Mucosal immunity to pathogenic intestinal bacteria

Healthy Intestinal Function Relies on Coordinated Enteric Nervous System, Immune System, and Epithelium Responses

During both health and disease, a coordinated response between the epithelium, immune system, and enteric nervous system is required for proper intestinal function. While each system responds to a number of common stimuli, their coordinated responses support digestion as well as responses and recovery following injury or pathogenic infections. In this review, we discuss how individual responses to common signals work together to support these critical functions.

Effects of polysaccharides from Fuzhuan brick tea on immune function and gut microbiota of cyclophosphamide-treated mice

In this study, cyclophosphamide (Cy) was used to treat mice to establish an immunosuppressant model in mice, and the regulatory effects of polysaccharides from Fuzhuan brick tea (FBTPSs) including crude FBTPSs (CFBTPSs) and the purified fraction (FBTPSs-3) on the immune function and gut microbiota of mice were investigated. The results showed that CFBTPSs and FBTPSs-3 restored the levels of body weight, feed intake, immune organ index, cytokine and immunoglobulin A in mice. The Cy-induced injury of gut including intestinal morphology and expression of tight junction proteins were also restored. Furthermore, CFBTPSs and FBTPSs-3 could significantly modulate gut microbiota by increasing the relative abundance of Muribaculaceae and reduceing the relative abundances of Lachnospiraceae, Helicobacteraceae, Clostridaceae, Desulfovibrionaceae and Deferribacteraceae. Moreover, the gut microbiota derived short-chain fatty acids might play an important role in improvement of immune function by FBTPSs. Our results showed that FBTPSs could regulate the immune function of mice, which provided evidences for the development of FBTPSs as potentially functional foods to improve human health.

Intestinal microbiota and its interaction to intestinal health in nursery pigs

The intestinal microbiota has gained increased attention from researchers within the swine industry due to its role in promoting intestinal maturation, immune system modulation, and consequently the enhancement of the health and growth performance of the host. This review aimed to provide updated scientific information on the interaction among intestinal microbiota, dietary components, and intestinal health of pigs. The small intestine is a key site to evaluate the interaction of the microbiota, diet, and host because it is the main site for digestion and absorption of nutrients and plays an important role within the immune system. The diet and its associated components such as feed additives are the main factors affecting the microbial composition and is central in stimulating a beneficial population of microbiota. The microbiota–host interaction modulates the immune system, and, concurrently, the immune system helps to modulate the microbiota composition. The direct interaction between the microbiota and the host is an indication that the mucosa-associated microbiota can be more effective in evaluating its effect on health parameters. It was demonstrated that the mucosa-associated microbiota should be evaluated when analyzing the interaction among diets, microbiota, and health. In addition, supplementation of feed additives aimed to promote the intestinal health of pigs should consider their roles in the modulation of mucosa-associated microbiota as biomarkers to predict the response of growth performance to dietary interventions.

Enteric neuroimmune interactions coordinate intestinal responses in health and disease

The enteric nervous system (ENS) of the gastrointestinal (GI) tract interacts with the local immune system bidirectionally. Recent publications have demonstrated that such interactions can maintain normal GI functions during homeostasis and contribute to pathological symptoms during infection and inflammation. Infection can also induce long-term changes of the ENS resulting in the development of post-infectious GI disturbances. In this review, we discuss how the ENS can regulate and be regulated by immune responses and how such interactions control whole tissue physiology. We also address the requirements for the proper regeneration of the ENS and restoration of GI function following the resolution of infection.

Supplementation with Exogenous Catalase from Penicillium notatum in the Diet Ameliorates Lipopolysaccharide-Induced Intestinal Oxidative Damage through Affecting Intestinal Antioxidant Capacity and Microbiota in Weaned Pigs

The present study aimed to explore the protective effects of exogenous catalase (CAT) from microorganisms against lipopolysaccharide (LPS)-induced intestinal injury and its molecular mechanism in weaned pigs. Fifty-four weaned pigs (21 days of age) were randomly allocated to CON, LPS, and LPS+CAT groups. The pigs in CON and LPS groups were fed a basal diet, whereas the pigs in LPS+CAT group fed the basal diet with 2,000 mg/kg CAT supplementation for 35 days. On day 36, six pigs were selected from each group, and LPS and LPS+CAT groups were administered with LPS (50 μg/kg body weight). Meanwhile, CON group was injected with an equivalent amount of sterile saline. Results showed that LPS administration damaged intestinal mucosa morphology and barrier. However, CAT supplementation alleviated the deleterious effects caused by LPS challenge through enhancing intestinal antioxidant capacity which was benefited to decrease proinflammatory cytokines concentrations and suppress enterocyte apoptosis. Besides, LPS-induced gut microbiota dysbiosis was significantly shifted by CAT through decreasing mainly Streptococcus and Escherichia-Shigella. Our study suggested that dietary supplemented with 2,000 mg/kg catalase was conducive to improve intestinal development and protect against LPS-induced intestinal mucosa injury via enhancing intestinal antioxidant capacity and altering microbiota composition in weaned pigs.

IMPORTANCE Exogenous CAT derived from microorganisms has been widely used in food, medicine, and other industries. Recent study also found that exogenous CAT supplementation could improve growth performance and antioxidant capacity of weaned pigs. However, it is still unknown that whether dietary exogenous CAT supplementation can provide a defense against the oxidative stress-induced intestinal damage in weaned pigs. Our current study suggested that dietary supplemented with 2,000 mg/kg CAT was conducive to improve intestinal development and protect against LPS-induced intestinal mucosa injury via enhancing intestinal antioxidant capacity and altering microbiota composition in weaned pigs. Moreover, this study will also assist in developing of CAT produced by microorganisms to attenuate various oxidative stress-induced injury or diseases.

A dysbiotic gut microbiome suppresses antibody mediated-protection against Vibrio cholerae

Cholera is a severe diarrheal disease that places a significant burden on global health. Cholera's high morbidity demands effective prophylactic strategies, but oral cholera vaccines exhibit variable efficacy in human populations. One contributor of variance in human populations is the gut microbiome, which in cholera-endemic areas is modulated by malnutrition, cholera, and non-cholera diarrhea. We conducted fecal transplants from healthy human donors and model communities of either human gut microbes that resemble healthy individuals or those of individuals recovering from diarrhea in various mouse models. We show microbiome-specific effects on host antibody responses against Vibrio cholerae, and that dysbiotic human gut microbiomes representative of cholera-endemic areas suppress the immune response against V. cholerae via CD4+ lymphocytes. Our findings suggest that gut microbiome composition at time of infection or vaccination may be pivotal for providing robust mucosal immunity, and suggest a target for improved prophylactic and therapeutic strategies for cholera.

