Alteration of V beta usage and cytokine production of CD4+ TCR beta beta homodimer T cells by elimination of Bacteroides vulgatus prevents colitis in TCR alpha-chain-deficient mice

Assessment of the piroxicam-incited model of synchronized colitis in T-cell receptor alpha chain-deficient mice

BACKGROUND

A multitude of mouse models are utilized to emulate and study intestinal inflammation. T-cell receptor alpha chain (TCRα)-deficient mice are used as a model of spontaneous colitis that has similarities with human ulcerative colitis. However, colitis is triggered late in the life of the mouse (age: 4-5 months), and inflammation does not develop at the same time in different mice. A previously conducted study reported that the administration of the drug piroxicam triggered predictable and early colitis in TCRα-deficient mice at the age of 6-8 weeks. However, a detailed characterization of ensuing inflammation was not provided.

METHODS

We conducted an in-depth examination of piroxicam-triggered colitis in TCRα-deficient mice, with emphasis on spatial histopathologic changes and analysis of expression of inflammatory markers. Furthermore, we tested amelioration of colitis with dexamethasone.

RESULTS

We confirmed that piroxicam induced a time-prescribed colitis and did so in the proximal colon as well as the cecum of TCRα-deficient mice. Piroxicam administration was observed to induce epithelial hyperplasia, goblet cell loss, and leukocyte infiltration with occasional ulceration. A Swiss roll technique was used to examine the colon and cecum in its entirety. Importantly, we observed that inflammation was multifocal segmental, with areas of tissue damage in between healthy tissue. In addition, we observed variability in the severity of inflammation among replicate animals and treatments, and that the administration of dexamethasone only partially ameliorated inflammation in the proximal colon.

CONCLUSIONS

Piroxicam consistently induced multifocal segmental colitis in the proximal colon and cecum, although the degree of inflammation was reduced in the latter. Importantly, spatial variability in inflammation in the large intestine and the inter-replicate variation in the severity of inflammation must be taken into consideration when utilizing this murine model of synchronized colitis.

Using 16S rDNA and metagenomic sequencing technology to analyze the fecal microbiome of children with avoidant/restrictive food intake disorder

To investigate the gut microbiota distribution and its functions in children with avoidant/restrictive food intake disorder (ARFID). A total of 135 children were enrolled in the study, including 102 children with ARFID and 33 healthy children. Fecal samples were analyzed to explore differences in gut microbiota composition and diversity and functional differences between the ARFID and healthy control (HC) groups via 16S rDNA and metagenomic sequencing. The gut microbiota composition and diversity in children with ARFID were different from those in heathy children, but there is no difference in the composition and diversity of gut microbiota between children at the age of 3-6 and 7-12 with ARFID. At the phylum level, the most abundant microbes in the two groups identified by 16S rDNA and metagenomic sequencing were the same. At the genus level, the abundance of Bacteroides was higher in the ARFID group (P > 0.05); however, different from the result of 16SrDNA sequencing, metagenomic sequencing showed that the abundance of Bacteroides in the ARFID group was significantly higher than that in the HC group (P = 0.041). At the species level, Escherichia coli, Streptococcus thermophilus and Lachnospira eligens were the most abundant taxa in the ARFID group, and Prevotella copri, Bifidobacterium pseudocatenulatum, and Ruminococcus gnavus were the top three microbial taxa in the HC group; there were no statistically significant differences between the abundance of these microbial taxa in the two groups. LefSe analysis indicated a greater abundance of the order Enterobacterales and its corresponding family Enterobacteriaceae, the family Bacteroidaceae and corresponding genus Bacteroides, the species Bacteroides vulgatus in ARFID group, while the abundance of the phylum Actinobacteriota and its corresponding class Actinobacteria , the order Bifidobacteriales and corresponding family Bifidobacteriaceae, the genus Bifidobacterium were enriched in the HC group. There were no statistically significant differences in the Chao1, Shannon and Simpson indices between the Y1 and Y2 groups (P = 0.1, P = 0.06, P = 0.06). At the phylum level, Bacillota, Bacteroidota, Proteobacteria and Actinobacteriota were the most abundant taxa in both groups, but there were no statistically significant differences among the abundance of these bacteria (P = 0.958, P = 0.456, P = 0.473, P = 0.065). At the genus level, Faecalibacterium was more abundant in the Y2 group than in the Y1 group, and the difference was statistically significant (P = 0.037). The KEGG annotation results showed no significant difference in gut microbiota function between children with ARFID and healthy children; however, GT26 was significantly enriched in children with ARFID based on the CAZy database. The most abundant antibiotic resistance genes in the ARFID group were the vanT, tetQ, adeF, ermF genes, and the abundance of macrolide resistance genes in the ARFID group was significantly higher than that in the HC group (P = 0.041). Compared with healthy children, children with ARFID have a different distribution of the gut microbiota and functional genes. This indicates that the gut microbiome might play an important role in the pathogenesis of ARFID.Clinical trial registration: ChiCTR2300074759.

Protective effects of different Bacteroides vulgatus strains against lipopolysaccharide-induced acute intestinal injury, and their underlying functional genes

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Different Bacteroides vulgatus strains have varying effects on inflammatory diseases.

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B. vulgatus FTJS7K1 was screened due to its role in alleviating inflammation.

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B. vulgatus FTJS7K1 can modulate gut microbial community.

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B. vulgatus FTJS7K1 can regulate the levels of related cytokines.

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The genes about SCFAs secretion are responsible for the anti-inflammatory effect.

Introduction

The roles of Bacteroides species in alleviating inflammation and intestinal injury has been widely demonstrated, but few studies have focused on the roles of Bacteroides vulgatus.

Objectives

In this study, four B. vulgatus strains were selected, based on their genomic characteristics, to assess their ability to alleviate lipopolysaccharide (LPS)-induced acute intestinal injury in C57BL/6J mice.

Methods

Alterations in the intestinal microbiota, intestinal epithelial permeability, cytokine level, short-chain fatty acid (SCFA) concentration, and immune responses were investigated following LPS-induced acute intestinal injury in C57BL/6J mice.

Results

Severe histological damage and a significant change in cytokine expression was observed in the mouse colon tissues 24 h after LPS administration. Oral administration of different B. vulgatus strains showed different effects on the assessed parameters of the mice; particularly, only the administration of B. vulgatus FTJS7K1 was able to protect the architectural integrity of the intestinal epithelium. B. vulgatus FTJS7K1 also negated the LPS-induced changes in cytokine mRNA expression in the colon tissues, and in the proportion of regulatory T cells in the mesenteric lymph node. Compared with the LPS group, the B. vulgatus FTJS7K1 group showed significantly increased abundance of Lactobacillus, Akkermansia, and Bifidobacterium, and decreased abundance of Faecalibaculum. The B. vulgatus FTJS7K1 group also showed significantly increased concentration of SCFAs in fecal samples. The results of genomic analysis showed that these protective roles of B. vulgatus FTJS7K1 may be mediated through specific genes associated with defense mechanisms and metabolism (e.g., the secretion of SCFAs).

