota on osteoimmune response effects in postpubertal skeletal development. Sex-matched C57BL/6T mice were administered broad-spectrum antibiotics or vehicle-control from the age of 6 to 12 weeks. Antibiotic alterations in gut bacterial composition and skeletal morphology were sex dependent. Antibiotics did not influence osteoblastogenesis or endochondral bone formation, but notably enhanced osteoclastogenesis. Unchanged Tnf or Ccl3 expression in marrow and elevated tumor necrosis factor-α and chemokine (C-C motif) ligand 3 in serum indicated that the pro-osteoclastic effects of the antibiotics are driven by increased systemic inflammation. Antibiotic-induced broad changes in adaptive and innate immune cells in mesenteric lymph nodes and spleen demonstrated that the perturbation of gut microbiota drives a state of dysbiotic hyperimmune response at secondary lymphoid tissues draining local gut and systemic circulation. Antibiotics up-regulated the myeloid-derived suppressor cells, immature myeloid progenitor cells known for immunosuppressive properties in pathophysiologic inflammatory conditions. Myeloid-derived suppressor cell-mediated immunosuppression can be antigen specific. Therefore, antibiotic-induced broad suppression of major histocompatibility complex class II antigen presentation genes in bone marrow discerns that antibiotic perturbation of gut microbiota dysregulates critical osteoimmune cross talk.

The interplay of type 2 immunity, helminth infection and the microbiota in regulating metabolism

Type 2 immunity has recently emerged as a critical player in metabolic status, with numerous studies investigating the role of type 2 immune cells within adipose tissue. Metabolic dysfunction is often characterised as a low-grade or chronic inflammatory state within tissues, and type 2 immunity may facilitate a return to metabolic homeostasis. A complex network of type 2 resident cells including M2 macrophages, eosinophils and ILC2s has been identified within adipose tissue. Although the effector cells in this equilibrium have not been clearly identified, any alteration of the type 2 microenvironment resulted in an altered metabolic state. Historically, the type 2 immune response has been associated with helminth infection. The type 2 immune response drives host resistance and plays an important role in promoting tissue repair following the migration of helminth larvae through tissues. Although helminths are largely eradicated in developed countries, infection rates remain high in poor communities within the developing world. Interestingly, there is strong evidence that helminth infection is inversely correlated with autoimmune or inflammatory disorders. Recently, an increasing amount of epidemiological and field studies suggest that it could be the same for obesity and metabolic syndrome. In the current review, we summarise the literature linking type 2 immunity to improved adipose tissue function. We then discuss more recent evidence indicating that helminth infection can provide protection against metabolic syndrome. Lastly, we explore the possible contributions of altered nutrient uptake, adipose tissue function and/or the intestinal microbiota with the ability of helminths to alter metabolic status.

Serotonin and tryptophan metabolites, autoantibodies and gut microbiome in APECED

Objective Intestinal autoimmunity with gastrointestinal (GI) dysfunction has been shown in patients with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED). Patients lack entero-endocrine (EE) cells and have circulating autoantibodies (Aabs) against critical enzymes in serotonin (5-HT) biosynthesis. Design We sought to determine the serum levels of 5-HT, tryptophan (Trp) metabolites and L-DOPA in 37 Finnish APECED patients and to correlate their abundance with the presence of TPH and AADC Aabs, GI dysfunction and depressive symptoms. We also performed an exploratory analysis of the gut microbiome. Methods Serum 5-HT, L-DOPA and Trp metabolite levels were determined by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). TPH and AADC Aabs were measured by ELISA. Depression was assessed with a structured RBDI questionnaire. The V3-V4 regions of the bacterial 16S rRNA gene were sequenced for gut microbiome exploration. Results Serum 5-HT levels were significantly decreased (130 ± 131 nmol/L vs 686 ± 233 nmol/L, P < 0.0001) in APECED patients with TPH-1 (±AADC) Aabs compared to controls and patients with only AADC Aabs. Reduced 5-HT levels correlated with constipation. The genus Escherichia/Shigella was overrepresented in the intestinal microbiome. No correlation between serum Trp, 5-HT or l-DOPA levels and the RBDI total score, fatigue or sleep disorders was found. Conclusions This exploratory study found low serum levels of 5-HT to be associated with constipation and the presence of TPH-1 and AADC Aabs, but not with symptoms of depression. Hence, serum 5-HT, TPH1 and AADC Aabs should be determined in APECED patients presenting with GI symptoms.

Targeting Innate and Adaptive Immune Responses to Cure Chronic HBV Infection

Fewer than 1% of chronic hepatitis B virus infections per year are cured with antiviral treatment. This creates a need for long-term treatment, which poses challenges for patients and health systems. Because cure is accompanied by recovery of antiviral immunity, a combination of direct-acting antiviral agents and immunotherapy are likely to be required. Extensive efforts have been made to identify determinants of the failed immune response to hepatitis B virus in patients with chronic infection. We review mechanisms of immune dysfunction in patients with chronic hepatitis B virus infection, immunotherapy strategies in development, and the challenges associated with successful implementation of immunotherapy.

Genetic diversity of Escherichia coli in gut microbiota of patients with Crohn's disease discovered using metagenomic and genomic analyses

Background

Crohn’s disease is associated with gut dysbiosis. Independent studies have shown an increase in the abundance of certain bacterial species, particularly Escherichia coli with the adherent-invasive pathotype, in the gut. The role of these species in this disease needs to be elucidated.

Methods

We performed a metagenomic study investigating the gut microbiota of patients with Crohn’s disease. A metagenomic reconstruction of the consensus genome content of the species was used to assess the genetic variability.