Role of TLR5 in the Translocation and Dissemination of Commensal Bacteria in the Intestine after Traumatic Hemorrhagic Shock

Enterogenous infection is a major cause of death during traumatic hemorrhagic shock (THS). It has been reported that Toll-like receptor 5 (TLR5) plays an integral role in regulating mucosal immunity and intestinal homeostasis of the microbiota. However, the roles played by TLR5 on intestinal barrier maintenance and commensal bacterial translocation post-THS are poorly understood. In this research, we established THS models in wild-type (WT) and Tlr5^-/- (genetically deficient in TLR5 expression) mice. We found that THS promoted bacterial translocation, while TLR5 deficiency played a protective role in preventing commensal bacteria dissemination after THS. Furthermore, intestinal microbiota analysis uncovered that TLR5 deficiency enhanced the mucosal biological barrier by decreasing RegIIIγ-mediated bactericidal activity against G⁺ anaerobic bacteria. We then sorted small intestinal TLR5⁺ lamina propria dendritic cells (LPDCs) and analyzed T_H1 differentiation in the intestinal lamina propria and a coculture system consisting of LPDCs and naïve T cells. Although TLR5 deficiency attenuated the regulation of T_H1 polarization by LPDCs, it conferred stability to the cells during THS. Moreover, retinoic acid (RA) released from TLR5⁺ LPDCs could play a key role in modulating T_H1 polarization. We also found that gavage administration of RA alleviated bacterial translocation in THS-treated WT mice. In summary, we documented that TLR5 signaling plays a pivotal role in regulating RegIIIγ-induced killing of G⁺ anaerobic bacteria, and LPDCs mediated T_H1 differentiation via RA. These processes prevent intestinal bacterial translocation and enterogenous infection after THS, suggesting that therapeutically targeting LPDCs or gut microbiota can interfere with bacterial translocation after THS.

The Functional Role of Lactoferrin in Intestine Mucosal Immune System and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is one of the main types of intestinal inflammatory diseases with intestine mucosal immune disorder. Intestine mucosal immune system plays a remarkable and important role in the etiology and pathogenesis of IBD. Therefore, understanding the intestine mucosal immune mechanism is a key step to develop therapeutic interventions for IBD. Intestine mucosal immune system and IBD are influenced by various factors, such as inflammation, gut permeability, gut microbiota, and nutrients. Among these factors, emerging evidence show that nutrients play a key role in inflammation activation, integrity of intestinal barrier, and immune cell modulation. Lactoferrin (LF), an iron-binding glycoprotein belonging to transferrin family, is a dietary bioactive component abundantly found in mammalian milk. Notably, LF has been reported to perform diverse biological functions including antibacterial activity, anti-inflammatory activity, intestinal barrier protection, and immune cell modulation, and is involved in maintaining intestine mucosal immune homeostasis. The improved understanding of the properties of LF in intestine mucosal immune system and IBD will facilitate its application in nutrition, clinical medicine, and health. Herein, this review outlines the recent advancements on LF as a potential therapeutic intervention for IBD associated with intestine mucosal immune system dysfunction. We hope this review will provide a reference for future studies and lay a theoretical foundation for LF-based therapeutic interventions for IBD by understanding the particular effects of LF on intestine mucosal immune system.

Mucin-Type O-Glycans: Barrier, Microbiota, and Immune Anchors in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), which affects about 7 million people globally, is a chronic inflammatory condition of the gastrointestinal tract caused by gut microbiota alterations, immune dysregulation, and genetic and environmental factors. The association of microbial and immune molecules with mucin-type O-glycans has been increasingly noticed by researchers. Mucin is the main component of mucus, which forms a protective barrier between the microbiota and immune cells in the colon. Mucin-type O-glycans alter the diversity of gastrointestinal microorganisms, which in turn increases the level of O-glycosylation of host intestinal proteins via the utilization of glycans. Additionally, alterations in mucin-type O-glycans not only increase the activity and stability of immune cells but are also involved in the maintenance of intestinal mucosal immune tolerance. Although there is accumulating evidence indicating that mucin-type O-glycans play an important role in IBD, there is limited literature that integrates available data to present a complete picture of exactly how O-glycans affect IBD. This review emphasizes the roles of the mucin-type O-glycans in IBD. This seeks to provide a better understanding and encourages future studies on IBD glycosylation and the design of novel glycan-inspired therapies for IBD.

Dynamic Interaction Between Mucosal Immunity and Microbiota Drives Nose and Pharynx Homeostasis of Common Carp (Cyprinus carpio) After SVCV Infection

The crosstalk between the immune system and microbiota drives an amazingly complex mutualistic symbiosis. In mammals, the upper respiratory tract acts as a gateway for pathogen invasion, and the dynamic interaction between microbiota and mucosal immunity on its surface can effectively prevent disease development. However, the relationship between virus-mediated mucosal immune responses and microbes in lower vertebrates remains uncharacterized. In this study, we successfully constructed an infection model by intraperitoneally injecting common carp (Cyprinus carpio) with spring viremia of carp virus (SVCV). In addition to the detection of the SVCV in the nose and pharynx of common carp, we also identified obvious histopathological changes following viral infection. Moreover, numerous immune-related genes were significantly upregulated in the nose and pharynx at the peak of SVCV infection, after which the expression levels decreased to levels similar to those of the control group. Transcriptome sequencing results revealed that pathways associated with bacterial infection in the Toll-like receptor pathway and the Nod-like receptor pathway were activated in addition to the virus-related Rig-I-like receptor pathway after SVCV infection, suggesting that viral infection may be followed by opportunistic bacterial infection in these mucosal tissues. Using 16S rRNA gene sequencing, we further identified an upward trend in pathogenic bacteria on the mucosal surface of the nose and pharynx 4 days after SVCV infection, after which these tissues eventually reached new homeostasis. Taken together, our results suggest that the dynamic interaction between mucosal immunity and microbiota promotes the host to a new ecological state.

Psychological stress impairs IL22-driven protective gut mucosal immunity against colonising pathobionts

Crohn's disease is an inflammatory disease of the gastrointestinal tract characterized by an aberrant response to microbial and environmental triggers. This includes an altered microbiome dominated by Enterobacteriaceae and in particular adherent-invasive E. coli (AIEC). Clinical evidence implicates periods of psychological stress in Crohn's disease exacerbation, and disturbances in the gut microbiome might contribute to the pathogenic mechanism. Here we show that stress-exposed mice develop ileal dysbiosis, dominated by the expansion of Enterobacteriaceae. In an AIEC colonisation model, stress-induced glucocorticoids promote apoptosis of CD45+CD90+ cells that normally produce IL-22, a cytokine that is essential for the maintenance of ileal mucosal barrier integrity. Blockade of glucocorticoid signaling or administration of recombinant IL-22 restores mucosal immunity, prevents ileal dysbiosis, and blocks AIEC expansion. We conclude that psychological stress impairs IL-22-driven protective immunity in the gut, which creates a favorable niche for the expansion of pathobionts that have been implicated in Crohn's disease. Importantly, this work also shows that immunomodulation can counteract the negative effects of psychological stress on gut immunity and hence disease-associated dysbiosis.

Probiotics Treatment of Leg Diseases in Broiler Chickens: a Review

Normal development and growth of bones are critical for poultry. With the rapid growth experienced by broiler chickens, higher incidences of leg weakness and lameness are common problems in adolescent meat-type poultry that present huge economic and welfare issues. Leg disorders such as angular bone deformities and tibial dyschondroplasia have become common in broilers and are associated with poor growth, high mortality rates, increased carcass condemnation, and downgrading at slaughter. Probiotics have shown promise for a variety of health purposes, including preventing diarrhea, elevating carcass quality, and promoting growth of the poultry. In addition, recent studies have indicated that probiotics can maintain the homeostasis of the gut microbiota and improve the health of the gastrointestinal tract, which confers a potentially beneficial effect on bone health. This review mainly describes the occurrence of broiler leg disease and the role of probiotics in bone health through regulating the gut microbiota and improving intestinal function, thus providing a relevant theoretical basis for probiotics to hinder the development of skeletal disorders in broiler chickens.