Conclusions

Our findings suggest that the protective role of B. vulgatus FTJS7K1 appear to be via modulation of cytokine production in the colon tissue and regulation of the structure of the gut microbiota. These results provide support for the screening of the Bacteroides genus for next-generation probiotics.

Roles of intestinal bacteroides in human health and diseases

Bacteroides, an abundant genus in the intestines of mammals, has been recently considered as the next generation probiotics (NGP) candidate due to its potential role in promoting host health. However, the role of Bacteroides in the development of intestinal dysfunctions such as diarrhea, inflammatory bowel disease, and colorectal cancer should not be overlooked. In the present study, we focused on nine most widely occurred and abundant Bacteroides species and discussed their roles in host immunity, glucose and lipid metabolism and the prevention or induction of diseases. Besides, we also discussed the current methods used in the safety evaluation of Bacteroides species and key opinions about the concerns of these strains for the future use.

Sialylation and fucosylation modulate inflammasome-activating eIF2 Signaling and microbial translocation during HIV infection

An emerging paradigm suggests that gut glycosylation is a key force in maintaining the homeostatic relationship between the gut and its microbiota. Nevertheless, it is unclear how gut glycosylation contributes to the HIV-associated microbial translocation and inflammation that persist despite viral suppression and contribute to the development of several comorbidities. We examined terminal ileum, right colon, and sigmoid colon biopsies from HIV-infected virally-suppressed individuals and found that gut glycomic patterns are associated with distinct microbial compositions and differential levels of chronic inflammation and HIV persistence. In particular, high levels of the pro-inflammatory hypo-sialylated T-antigen glycans and low levels of the anti-inflammatory fucosylated glycans were associated with higher abundance of glycan-degrading microbial species (in particular, Bacteroides vulgatus), a less diverse microbiome, higher levels of inflammation, and higher levels of ileum-associated HIV DNA. These findings are linked to the activation of the inflammasome-mediating eIF2 signaling pathway. Our study thus provides the first proof-of-concept evidence that a previously unappreciated factor, gut glycosylation, is a force that may impact the vicious cycle between HIV infection, microbial translocation, and chronic inflammation.

Polysaccharides from Chrysanthemum morifolium Ramat ameliorate colitis rats by modulating the intestinal microbiota community

The gut microflora dysbiosis has been closely related with the inflammatory bowel disease (IBD). In this study, the effect of polysaccharides from Chrysanthemum morifolium Ramat on the gut microbiota was evaluated by ulcerative colitis (UC) rat model. Physiological and pathological analyses suggested that Chrysanthemum polysaccharides possessed notably protective effects on UC in vivo. Based on the Illumina MiSeq platform, 16S rRNA sequencing of the rat colonic contents indicated that the intestinal flora structure remarkably changed in the model rats and the tendency was alleviated to a certain degree by treatment with different dosages of Chrysanthemum polysaccharides. In normal groups, there were more Firmicutes than Bacteroidetes, but this change lost at the pathological state. Following Chrysanthemum polysaccharides, rising Firmicutes/Bacteroidetes ratio was validated. Besides the microbial diversity and the community richness of the UC rats were improved by Chrysanthemum polysaccharides, the composition of intestinal microflora in the model group were also restored after oral administration of Chrysanthemum polysaccharides. The abundance of opportunistic pathogens was decreased (Escherichia, Enterococcus and Prevotella), while the levels of protective bacteria such as Butyricicoccus and Clostridium (butyrate-producing bacteria), Lactobacillus and Bifidobacterium (probiotics), Lachnospiraceae and Rikenellaceae elevated in various degrees. Correlation analysis between intestinal flora and biochemical factors suggested that the relative abundance of protective bacteria was positively correlated with the levels of anti-inflammatory cytokines such as IL-4, IL-10 and IL-11, while aggressive bacteria were positively correlated with proinflammatory cytokine such as IL-23、IL-6、 IF-17、TNF-α、IL-1β and IFN-γ. The above results showed that the intestinal flora were closely related to the secretion and expression of cytokines in the body, and they interacted with each other to regulate immune function. Thus, Chrysanthemum polysaccharides could ameliorate ulcerative colitis by fostering beneficial intestinal flora growth, modulating the balance of intestinal microecology and restoring the immune system.

Towards an integrated understanding of the therapeutic utility of exclusive enteral nutrition in the treatment of Crohn's disease

Crohn's disease (CD) is a chronic disease characterized by episodic and disabling inflammation of the gastrointestinal tract in genetically susceptible individuals. The incidence and prevalence of CD is rising rapidly across the world emphasising that disease risk is also influenced by environmental and lifestyle factors, as well as the microbial community resident in the gut. Childhood-onset CD is associated with an aggressive disease course that can adversely impact patient growth and development. There is no cure for CD however new onset and recurrent cases of paediatric CD are often responsive to exclusive enteral nutrition (EEN) treatment. EEN treatment involves the exclusive consumption of an elemental or polymeric formula for several weeks and it is well established as a primary intervention strategy. EEN treatments typically achieve remission rates of over 80% and importantly they are associated with a high rate of mucosal healing, far superior to steroids, which is prognostic of improved long-term health outcomes. Furthermore, they are safe, have few side effects, and improve nutritional status and linear growth. Surprisingly, despite the utility of EEN our understanding of the host-microbe-diet interactions that underpin clinical remission and mucosal healing are limited. Here, we review the current state of knowledge and propose that the induction of autophagy, in addition to modulation of the microbiota and coordinated effects on inflammation and epithelial cell biology, may be critical for the therapeutic effects associated with EEN. A better understanding of EEN treatment will provide new opportunities to restore gut homeostasis and prolong periods of remission, as well as provide new insights into the factors that trigger and perhaps prevent CD.

Specific members of the predominant gut microbiota predict pouchitis following colectomy and IPAA in UC

OBJECTIVE

Pouchitis is the most common complication after colectomy with ileal pouch-anal anastomosis (IPAA) for UC and the risk is the highest within the 1st year after surgery. The pathogenesis is not completely understood but clinical response to antibiotics suggests a role for gut microbiota. We hypothesised that the risk for pouchitis can be predicted based on the faecal microbial composition before colectomy.

DESIGN

Faecal samples from 21 patients with UC undergoing IPAA were prospectively collected before colectomy and at predefined clinical visits at 1 month, 3 months, 6 months and 12 months after IPAA. The predominant microbiota was analysed using community profiling with denaturing gradient gel electrophoresis followed by quantitative real-time PCR validation.