Results

The abnormal shifts in the microbial community structures in Crohn’s disease were heterogeneous among the patients. The metagenomic data suggested the existence of multiple E. coli strains within individual patients. We discovered that the genetic diversity of the species was high and that only a few samples manifested similarity to the adherent-invasive varieties. The other species demonstrated genetic diversity comparable to that observed in the healthy subjects. Our results were supported by a comparison of the sequenced genomes of isolates from the same microbiota samples and a meta-analysis of published gut metagenomes.

Conclusions

The genomic diversity of Crohn’s disease-associated E. coli within and among the patients paves the way towards an understanding of the microbial mechanisms underlying the onset and progression of the Crohn’s disease and the development of new strategies for the prevention and treatment of this disease.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5306-5) contains supplementary material, which is available to authorized users.

The role of the microbiota in infectious diseases

The human body is colonized by a diverse community of microorganisms collectively referred to as the microbiota. Here, we describe how the human microbiota influences susceptibility to infectious diseases using examples from the respiratory, gastrointestinal and female reproductive tract. We will discuss how interactions between the host, the indigenous microbiota and non-native microorganisms, including bacteria, viruses and fungi, can alter the outcome of infections. This Review Article will highlight the complex mechanisms by which the microbiota mediates colonization resistance, both directly and indirectly, against infectious agents. Strategies for the therapeutic modulation of the microbiota to prevent or treat infectious diseases will be discussed, and we will review potential therapies that directly target the microbiota, including prebiotics, probiotics, synbiotics and faecal microbiota transplantation.

Systemic instruction of cell-mediated immunity by the intestinal microbiome

Recent research has shed light on the plethora of mechanisms by which the gastrointestinal commensal microbiome can influence the local immune response in the gut (in particular, the impact of the immune system on epithelial barrier homeostasis and ensuring microbial diversity). However, an area that is much less well explored but of tremendous therapeutic interest is the impact the gut microbiome has on systemic cell-mediated immune responses. In this commentary, we highlight some key studies that are beginning to broadly examine the different mechanisms by which the gastrointestinal microbiome can impact the systemic immune compartment. Specifically, we discuss the effects of the gut microbiome on lymphocyte polarisation and trafficking, tailoring of resident immune cells in the liver, and output of circulating immune cells from the bone marrow. Finally, we explore contexts in which this new understanding of long-range effects of the gut microbiome can have implications, including cancer therapies and vaccination.

Clinician Guide to Microbiome Testing

Recent recognition that the intestinal microbiome plays potential roles in the pathogenesis of multiple common diseases has led to a growing interest in personalized microbiome analysis among clinical investigators and patients. Permissibility of direct access testing has allowed the emergence of commercial companies offering microbiome analysis to patients seeking to gain a better understanding of their symptoms and disease conditions. In turn, physicians are often asked to help with interpretation of such tests or even requested by their patients to order them. Therefore, physicians need to have a basic understanding of the current state of microbiome science. This review examines how the perspective of microbial ecology, which is fundamental to understanding the microbiome, updates the classical version of the germ theory of disease. We provide the essential vocabulary of microbiome science and describe its current limitations. We look forward to the future when microbiome diagnostics may live up to its potential of becoming integral to clinical care that will become increasingly individualized, and microbiome analysis may become incorporated into that future paradigm. However, we caution patients and providers that the current microbiome tests, given the state of knowledge and technology, do not provide much value in clinical decisions. Considerable research remains to be carried out to make this objective a reality.

Characterisation of gut, lung, and upper airways microbiota in patients with non-small cell lung carcinoma: Study protocol for case-control observational trial

BACKGROUND

Several studies have confirmed the important role of the gut microbiota in the regulation of immune functions and its correlation with different diseases, including cancer. While brain-gut and liver-gut axes have already been demonstrated, the existence of a lung-gut axis has been suggested more recently, with the idea that changes in the gut microbiota could affect the lung microbiota, and vice versa. Likewise, the close connection between gut microbiota and cancer of proximal sites (intestines, kidneys, liver, etc.) is already well established. However, little is known whether there is a similar relation when looking at world's number one cause of death from cancer-lung cancer.

OBJECTIVE

Firstly, this study aims to characterise the gut, lung, and upper airways (UAs) microbiota in patients with non-small cell lung cancer (NSCLC) treated with surgery or neoadjuvant chemotherapy plus surgery. Secondly, it aims to evaluate a chemotherapy effect on site-specific microbiota and its influence on immune profile. To our knowledge, this is the 1st study that will analyse multi-site microbiota in NSCLC patients along with site-specific immune response.

METHODS

The study is a case-controlled observational trial. Forty NSCLC patients will be divided into 2 groups depending on their anamnesis: Pchir, patients eligible for surgery, or Pct-chir, patients eligible for neoadjuvant chemotherapy plus surgery. Composition of the UAs (saliva), gut (faeces), and lung microbiota (from broncho-alveolar lavage fluid (BALF) and 3 lung pieces: "healthy" tissue distal to tumour, peritumoural tissue and tumour itself) will be analysed in both groups. Immune properties will be evaluated on the local (evaluation of the tumour immune cell infiltrate, tumour classification and properties, immune cell phenotyping in BALF; human neutrophil protein (HNP) 1-3, β-defensin 2, and calprotectin in faeces) and systemic level (blood cytokine and immune cell profile). Short-chain fatty acids (SCFAs) (major products of bacterial fermentation with an effect on immune system) will be dosed in faecal samples. Other factors such as nutrition and smoking status will be recorded for each patient. We hypothesise that smoking status and tumour type/grade will be major factors influencing both microbiota and immune/inflammatory profile of all sampling sites. Furthermore, due to non-selectivity, the same effect is expected from chemotherapy.