Effect of dark environment on intestinal flora and expression of genes related to liver metabolism in zebrafish (Danio rerio)

To explore the effects of dark environment on intestinal flora and expression of genes related to liver metabolism in zebrafish, a total of 60 zebrafish were fed for 21 days (24 h dark treatments or 14/10 h light/dark cycle), and the influence of dark environment on gut microbes and liver gene expression was studied using sequencing analysis of intestinal flora and liver. The results showed that the body weight of fish was significantly increased in the dark group than that in the control group (P < 0.05). Compared with the control group, dark environment treatment changed the composition of dominant flora, increased the abundance of unconventional bacteria and reduced probiotics in the intestine of zebrafish. Of these, the ratio of Bacteroidetes to Firmicutes in the intestine was reduced. The genome expression of the liver showed significant changes, and liver metabolites were also affected. Meanwhile, dark environment decreased gene expression associated with changes in blood glucose, lipid metabolism and immunization. Dark environment also caused liver steatosis as observed by histological study. This study shows that dark environment treatment has an important impact on liver metabolism and intestinal microbes in zebrafish.

Microbiota-derived extracellular vesicles in interkingdom communication in the gut

The intestine is fundamental in controlling human health. Intestinal epithelial and immune cells are continuously exposed to millions of microbes that greatly impact on intestinal epithelial barrier and immune function. This microbial community, known as gut microbiota, is now recognized as an important partner of the human being that actively contribute to essential functions of the intestine but also of distal organs. In the gut ecosystem, bidirectional microbiota-host communication does not involve direct cell contacts. Both microbiota and host-derived extracellular vesicles (EVs) are key players of such interkingdom crosstalk. There is now accumulating body of evidence that bacterial secreted vesicles mediate microbiota functions by transporting and delivering into host cells effector molecules that modulate host signalling pathways and cell processes. Consequently, vesicles released by the gut microbiota may have great influence on health and disease. Here we review current knowledge on microbiota EVs and specifically highlight their role in controlling host metabolism, intestinal barrier integrity and immune training.

Epigallocatechin Gallate (EGCG) Promotes the Immune Function of Ileum in High Fat Diet Fed Mice by Regulating Gut Microbiome Profiling and Immunoglobulin Production

This study aimed to investigate the regulatory effect of epigallocatechin gallate (EGCG) on the composition of the gut microbiome, the transcriptomic profiling of ileum, and their interplay in high fat diet (HFD) induced obese mice. Intragastric administration of EGCG to C57BL/6J mice for 14 consecutive weeks remarkably decreased HFD induced excessive fat deposition (p < 0.001), and the increment of serum TG, TC, HDL-C (p < 0.05), as well as improved glucose tolerance (p < 0.001). EGCG shifted the gut microbiota mainly by elevating the relative abundance of Parasutterrlla, Bacteroides, and Akkermansia (p < 0.01), decreasing that of norank_f_Erysipelotrichaceae, unclassified_f_Ruminococcaceae, Anaerotruncus, Roseburia, norank_Lachnospiraceae, and Lachnospiraceae_UCG_006 (p < 0.01) at the genus level. In addition, EGCG affected the transcriptomic profiling of ileum, and the differentially expressed (DE) genes after HFD or/and EGCG treatment were mostly enriched in the immune reaction of ileum, such as the GO term of “immune effector process” and “phagocytosis, recognition.” Furthermore, the KEGG category of “immune diseases,” “immune system,” and “infection diseases: bacterial” were commonly enriched by the DE genes of the two treatments. Among those DE genes, 16 immunoglobulins heavy chain variable region encoded genes (Ighvs) and other immunity-related genes, such as complement component 2 (C2), interferon-induced transmembrane protein 1 (Iftm1), polymeric immunoglobulin receptor (pigR), and alanyl aminopeptidase (Anpep), were highly correlated with the shifted microbes in the gut (p < 0.05, absolute r > 0.5). Overall, the results suggested that EGCG ameliorated the HFD induced metabolic disorder mainly by regulating gut microbiome profiling and the immunoglobulin production of ileum, while the genes expressed in the ileum, especially Ighvs, C2, Iftm1, pigR, and Anpep, might play important roles in coordinating the immunity of mice regarding the gut microbes and the host interactions.

Gut microbiota and neuropsychiatric disorders: Implications for neuroendocrine-immune regulation

Recently, increasing evidence has shown gut microbiota dysbiosis might be implicated in the physiological mechanisms of neuropsychiatric disorders. Altered microbial community composition, diversity and distribution traits have been reported in neuropsychiatric disorders. However, the exact pathways by which the intestinal microbiota contribute to neuropsychiatric disorders remain largely unknown. Given that the onset and progression of neuropsychiatric disorders are characterized with complicated alterations of neuroendocrine and immunology, both of which can be continually affected by gut microbiota via "microbiome-gut-brain axis". Thus, we assess the complicated crosstalk between neuroendocrine and immunological regulation might underlie the mechanisms of gut microbiota associated with neuropsychiatric disorders. In this review, we summarized clinical and preclinical evidence on the role of the gut microbiota in neuropsychiatry disorders, especially in mood disorders and neurodevelopmental disorders. This review may elaborate the potential mechanisms of gut microbiota implicating in neuroendocrine-immune regulation and provide a comprehensive understanding of physiological mechanisms for neuropsychiatric disorders.

A Single Human-Relevant Fast Food Meal Rapidly Reorganizes Metabolomic and Transcriptomic Signatures in a Gut Microbiota-Dependent Manner

BACKGROUND

A major contributor to cardiometabolic disease is caloric excess, often a result of consuming low cost, high calorie fast food. Studies have demonstrated the pivotal role of gut microbes contributing to cardiovascular disease in a diet-dependent manner. Given the central contributions of diet and gut microbiota to cardiometabolic disease, we hypothesized that microbial metabolites originating after fast food consumption can elicit acute metabolic responses in the liver.

METHODS

We gave conventionally raised mice or mice that had their microbiomes depleted with antibiotics a single oral gavage of a liquified fast food meal or liquified control rodent chow meal. After four hours, mice were sacrificed and we used untargeted metabolomics of portal and peripheral blood, 16S rRNA gene sequencing, targeted liver metabolomics, and host liver RNA sequencing to identify novel fast food-derived microbial metabolites and their acute effects on liver function.

RESULTS

Several candidate microbial metabolites were enriched in portal blood upon fast food feeding, and were essentially absent in antibiotic-treated mice. Strikingly, at four hours post-gavage, fast food consumption resulted in rapid reorganization of the gut microbial community and drastically altered hepatic gene expression. Importantly, diet-driven reshaping of the microbiome and liver transcriptome was dependent on an intact microbial community and not observed in antibiotic ablated animals.

CONCLUSIONS

Collectively, these data suggest a single fast food meal is sufficient to reshape the gut microbial community in mice, yielding a unique signature of food-derived microbial metabolites. Future studies are in progress to determine the contribution of select metabolites to cardiometabolic disease progression and the translational relevance of these animal studies.

Foxo1 controls gut homeostasis and commensalism by regulating mucus secretion

Mucus produced by goblet cells in the gastrointestinal tract forms a biological barrier that protects the intestine from invasion by commensals and pathogens. However, the host-derived regulatory network that controls mucus secretion and thereby changes gut microbiota has not been well studied. Here, we identify that Forkhead box protein O1 (Foxo1) regulates mucus secretion by goblet cells and determines intestinal homeostasis. Loss of Foxo1 in intestinal epithelial cells (IECs) results in defects in goblet cell autophagy and mucus secretion, leading to an impaired gut microenvironment and dysbiosis. Subsequently, due to changes in microbiota and disruption in microbiome metabolites of short-chain fatty acids, Foxo1 deficiency results in altered organization of tight junction proteins and enhanced susceptibility to intestinal inflammation. Our study demonstrates that Foxo1 is crucial for IECs to establish commensalism and maintain intestinal barrier integrity by regulating goblet cell function.