RESULTS

Cluster analysis before colectomy distinguished patients with pouchitis from those with normal pouch during the 1st year of follow-up. In patients developing pouchitis, an increase of Ruminococcus gnavus (p<0.001), Bacteroides vulgatus (p=0.043), Clostridium perfringens (p=0.011) and a reduction of two Lachnospiraceae genera (Blautia (p=0.04), Roseburia (p=0.008)) was observed. A score combining these five bacterial risk factors was calculated and presence of at least two risk factors showed a sensitivity and specificity of 100% and 63.6%, respectively.

CONCLUSIONS

Presence of R. gnavus, B. vulgatus and C. perfringens and absence of Blautia and Roseburia in faecal samples of patients with UC before surgery is associated with a higher risk of pouchitis after IPAA. Our findings suggest new predictive and therapeutic strategies in patients undergoing colectomy with IPAA.

Lack of Adrenomedullin Results in Microbiota Changes and Aggravates Azoxymethane and Dextran Sulfate Sodium-Induced Colitis in Mice

The link between intestinal inflammation, microbiota, and colorectal cancer is intriguing and the potential underlying mechanisms remain unknown. Here we evaluate the influence of adrenomedullin (AM) in microbiota composition and its impact on colitis with an inducible knockout (KO) mouse model for AM. Microbiota composition was analyzed in KO and wild type (WT) mice by massive sequencing. Colitis was induced in mice by administration of azoxymethane (AOM) followed by dextran sulfate sodium (DSS) in the drinking water. Colitis was evaluated using a clinical symptoms index, histopathological analyses, and qRT-PCR. Abrogation of the adm gene in the whole body was confirmed by PCR and qRT-PCR. KO mice exhibit significant changes in colonic microbiota: higher proportion of δ-Proteobacteria class; of Coriobacteriales order; and of other families and genera was observed in KO feces. Meanwhile these mice had a lower proportion of beneficial bacteria, such as Lactobacillus gasseri and Bifidobacterium choerinum. TLR4 gene expression was higher (p < 0.05) in KO animals. AM deficient mice treated with DSS exhibited a significantly worse colitis with profound weight loss, severe diarrhea, rectal bleeding, colonic inflammation, edema, infiltration, crypt destruction, and higher levels of pro-inflammatory cytokines. No changes were observed in the expression levels of adhesion molecules. In conclusion, we have shown that lack of AM leads to changes in gut microbiota population and in a worsening of colitis conditions, suggesting that endogenous AM is a protective mediator in this pathology.

Human Peripheral CD4(+) Vδ1(+) γδT Cells Can Develop into αβT Cells

The lifelong generation of αβT cells enables us to continuously build immunity against pathogens and malignancies despite the loss of thymic function with age. Homeostatic proliferation of post-thymic naïve and memory T cells and their transition into effector and long-lived memory cells balance the decreasing output of naïve T cells, and recent research suggests that also αβT-cell development independent from the thymus may occur. However, the sites and mechanisms of extrathymic T-cell development are not yet understood in detail. γδT cells represent a small fraction of the overall T-cell pool, and are endowed with tremendous phenotypic and functional plasticity. γδT cells that express the Vδ1 gene segment are a minor population in human peripheral blood but predominate in epithelial (and inflamed) tissues. Here, we characterize a CD4⁺ peripheral Vδ1⁺ γδT-cell subpopulation that expresses stem-cell and progenitor markers and is able to develop into functional αβT cells ex vivo in a simple culture system and in vivo. The route taken by this process resembles thymic T-cell development. However, it involves the re-organization of the Vδ1⁺ γδTCR into the αβTCR as a consequence of TCR-γ chain downregulation and the expression of surface Vδ1⁺Vβ⁺ TCR components, which we believe function as surrogate pre-TCR. This transdifferentiation process is readily detectable in vivo in inflamed tissue. Our study provides a conceptual framework for extrathymic T-cell development and opens up a new vista in immunology that requires adaptive immune responses in infection, autoimmunity, and cancer to be reconsidered.

Changes of faecal microbiota in patients with Crohn's disease treated with an elemental diet and total parenteral nutrition

BACKGROUND

Intestinal microbiota contributes to the pathogenesis of Crohn's disease. Elemental diet and total parenteral nutrition are effective therapies for Crohn's disease; however, changes of microbiota as a result of both treatments have not been fully elucidated.

AIM

To elucidate changes of faecal microbiota in Crohn's disease patients treated with elemental diet and total parenteral nutrition.

METHODS

Stool samples were collected from 33 active Crohn's disease patients and 17 healthy subjects, and recollected after elemental diet (8 patients) and total parenteral nutrition (9 patients). Terminal restriction fragment length polymorphism analysis of bacterial 16srDNA was performed to evaluate the whole microbiota. Specific quantitative PCR was then used to determine populations of predominant bacterial groups.

RESULTS

In Crohn's disease patients, the number of terminal restriction fragments, which reflects bacterial species, was significantly lower. Populations of total bacteria and Bifidobacterium were significantly lower and the ratio of Enterococcus was higher. The number of terminal restriction fragments was significantly decreased after total parenteral nutrition, but not after elemental diet. Population of Bacteroides fragilis significantly decreased after elemental diet, while population of Enterococcus significantly increased after total parenteral nutrition.

CONCLUSION

Faecal microbiota in Crohn's disease patients was markedly different from healthy subjects. Species diversity was reduced by total parenteral nutrition, but not by elemental diet.

Animal models of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory condition that is medicated by genetic, immune, and environmental factors. At least 66 different kinds of animal models have been established to study IBD, which are classified primarily into chemically induced, cell-transfer, congenial mutant, and genetically engineered models. These IBD models have provided significant contributions to not only dissect the mechanism but also develop novel therapeutic strategies for IBD. In addition, recent advances on genetically engineered techniques such as cell-specific and inducible knockout as well as knockin mouse systems have brought novel concepts on IBD pathogenesis to the fore. Further, mouse models, which lack some IBD susceptibility genes, have suggested more complicated mechanism of IBD than previously predicted. This chapter summarizes the distinct feature of each murine IBD model and discusses the previous and current lessons from the IBD models.

Corticotropin-releasing factor secretion from dendritic cells stimulated by commensal bacteria

AIM: To study the production and secretion of corticotropin-releasing factor (CRF) by dendritic cells and the influence of commensal bacteria.

METHODS: JAWSII cells (ATCC CRL-11904), a mouse dendritic cell line, were seeded into 24-well culture plates and grown for 3 d. Commensal bacterial strains of Clostridium clostrodiiforme (JCM1291), Bacteroides vulgatus (B. vulgatus) (JCM5856), Escherichia coli (JCM1649), or Fusobacterium varium (F. varium) (ATCC8501) were added to the cells except for the control well, and incubated for 2 h. After incubation, we performed enzyme-linked immunosorbent assay for the cultured medium and reverse transcription polymerase chain reaction for the dendritic cells, and compared these values with controls.