Response to Fungal Dysbiosis by Gut-Resident CX3CR1+ Mononuclear Phagocytes Aggravates Allergic Airway Disease

Sensing of the gut microbiota, including fungi, regulates mucosal immunity. Whether fungal sensing in the gut can influence immunity at other body sites is unknown. Here we show that fluconazole-induced gut fungal dysbiosis has persistent effects on allergic airway disease in a house dust mite challenge model. Mice with a defined community of bacteria, but lacking intestinal fungi were not susceptible to fluconazole-induced dysbiosis, while colonization with a fungal mixture recapitulated the detrimental effects. Gut-resident mononuclear phagocytes (MNPs) expressing the fractalkine receptor CX3CR1 were essential for the effect of gut fungal dysbiosis on peripheral immunity. Depletion of CX3CR1⁺ MNPs or selective inhibition of Syk signaling downstream of fungal sensing in these cells ameliorated lung allergy. These results indicate that disruption of intestinal fungal communities can have persistent effects on peripheral immunity and aggravate disease severity through fungal sensing by gut-resident CX3CR1⁺ MNPs.

A complex auxiliary: IL-17/Th17 signaling during type 1 diabetes progression

Type 1 diabetes (T1D) is an autoimmune disease centered around the loss of the beta cells of the islets of Langerhans, and consequent inability of the islets to produce the insulin necessary to maintain glycemic control. While most therapeutic approaches have been centered on insulin replacement, newer approaches to target the underlying immune response have become an area of focus. However, the immune landscape in T1D is extremely complex, and the roles played by individual cytokines during disease progression are incompletely understood, making the development of immunotherapies very difficult. In this review, we discuss the complex auxiliary role played by IL-17, both around the islet and in peripheral tissues such as the gut and kidney, which might influence T1D progression. Through our re-analysis of the key factors involved IL-17 signaling in recently published single-cell sequencing and sorted-cell bulk sequencing datasets, we find supporting evidence for the general existence of the signaling apparatus in islet endocrine cells. We also explore the emerging evidence of IL-17 serving as an influential factor in diabetic complications that affect distal tissues. While anti-IL-17 therapies are emerging as an option for psoriasis and other autoimmune disorders, we highlight here a number of questions that would need to be addressed before their potential applicability to treating T1D can be fully evaluated.

T-Cell Exhaustion in Chronic Infections: Reversing the State of Exhaustion and Reinvigorating Optimal Protective Immune Responses

T-cell exhaustion is a phenomenon of dysfunction or physical elimination of antigen-specific T cells reported in human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) infections as well as cancer. Exhaustion appears to be often restricted to CD8+ T cells responses in the literature, although CD4+ T cells have also been reported to be functionally exhausted in certain chronic infections. Although our understanding of the molecular mechanisms associated with the transcriptional regulation of T-cell exhaustion is advancing, it is imperative to also explore the central mechanisms that control the altered expression patterns. Targeting metabolic dysfunctions with mitochondrion-targeted antioxidants are also expected to improve the antiviral functions of exhausted virus-specific CD8+ T cells. In addition, it is crucial to consider the contributions of mitochondrial biogenesis on T-cell exhaustion and how mitochondrial metabolism of T cells could be targeted whilst treating chronic viral infections. Here, we review the current understanding of cardinal features of T-cell exhaustion in chronic infections, and have attempted to focus on recent discoveries, potential strategies to reverse exhaustion and reinvigorate optimal protective immune responses in the host.

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.

Gut Microbiota as a Modulator of Paneth Cells During Parenteral Nutrition in Mice

BACKGROUND

Parenteral nutrition (PN) leads to decreased production of Paneth cell-derived antimicrobial peptides and is accompanied by dysbiosis of the gut. The role of gut microbiota in regulating Paneth cell function during PN is unknown.

METHODS

Male C57BL/6 mice received either an antibiotic cocktail (Abx) or nothing (Normal) in their drinking water for 2 weeks before being fed either standard laboratory chow (Abx-Chow and Normal-Chow) or a continuous infusion of PN solution (Abx-PN and Normal-PN) for 7 days. In a separate experiment, the intestinal contents of mice having received 7 days of Chow or PN were transferred by gavage to germ-free (GF) mice.

RESULTS

Antibiotic treatment decreased the protein levels of lysozyme and RegIIIγ and the mRNA level of α-defensin 5, with no further effect by PN compared with chow. However, these measurements were higher in Abx-PN mice than in Normal-PN mice. When compared with Chow→GF, PN→GF mice demonstrated lower body weight, shorter intestinal length, severe atrophy of the ileum villus, and lower levels of lysozyme and RegIIIγ protein and α-defensin 5 mRNA. Interleukin (IL)-22 and IL-17 mRNA levels declined in the ileum. Principal component analysis revealed major differences between the metabolite compositions of the Chow and PN, as well as the Chow→GF and PN→GF groups that appears to indicate aberrant tryptophan metabolism.

CONCLUSIONS

Gut microbiota plays a vital role in PN-related Paneth cell dysfunction. Dysbiosis during PN might alter the production of microbial metabolites, thereby influencing the production of Paneth cell-derived antimicrobial peptides.

On cell death in the intestinal epithelium and its impact on gut homeostasis

PURPOSE OF REVIEW

Both apoptotic and nonapoptotic cell extrusion preserve the barrier functions of epithelia. Live cell extrusion is the paradigm for homeostatic renewal of intestinal epithelial cells (IEC). By extension, as extruded cells are not apoptotic, this form of cell shedding is thought to be largely ignored by lamina propria phagocytes and without immune consequence.

RECENT FINDINGS

Visualization of apoptotic IEC inside distinct subsets of intestinal phagocytes during homeostasis has highlighted apoptosis as a normal component of the natural turnover of the intestinal epithelium. Analysis of phagocytes with or without apoptotic IEC corpses has shown how apoptotic IEC constrain inflammatory pathways within phagocytes and induce immunosuppressive regulatory CD4 T-cell differentiation. Many of the genes involved overlap with susceptibility genes for inflammatory bowel disease (IBD).

