Lysates of Methylococcus capsulatus Bath induce a lean-like microbiota, intestinal FoxP3+RORγt+IL-17+ Tregs and improve metabolism.

Interactions between host and gut microbial communities are modulated by diets and play pivotal roles in immunological homeostasis and health. We show that exchanging the protein source in a high fat, high sugar, westernized diet from casein to whole-cell lysates of the non-commensal bacterium Methylococcus capsulatus Bath is sufficient to reverse western diet-induced changes in the gut microbiota to a state resembling that of lean, low fat diet-fed mice, both under mild thermal stress (T22 °C) and at thermoneutrality (T30 °C). Concomitant with microbiota changes, mice fed the Methylococcus-based western diet exhibit improved glucose regulation, reduced body and liver fat, and diminished hepatic immune infiltration. Intake of the Methylococcu-based diet markedly boosts Parabacteroides abundances in a manner depending on adaptive immunity, and upregulates triple positive (Foxp3+RORγt+IL-17+) regulatory T cells in the small and large intestine. Collectively, these data point to the potential for leveraging the use of McB lysates to improve immunometabolic homeostasis.

Immunogenic Properties of Lactobacillus plantarum Producing Surface-Displayed Mycobacterium tuberculosis Antigens.

Tuberculosis (TB) remains among the most deadly diseases in the world. The only available vaccine against tuberculosis is the bacille Calmette-Guérin (BCG) vaccine, which does not ensure full protection in adults. There is a global urgency for the development of an effective vaccine for preventing disease transmission, and it requires novel approaches. We are exploring the use of lactic acid bacteria (LAB) as a vector for antigen delivery to mucosal sites. Here, we demonstrate the successful expression and surface display of a Mycobacterium tuberculosis fusion antigen (comprising Ag85B and ESAT-6, referred to as AgE6) on Lactobacillus plantarum The AgE6 fusion antigen was targeted to the bacterial surface using two different anchors, a lipoprotein anchor directing the protein to the cell membrane and a covalent cell wall anchor. AgE6-producing L. plantarum strains using each of the two anchors induced antigen-specific proliferative responses in lymphocytes purified from TB-positive donors. Similarly, both strains induced immune responses in mice after nasal or oral immunization. The impact of the anchoring strategies was reflected in dissimilarities in the immune responses generated by the two L. plantarum strains in vivo The present study comprises an initial step toward the development of L. plantarum as a vector for M. tuberculosis antigen delivery. IMPORTANCE: This work presents the development of Lactobacillus plantarum as a candidate mucosal vaccine against tuberculosis. Tuberculosis remains one of the top infectious diseases worldwide, and the only available vaccine, bacille Calmette-Guérin (BCG), fails to protect adults and adolescents. Direct antigen delivery to mucosal sites is a promising strategy in tuberculosis vaccine development, and lactic acid bacteria potentially provide easy, safe, and low-cost delivery vehicles for mucosal immunization. We have engineered L. plantarum strains to produce a Mycobacterium tuberculosis fusion antigen and to anchor this antigen to the bacterial cell wall or to the cell membrane. The recombinant strains elicited proliferative antigen-specific T-cell responses in white blood cells from tuberculosis-positive humans and induced specific immune responses after nasal and oral administrations in mice.

Activation of the bile acid receptor TGR5 enhances LPS-induced inflammatory responses in a human monocytic cell line.

INTRODUCTION: Bile acids are recognized as signaling molecules, mediating their effects both through the cell surface receptor TGR5 and the nuclear receptor FXR. After a meal, approximately 95% of the bile acids are transported from terminal ileum and back to the liver via the portal vein, resulting in postprandial elevations of bile acids in blood. During the digestion of fat, components from the microbiota, including LPS, are thought to reach the circulation where it may lead to inflammatory responses after binding TLR4 immune cells. Both LPS and bile acids are present in blood after a high-fat meal; we therefore wanted to study consequences of a possible interplay between TGR5 and TLR4 in human monocytes. METHODS: The monocytic cell line U937 stably transfected with the NF-κB reporter plasmid 3x-κB-luc was used as a model system to study the effects of TGR5 and TLR4. Activation of MAP kinases was studied to reveal functional consequences of triggering TGR5 in U937 cells. Effects of TGR5 and TLR4 activation were monitored using NF-κB luciferase assay and by quantification of the pro-inflammatory cytokines IL-6 and IL-8 using ELISA. RESULTS: In this study, results show that triggering TGR5 with the specific agonist betulinic acid (BA), and the bile acids CDCA or DCA, activated both the main MAP kinases ERK1/2, p38 and JNK, and the NF-κB signaling pathway. We further demonstrated that co-triggering of TLR4 and TGR5 enhanced the activation of NF-κB and the release of inflammatory cytokines in a synergistic manner compared to triggering of TLR4 alone. CONCLUSIONS: Thus, two different and simultaneous events associated with the digestive process coordinately affect the function of human monocytes and contribute to enhanced inflammation. Because elevated levels of circulatory LPS may contribute to the development of insulin resistance, the results from this study suggest that bile acids through the activation of TGR5 may have a role in the development of insulin resistance as well.