RESULTS: The level of CRF secretion by control dendritic cells was 40.4 ± 6.2 pg/mL. The CRF levels for cells incubated with F. varium and B. vulgatus were significantly higher than that of the control (P < 0.0001). CRF mRNA was present in the control sample without bacteria, and CRF mRNA levels in all samples treated with bacteria were above that of the control sample. F. varium caused the greatest increase in CRF mRNA expression.

CONCLUSION: Our results suggest that dendritic cells produce CRF, a process augmented by commensal bacteria.

Ulcerative colitis and irritable bowel patients exhibit distinct abnormalities of the gut microbiota

BACKGROUND

Previous studies suggest a link between gut microbiota and the development of ulcerative colitis (UC) and irritable bowel syndrome (IBS). Our aim was to investigate any quantitative differences in faecal bacterial compositions in UC and IBS patients compared to healthy controls, and to identify individual bacterial species that contribute to these differences.

METHODS

Faecal microbiota of 13 UC patients, 11 IBS patients and 22 healthy volunteers were analysed by PCR-Denaturing Gradient Gel Electrophoresis (DGGE) using universal and Bacteroides specific primers. The data obtained were normalized using in-house developed statistical method and interrogated by multivariate approaches. The differentiated bands were excised and identified by sequencing the V3 region of the 16S rRNA genes.

RESULTS

Band profiles revealed that number of predominant faecal bacteria were significantly different between UC, IBS and control group (p < 10-4). By assessing the mean band numbers in UC (37 ± 5) and IBS (39 ± 6), compared to the controls (45 ± 3), a significant decrease in bacterial species is suggested (p = 0.01). There were no significant differences between IBS and UC. Biodiversity of the bacterial species was significantly lower in UC (μ = 2.94, σ = 0.29) and IBS patients (μ = 2.90, σ = 0.38) than controls (μ = 3.25, σ = 0.16; p = 0.01). Moreover, similarity indices revealed greater biological variability of predominant bacteria in UC and IBS compared to the controls (median Dice coefficients 76.1% (IQR 70.9 - 83.1), 73.8% (IQR 67.0 - 77.5) and 82.9% (IQR 79.1 - 86.7) respectively). DNA sequencing of discriminating bands suggest that the presence of Bacteroides vulgatus, B. ovatus, B. uniformis, and Parabacteroides sp. in healthy volunteers distinguishes them from IBS and UC patients. DGGE profiles of Bacteroides species revealed a decrease of Bacteroides community in UC relative to IBS and controls.

CONCLUSION

Molecular profiling of faecal bacteria revealed abnormalities of intestinal microbiota in UC and IBS patients, while different patterns of Bacteroides species loss in particular, were associated with UC and IBS.

Diversity of caecal bacteria is altered in interleukin-10 gene-deficient mice before and after colitis onset and when fed polyunsaturated fatty acids

Interleukin-10 gene-deficient (Il10(-/-)) mice show a hyper-reaction to normal intestinal bacteria and develop spontaneous colitis similar to that of human Crohn's disease when raised under conventional (but not germ-free) conditions. The lack of IL10 protein in these mice leads to changes in intestinal metabolic and signalling processes. The first aim of this study was to identify changes in the bacterial community of the caeca at 7 weeks of age (preclinical colitis) and at 12 weeks of age (when clinical signs of colitis are present), and establish if there were any changes that could be associated with the mouse genotype. We have previously shown that dietary n-3 and n-6 polyunsaturated fatty acids (PUFA) have anti-inflammatory effects and affect colonic gene expression profiles in Il10(-/-) mice; therefore, we also aimed to test the effect of the n-3 PUFA eicosapentaenoic acid (EPA) and the n-6 PUFA arachidonic acid (AA) on the bacterial community of caeca in both Il10(-/-) and C57 mice fed these diets. The lower number of caecal bacteria observed before colitis (7 weeks of age) in Il10(-/-) compared to C57 mice suggests differences in the intestinal bacteria that might be associated with the genotype, and this could contribute to the development of colitis in this mouse model. The number and diversity of caecal bacteria increased after the onset of colitis (12 weeks of age). The increase in caecal Escherichia coli numbers in both inflamed Il10(-/-) and healthy C57 mice might be attributed to the dietary PUFA (especially dietary AA), and thus not be a cause of colitis development. A possible protective effect of E. coli mediated by PUFA supplementation and associated changes in the bacterial environment could be a subject for further investigation to define the mode of action of PUFA in colitis.

Change of intestinal microbiota with elemental diet and its impact on therapeutic effects in a murine model of chronic colitis

Elemental diet (ED) has been used as an enteral nutritional therapy for Crohn's disease. However, the precise mechanisms of ED remain unclear. In interleukin-10 (IL-10)-deficient cell-transferred mice, we investigated the change of intestinal microbiota with ED using molecular terminal-restriction fragment length polymorphism (T-RFLP) analysis and culture method, and evaluated its influence on therapeutic effects of ED. ED significantly suppressed intestinal inflammation. The total amount of bacteria in colitis mice fed the regular diet was higher than in normal mice but decreased in colitis mice fed ED. T-RFLP profiles of the ED group markedly differed from those of the regular diet groups. The diversity of bacterial species in the ED group decreased to 60% of that found in the regular diet groups. Among the cultivated bacteria, the change in lactic acid bacteria composition was remarkable. Lactobacillus reuteri and L. johnsonii decreased and Enterococcus faecalis and E. durans increased in the ED group. The culture supernatant of L. reuteri isolates induced significant tumor necrosis factor-alpha (TNF-alpha) and IL-6 activity in RAW 264 cells, while the culture supernatant of E. faecalis and E. durans barely induced their activity. These data suggested that reduction in amount and diversity of intestinal microbiota and decrease of proinflammatory cytokines via a change in composition of lactic acid bacteria by ED seem to contribute to reduction of bowel inflammation in this model.

Faecal microbiota profile of Crohn's disease determined by terminal restriction fragment length polymorphism analysis

BACKGROUND

Terminal restriction fragment length polymorphism (T-RFLP) analyses are powerful tools to assess the diversity of complex microbiota. T-RFLPs permit rapid comparisons of microbiota from many samples.

AIM

To perform T-RFLP analyses of faecal microbiota in Crohn's disease (CD) patients to investigate potential alterations in faecal microbial communities and furthermore to analyse the effects of elemental diet on faecal microbiota profiles.

METHODS

Thirty-four patients with CD and 30 healthy individuals were enrolled in the study. DNA was extracted from stool samples and 16S rRNA genes were amplified by PCR. PCR products were digested with BslI restriction enzymes and T-RF lengths were determined.