SUMMARY

Excessive IEC death and loss-of-barrier function is characteristic of IBD. As regulatory and tolerogenic mechanisms are broken in IBD, a molecular understanding of the precise triggers and modes of IEC death as well as their consequences on intestinal inflammation is necessary. This characterization should guide new therapies that restore homeostatic apoptosis, along with its associated programs of immune tolerance and immunosuppression, to achieve mucosal healing and long-term remission.

Pretransplant Serum Citrulline Predicts Acute Graft-versus-Host Disease

Post-transplant biomarkers of acute graft-versus-host disease (aGVHD) and nonrelapse mortality (NRM) after allogeneic hematopoietic cell transplantation (allo-HCT) have been extensively studied. However, pretransplant biomarkers may provide a greater window of opportunity to intervene. We measured serum biomarkers of various aspects of gut barrier physiology before HCT (median, day -7) and 7 and 28 days post-HCT in 95 consecutive allo-HCT recipients enrolled in an open-label biorepository protocol. Biomarkers included citrulline for total functional enterocyte mass, Reg3a for antibacterial activity of the gut, and intestinal fatty acid binding protein (I-FABP) for enterocyte turnover. Compared to 16 healthy control subjects, we demonstrated that patients came to transplant with abnormal levels of all 3 biomarkers (P < .05), reflecting residual damage from prior chemotherapy. All 3 biomarkers initially declined from pre-HCT to day +7 (more pronounced after myeloablative than reduced-intensive conditioning) followed by a recovery phase and return toward pre-HCT values by day +28. A lower pre-HCT citrulline was independently associated with a higher risk of aGVHD grades II to IV (hazard ratio, 1.32; 95% confidence interval, 1.03 to 1.69; P = .02), and this association was not specific to gut GVHD. The strongest correlate of NRM was a higher level of Reg3a at day +7 (P < .001). I-FABP did not predict transplant outcomes. In conclusion, pre-HCT serum citrulline levels identify patients at high risk for developing aGVHD. Our results suggest that pre-HCT interventions to augment the gut barrier may decrease the risk of aGVHD.

The Digestive Health among Participants of the Woodstock Rock Festival in Poland-A Cross-Sectional Survey

Alterations of gut microbiota, intestinal barrier and the gut-brain axis may be involved in pathophysiology of functional gastrointestinal disorders. Our aim was to assess the prevalence of digestive tract symptoms and identify common variables potentially disrupting the gut-brain axis among participants of the Woodstock Festival Poland, 2017. In total 428 people filled in a questionnaire assessing health of their digestive tract. The investigator collected answers on an electronic device, while the study participant responded using a paper version of the same questionnaire. Liver and gallbladder related symptoms were the most prevalent among our study group (n = 266, 62%), however symptoms related to altered intestinal permeability were found to be the most intensive complaints. In females the intensity of gastrointestinal complaints was higher compared to men (p < 0.05), as well as the incidence of factors with the potential to alter gut-brain axis (p < 0.0001). Chronic psychological distress, intake of non-steroidal anti-inflammatory drugs (NSAIDs) and antibiotics, were the most common associations with gastrointestinal symptoms, which were the most prevalent in females. Further attention should be focused on stress as one of the main factors negatively influencing public health.

Impact of Diet-Modulated Butyrate Production on Intestinal Barrier Function and Inflammation

A major challenge in affluent societies is the increase in disorders related to gut and metabolic health. Chronic over nutrition by unhealthy foods high in energy, fat, and sugar, and low in dietary fibre is a key environmental factor responsible for this development, which may cause local and systemic inflammation. A low intake of dietary fibre is a limiting factor for maintaining a viable and diverse microbiota and production of short-chain fatty acids in the gut. A suppressed production of butyrate is crucial, as this short-chain fatty acid (SCFA) can play a key role not only in colonic health and function but also at the systemic level. At both sites, the mode of action is through mediation of signalling pathways involving nuclear NF-κB and inhibition of histone deacetylase. The intake and composition of dietary fibre modulate production of butyrate in the large intestine. While butyrate production is easily adjustable it is more variable how it influences gut barrier function and inflammatory markers in the gut and periphery. The effect of butyrate seems generally to be more consistent and positive on inflammatory markers related to the gut than on inflammatory markers in the peripheral tissue. This discrepancy may be explained by differences in butyrate concentrations in the gut compared with the much lower concentration at more remote sites.

Effects of Substance Use and Sex Practices on the Intestinal Microbiome During HIV-1 Infection

Background

Human immunodeficiency virus type 1 (HIV-1) infection alters the human intestinal microbiome; however, behavioral factors driving these changes remain poorly defined. Here we examine the effects of substance use and sex behavior on the microbiome during HIV-1 infection.

Methods

Archival rectal swab specimens, urine drug test results, and responses to substance use and sex behavior questionnaires were obtained from 37 HIV-positive participants at 2 time points, separated by 6 months, in a cohort examining the effects of substance use in men who have sex with men (MSM). Microbiome profiling was performed using 16S ribosomal RNA gene sequencing, and associations with behavioral factors were examined using 0-inflated negative binomial regression. Further analysis of selected variables of interest was performed using propensity scores to account for multiple confounders.

Results

Using permutational multivariate analysis of variance, we found that receptive anal intercourse, methamphetamine use, and marijuana use were among the most important drivers of microbiome variation. Propensity score-adjusted analyses revealed that methamphetamine use and marijuana use displayed unique associations; methamphetamine use was associated with an increased abundance of Porphyromonas and Granulicatella organisms and a decreased abundance of Ruminococcus, Collinsella, and Parabacteroides organisms, whereas marijuana use was associated with an increased abundance of Ruminococcus, Clostridium cluster IV, Solobacterium, and Fusobacterium organisms and a decreased abundance of Acidaminococcus, Prevotella, Dialister, Anaerostipes, and Dorea organisms.