Overview on the Prevalence of Fungal Infections, Immune Response, and Microbiome Role in COVID-19 Patients

Patients with severe COVID-19, such as individuals in intensive care units (ICU), are exceptionally susceptible to bacterial and fungal infections. The most prevalent fungal infections are aspergillosis and candidemia. Nonetheless, other fungal species (for instance, Histoplasma spp., Rhizopus spp., Mucor spp., Cryptococcus spp.) have recently been increasingly linked to opportunistic fungal diseases in COVID-19 patients. These fungal co-infections are described with rising incidence, severe illness, and death that is associated with host immune response. Awareness of the high risks of the occurrence of fungal co-infections is crucial to downgrade any arrear in diagnosis and treatment to support the prevention of severe illness and death directly related to these infections. This review analyses the fungal infections, treatments, outcome, and immune response, considering the possible role of the microbiome in these patients. The search was performed in Medline (PubMed), using the words "fungal infections COVID-19", between 2020-2021.

Clostridium butyricum CB1 up-regulates FcRn expression via activation of TLR2/4-NF-κB signaling pathway in porcine small intestinal cells

The neonatal Fc receptor (FcRn) mediates the bidirectional transport of immunoglobulin G (IgG) across hyperpolarized epithelial cells. Overexpression of FcRn increases serum IgG and humoral immune response. Probiotics can improve the host's serum and intestinal mucosal IgG. However, whether probiotics regulate FcRn and its specific mechanism are still unclear. Our research showed that heat inactivated Clostridium butyricum CB1 (heat-inactivated CB1) up-regulated FcRn expression in porcine small intestinal epithelial (IPI-2I) cells. Furthermore, heat-inactivated CB1 stimulation activated the nuclear factor kappa B (NF-κB) signaling pathway. Moreover, FcRn expression decreased after blocking the NF-κB signaling pathway by NF-κB inhibitor BAY11-7028, suggesting that heat-inactivated CB1 induced FcRn expression via the NF-κB signaling pathway. Using small interfering RNAs (siRNAs), we found that knockdown of TLR2/4, MyD88 and TRIF reduced NF-κB activity induced by heat-inactivated CB1, as well as up-regulation of FcRn expression after heat-inactivated CB1 stimulation. Taken together, our data indicated that heat-inactivated CB1 up-regulated FcRn expression via TLR2/4-MyD88/TRIF-NF-κB signaling pathway. These results provided a new perspective for us to understand the enhancement of C. butyricum on intestinal mucosal immunity.

Shell-mediated phagocytosis to reshape viral-vectored vaccine-induced immunity

Adenovirus (Ad) has been extensively developed as a gene delivery vector, but the potential side effect caused by systematic immunization remains one major obstacle for its clinical application. Needle-free mucosal immunization with Ad-based vaccine shows advantages but still faces poor mucosal responses. We herein report that the chemical engineering of single live viral-based vaccine effectively modulated the location and pattern of the subsequently elicited immunity. Through precisely assembly of functional materials onto single live Ad particle, the modified virus entered host cell in a phagocytosis-dependent manner, which is completely distinct from the receptor-mediated entry of native Ad. RNA-Seq data further demonstrated that the modified Ad-induced innate immunity was sharply reshaped via phagocytosis-related pathway, therefore promoting the activation and mature of antigen presentation cells (APC). Moreover, the functional shell enabled the modified Ad-based vector with enhanced muco-adhesion to nasal tissues in mice, and then prolonged resident time onto mucosal surface, leading to the robust mucosal IgA production and T cell immunity at local and even remote mucosal-associated lymphoid tissues. This study demonstrated that vaccine-induced immunity can be well modulated by chemistry engineering, and this method provides the rational design for needle-free mucosa-targeting vaccine against a variety of emerging infectious diseases.

Titanium dioxide particles from the diet: involvement in the genesis of inflammatory bowel diseases and colorectal cancer

The gastrointestinal tract is a complex interface between the external environment and the immune system. Its ability to control uptake across the mucosa and to protect the body from damage of harmful substances from the lumen is defined as the intestinal barrier function (IBF). The IBF involves four elements: the intestinal microbiota, the mucus layer, the epithelium and the immune system. Its dysfunction is linked with human diseases including inflammatory, metabolic, infectious, autoimmune and neurologic disorders. Most of these diseases are complex and involve genetic, psychological and environmental factors. Over the past 10 years, many genetic polymorphisms predisposing to inflammatory bowel disease (IBD) have been identified. Yet, it is now clear that they are insufficient to explain the onset of these chronic diseases. Although it has been evidenced that some environmental factors such as cigarette smoking or carbohydrate intake are associated with IBD, other environmental factors also present potential health risks such as ingestion of food additives introduced in the human diet, including those composed of mineral particles, by altering the four elements of the intestinal barrier function. The aim of this review is to provide a critical opinion on the potential of TiO₂ particles, especially when used as a food additive, to alter the four elements of the intestinal barrier function, and consequently to evaluate if this additive would likely play a role in the development and/or exacerbation of IBD.

Mucosal vaccines - fortifying the frontiers

Mucosal vaccines offer the potential to trigger robust protective immune responses at the predominant sites of pathogen infection. In principle, the induction of adaptive immunity at mucosal sites, involving secretory antibody responses and tissue-resident T cells, has the capacity to prevent an infection from becoming established in the first place, rather than only curtailing infection and protecting against the development of disease symptoms. Although numerous effective mucosal vaccines are in use, the major advances seen with injectable vaccines (including adjuvanted subunit antigens, RNA and DNA vaccines) have not yet been translated into licensed mucosal vaccines, which currently comprise solely live attenuated and inactivated whole-cell preparations. The identification of safe and effective mucosal adjuvants allied to innovative antigen discovery and delivery strategies is key to advancing mucosal vaccines. Significant progress has been made in resolving the mechanisms that regulate innate and adaptive mucosal immunity and in understanding the crosstalk between mucosal sites, and this provides valuable pointers to inform mucosal adjuvant design. In particular, increased knowledge on mucosal antigen-presenting cells, innate lymphoid cell populations and resident memory cells at mucosal sites highlights attractive targets for vaccine design. Exploiting these insights will allow new vaccine technologies to be leveraged to facilitate rational mucosal vaccine design for pathogens including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and for cancer.

Trends in liposomal nanocarrier strategies for the oral delivery of biologics

The number of approved macromolecular drugs such as peptides, proteins and antibodies steadily increases. Since drugs with high molecular weight are commonly not suitable for oral delivery, research on carrier strategies enabling oral administration is of vital interest. In past decades, nanocarriers, in particular liposomes, have been exhaustively investigated as oral drug-delivery platform. Despite their successful application as parenteral delivery vehicles, liposomes have up to date not succeeded for oral administration. However, a plenitude of approaches aiming to increase the oral bioavailability of macromolecular drugs administered by liposomal formulations has been published. Here, we summarize the strategies published in the last 10 years (vaccine strategies excluded) with a main focus on strategies proven efficient in animal models.