Computational and experimental analysis of the secretome of Methylococcus capsulatus (Bath).

The Gram-negative methanotroph Methylococcus capsulatus (Bath) was recently demonstrated to abrogate inflammation in a murine model of inflammatory bowel disease, suggesting interactions with cells involved in maintaining mucosal homeostasis and emphasizing the importance of understanding the many properties of M. capsulatus. Secreted proteins determine how bacteria may interact with their environment, and a comprehensive knowledge of such proteins is therefore vital to understand bacterial physiology and behavior. The aim of this study was to systematically analyze protein secretion in M. capsulatus (Bath) by identifying the secretion systems present and the respective secreted substrates. Computational analysis revealed that in addition to previously recognized type II secretion systems and a type VII secretion system, a type Vb (two-partner) secretion system and putative type I secretion systems are present in M. capsulatus (Bath). In silico analysis suggests that the diverse secretion systems in M.capsulatus transport proteins likely to be involved in adhesion, colonization, nutrient acquisition and homeostasis maintenance. Results of the computational analysis was verified and extended by an experimental approach showing that in addition an uncharacterized protein and putative moonlighting proteins are released to the medium during exponential growth of M. capsulatus (Bath).

Omega-3 and omega-6 PUFAs induce the same GPR120-mediated signalling events, but with different kinetics and intensity in Caco-2 cells.

BACKGROUND: Omega-3 PUFAs are known to have anti-inflammatory properties, and different mechanisms are involved. GPR120 is a G-protein coupled receptor that has recently received attention because of its anti-inflammatory signalling properties after binding omega-3 PUFAs. However, both omega-3 and omega-6 PUFAs are natural GPR120 ligands. The aim of this study was to study possible differences in GPR120-mediated signalling events after treatment with different long-chain PUFAs in intestinal epithelial cells. We also investigated possible GPR120-mediated anti-inflammatory effects of different long-chain PUFAs that may be relevant in the understanding of how dietary PUFAs influence inflammatory responses in inflammatory diseases such as IBD. METHODS: We used Caco-2 cells as a model system to study GPR120-mediated signalling events because we found this cell line to express GPR120, but not GPR40, another plasma membrane receptor for medium- and long chain fatty acids. Increase in cytosolic Ca2+concentration, activation of MAP kinase ERK1/2 and the inhibition of IL-1ß induced NF-κB activity were studied to reveal potential differences in the activation of GPR120 by the omega-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the omega-6 PUFA arachidonic acid (AA). RESULTS: We found that EPA, DHA and AA enhanced the cytosolic concentration of the second messenger Ca2+ with the same efficiency, but with different kinetics. Both omega-3 and omega-6 PUFAs activated MAP kinase ERK1/2, but differences regarding kinetics and intensity were also observed in this pathway. ERK1/2 activation was shown to be dependent upon EGFR and Raf-1. We further investigated the ability of EPA, DHA and AA to inhibit NF-κB activity in Caco-2 cells. All PUFAs tested were able to inhibit IL-1ß induced breakdown of IκBα after binding to GPR120, but with different potency. CONCLUSIONS: Our results show that EPA, DHA and AA elicit the same signalling events, but with different kinetics and efficiency through GPR120 in Caco-2 cells. We show, for the first time, that both omega-3 and omega-6 PUFAs inhibit NF-κB activation in intestinal epithelial cells. Our results may be important for understanding how dietary PUFAs influence inflammatory processes relevant in delineating effects of PUFAs in the treatment of IBD.

The noncommensal bacterium Methylococcus capsulatus (Bath) ameliorates dextran sulfate (Sodium Salt)-Induced Ulcerative Colitis by influencing mechanisms essential for maintenance of the colonic barrier function.

Dietary inclusion of a bacterial meal has recently been shown to efficiently abolish soybean meal-induced enteritis in Atlantic salmon. The objective of this study was to investigate whether inclusion of this bacterial meal in the diet could abrogate disease development in a murine model of epithelial injury and colitis and thus possibly have therapeutic potential in human inflammatory bowel disease. C57BL/6N mice were fed ad libitum a control diet or an experimental diet containing 254 g/kg of body weight BioProtein, a bacterial meal consisting of Methylococcus capsulatus (Bath), together with the heterogenic bacteria Ralstonia sp., Brevibacillus agri, and Aneurinibacillus sp. At day 8, colitis was induced by 3.5% dextran sulfate sodium (DSS) ad libitum in the drinking water for 6 days. Symptoms of DSS treatment were less profound after prophylactic treatment with the diet containing the BioProtein. Colitis-associated parameters such as reduced body weight, colon shortening, and epithelial damage also showed significant improvement. Levels of acute-phase reactants, proteins whose plasma concentrations increase in response to inflammation, and neutrophil infiltration were reduced. On the other, increased epithelial cell proliferation and enhanced mucin 2 (Muc2) transcription indicated improved integrity of the colonic epithelial layer. BioProtein mainly consists of Methylococcus capsulatus (Bath) (88%). The results that we obtained when using a bacterial meal consisting of M. capsulatus (Bath) were similar to those obtained when using BioProtein in the DSS model. Our results show that a bacterial meal of the noncommensal bacterium M. capsulatus (Bath) has the potential to attenuate DSS-induced colitis in mice by enhancing colonic barrier function, as judged by increased epithelial proliferation and increased Muc2 transcription.