Conclusions

Drug use and sex behavior are important factors associated with intestinal dysbiosis during chronic HIV-1 infection among young MSM.

Successful transplantation of guinea pig gut microbiota in mice and its effect on pneumonic plague sensitivity

Microbiota-driven variations in the inflammatory response are predicted to regulate host responses to infection. Increasing evidence indicates that the gastrointestinal and respiratory tracts have an intimate relationship with each other. Gut microbiota can influence lung immunity whereby gut-derived injurious factors can reach the lungs and systemic circulation via the intestinal lymphatics. The intestinal microbiota’s ability to resist colonization can be extended to systemic infections or to pathogens infecting distant sites such as the lungs. Unlike the situation with large mammals, the microtus Yersinia pestis 201 strain exhibits strong virulence in mice, but nearly no virulence to large mammals (such as guinea pigs). Hence, to assess whether the intestinal microbiota from guinea pigs was able to affect the sensitivity of mice to challenge infection with the Y. pestis 201 strain, we fed mice with guinea pig diets for two months, after which they were administered 0.5 ml of guinea pig fecal suspension for 30 days by oral gavage. The stools from each mouse were collected on days 0, 15, and 30, DNA was extracted from them, and 16S rRNA sequencing was performed to assess the diversity and composition of the gut microbiota. We found that the intestinal microbiota transplants from the guinea pigs were able to colonize the mouse intestines. The mice were then infected with Yersinia pestis 201 by lung invasion, but no statistical difference was found in the survival rates of the mice that were colonized with the guinea pig’s gut microbiota and the control mice. This indicates that the intestinal microbiota transplantation from the guinea pigs did not affect the sensitivity of the mice to pneumonic plague.

An update on the role of gut microbiota in chronic inflammatory diseases, and potential therapeutic targets

The human microbiome plays a critical role in human health, having metabolic, protective, and trophic functions, depending upon its' exact composition. This composition is affected by a number of factors, including the genetic background of the individual, early life factors (including method of birth, length of breastfeeding) and nature of the diet and other environmental exposures (including cigarette smoking) and general life habits. It plays a key role in the control of inflammation, and in turn, its' composition is significantly influenced by inflammation. Areas covered: We consider metabolic, protective, and trophic functions of the microbiome and influences through the lifespan from post-partum effects, to diet later in life in healthy older adults, the effects of aging on both its' composition, and influence on health and potential therapeutic targets that may have anti-inflammatory effects. Expert commentary: The future will see the growth of more effective therapies targeting the microbiome particularly with respect to the use of specific nutrients and diets personalized to the individual.

Autoimmune phenotypes in schizophrenia reveal novel treatment targets

Typical and atypical antipsychotics are the first-line treatments for schizophrenia, but these classes of drugs are not universally effective, and they can have serious side effects that impact compliance. Antipsychotic drugs generally target the dopamine pathways with some variation. As research of schizophrenia pathophysiology has shifted away from a strictly dopamine-centric focus, the development of new pharmacotherapies has waned. A field of inquiry with centuries-old roots is gaining traction in psychiatric research circles and may represent a new frontier for drug discovery in schizophrenia. At the forefront of this investigative effort is the immune system and its many components, pathways and phenotypes, which are now known to actively engage the brain. Studies in schizophrenia reveal an intricate association of environmentally-driven immune activation in concert with a disrupted genetic template. A consistent conduit through this gene-environmental milieu is the gut-brain axis, which when dysregulated can generate pathological autoimmunity. In this review, we present epidemiological and biochemical evidence in support of an autoimmune component in schizophrenia and depict gut processes and a dysbiotic microbiome as a source and perpetuator of autoimmune dysfunction in the brain. Within this framework, we review the role of infectious agents, inflammation, gut dysbioses and autoantibody propagation on CNS pathologies such as neurotransmitter receptor hypofunction and complement pathway-mediated synaptic pruning. We then review the new pharmacotherapeutic horizon and novel agents directed to impact these pathological conditions. At the core of this discourse is the understanding that schizophrenia is etiologically and pathophysiologically heterogeneous and thus its treatment requires individualized attention with disease state variants diagnosed with objective biomarkers.

Role of Short Chain Fatty Acids in Controlling Tregs and Immunopathology During Mucosal Infection

Interactions between mucosal tissues and commensal microbes control appropriate host immune responses and inflammation, but very little is known about these interactions. Here we show that the depletion of resident bacteria using antibiotics (Abx) causes oral and gut immunopathology during oropharyngeal candidiasis (OPC) infection. Antibiotic treatment causes reduction in the frequency of Foxp3+ regulatory cells (T_regs) and IL-17A producers, with a concomitant increase in oral tissue pathology. While C. albicans (CA) is usually controlled in the oral cavity, antibiotic treatment led to CA dependent oral and gut inflammation. A combination of short chain fatty acids (SCFA) controlled the pathology in Abx treated mice, correlating to an increase in the frequency of Foxp3+, IL-17A+, and Foxp3+IL-17A+ double positive (T_reg17) cells in tongue and oral draining lymph nodes. However, SCFA treatment did not fully reverse the gut inflammation suggesting that resident microbiota have SCFA independent homeostatic mechanisms in gut mucosa. We also found that SCFA potently induce Foxp3 and IL-17A expression in CD4+ T cells_, depending on the cytokine milieu in vitro. Depletion of T_regs alone in FDTR mice recapitulated oral inflammation in CA infected mice, showing that Abx mediated reduction of T_regs was involved in infection induced pathology. SCFA did not control inflammation in T_reg depleted mice in CA infected FDTR mice, showing that Foxp3⁺ T cell induction was required for the protective effect mediated by SCFA. Taken together, our data reveal that SCFA derived from resident bacteria play a critical role in controlling immunopathology by regulating T cell cytokines during mucosal infections. This study has broader implications on protective effects of resident microbiota in regulating pathological infections.