RESULTS

Faecal microbial communities were classified into seven clusters. Almost all healthy individuals (28/30) were included in cluster I, II and III, but the majority of CD patients (25/34) could be divided into another four clusters (cluster IV-VII). Prediction of bacteria based on the BslI-digested T-RFLP database showed a significant decrease in Clostridium cluster IV, Clostridium cluster XI and subcluster XIVa in CD patients. In contrast, Bacteroides significantly increased in CD patients. Significant increases in Enterobacteriales were also observed in CD patients. Furthermore, elemental diets modulated faecal bacterial communities in CD patients.

CONCLUSIONS

Terminal restriction fragment length polymorphism analyses showed that the diversity of faecal microbiota in patients with CD differed from that of healthy individuals. Furthermore, elemental diets modulated faecal microbiota composition, and this effect may be involved in mechanisms of clinical effects of elemental diet.

Probiotics and prebiotics in inflammatory bowel disease: microflora 'on the scope'

The intestinal microflora is a large bacterial community that colonizes the gut, with a metabolic activity equal to an organ and various functions that affect the physiology and pathology of the host's mucosal immune system. Intestinal bacteria are useful in promotion of human health, but certain components of microflora, in genetically susceptible individuals, contribute to various pathological disorders, including inflammatory bowel disease. Clinical and experimental observations indicate an imbalance in protective and harmful microflora components in these disorders. Manipulation of gut flora to enhance its protective and beneficial role represents a promising field of new therapeutic strategies of inflammatory bowel disease. In this review, we discuss the implication of gut flora in the intestinal inflammation that justifies the role of probiotics and prebiotics in the prevention and treatment of inflammatory bowel disease and we address the evidence for therapeutic benefits from their use in experimental models of colitis and clinical trials.

Does the intestinal bifidobacterial colonisation affect bacterial translocation?

The aim of this work was to investigate the possible role of the intestinal anaerobic flora (especially bifidobacteria) in regulating bacterial translocation (BT) which can be defined as the passage of intestinal microbes through the mucosa to internal organs. Default in BT regulation concurs with pathogenesis of sepsis in various human conditions, such as acute pancreatitis, cirrhosis, necrotising enterocolitis or multiple organ failure. The intestinal flora was studied in human flora associated mice (HF mice) and BT was quantified in Peyer's patches (PP), blood, spleen, liver and lungs. HF mice displayed a heterogenic intestinal colonisation with bifidobacteria. High colonisation of both caecum and colon by bifidobacteria led to a poorer bacterial contamination of blood, liver and lungs. Moreover, ileal, caecal and colonic bifidobacterial counts negatively correlated with the bacterial dissemination (number of contaminated organs per mouse). In contrast, Bacteroides fragilis group counts positively correlated with bacteraemia, lungs contamination or bacterial dissemination. Additionally, clostridia localised in the colon affected bacterial uptake by PP and lungs contamination as indicated by positive correlations between bacterial populations in these respective locations. These results indicate that bifidobacteria, when established in high counts, reduced BT to liver, blood and lungs, whereas B. fragilis group favoured the bacterial passage. Clostridia established in the distal ileum also seemed to favour BT to lungs. The manipulation of the bacterial flora to optimise the regulatory effect on BT should therefore focus on the selective promotion of bifidobacteria and avoid an increase in potentially detrimental populations such as B. fragilis group and clostridia.

Imbalance in intestinal microflora constitution could be involved in the pathogenesis of inflammatory bowel disease

Since genetically engineered animal models of inflammatory bowel disease (IBD) do not develop colitis under germ-free conditions, the intestinal microflora is thought to be one of the most important environmental factors associated with IBD. To understand the involvement of intestinal microflora in the pathogenesis of IBD, we analyzed the constituents of intestinal microflora in IBD. Faecal samples from 73 patients with ulcerative colitis (UC) and 23 patients with Crohn's disease (CD) were analyzed by quantitative PCR using 16S rRNA gene-targeted group-specific primers for Bacteroides fragilis group, Bifidobacterium, Clostridium coccoides groups, Clostridium leptum subgroup, Atopobium cluster, and seven species of Bacteroides. We analyzed the distribution of the predominant microflora by fluorescence in situ hybridization (FISH) using group-specific probes. We also examined the concentration of faecal organic acids produced by intestinal microflora. Contrary to previous reports, we found that the B. fragilis group was significantly decreased in the faeces of patients with IBD. Moreover, B. vulgatus was the predominant microflora in healthy controls and relatively decreased among IBD patients. Most of the microflora adhering to the colonic mucosa surrounding the mucus layer comprised C. coccoides group and Bifidobacterium. B. fragilis group mainly inhabited the faeces, but did not adhere to or invade the mucosa. The concentrations of propionic and butyric acids in the faeces were significantly decreased in patients with IBD. These findings indicate that IBD is not caused by a specific intestinal bacterial cluster or species and that disordered intestinal microflora could be involved in the pathogenesis of IBD.

The immune response in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD), collectively referred to as inflammatory bowel disease (IBD), present with differing histologic and cytokine profiles. While the precise mechanisms underlying the development of IBD are not known, sufficient data have been collected to suggest that it results from a complex interplay of genetic, environmental, and immunologic factors. Animal models of colitis, along with a more detailed understanding of the immune response in the normal bowel, have led to unifying hypotheses regarding the pathogenesis. An inappropriate mucosal immune response to normal intestinal constituents is a key feature, leading to an imbalance in local pro- and anti-inflammatory cytokines. Neutrophil and monocyte influx occurs with subsequent secretion of oxygen radicals and enzymes, leading to tissue damage. Therapy of IBD has improved and expanded as the understanding of disease mechanisms has evolved. Pharmacologic agents such as aminosalicylates, azathioprine/6-mercaptopurine, or steroids are the mainstays of therapy. Newer agents including monoclonal antibodies targeted to specific proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), have emerged and provide great clinical benefit, but unknown long-term toxicity and immunogenicity may limit their use.

Epithelial barrier disruption allows nondisease-causing bacteria to initiate and sustain IBD in the IL-10 gene-deficient mouse

BACKGROUND

In the IL-10 gene-deficient mouse model, development of intestinal inflammation is associated with a defect in epithelial barrier integrity that is thought to allow sufficient passage of bacteria or bacterial antigens to initiate a mucosal immune response. Microbial monoassociation experiments into axenic animals have shown that some, but not all, endogenous bacteria will initiate an intestinal inflammatory response. For instance, Bacteroides vulgatus does not initiate intestinal inflammation in axenic IL-10 gene-deficient mice. We investigated whether B. vulgatus requires concomitant disruption of the intestinal epithelial barrier integrity in order to initiate an inflammatory response.