Green tea polyphenol epigallocatechin-3-gallate alleviates nonalcoholic fatty liver disease and ameliorates intestinal immunity in mice fed a high-fat diet

Green tea polyphenol epigallocatechin-3-gallate (EGCG) may help prevent metabolic syndrome and nonalcoholic fatty liver disease (NAFLD). However, the underlying mechanisms of its protective effects are complicated and remain unclear. With the gut-liver axis theory as a foundation, the present study investigated the effects of EGCG on intestinal mucosal immunity in male C57BL/6 mice fed a high-fat Western diet or the diet supplemented with 0.4% dietary EGCG (w/w) for 14 weeks. Dietary EGCG supplementation effectively prevented changes-including excessive accumulation of visceral and hepatic fat, abnormal liver function, and elevated concentrations of serum and liver inflammatory cytokines-known to be caused by high-fat diets. In addition, serum lipopolysaccharide concentrations decreased by 94.3%. RNA sequencing data of differentially expressed genes in ileal samples among three groups indicated that most of the pathways in the Kyoto Encyclopedia of Genes and Genomes in the first 20 enrichment levels were related to immunity and inflammatory reactions. Real-time reverse transcription quantitative polymerase chain reaction was used to determine alterations in expression levels of key genes related to intestinal immune function and inflammatory responses from ileal and colonic samples. Changes in secretory immunoglobulin A in the small intestine, serum, and feces further demonstrated improved intestinal mucosal immunity in the EGCG-treated mice. In conclusion, dietary EGCG effectively prevented the development of NAFLD and significantly improved intestinal mucosal immunity in mice with obesity induced by a high-fat diet. However, whether improved intestinal immune function is the key mechanism underlying the health benefits of dietary EGCG warrants further research.

Melatonin alleviates Ochratoxin A-induced liver inflammation involved intestinal microbiota homeostasis and microbiota-independent manner

Melatonin (MEL) shows an anti-inflammatory effect and regulates intestinal microbiota communities in animals and humans; Ochratoxin A (OTA) induces liver inflammation through intestinal microbiota. However, it remains to know whether MEL alleviates the liver inflammation induced by OTA. In this study, MEL reversed various adverse effects induced by OTA. MEL recovered the swarming and motility of intestinal microbiota, decreased the accumulation of lipopolysaccharide (LPS), enhanced the tight junction proteins of jejunum and cecum segments; ultimately alleviated OTA-induced liver inflammation in ducks. However, it is worth noting that MEL still had positive effects on the OTA-exposed ducks after antibiotic treatment. These results suggest that both the maintenance of intestinal microbiota homeostasis and intestinal microbiota-independent manner involved the MEL anti-inflammatory function in OTA-induced liver inflammation. MEL represent a promising protective approach for OTA, even other mycotoxins.

Role of microbiota and related metabolites in gastrointestinal tract barrier function in NAFLD

The Gastrointestinal (GI) tract is composed of four main barriers: microbiological, chemical, physical and immunological. These barriers play important roles in maintaining GI tract homeostasis. In the crosstalk between these barriers, microbiota and related metabolites have been shown to influence GI tract barrier integrity, and alterations of the gut microbiome might lead to an increase in intestinal permeability. As a consequence, translocation of bacteria and their products into the circulatory system increases, reaching proximal and distal tissues, such as the liver. One of the most prevalent chronic liver diseases, Nonalcoholic Fatty Liver Disease (NAFLD), has been associated with an altered gut microbiota and barrier integrity. However, the causal link between them has not been fully elucidated yet. In this review, we aim to highlight relevant bacterial taxa and their related metabolites affecting the GI tract barriers in the context of NAFLD, discussing their implications in gut homeostasis and in disease.

A Potential Prophylactic Probiotic for Inflammatory Bowel Disease: The Overall Investigation of Clostridium tyrobutyricum ATCC25755 Attenuates LPS-Induced Inflammation via Regulating Intestinal Immune Cells

SCOPE

This study aims to roundly investigate whether Clostridium tyrobutyricum (Ct) alleviates inflammation via regulating immune cells in the small intestines.

METHODS AND RESULTS

Mice are pre-treated with different concentrations of Ct follow by LPS stimulation. Ct maintains the mice body weight under inflammation. In response to LPS, 10⁷ CFU mL^-1 Ct decreases the mRNA expression of inflammatory cytokines in the duodenum, while 10⁸ CFU mL^-1 Ct reduces inflammatory cytokines expression in both duodenum and ileum and protected intestinal morphology. The small intestinal immune cells are analyzed using flow cytometry. Ct decreases the numbers of macrophages and mast cells in the intestines in response to LPS. In the duodenum, Ct enhances dentritic cells (DCs), regulatory T cells (Tregs), and T helper cell 17 (Th17) proportions. Ct decreases DCs and Tregs proportions, while enhances Th17 numbers in the ileum. The underlying mechanism of Ct in preventing inflammation may rely on the physiological immune cell composition of the intestines. In response to LPS, Ct may mainly stimulate Tregs via activating DCs in the duodenum while trigger Th17 cells in the ileum, thereby maintaining the intestinal homeostasis.

CONCLUSION

Ct alleviates the LPS-induce inflammation via regulating different immune cell types in the small intestines, highlighting that Ct is a potential prophylactic probiotic in intestinal diseases.

Iron Reshapes the Gut Microbiome and Host Metabolism

Compelling studies have established that the gut microbiome is a modifier of metabolic health. Changes in the composition of the gut microbiome are influenced by genetics and the environment, including diet. Iron is a potential node of crosstalk between the host-microbe relationship and metabolic disease. Although iron is well characterized as a frequent traveling companion of metabolic disease, the role of iron is underappreciated because the mechanisms of iron's influence on host metabolism are poorly characterized. Both iron deficiency and excessive amounts leading to iron overload can have detrimental effects on cardiometabolic health. Optimal iron homeostasis is critical for regulation of host immunity and metabolism in addition to regulation of commensal and pathogenic enteric bacteria. In this article we review evidence to support the notion that altering composition of the gut microbiome may be an important route via which iron impacts cardiometabolic health. We discuss reshaping of the microbiome by iron, the physiological significance and the potential for therapeutic interventions.

Probiotics/ prebiotics in viral respiratory infections: implication for emerging pathogens

BACKGROUND

Viral respiratory infections could result in perturbation of the gut microbiota due to a probable cross-talk between lungs and gut microbiota. This can affect the pulmonary health and the gastrointestinal system.

OBJECTIVE

This review aimed to discuss the impact of probiotics/ prebiotics and supplements on the prevention and treatment of respiratory infections, especially emerging pathogens.

METHODS

The data were searched were searched in PubMed, Scopus, Google Scholar, Google Patents, and The Lens-Patent using keywords of probiotics and viral respiratory infections in the title, abstract, and keywords.

RESULT

Probiotics consumption could decrease the susceptibility to viral respiratory infections, such as COVID-19 and simultaneously enhance vaccine efficiency in infectious disease prevention through the immune system enhancement. Probiotics improve the gut microbiota and the immune system via regulating the innate system response and production of anti-inflammatory cytokines. Moreover, treatment with probiotics contributes to the intestinal homeostasis restitution under antibiotic pressure and decreasing the risk of secondary infections due to viral respiratory infections. Probiotics present varied performances in different conditions; thus, promoting their efficacy through combining with supplements (prebiotics, postbiotics, nutraceuticals, berberine, curcumin, lactoferrin, minerals, and vitamins) is important. Several supplements reported to enhance the probiotics' efficacy and their mechanisms as well as probiotics related patents are summarized in this review. Using nanotechnology and microencapsulation techniques can also improve probiotics efficiency.

CONCLUSION

Given the global challenge of COVID-19, probiotic/prebiotic and following nutritional guidelines should be regarded seriously. Additionally, their role as an adjuvant in vaccination for immune response augmentation needs attention.