Maternal Soluble Fiber Diet during Pregnancy Changes the Intestinal Microbiota, Improves Growth Performance, and Reduces Intestinal Permeability in Piglets

Increasing evidence suggests that maternal diet during pregnancy modifies an offspring's microbiota composition and intestinal development in a long-term manner. However, the effects of maternal soluble fiber diet during pregnancy on growth traits and the developing intestine are still underexplored. Sows were allocated to either a control or 2.0% pregelatinized waxy maize starch plus guar gum (SF) dietary treatment during gestation. Growth performance, diarrhea incidence, gut microbiota composition and metabolism, and gut permeability and inflammation status of 14-day-old suckling piglets were analyzed. The maternal SF diet improved the growth rate and decreased the incidence of diarrhea in the piglets. Next-generation sequencing analysis revealed that the intestinal microbiota composition was altered by a maternal SF diet. The fecal and plasma levels of acetate and butyrate were also increased. Furthermore, a maternal SF diet reduced the levels of plasma zonulin and fecal lipocalin-2 but increased the plasma concentrations of interleukin 10 (IL-10) and transforming growth factor β (TGF-β). Additionally, the increased relative abundances of Lactobacillus spp. in SF piglets were positively correlated with growth rate, while the decreased abundances of Bilophila spp. were positively correlated with fecal lipocalin-2 levels. Our data reveal that a maternal SF diet during pregnancy has remarkable effects on an offspring's growth traits and intestinal permeability and inflammation, perhaps by modulating the composition and metabolism of gut microbiota.IMPORTANCE Although the direct effects of dietary soluble fiber on gut microbiota have been extensively studied, the more indirect effects of maternal nutrition solely during pregnancy on the development of the offspring's intestine are until now largely unexplored. Our data show that a maternal soluble fiber diet during pregnancy is independently associated with changes in the intestinal microbiota composition and metabolism of suckling piglets. These findings have direct implications for refining dietary recommendations in pregnancy. Moreover, a maternal soluble fiber diet reduces intestinal permeability and prevents intestinal inflammation and an excessive systemic immune response of suckling piglets. Therefore, the suckling piglets' resistance to disease was enhanced, diarrhea was reduced, and weight gain was raised. Additionally, the changes in gut microbiota in response to a maternal soluble fiber diet may also be directly correlated with the offspring's growth and gut development.

Utilization of Host-Derived Glycans by Intestinal Lactobacillus and Bifidobacterium Species

Members of the genus Lactobacillus are commonly found at the gastrointestinal tract and other mucosal surfaces of humans. This genus includes various species with a great number of potentially probiotic bacteria. Other often-used probiotic species belong to Bifidobacterium, a genus almost exclusively associated with the gut. As probiotics must survive and be metabolically active at their target sites, namely host mucosal surfaces, consumption of host-produced glycans is a key factor for their survival and activity. The ability to metabolize glycans such as human milk oligosaccharides (HMOs), glycosaminoglycans and the glycan moieties of glycoproteins and glycolipids found at the mucosal surfaces grants a competitive advantage to lactobacilli and bifidobacteria. The analyses of the great number of sequenced genomes from these bacteria have revealed that many of them encode a wide assortment of genes involved in the metabolism and transport of carbohydrates, including several glycoside hydrolases required for metabolizing the carbohydrate moieties of mucins and HMOs. Here, the current knowledge on the genetic mechanisms, known catabolic pathways and biochemical properties of enzymes involved in the utilization of host-produced glycans by lactobacilli and bifidobacteria will be summarized.

Bridging Systemic Immunity with Gastrointestinal Immune Responses via Oil-in-Polymer Capsules

As peripheral lymphocytes are typically excluded from the gastrointestinal lymph tissues, current parenteral vaccinations fail to simultaneously induce systemic and mucosal responses. To break the natural barrier, "immunoticket" capsules are developed and heralded, which are designed with positive charged shells and oily core to spatiotemporally deliver antigens and all-trans retinoic acid (RA). After intramuscular vaccinations, these capsules function as an immunoticket to cultivate peripheral dendritic cells (DCs) with gut-homing receptors (CCR9). By hitchhiking on the concentration gradient of the CC-motif chemokine ligand 25 (CCL25), the primed DCs would home to the gut associated lymphoid tissues (GALTs) and induce antigen-specific IgA secretion and T cell engagements. Compared with the currently employed RA-involving formulations, the immunoticket capsules stimulate enhanced RA-mediated gut-tropism by mounting the inflammatory innate immunity. Through controlling the RA payload, the potential regulatory T cell engagement is circumvented. In ovalbumin (OVA) and EV71 vaccinations, the immunoticket capsules induce potent serum IgG titer and antigen-specific cytotoxic T cells in the peripheral lymph tissues, as well as robust IgA secretion and T cell engagements on gastrointestinal sites. The data suggest the potential of the immunotickets to serve as a facile, effective, and safe strategy to provide comprehensive immune responses against gastrointestinal infections and diseases.

Osteoarthritis induced by destabilization of the medial meniscus is reduced in germ-free mice

OBJECTIVE

To determine the contribution of the gut microbiota to the development of injury-induced osteoarthritis (OA).