METHODS

We first identified a dose of the indomethacin that would cause a primary disruption of the epithelial barrier without causing intestinal inflammation. IL-10 axenic mice were then administered this dose of indomethacin in their drinking water for 7 days and concomitantly monoassociated, by oral gavage, with B. vulgatus.

RESULTS

Indomethacin treatment (2 microg/g/d) for 7 days resulted in disruption of epithelial barrier integrity, but it caused neither a systemic inflammatory response nor a mucosal inflammatory response in the colon or cecum. Monoassociation with B. vulgatus alone did not lead to a mucosal inflammatory response, despite a measurable systemic response. In contrast, administration of indomethacin plus B. vulgatus-monoassociation resulted in a marked intestinal inflammatory response in colon and cecum.

CONCLUSIONS

Our data show that, in a genetically predisposed animal model, the nondisease-causing endogenous bacteria, B. vulgatus, is able to cause an intestinal inflammatory response provided that disruption of the intestinal epithelial barrier has occurred.

Terminal restriction fragment length polymorphism analysis of the diversity of fecal microbiota in patients with ulcerative colitis

BACKGROUND

Terminal restriction fragment length polymorphism (T-RFLP) analysis is a powerful tool to assess the diversity of complexed microbiota. This permits rapid comparison of microbiota from many samples. In this study, we performed T-RFLP analysis of the fecal microbiota from patients with ulcerative colitis (UC).

METHODS

Forty-four patients with UC (23 women and 21 men, median age 25 years) and 46 healthy individuals (25 women and 21 men, median age 34 years) were enrolled in this study. DNA was extracted from their stool samples, and the 16S rRNA genes were amplified by PCR. The PCR products were then digested with HhaI and/or MspI restriction enzymes, and the length of the T-RF was determined.

RESULTS

The fecal microbial communities were classified in 8 clusters. Almost all the healthy individuals (39 of 46) were included in cluster I, and most of the UC patients could be divided into the other 7 clusters, indicating that fecal bacterial communities are different between healthy individuals and active UC patients. Some T-RFs, derived from the unclassified bacteria, Ruminococcus, Eubacterium, Fusobacterium, gammaproteobacteria, unclassified Bacteroides, and unclassified Lactobacillus, were detected in the UC patients, but not in the healthy individuals. The T-RFLP patterns were also different between the active patients and inactive (remission) patients. The T-RF derived from the unclassified bacteria, Ruminococcus and Eubacterium, and the T-RFs derived from the unclassified bacteria, Eubacterium, and Fusobacterium were predominantly detected in the active patients not the inactive patients. In contrast, the T-RFs derived from Lactobacillus and unclassified Lactobacillus were more predominant in the inactive (remission) patients. In 4 patients with proctitis, the pattern of fecal microbial diversity was very similar.

CONCLUSIONS

T-RFLP analyses showed that the diversity of fecal microbiota in patients with UC was different from that in healthy individuals. Unclassified bacteria, as well as known bacteria, can contribute to alterations in the bacterial diversity of UC patients.

Therapeutic effects of roxithromycin in interleukin-10-deficient colitis

BACKGROUND

A limited number of therapeutic strategies are currently available to treat patients with inflammatory bowel disease (IBD). Interleukin-10 (IL-10)-deficient mice, well characterized as an experimental model of IBD, develop severe chronic colitis because of aberrant Th1 responses. Roxithromycin (RXM), a macrolide antibiotic, has received attention because it offers not only antibacterial but also immunosuppressive effects. We examined the immunosuppressive effect of RXM on the development of IBD.

METHODS

To test the efficacy of short-term administration of RXM, elder IL-10-deficient mice (16-20 weeks old) with established colitis were orally treated for 10 days with RXM (20 mg/kg per day). To test the long-term preventive effects of RXM, for 20 weeks young adult IL-10-deficient mice (4-5 weeks old) also were administered RXM orally (20 mg/kg per day).

RESULTS

The short-term treatment-oriented administration of RXM reduced the degree of inflammatory change and lowered serum amyloid A in IL-10-deficient mice with severe colitis. Mononuclear cells from the lamina propria of RXM-treated large intestines showed lower production of IFN-gamma than did those from diseased mice that were untreated. Long-term prevention-oriented administration of RXM suppressed the development of severe colitis and decreased production of IFN-gamma and IL-12. In addition to its expected immunosuppressive effect, RXM treatment also decreased the level of Bacteroides vulgatus, a Gram-negative anaerobe.

CONCLUSIONS

The anti-inflammatory changes observed in IL-10-deficient mice resulted from the efficacy of RXM as an immunosuppressant as well as from its efficacy as an antibiotic. According to our findings, RXM would seem to have significant potential as a preventive and/or therapeutic agent for IBD.

Oral feeding of Bifidobacterium bifidum (BGN4) prevents CD4(+) CD45RB(high) T cell-mediated inflammatory bowel disease by inhibition of disordered T cell activation

Probiotics have been considered as preventive agents for the control of inflammatory bowel disease (IBD). In this study, we assessed the immunomodulatory effect of Bifidobacterium bifidum BGN4 on the control of IBD using the CD4(+) CD45RB(high) T cell transfer disease model. The mice were fed for 4 weeks with either a conventional diet containing only skim milk or a diet containing skim milk with 0.3% (w/w) BGN4. The BGN4-fed mice showed normal weight growth, fewer clinical symptoms such as thickened wall and inflammatory cell infiltration, and lower levels of CD4(+) T lymphocyte infiltration and inflammatory cytokine productions than the skim milk-fed mice with IBD in the large intestine. Suppression of these cytokine productions, particularly IFN-gamma and MCP-1, through BGN4 treatment was also observed in the in vitro co-culture between intestinal epithelial cells and T cells. These findings suggested that a BGN4 supplemented diet could be helpful for the control of aberrant immune responses in the intestinal tissue.

IgG transport across mucosal barriers by neonatal Fc receptor for IgG and mucosal immunity

Mucosal secretions of the human gastrointestinal, respiratory, and genital tracts contain significant quantities of IgG. The neonatal Fc receptor for IgG (FcRn) plays a major role in regulating host IgG levels and transporting IgG and associated antigens across polarized epithelial barriers. The FcRn can then recycle the IgG/antigen complex back across the intestinal barrier into the lamina propria for processing by dendritic cells and presentation to CD4(+) T cells in regional organized lymphoid structures. FcRn, through its ability to secrete and absorb IgG, thus integrates luminal antigen encounters with systemic immune compartments and, as such, provides essential host defense and immunoregulatory functions at the mucosal surfaces.