Enteric Fever Diagnosis: Current Challenges and Future Directions

Enteric fever is a life-threatening systemic febrile disease caused by Salmonella enterica serovars Typhi and Paratyphi (S. Typhi and S. Paratyphi). Unfortunately, the burden of the disease remains high primarily due to the global spread of various drug-resistant Salmonella strains despite continuous advancement in the field. An accurate diagnosis is critical for effective control of the disease. However, enteric fever diagnosis based on clinical presentations is challenging due to overlapping symptoms with other febrile illnesses that are also prevalent in endemic areas. Current laboratory tests display suboptimal sensitivity and specificity, and no diagnostic methods are available for identifying asymptomatic carriers. Several research programs have employed systemic approaches to identify more specific biomarkers for early detection and asymptomatic carrier detection. This review discusses the pros and cons of currently available diagnostic tests for enteric fever, the advancement of research toward improved diagnostic tests, and the challenges of discovering new ideal biomarkers and tests.

Formation of Autoimmune Lesions Is Independent of Antibiotic Treatment in NOD Mice

The relationship between autoimmunity and changes in intestinal microbiota is not yet fully understood. In this study, the role of intestinal microbiota in the onset and progression of autoimmune lesions in non-obese diabetic (NOD) mice was evaluated by administering antibiotics to alter their intestinal microenvironment. Flow cytometric analysis of spleen cells showed that antibiotic administration did not change the proportion or number of T and B cells in NOD mice, and pathological analysis demonstrated that autoimmune lesions in the salivary glands and in the pancreas were also not affected by antibiotic administration. These results suggest that the onset and progression of autoimmunity may be independent of enteral microbiota changes. Our findings may be useful for determining the appropriate use of antibiotics in patients with autoimmune diseases who are prescribed drugs to maintain systemic immune function.

Resident bacteria contribute to opportunistic infections of the respiratory tract

Opportunistic pathogens frequently cause volatile infections in hosts with compromised immune systems or a disrupted normal microbiota. The commensalism of diverse microorganisms contributes to colonization resistance, which prevents the expansion of opportunistic pathogens. Following microbiota disruption, pathogens promptly adapt to altered niches and obtain growth advantages. Nevertheless, whether and how resident bacteria modulate the growth dynamics of invasive pathogens and the eventual outcome of such infections are still unclear. Here, we utilized birds as a model animal and observed a resident bacterium exacerbating the invasion of Avibacterium paragallinarum (previously Haemophilus paragallinarum) in the respiratory tract. We first found that negligibly abundant Staphylococcus chromogenes, rather than Staphylococcus aureus, played a dominant role in Av. paragallinarum-associated infectious coryza in poultry based on epidemic investigations and in vitro analyses. Furthermore, we determined that S. chromogenes not only directly provides the necessary nutrition factor nicotinamide adenine dinucleotide (NAD⁺) but also accelerates its biosynthesis and release from host cells to promote the survival and growth of Av. paragallinarum. Last, we successfully intervened in Av. paragallinarum-associated infections in animal models using antibiotics that specifically target S. chromogenes. Our findings show that opportunistic pathogens can hijack commensal bacteria to initiate infection and expansion and suggest a new paradigm to ameliorate opportunistic infections by modulating the dynamics of resident bacteria.

There is an urgent need for novel intervention strategies and techniques to address the increasing dissemination of multidrug-resistant Gram-negative bacterial pathogens. More importantly, secondary bacterial infections are common in clinical practice, whereas the growth dynamics of each individual in such coinfections are still complicated and elusive. In the current study, we first identified Staphylococcus spp., especially negligibly abundant S. chromogenes, facilitating the pathogenesis of Av. paragallinarum, a Gram-negative bacterium responsible for severe and acute avian respiratory disease worldwide. Furthermore, we developed therapeutic strategies using specific antibiotics against Staphylococcus spp. to relieve clinical symptoms and reduce Av. paragallinarum-associated infections in chickens. These results show that implementation of a proper intervention strategy can prevent opportunistic infections by regulating the microbiota and elucidate the development of alternative approaches for treating Gram-negative pathogenic bacterial infections.

The Autoantigen Repertoire and the Microbial RNP World

Although autoimmunity and autoimmune disease (AID) are relatively common, the repertoire of autoantigens is paradoxically very limited. Highly enriched in this autoantigen repertoire are nucleic acids and their binding proteins, which together form large macromolecular structures. Most of these complexes are of ancient evolutionary origin, with homologs throughout multiple kingdoms of life. Why and if these nucleic acid-protein particles drive the development of autoimmunity remains unresolved. Recent advances in our understanding of the microbiome may provide clues about the origins of autoimmunity - and the particular puzzle of why the autoantigen repertoire is so particularly enriched in ribonucleoprotein particles (RNPs). We discuss the possibility that autoimmunity to some RNPs may arise from molecular mimicry to microbial orthologs.

Alteration of Colonic Mucin Composition and Cytokine Expression in Acute Swine Dysentery

Swine dysentery (SD) is an enteric disease associated with strongly β-hemolytic Brachyspira spp. that cause mucohemorrhagic diarrhea primarily in grower-finisher pigs. We characterized alteration of colonic mucin composition and local cytokine expression in the colon of pigs with acute SD after B. hyodysenteriae (Bhyo) infection and fed either a diet containing 30% distillers dried grains with solubles (DDGS) or a control diet. Colonic tissue samples from 9 noninoculated pigs (Control, N = 4; DDGS, N = 5) and 10 inoculated pigs experiencing acute SD (Bhyo, N = 4; Bhyo-DDGS, N = 6) were evaluated. At the apex of the spiral colon, histochemical staining with high-iron diamine-Alcian blue revealed increased sialomucin (P = .008) and decreased sulfomucin (P = .027) in Bhyo pigs relative to controls, with a dietary effect for sulfomucin. Noninoculated pigs fed DDGS had greater expression of sulfomucin (P = .002) compared to pigs fed the control diet. Immunohistochemically, there was de novo expression of mucin 5AC (MUC5AC) in the Bhyo group while mucin 2 (MUC2) expression was not significantly different between groups. RNA in situ hybridization to detect the pro-inflammatory cytokine IL-1β often showed increased expression in the Bhyo group although without statistical significance, and this was not correlated with MUC5AC or MUC2 expression, suggesting IL-1β is not a major regulator of their secretion in acute SD. Expression of the anti-inflammatory cytokine TGF-β1 was significantly suppressed in the Bhyo group compared to controls (P = .005). This study reveals mucin and cytokine alterations in the colon of pigs with experimentally induced SD and related dietary effects of DDGS.

Bioactive compounds and probiotics-a ray of hope in COVID-19 management

The use of bioactive compounds and probiotic bacteria against the viral diseases in human is known for a long time. Anti-viral, anti-inflammatory and anti-allergic properties of bioactive compounds and bacteria with probiotic properties in respiratory viral diseases may have significance to enhance immunity. This review highlights some of the important bioactive compounds and probiotic bacteria, suggesting them as a ray of hope in the milieu of the COVID-19 management.

Therapeutic implications of functional tea ingredients for ameliorating inflammatory bowel disease: a focused review

Inflammatory bowel disease (IBD) is a chronic gastro-intestinal disorders of unknown etiology. There are several drugs approved for treating IBD patients with active disease, including first-line use of aminosalicylates, and secondary choices of immunomodulators and other therapies. These medications might manage disease symptoms, but have also shown significant side-effects in IBD patients. Tea is the second largest beverage in the world and its main active ingredients including tea polyphenols, polysaccharides and tea pigments have been shown promising anti-inflammatory and antioxidant properties. In this review, we summarize the influence of different tea varieties including green tea, black tea and dark tea as potential nutritional therapy for preventing and treating IBD, and discuss the mechanisms of tea ingredients involved in the regulation of oxidative stress, inflammation, signaling pathways, and gut microbiota that could benefit for IBD disease management. Our observation directs further basic and clinical investigations on tea polyphenols and their derivatives as novel IBD therapeutic agents.