DESIGN

OA was induced using the destabilized medial meniscus (DMM) model in 20 germ-free (GF) C57BL/6J male mice housed in a gnotobiotic facility and 23 strain-matched specific pathogen free (SPF) mice in 2 age groups -13.5 weeks avg age at DMM (17 SPF and 15 GF) and 43 weeks avg age at DMM (6 SPF and 5 GF). OA severity was measured using scores for articular cartilage structure (ACS), loss of safranin O (SafO) staining, osteophyte size, and synovial hyperplasia. Microbiome analysis by 16S rRNA amplicon sequencing was performed on stool samples and LPS and LPS binding protein (LBP) were measured in plasma.

RESULTS

Compared to the SPF DMM mice, the maximum (MAX) ACS score per joint was 28% lower (p = 0.036) in GF DMM mice while the SafO sum score of all sections evaluated per joint was decreased by 31% (p = 0.009). The differences between SPF and GF mice in these scores were greater when only the younger mice were included in the analysis. The younger GF DMM mice also had significant reductions in osteophyte size (36%, P = 0.0119) and LBP (27%, P = 0.007) but not synovial scores or LPS. Differences in relative abundance of a number of Operational Taxonomic Units (OTUs) were noted between SPF mice with high vs low maximum ACS scores.

CONCLUSIONS

These results suggest factors related to the gut microbiota promote the development of OA after joint injury.

Nasal microbiota clusters associate with inflammatory response, viral load, and symptom severity in experimental rhinovirus challenge

The role of nasal and fecal microbiota in viral respiratory infections has not been established. We collected nasal swabs and washes, and fecal samples in a clinical study assessing the effect of probiotic Bifidobacterium animalis subsp. lactis Bl-04 on experimental rhinovirus infection. The nasal and fecal microbiota were characterized by 16S rRNA gene sequencing. The resulting data were compared with nasal inflammatory marker concentrations, viral load, and clinical symptoms. By using unsupervised clustering, the nasal microbiota divided into six clusters. The clusters predominant of Staphylococcus, Corynebacterium/Alloiococcus, Moraxella, and Pseudomonadaceae/Mixed had characteristic inflammatory marker and viral load profiles in nasal washes. The nasal microbiota clusters of subjects before the infection associated with the severity of clinical cold symptoms during rhinovirus infection. Rhinovirus infection and probiotic intervention did not significantly alter the composition of nasal or fecal microbiota. Our results suggest that nasal microbiota may influence the virus load, host innate immune response, and clinical symptoms during rhinovirus infection, however, further studies are needed.

Recipient single nucleotide polymorphisms in Paneth cell antimicrobial peptide genes and acute graft-versus-host disease: analysis of BMT CTN-0201 and -0901 samples

Host genetics shape the gut microbiota, and gut dysbiosis increases the risk of acute graft-versus-host disease (aGVHD). Paneth cells and microbiota have interactions that contribute to immune regulation. α-defensin-5 (HD5) and regenerating islet-derived protein 3 alpha (Reg3A) are the most abundant Paneth cell antimicrobial peptides (AMPs). We hypothesized that single nucleotide polymorphisms (SNPs) in the genes for HD5 (DEFA5) and Reg3A (REG3A) predict aGVHD risk. We analysed pre-transplant recipient peripheral blood mononuclear cell samples from randomized Blood and Marrow Transplant Clinical Trials Network (BMT CTN) studies 0201 (94 patients with bone marrow and 93 with peripheral blood grafts) and 0901 (86 patients with myeloablative and 77 with reduced-intensity conditioning; all using peripheral blood grafts). In multivariable analysis (with a SNP × graft source interaction term in CTN-0201 and a SNP × conditioning intensity term in CTN-0901), DEFA5 rs4415345 and rs4610776 were associated with altered incidence of aGVHD grade II-IV [rs4415345 G vs. C: hazard ratio (HR) 0·58, 95% confidence interval (95% CI) 0·37-0·92, P = 0·02; rs4610776 T vs. A: HR 1·53, 95% CI 1·01-2·32, P = 0·05] in CTN-0201, but not CTN-0901, suggesting a stronger effect in bone marrow allografts. REG3A SNP was not associated with aGVHD. Host genetics may influence aGVHD risk by modulating Paneth cell function.

The interaction between invariant Natural Killer T cells and the mucosal microbiota

The surface of mammalian bodies is colonized by a multitude of microbial organisms, which under normal conditions support the host and are considered beneficial commensals. This requires, however, that the composition of the commensal microbiota is tightly controlled and regulated. The host immune system plays an important role in the maintenance of this microbiota composition. Here we focus on the contribution of one particular immune cell type, invariant Natural Killer T (iNKT) cells, in this process. The iNKT cells are a unique subset of T cells characterized by two main features. First, they express an invariant T-cell receptor that recognizes glycolipid antigens presented by CD1d, a non-polymorphic major histocompatibility complex class I-like molecule. Second, iNKT cells develop as effector/memory cells and swiftly exert effector functions, like cytokine production and cytotoxicity, after activation. We outline the influence that the mucosal microbiota can have on iNKT cells, and how iNKT cells contribute to the maintenance of the microbiota composition.

