Central Nervous System Demyelinating Disease Protection by the Human Commensal Bacteroides fragilis Depends on Polysaccharide A Expression

Section of Neurology, Department of Medicine, Dartmouth Medical School, Lebanon, NH 03756, USA.
The Journal of Immunology (Impact Factor: 4.92). 10/2010; 185(7):4101-8. DOI: 10.4049/jimmunol.1001443
Source: PubMed


The importance of gut commensal bacteria in maintaining immune homeostasis is increasingly understood. We recently described that alteration of the gut microflora can affect a population of Foxp3(+)T(reg) cells that regulate demyelination in experimental autoimmune encephalomyelitis (EAE), the experimental model of human multiple sclerosis. We now extend our previous observations on the role of commensal bacteria in CNS demyelination, and we demonstrate that Bacteroides fragilis producing a bacterial capsular polysaccharide Ag can protect against EAE. Recolonization with wild type B. fragilis maintained resistance to EAE, whereas reconstitution with polysaccharide A-deficient B. fragilis restored EAE susceptibility. Enhanced numbers of Foxp3(+)T(reg) cells in the cervical lymph nodes were observed after intestinal recolonization with either strain of B. fragilis. Ex vivo, CD4(+)T cells obtained from mice reconstituted with wild type B. fragilis had significantly enhanced rates of conversion into IL-10-producing Foxp3(+)T(reg) cells and offered greater protection against disease. Our results suggest an important role for commensal bacterial Ags, in particular B. fragilis expressing polysaccharide A, in protecting against CNS demyelination in EAE and perhaps human multiple sclerosis.

Download full-text


Available from: Javier Ochoa-Repáraz, May 01, 2014
  • Source
    • "However, in follow-up studies, it was demonstrated that antigens from particular bacteria such as B. fragilis could also have a protective effect [42]. It was suggested that the presence or absence of polysaccharide A might be decisive for beneficial or harmful outcomes of EAE [42]. Also in MS not the mere presence of gut microbiota could be a key criterion for the development of or the protection against the disease, but a state of dysbiosis in favor of an autoimmune response directed against CNS antigens. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background The etiology of multiple sclerosis (MS) has remained unclear, but a causative contribution of factors outside the central nervous system (CNS) is conceivable. It was recently suggested that gut bacteria trigger the activation of CNS-reactive T cells and the development of demyelinative disease. Methods C57BL/6 (B6) mice were kept either under specific pathogen free or conventional housing conditions, immunized with the myelin basic protein (MBP)–proteolipid protein (PLP) fusion protein MP4 and the development of EAE was clinically monitored. The germinal center size of the Peyer’s patches was determined by immunohistochemistry in addition to the level of total IgG secretion which was assessed by ELISPOT. ELISPOT assays were also used to measure MP4-specific T cell and B cell responses in the Peyer’s patches and the spleen. Ear swelling assays were performed to determine the extent of delayed-type hypersensitivity reactions in specific pathogen free and conventionally housed mice. Results In B6 mice that were actively immunized with MP4 and kept under conventional housing conditions clinical disease was significantly attenuated compared to specific pathogen free mice. Conventionally housed mice displayed increased levels of IgG secretion in the Peyer’s patches, while the germinal center formation in the gut and the MP4-specific TH17 response in the spleen were diminished after immunization. Accordingly, these mice displayed an attenuated delayed type hypersensitivity (DTH) reaction in ear swelling assays. Conclusions The data corroborate the notion that housing conditions play a substantial role in the induction of murine EAE and suggest that the presence of gut bacteria might be associated with a decreased immune response to antigens of lower affinity. This concept could be of importance for MS and calls for caution when considering the therapeutic approach to treat patients with antibiotics.
    Full-text · Article · Jun 2014 · PLoS ONE
  • Source
    • "Moreover, our unexpected results, which did not show a decrease in microbial load but instead a tendency towards an increase, are discordant with previous studies using either qPCR [10], [12] or culture methods [34], [35], [36], [37] (Table S1). These authors reported, as expected, a significant decrease in microbial load after 3 to 7 days antibiotic intake. "
    [Show abstract] [Hide abstract]
    ABSTRACT: From birth onwards, the human gut microbiota rapidly increases in diversity and reaches an adult-like stage at three years of age. After this age, the composition may fluctuate in response to external factors such as antibiotics. Previous studies have shown that resilience is not complete months after cessation of the antibiotic intake. However, little is known about the short-term effects of antibiotic intake on the gut microbial community. Here we examined the load and composition of the fecal microbiota immediately after treatment in 21 patients, who received broad-spectrum antibiotics such as fluoroquinolones and β-lactams. A fecal sample was collected from all participants before treatment and one week after for microbial load and community composition analyses by quantitative PCR and pyrosequencing of the 16S rRNA gene, respectively. Fluoroquinolones and β-lactams significantly decreased microbial diversity by 25% and reduced the core phylogenetic microbiota from 29 to 12 taxa. However, at the phylum level, these antibiotics increased the Bacteroidetes/Firmicutes ratio (p = 0.0007, FDR = 0.002). At the species level, our findings unexpectedly revealed that both antibiotic types increased the proportion of several unknown taxa belonging to the Bacteroides genus, a Gram-negative group of bacteria (p = 0.0003, FDR<0.016). Furthermore, the average microbial load was affected by the treatment. Indeed, the β-lactams increased it significantly by two-fold (p = 0.04). The maintenance of or possible increase detected in microbial load and the selection of Gram-negative over Gram-positive bacteria breaks the idea generally held about the effect of broad-spectrum antibiotics on gut microbiota.
    Full-text · Article · Apr 2014 · PLoS ONE
  • Source
    • "Host-bacterial interactions are not limited to balancing protection against pathogens with tolerance to commensal bacteria: commensal bacteria also drive the development of the mammalian immune system. For example, Bacteroides fragilis, a member of the normal human microbiome, produces polysaccharide A, which regulates the systemic murine helper T cell (Th)1-Th2 balance [8] and induces the development of interleukin (IL)-10-producing regulatory T cells that protect against murine colitis and experimental autoimmune encephalomyelitis [9], [11]. Murine segmented filamentous bacterium (SFB) contributes to Th17 cell maturation [6] by stimulating dendritic cells to drive T cell differentiation through yet-uncharacterized mechanisms that may involve adhesion proteins, glycan utilization enzymes, or uptake of metals such as iron [12], [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Interleukin (IL)-1 signaling plays a critical role in intestinal immunology. Here, we report that the major population of intestinal lamina propria lymphocytes expressing IL-1 receptor 1 (IL-1R1) is the lymphoid tissue inducer (LTi)-like cell, a type of innate lymphoid cell. These cells are significant producers of IL-22, and this IL-22 production depends on IL-1R1 signaling. LTi-like cells are required for defense against Salmonella enterica serovar Typhimurium. Moreover, colonic LTi-like cell numbers depend on the presence of the intestinal microbiota. LTi-like cells require IL-1R1 for production of protective cytokines and confer protection in infectious colitis, and their cell numbers in the colon depend upon having a microbiome.
    Full-text · Article · Jun 2013 · PLoS ONE
Show more