Role of Polymeric Immunoglobulin Receptor in IgA and IgM Transcytosis

Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the polymeric immunoglobulin receptor (pIgR). Secreted IgA and IgM have vital roles in mucosal immunity in response to pathogenic infections. Binding and recognition of polymeric IgA and IgM by pIgR require the joining chain (J chain), a small protein essential in the formation and stabilization of polymeric Ig structures. Recent studies have identified marginal zone B and B1 cell-specific protein (MZB1) as a novel regulator of polymeric IgA and IgM formation. MZB1 might facilitate IgA and IgM transcytosis by promoting the binding of J chain to Ig. In this review, we discuss the roles of pIgR in transcytosis of IgA and IgM, the roles of J chain in the formation of polymeric IgA and IgM and recognition by pIgR, and focus particularly on recent progress in understanding the roles of MZB1, a molecular chaperone protein.

Developing smarter vaccines for paratuberculosis: From early biomarkers to vaccine design

Vaccines for paratuberculosis have been used for over a hundred years but the disease continues to affect ruminant health and livestock industries globally. Mycobacterium avium subspecies paratuberculosis which causes the disease also known as Johne's disease is a subversive pathogen able to undermine both innate and adaptive host defense mechanisms. This review focuses on early protective immune pathways that lead to some animals becoming resilient to infection to provide a road map for designing better vaccines and emphasizes the need for harnessing the potential of mucosal immunity.

2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside, a major bioactive component from Polygoni multiflori Radix (Heshouwu) suppresses DSS induced acute colitis in BALb/c mice by modulating gut microbiota

BACKGROUND

Inflammatory bowel disease (IBD) includes ulcerative colitis (UC) and Crohn's disease (CD), which is a common idiopathic digestive disease without a specific cure or treatment for improvement. Because Polygoni multiflori Radix has a traditional medicinal use to treat intestinal diseases, and the water extract of this herbal medicine had a positive influence on dextran sulfate sodium (DSS) induced UC model in our study. Meanwhile 2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside (TSG) as the major component of the water extract of Polygoni multiflori Radix with yield of more than 10% exhibited the remarkable anti-inflammatory activity in vivo and in vitro, we predicted that TSG may contribute to benefit intestinal tract presented by the water extract of Polygoni multiflori Radix. Therefore, the present study aims to explore the pharmacological effect of this compound on UC model and its possible mechanism to regulate intestinal function through gut microbiota.

METHODS

Ulcerative colitis model was established in BALb/c mice by continuously administrating 3% (w/v) DSS aqueous solution for one week. The disease activity index (DAI), colon length, histopathological examination by H&E and the levels of tight junction proteins (TJP) by immunofluorescence staining were performed in ulcerative colitis model following the protocol. Furthermore, the levels of main inflammatory factors like TNF-α, IL-β, IL-6, and IL-10 were analyzed by the ELIZA kits for the further confirmation of anti-inflammatory activity of TSG on ulcerative colitis model. Finally, 16S rDNA sequencing technology was conducted to explore the composition and relative abundance of gut microbiota of different treatment groups.

RESULTS

TSG treatments effectively increased body weight about 5% of those in DSS group (p < 0.001) as well remarkably reduced the DAI scores to the 50% of those in DSS group (p < 0.001) in the UC model. TSG treatments of either 25 mg/kg (TSG-25) or 100 mg/kg (TSG-100) dosage restored epithelial barrier structure and exhibited obviously intact colon histology with reduced signs of inflammatory cells infiltration, preserved epithelia barrier, restored crypt structure, and increased numbers of goblet cells. TSG treatments could markedly lessen the histopathologic score two or three times than those in DSS group (p < 0.001). Especially for TSG-100 treatment, the fluorescence intensity of ZO-1 and Occludin were nearly back to 80% of those in normal group, and were 1.5 times more than those in the DSS group (p < 0.001). Additionally, direct evidence pointed to TSG as a therapeutically active molecule in the prevention and treatment of UC by significantly reducing the production of these pro-inflammatory cytokines like TNF-α, IL-1β, and IL-6 (p < 0.05-0.001) and increasing the levels of anti-inflammatory cytokine IL-10 (p < 0.05-0.001). Finally, it was found TSG treatments significantly raised the relative abundances of Firmicutes and Bacteroidetes with a dose-dependently and improved the homeostasis of the gut microbiota composition which disrupted by DSS through increasing genus level Lachnospiraceae_NK4A136 and decreasing genus level of Helicobacter, Bacteroides, Parabacteroides.

CONCLUSION

The present results suggested that TSG treatments had a desirable pharmacological effect on acute colitis induced by DSS in the mice as well showed the possible mechanism relate to improve the intestinal function through balancing the gut microbiota of intestinal flora.

Sensory Nociceptive Neurons Contribute to Host Protection During Enteric Infection With Citrobacter rodentium

BACKGROUND

Neurons are an integral component of the immune system that functions to coordinate responses to bacterial pathogens. Sensory nociceptive neurons that can detect bacterial pathogens are found throughout the body with dense innervation of the intestinal tract.

METHODS

In this study, we assessed the role of these nerves in the coordination of host defenses to Citrobacter rodentium. Selective ablation of nociceptive neurons significantly increased bacterial burden 10 days postinfection and delayed pathogen clearance.

RESULTS

Because the sensory neuropeptide CGRP (calcitonin gene-related peptide) regulates host responses during infection of the skin, lung, and small intestine, we assessed the role of CGRP receptor signaling during C rodentium infection. Although CGRP receptor blockade reduced certain proinflammatory gene expression, bacterial burden and Il-22 expression was unaffected.

CONCLUSIONS

Our data highlight that sensory nociceptive neurons exert a significant host protective role during C rodentium infection, independent of CGRP receptor signaling.

Healthy Gut, Healthy Bones: Targeting the Gut Microbiome to Promote Bone Health

Over the past decade, the use of probiotics to modify the gut microbiome has become a public spotlight in reducing the severity of a number of chronic diseases such as autoimmune disease, diabetes, cancer and cardiovascular disease. Recently, the gut microbiome has been shown to play an important role in regulating bone mass. Therefore, targeting the gut microbiome may be a potential alternative avenue for those with osteopenia or osteoporosis. In this mini-review, we take the opportunity to delve into how the different components of the gut work together and how the gut-related diseases impact on bone health.

Preventive and Therapeutic Spermidine Treatment Attenuates Acute Colitis in Mice

Inflammatory bowel disease (IBD) is associated with acute and chronic inflammation of the gastrointestinal tract and has emerged to be a global disease. Spermidine, a natural polyamine, plays a critical role in maintaining cellular homeostasis. Herein, we investigated the impact and mechanism of spermidine on both dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-induced colitis in mice. We found that spermidine exerted protective effects against acute colitis, evidenced by reduced disease activity index (DAI) and colonic inflammation, increased colonic length, and upregulated tight junction proteins in these two colitis models. Importantly, spermidine exerted significant therapeutic and preventive effects against DSS-induced colitis. Pre- and post-treatment with spermidine reduced the expression of proinflammatory cytokines, phosphorylation of (nuclear factor-κB) NF-κB and (mitogen-activated protein kinase) MAPK, and the activation of F4/80 macrophages and T cells in the colon. Furthermore, spermidine upregulated M2 macrophage markers, whereas it downregulated M1 markers in the inflamed colons. In parallel, spermidine reduced M1 pro-inflammatory markers and enhanced M2 anti-inflammatory genes in RAW264.7 cells. These results revealed that spermidine-ameliorated colitis might be through the regulation of M1/M2 macrophage polarization. In addition, spermidine treatment also alleviated LPS/TNF-α-induced inflammation in Caco-2 cells. Taken together, spermidine prevented and reversed colonic inflammation in colitis mice and might be a promising candidate for IBD intervention.