Therapeutic approaches targeting intestinal microflora in inflammatory bowel disease

Inflammatory bowel diseases, ulcerative colitis, and Crohn’s disease, are chronic intestinal disorders of unknown etiology in which in genetically susceptible individuals, the mucosal immune system shows an aberrant response towards commensal bacteria. The gastrointestinal tract has developed ingenious mechanisms to coexist with its autologous microflora, but rapidly responds to invading pathogens and then returns to homeostasis with its commensal bacteria after the pathogenic infection is cleared. In case of disruption of this tightly-regulated homeostasis, chronic intestinal inflammation may be induced. Previous studies showed that some commensal bacteria are detrimental while others have either no influence or have a protective action. In addition, each host has a genetically determined response to detrimental and protective bacterial species. These suggest that therapeutic manipulation of imbalance of microflora can influence health and disease. This review focuses on new insights into the role of commensal bacteria in gut health and disease, and presents recent findings in innate and adaptive immune interactions. Therapeutic approaches to modulate balance of intestinal microflora and their potential mechanisms of action are also discussed.

An elemental diet controls inflammation in indomethacin-induced small bowel disease in rats: the role of low dietary fat and the elimination of dietary proteins

Elemental diets (EDs) are effective in treating Crohn's disease. We hypothesize that low dietary fat and amino acids used as the sole nitrogen source are the major contributors for the success of EDs. We examined the influences of the addition of dietary fat and protein to an ED using an indomethacin-induced inflammation model in rat small intestine. In the ED-fed rats, the intestinal damage score was decreased compared with that in the standard chow group with decreasing intestinal permeability. By supplementing an ED with soybean oil (SO), intestinal permeability was increased to a level similar to that of the standard chow group. For this group, the intestinal damage score also increased compared with that of the ED group but did not reach the levels observed in the standard chow group. The addition of dietary proteins (using heat-denatured pancreatin) resulted in intestinal damage scores that were significantly higher than those of the ED+SO-fed group. The dietary protein increased the intestinal damage score. These results suggest that EDs control inflammation by decreasing intestinal permeability and the elimination of dietary proteins.

Association with selected bacteria does not cause enterocolitis in IL-10 gene-deficient mice despite a systemic immune response

Resident bacteria have been implicated to play a major role in the development of inflammatory bowel disease. While luminally sterile IL-10 gene-deficient mice remain disease-free, their conventionally raised littermates develop enterocolitis associated with increased numbers of luminal and mucosal adherent bacteria. To investigate the role of defined bacteria on the initiation and development of this enterocolitis, we associated luminally sterile IL-10 gene-deficient mice with pure strains of resident bacteria. Axenic, luminally sterile mice were either monoassociated with viridans group Streptococcus or Clostridium sordellii or co-associated with Bacteroides vulgatus and Clostridium sordellii. Seven to 22 weeks later the mice were analyzed for intestinal histologic injury, epithelial permeability, and an inflammatory immune response to bacterial antigens. Despite optimal colonization none of the tested bacteria caused intestinal inflammation, release of inflammatory cytokines from the epithelia, or disruption of the epithelial barrier integrity. However, in the case of association with Bacteroides vulgatus and Clostridium sordellii, a systemic immune response to bacterial-derived antigens was measured, with a magnitude similar to that seen in conventional sick Il-10 gene-deficient mice. This response was not detected in mice associated with viridans group Streptococcus. We conclude that colonization of the intestinal lumen with individual bacterial species may not be sufficient to alter epithelial barrier integrity, increase intestinal cytokine release, or cause intestinal inflammation in susceptible IL-10 gene-deficient mice, despite the ability of these same bacteria to stimulate a systemic response.

Colitis in mice lacking the common cytokine receptor gamma chain is mediated by IL-6-producing CD4+ T cells

BACKGROUND & AIMS

Mice that have a truncated mutation of the common cytokine receptor gamma chain (CR gamma -/Y) are known to spontaneously develop colitis. To identify the pathologic elements responsible for triggering this localized inflammatory disease, we elucidated and characterized aberrant T cells and their enteropathogenic cytokines in CR gamma -/Y mice with colitis.

METHODS

The histologic appearance, cell population, T-cell receptor V beta usage, and cytokine production of lamina propria lymphocytes were assessed. CR gamma -/Y mice were treated with anti-interleukin (IL)-6 receptor monoclonal antibody to evaluate its ability to control colitis, and splenic CD4 + T cells from the same mouse model were adoptively transferred into SCID mice to see if they spurred the appearance of colitis.

RESULTS

We found marked thickening of the large intestine, an increase in crypt depth, and infiltration of the colonic lamina propria and submucosa with mononuclear cells in the euthymic CR gamma -/Y mice, but not in the athymic CR gamma -/Y mice, starting at the age of 8 weeks. Colonic CD4 + T cells with high expressions of antiapoptotic Bcl-x and Bcl-2 were found to use selected subsets (V beta 14) of T-cell receptor and to exclusively produce IL-6. Treatment of CR gamma -/Y mice with anti-IL-6 receptor monoclonal antibody prevented the formation of colitis via the induction of apoptosis in IL-6-producing CD4 + T cells. Adoptive transfer of pathologic CD4 + T cells induced colitis in the recipient SCID mice.

CONCLUSIONS

Colonic IL-6-producing thymus-derived CD4 + T cells are responsible for the development of colitis in CR gamma -/Y mice.

Immune networks in animal models of inflammatory bowel disease

The animal models of inflammatory bowel disease provide a framework to define the immunopathogenesis of intestinal inflammation. Studies in these models support the hypothesis that exaggerated immune responses to normal enteric microflora are involved in the initiation and perpetuation of chronic intestinal inflammation. A major pathway involves development of acquired immune responses by the interactions of CD4+ T-cell receptor alphabeta T cells with antigen-presenting cells (dendritic cells). Immunoregulatory cells, including Tr1 cells, Th3 cells, and CD4+ CD25+ T cells and B cells, directly or indirectly affect the T-cell receptor alphabeta T cell-induced immune responses and bridge innate and acquired immunity. The study of these complicated immune networks provides the rationale for the development of new therapeutic interventions in inflammatory bowel disease.

The role of endogenous bacterial flora: bystander or the necessary prerequisite?

Abundant experimental and clinical data incriminate microbial factors in the pathogenesis of inflammatory bowel diseases. Commensal bacteria, and their products, provide the constant antigenic stimulus to disequilibrate the mucosal immune system towards an overly aggressive response in a genetically susceptible host with reduced tolerance towards the autologous flora. Not all bacteria have equal proinflammatory capabilities. Some may be even beneficial as demonstrated by the anti-inflammatory effects of so-called probiotics. Further investigations are needed to translate the clear experimental and clinical evidence into benefit for the patients.