Aryl hydrocarbon receptor/IL-22/Stat3 signaling pathway is involved in the modulation of intestinal mucosa antimicrobial molecules by commensal microbiota in mice

Compelling evidence demonstrates the crucial role of the commensal microbiota in host physiology and the detrimental effects of its perturbations following antibiotic treatment. However, the effects of commensal microbiota on intestinal mucosa antimicrobial molecules have not been elucidated systematically. Here, we investigate the impacts of antibiotic-induced depletion and subsequent restoration of the intestinal microbiota on the murine antimicrobial molecules in intestinal mucosa. Our results demonstrate that depletion of commensal microbiota leads to intestinal mucosa atrophy and reduction of antimicrobial molecules, including lysozyme, regenerating islet-derived protein 3 gamma (RegIIIγ), and cryptdin 5 mRNA, whereas subsequent reconstitution of intestinal microbiota by fecal microbiota transplantation (FMT) rescues mucosa morphology and antimicrobials. Importantly, our study shows that down-regulation of aryl hydrocarbon receptor (AhR), interleukin-22 (IL-22), and phosphorylated Stat3 (p-Stat3) is associated with decreased antimicrobials, which might mediate the antibiotic-associated intestinal mucosa injury. Last, exogenous activation of the AhR/IL-22/Stat3 signaling pathway with the AhR agonist 6-formylindolo(3,2-b)carbazole (Ficz) rescued antimicrobial molecule levels markedly after antibiotic treatment to levels similar to those following reconstitution of intestinal microbiota by FMT. Together, our results demonstrate that the AhR/IL-22/Stat3 signaling pathway is involved in the modulation of intestinal mucosa antimicrobial molecules by commensal microbiota and suggest this pathway as a promising target in the treatment of antibiotic-associated gut barrier damage.

Immune System Dysregulation During Spaceflight: Potential Countermeasures for Deep Space Exploration Missions

Recent studies have established that dysregulation of the human immune system and the reactivation of latent herpesviruses persists for the duration of a 6-month orbital spaceflight. It appears certain aspects of adaptive immunity are dysregulated during flight, yet some aspects of innate immunity are heightened. Interaction between adaptive and innate immunity also seems to be altered. Some crews experience persistent hypersensitivity reactions during flight. This phenomenon may, in synergy with extended duration and galactic radiation exposure, increase specific crew clinical risks during deep space exploration missions. The clinical challenge is based upon both the frequency of these phenomena in multiple crewmembers during low earth orbit missions and the inability to predict which specific individual crewmembers will experience these changes. Thus, a general countermeasure approach that offers the broadest possible coverage is needed. The vehicles, architecture, and mission profiles to enable such voyages are now under development. These include deployment and use of a cis-Lunar station (mid 2020s) with possible Moon surface operations, to be followed by multiple Mars flyby missions, and eventual human Mars surface exploration. Current ISS studies will continue to characterize physiological dysregulation associated with prolonged orbital spaceflight. However, sufficient information exists to begin consideration of both the need for, and nature of, specific immune countermeasures to ensure astronaut health. This article will review relevant in-place operational countermeasures onboard ISS and discuss a myriad of potential immune countermeasures for exploration missions. Discussion points include nutritional supplementation and functional foods, exercise and immunity, pharmacological options, the relationship between bone and immune countermeasures, and vaccination to mitigate herpes (and possibly other) virus risks. As the immune system has sentinel connectivity within every other physiological system, translational effects must be considered for all potential immune countermeasures. Finally, we shall discuss immune countermeasures in the context of their individualized implementation or precision medicine, based on crewmember specific immunological biases.

Role of Microbiota and Tryptophan Metabolites in the Remote Effect of Intestinal Inflammation on Brain and Depression

The human gastrointestinal tract is inhabited by trillions of commensal bacteria collectively known as the gut microbiota. Our recognition of the significance of the complex interaction between the microbiota, and its host has grown dramatically over the past years. A balanced microbial community is a key regulator of the immune response, and metabolism of dietary components, which in turn, modulates several brain processes impacting mood and behavior. Consequently, it is likely that disruptions within the composition of the microbiota would remotely affect the mental state of the host. Here, we discuss how intestinal bacteria and their metabolites can orchestrate gut-associated neuroimmune mechanisms that influence mood and behavior leading to depression. In particular, we focus on microbiota-triggered gut inflammation and its implications in shifting the tryptophan metabolism towards kynurenine biosynthesis while disrupting the serotonergic signaling. We further investigate the gaps to be bridged in this exciting field of research in order to clarify our understanding of the multifaceted crosstalk in the microbiota–gut–brain interphase, bringing about novel, microbiota-targeted therapeutics for mental illnesses.

The gut microbiota metabolite indole alleviates liver inflammation in mice

The gut microbiota regulates key hepatic functions, notably through the production of bacterial metabolites that are transported via the portal circulation. We evaluated the effects of metabolites produced by the gut microbiota from aromatic amino acids (phenylacetate, benzoate, p-cresol, and indole) on liver inflammation induced by bacterial endotoxin. Precision-cut liver slices prepared from control mice, Kupffer cell (KC)-depleted mice, and obese mice ( ob/ ob) were treated with or without LPS and bacterial metabolites. We observed beneficial effects of indole that dose-dependently reduced the LPS-induced up-regulation of proinflammatory mediators at both mRNA and protein levels in precision-cut liver slices prepared from control or ob/ ob mice. KC depletion partly prevented the antiinflammatory effects of indole, notably through a reduction of nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain-containing 3 (NLRP3) pathway activation. In vivo, the oral administration of indole before an LPS injection reduced the expression of key proteins of the NF-κB pathway and downstream proinflammatory gene up-regulation. Indole also prevented LPS-induced alterations of cholesterol metabolism through a transcriptional regulation associated with increased 4β-hydroxycholesterol hepatic levels. In summary, indole appears as a bacterial metabolite produced from tryptophan that is able to counteract the detrimental effects of LPS in the liver. Indole could be a new target to develop innovative strategies to decrease hepatic inflammation.-Beaumont, M., Neyrinck, A. M., Olivares, M., Rodriguez, J., de Rocca Serra, A., Roumain, M., Bindels, L. B., Cani, P. D., Evenepoel, P., Muccioli, G. G., Demoulin, J.-B., Delzenne, N. M. The gut microbiota metabolite indole alleviates liver inflammation in mice.

Nanoparticle-Based Oral Drug Delivery Systems Targeting the Colon for Treatment of Ulcerative Colitis

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