Monoassociation of Preterm Germ-Free Piglets with Bifidobacterium animalis Subsp. lactis BB-12 and Its Impact on Infection with Salmonella Typhimurium

Preterm germ-free piglets were monoassociated with probiotic Bifidobacterium animalis subsp. lactis BB-12 (BB12) to verify its safety and to investigate possible protection against subsequent infection with Salmonella Typhimurium strain LT2 (LT2). Clinical signs of salmonellosis, bacterial colonization in the intestine, bacterial translocation to mesenteric lymph nodes (MLN), blood, liver, spleen, and lungs, histopathological changes in the ileum, claudin-1 and occludin mRNA expression in the ileum and colon, intestinal and plasma concentrations of IL-8, TNF-α, and IL-10 were evaluated. Both BB12 and LT2 colonized the intestine of the monoassociated piglets. BB12 did not translocate in the BB12-monoassociated piglets. BB12 was detected in some cases in the MLN of piglets, consequently infected with LT2, but reduced LT2 counts in the ileum and liver of these piglets. LT2 damaged the luminal structure of the ileum, but a previous association with BB12 mildly alleviated these changes. LT2 infection upregulated claudin-1 mRNA in the ileum and colon and downregulated occludin mRNA in the colon. Infection with LT2 increased levels of IL-8, TNF-α, and IL-10 in the intestine and plasma, and BB12 mildly downregulated them compared to LT2 alone. Despite reductions in bacterial translocation and inflammatory cytokines, clinical signs of LT2 infection were not significantly affected by the probiotic BB12. Thus, we hypothesize that multistrain bacterial colonization of preterm gnotobiotic piglets may be needed to enhance the protective effect against the infection with S. Typhimurium LT2.

Act Locally, Act Globally-Microbiota, Barriers, and Cytokines in Atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disease that is characterized by the formation and progressive growth of atherosclerotic plaques in the wall of arteries. Atherosclerosis is a major predisposing factor for stroke and heart attack. Various immune-mediated mechanisms are implicated in the disease initiation and progression. Cytokines are key mediators of the crosstalk between innate and adaptive immune cells as well as non-hematopoietic cells in the aortic wall and are emerging players in the regulation of atherosclerosis. Progression of atherosclerosis is always associated with increased local and systemic levels of pro-inflammatory cytokines. The role of cytokines within atherosclerotic plaque has been extensively investigated; however, the cell-specific role of cytokine signaling, particularly the role of cytokines in the regulation of barrier tissues tightly associated with microbiota in the context of cardiovascular diseases has only recently come to light. Here, we summarize the knowledge about the function of cytokines at mucosal barriers and the interplay between cytokines, barriers, and microbiota and discuss their known and potential implications for atherosclerosis development.

Maternal exposure to imazalil disrupts intestinal barrier and bile acids enterohepatic circulation tightly related IL-22 expression in F0, F1 and F2 generations of mice

There is a growing body of evidence linking maternal exposure of environmental pollutants to intestinal and metabolic diseases that can be conserved across multiple generations. Here, female C57BL/6 mice were treated imazalil (IMZ) at dietary levels of 0, 0.025‰ and 0.25‰ during the gestation and lactation periods. The results demonstrated that IMZ treatment not only induced significant changes in the mucus secretion and ionic transport, but also disrupted the expression of antimicrobial peptides in the intestine of F0, F1 and F2 generations. In addition, IMZ exposure altered BAs metabolism and the affected the expression levels of critical genes involved in BAs synthesis, signaling, transportation and apical uptake. The immune cell-produced cytokines were displaying extraordinary changes after IMZ exposure. In particular, whether it was in F0, F1-20d, F1-7 w or F2-20d, the expression of IL-22 had the trend of markedly increasing upon IMZ exposure. Correlation analyses revealed that the expression of IL-22 was positively correlated with the change of BAs metabolites. Together, all these results indicated that IMZ exposure was perceived as a major stress by the intestinal epithelium that strongly affected the intestinal barrier function (including mucus, CFTR, AMPs, inflammation), largely in response to an alteration of BAs metabolism.

Wheat germ glycoprotein regionally modulates immunosuppressed mouse intestinal immunity function from early life to adulthood

Wheat germ glycoprotein (WGP) is widely used due to its nutritional benefits and biological activity. This study evaluated the effects of WGP on intestinal-immunosuppressed mice from early life to adulthood and detected the underlying mechanism. The results revealed that WGP demonstrated no clinical side effects on the body index, serum total IgA level, protein expression and the morphology of intestine in newborn mice. In the phase of life, compared with the cyclophosphamide-treated group (CG), WGP clearly promoted the secretion of sIgA and effectively regulated the cytokine gene (IL-2, IFN-γ, TNF-α, IL-4, IL-6, IL-5, IL-17, and TGF-β1) expression in the intestine. Furthermore, WGP promoted the expression of CD40L and CD40, phosphorylation of IKKα/β and transcription of NF-κB-p65. The data as reported in this present analysis suggest that WGP can improve the intestinal immunity of newborn mice to adulthood via the CD40L-CD40-IKKα/β-NF-κB p65 signaling pathway.

Robust microbe immune recognition in the intestinal mucosa

The mammalian mucosal immune system acts as a multitasking mediator between bodily function and a vast diversity of microbial colonists. Depending on host-microbial interaction type, mucosal immune responses have distinct functions. Immunity to pathogen infection functions to limit tissue damage, clear or contain primary infection, and prevent or lower the severity of a secondary infection by conferring specific long-term adaptive immunity. Responses to nonpathogenic commensal or mutualistic microbes instead function to tolerate continuous colonization. Mucosal innate immune and epithelial cells employ a limited repertoire of innate receptors to program the adaptive immune response accordingly. Pathogen versus nonpathogen immune discrimination appears to be very robust, as most individuals successfully maintain life-long mutualism with their nonpathogenic microbiota, while mounting immune defense to pathogenic microbe infection specifically. However, the process is imperfect, which can have immunopathological consequences, but may also be exploited medically. Normally innocuous intestinal commensals in some individuals may drive serious inflammatory autoimmunity, whereas harmless vaccines can be used to fool the immune system into mounting a protective anti-pathogen immune response. In this article, we review the current knowledge on mucosal intestinal bacterial immune recognition focusing on T_H17 responses and identify commonalities between intestinal pathobiont and vaccine-induced T_H17 responses.

The emerging role of probiotics as a mitigation strategy against coronavirus disease 2019 (COVID-19)

COVID-19 is an acute respiratory infection accompanied by pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has affected millions of people globally. To date, there are no highly efficient therapies for this infection. Probiotic bacteria can interact with the gut microbiome to strengthen the immune system, enhance immune responses, and induce appropriate immune signaling pathways. Several probiotics have been confirmed to reduce the duration of bacterial or viral infections. Immune fitness may be one of the approaches by which protection against viral infections can be reinforced. In general, prevention is more efficient than therapy in fighting viral infections. Thus, probiotics have emerged as suitable candidates for controlling these infections. During the COVID-19 pandemic, any approach with the capacity to induce mucosal and systemic reactions could potentially be useful. Here, we summarize findings regarding the effectiveness of various probiotics for preventing virus-induced respiratory infectious diseases, especially those that could be employed for COVID-19 patients. However, the benefits of probiotics are strain-specific, and it is necessary to identify the bacterial strains that are scientifically established to be beneficial.