Prevention of gut inflammation by Bifidobacterium in dextran sulfate-treated gnotobiotic mice associated with Bacteroides strains isolated from ulcerative colitis patients

Indigenous Bacteroides strains are closely associated with the occurrence and exacerbation of ulcerative colitis (UC). In this study, we aimed to clarify the effect of Bifidobacterium strains, another major member of colonic bacteria, on the development of gut inflammation using gnotobiotic mouse models associated with Bacteroides strains isolated from UC patients. Dextran sulfate (DSS) administration induced inflammation in the large intestine, in particular of the cecum, in the gnotobiotic mice associated with three strains of Bacteroides vulgatus, judging from the myeloperoxidase activity, occult blood score, and IgG leakage into the intestinal contents. However, the severity of the inflammation was greatly reduced in the gnotobiotic mice associated with both B. vulgatus and Bifidobacterium strains. The severity of the cecal inflammation was well correlated with the concentration of succinic acid in the cecum. Bacteriologically, the density of B. vulgatus strain A (BV-A) greatly decreased and the predominant strain changed from BV-A to BV-B on additional association with Bifidobacterium strains. Among gnotobiotic mice associated with a single B. vulgatus strain, the severity of cecal inflammation in BV-A-associated mice was greater than that in BV-B-associated mice. Each Bifidobacterium strain produced compound(s) more effectively inhibiting the growth of BV-A than BV-B in in vitro culture. Taken together, these results suggest that the severity of DSS-induced gut inflammation is closely associated with a particular B. vulgatus strain, and that Bifidobacterium strains may repress exacerbation of intestinal inflammation through growth inhibition of the B. vulgatus strain.

Development of colitis in signal transducers and activators of transcription 6-deficient T-cell receptor alpha-deficient mice: a potential role of signal transducers and activators of transcription 6-independent interleukin-4 signaling for the generation of Th2-biased pathological CD4+ betabetaT cells

Forbidden CD4(+)betabeta T cells, which produce interleukin (IL)-4 predominantly, are a pathological subset in the development of colitis in T-cell receptor alpha chain (TCRalpha)-deficient mice. Stimulation of naive CD4(+) T cells with IL-4 induces Th2 development via the activation of signal transducers and activators of transcription (STAT) 6. In the present study, we had found that IL-4 enhanced the expression of STAT6 in CD4(+)betabeta T cells isolated from TCRalpha(-/-) mice with colitis, suggesting that the IL-4 signal in the CD4(+)betabeta T cells is mediated by STAT6. To further investigate the role of STAT6 in the development of colitis induced by TCRalpha deficiency, we generated double-deficient mice by crossing TCRalpha(-/-) mice and STAT6(-/-) mice. Surprisingly, STAT6 deficiency did not result in decreased severity of colitis in TCRalpha(-/-) mice. STAT6-deficient CD4(+)betabeta T cells produced IL-4 and intraperitoneal injection of anti-IL-4 monoclonal antibody in the nondiseased TCRalpha(-/-) and STAT6 double-deficient mice prevented the colitis formation, thus indicating that the cells differentiated into the Th2 phenotype have the ability to mediate the development of the colitis in the absence of STAT6.

The immunology of mucosal models of inflammation

In recent years the status of the inflammatory bowel diseases (IBDs) as canonical autoimmune diseases has risen steadily with the recognition that these diseases are, at their crux, abnormalities in mucosal responses to normally harmless antigens in the mucosal microflora and therefore responses to antigens that by their proximity and persistence are equivalent to self-antigens. This new paradigm is in no small measure traceable to the advent of multiple models of mucosal inflammation whose very existence is indicative of the fact that many types of immune imbalance can lead to loss of tolerance for mucosal antigens and thus inflammation centered in the gastrointestinal tract. We analyze the immunology of the IBDs through the lens of the murine models, first by drawing attention to their common features and then by considering individual models at a level of detail necessary to reveal their individual capacities to provide insight into IBD pathogenesis. What emerges is that murine models of mucosal inflammation have given us a road map that allows us to begin to define the immunology of the IBDs in all its complexity and to find unexpected ways to treat these diseases.

Monoassociation of SCID mice with Helicobacter muridarum, but not four other enterics, provokes IBD upon receipt of T cells

BACKGROUND & AIMS

Recently, a number of animal models for different aspects of inflammatory bowel disease (IBD) have been developed. The aim of this study was to use one of these to determine whether particular, ostensibly innocuous, intestinal bacteria could provoke or exacerbate IBD.

METHODS

Conventionally reared C.B17 SCID mice were compared with germ-free and gnotobiotic mice, monoassociated with 1 of 5 intestinal bacteria, after transfer of CD45RB(high) CD4(+) T cells from conventionally reared congenic BALB/c mice. Recipient mice were monitored over 7-12 weeks for clinical signs of IBD, and tissues were analyzed by histology/flow cytometry for abnormal inflammation and CD4(+) T cell outgrowth.

RESULTS

Neither germ-free mice nor mice monoassociated with segmented filamentous bacteria, Ochrobactrum anthropi, a nonpathogenic mutant of Listeria monocytogenes, or Morganella morganii developed any signs of IBD. In contrast, mice monoassociated with Helicobacter muridarum displayed an accelerated development of IBD in 5-6 weeks compared with 8-12 weeks observed in conventionally reared mice. The outgrowth of CD4(+) T cells in spleen and large intestine of H. muridarum monoassociated mice, as well as in conventionally reared mice was significantly higher than that in the other monoassociated mice.

CONCLUSIONS

Among the intestinal bacteria tested, H. muridarum can serve as a provocateur of IBD in this model.

The mucosal immune system: from specialized immune defense to inflammation and allergy

The mucosal immune system is a first line of defense against foreign antigens, including microbial and dietary antigens. Under normal circumstances, the mucosal immune system employs tightly regulated dynamic mucosal intra- and internets consisting of inductive and effector sites for the induction of an appropriate immunological homeostasis between the host and mucosal environments. The common mucosal immune system (CMIS), which interconnects between inductive (e.g. Peyer patch) and effector (e.g. intestinal lamina propria) tissues for the induction of the IgA response, is well characterized. Recent results provide strong evidence for the presence of a CMIS-independent IgA induction pathway. Two distinct subsets of mucosal IgA-committed B cells termed B-1 and B-2, are associated with CMIS-independence and CMIS-dependent cascades respectively. In some cases, the breakdown of this tightly regulated mucosal immune system leads to pathological responses to different gut environmental antigens. As a result, disorders such as inflammatory bowel disease (e.g. IBD) and allergic gastroenteropathy can be evoked in the gastrointestinal tissues. Recently, many studies have described possible molecular and cellular mechanisms for this dysfunction in the gastrointestinal tissues by using murine models with specific gene manipulation. In this review we summarize recent findings from our group concerning the CMIS-dependent and CMIS-independent IgA induction pathways and gastrointestinal diseases (IBD and intestinal allergic diseases). These observations may provide useful information for the development of new mucosal immune therapy.