Draft genome sequence of the methane-oxidizing bacterium Methylococcus capsulatus (Texas).

Methanotrophic bacteria perform major roles in global carbon cycles via their unique enzymatic activities that enable the oxidation of one-carbon compounds, most notably methane. Here we describe the annotated draft genome sequence of the aerobic methanotroph Methylococcus capsulatus (Texas), a type strain originally isolated from sewer sludge.

Surface display of N-terminally anchored invasin by Lactobacillus plantarum activates NF-κB in monocytes.

The probiotic lactic acid bacterium Lactobacillus plantarum is a potential delivery vehicle for mucosal vaccines because of its generally regarded as safe (GRAS) status and ability to persist at the mucosal surfaces of the human intestine. However, the inherent immunogenicity of vaccine antigens is in many cases insufficient to elicit an efficient immune response, implying that additional adjuvants are needed to enhance the antigen immunogenicity. The goal of the present study was to increase the proinflammatory properties of L. plantarum by expressing a long (D1 to D5 [D1-D5]) and a short (D4-D5) version of the extracellular domain of invasin from the human pathogen Yersinia pseudotuberculosis. To display these proteins on the bacterial surface, four different N-terminal anchoring motifs from L. plantarum were used, comprising two different lipoprotein anchors, a transmembrane signal peptide anchor, and a LysM-type anchor. All these anchors mediated surface display of invasin, and several of the engineered strains were potent activators of NF-κB when interacting with monocytes in cell culture. The most distinct NF-κB responses were obtained with constructs in which the complete invasin extracellular domain was fused to a lipoanchor. The proinflammatory L. plantarum strains constructed here represent promising mucosal delivery vehicles for vaccine antigens.

In vitro comparison of commensal, probiotic and pathogenic strains of Enterococcus faecalis.

In vivo studies have provided evidence that micro-organisms have important roles in immunological, digestive and respiratory functions, conferring health benefits on the host. Several in vitro methods have been advised for the initial screening of microbes with potential health effects. The objective of the present study was to employ such in vitro methodology to characterise different strains of Enterococcus faecalis. The characteristics of a commercial product marketed as a probiotic, Symbioflor-1 (Symbiopharm), were compared with the characteristics of both pathogenic and commensal strains. Tolerance towards low pH and viability after exposure to human gastric and duodenal juices were assayed. Symbioflor-1 was the most susceptible strain to these treatments when compared with the other E. faecalis strains. Furthermore, Symbioflor-1 exhibited the lowest adhesion capacity to intestinal epithelial cells (IEC) and mucus. Competitive binding studies using heparin indicated that glycosaminoglycans might be involved in the adhesion to IEC, but also that differences in these putative bacteria-host interactions do not cause the relative low adhesion capacity of Symbioflor-1. Maturation of dendritic cells (DC) after exposure to bacteria was assayed as an indication of an immunomodulatory effect. All strains induced a moderate elevation of the DC maturation markers CD83 and CD86; however, no strain-specific differences were detected. Correlations between in vitro and in vivo studies are discussed. Although in vitro assaying is a rational starting point for the selection of microbes with a potential health benefit, it is emphasised that human clinical trials are the definite tool for establishing probiotic status.

EP receptor expression in human intestinal epithelium and localization relative to the stem cell zone of the crypts.

There is substantial evidence for PGE2 affecting intestinal epithelial proliferation. PGE2 is also reported to be involved in the regulation of growth and differentiation in adult stem cells, both effects mediated by binding to EP-receptors. We have used the Lgr5 as a marker to scrutinize EP-receptor and COX expression in human intestinal epithelial cells with focus on the stem cell area of the crypts. Normal tissue from ileum and colon, but also duodenal biopsies from patients with untreated celiac disease, were investigated by immunohistochemistry and RT-PCR. The combination of fresh flash-frozen tissue and laser microdissection made it possible to isolate RNA from the epithelial cell layer, only. In the small intestine, Lgr5 labels cells are in the +4 position, while in the colon, Lgr5 positive cells are localized to the crypt bottoms. Epithelial crypt cells of normal small intestine expressed neither EP-receptor mRNA nor COX1/2. However, crypt cells in tissue from patients with untreated celiac disease expressed EP2/4 receptor and COX1 mRNA. In the colon, the situation was different. Epithelial crypt cells from normal colon were found to express EP2/4 receptor and COX1/2 transcripts. Thus, there are distinct differences between normal human small intestine and colon with regard to expression of EP2/4 receptors and COX1/2. In normal colon tissue, PGE2-mediated signaling through EP-receptors 2/4 could be involved in regulation of growth and differentiation of the epithelium, while the lack of EP-receptor expression in the small intestinal tissue exclude the possibility of a direct effect of PGE2 on the crypt epithelial cells.