Commensal gut bacteria: mechanisms of immune modulation

Does the buck stop with the bugs?: an overview of microbial dysbiosis in rheumatoid arthritis

The human body is an environmental niche which is home to diverse co-habiting microbes collectively referred as the human microbiome. Recent years have seen the in-depth characterization of the human microbiome and associations with diseases. Linking of the composition or number of the human microbiota with diseases and traits date back to the original work of Elie Metchnikoff. Recent advances in genomic technologies have opened up finer details and dynamics of this new science with higher precision. Microbe-rheumatoid arthritis connection, largely related to the gut and oral microbiomes, has showed up as a result - apart from several other earlier, well-studied candidate autoimmune diseases. Although evidence favouring roles of specific microbial species, including Porphyromonas, Prevotella and Leptotricha, has become clearer, mechanistic insights still continue to be enigmatic. Manipulating the microbes by traditional dietary modifications, probiotics, and antibiotics and by currently employed disease-modifying agents seems to modulate the disease process and its progression. In the present review, we appraise the existing information as well as the gaps in knowledge in this challenging field. We also discuss the future directions for potential clinical applications, including prevention and management of rheumatoid arthritis using microbial modifications.

Release of Periplasmic Nucleotidase Induced by Human Antimicrobial Peptide in E. coli Causes Accumulation of the Immunomodulator Adenosine

Previous work by our group described that human β-defensin-2 induces accumulation of extracellular adenosine (Ado) in E. coli cultures through a non-lytic mechanism causing severe plasmolysis. Here, we investigate the presence of AMP as a direct precursor and the involvement of a bacterial enzyme in the generation of extracellular Ado by treated bacteria. Following hBD-2 treatment, metabolites were quantified in the supernatants using targeted HPLC-MS/MS analysis. Microbial growth was monitored by optical density and cell viability was determined by colony forming units counts. Phosphatase activity was measured using chromogenic substrate pNPP. The results demonstrate that defensin-treated E. coli strain W releases AMP in the extracellular space, where it is converted to Ado by a bacterial soluble factor. An increase in phosphatase activity in the supernatant was observed after peptide treatment, similar to the effect of sucrose-induced osmotic stress, suggesting that the periplasmic 5'nucleotidase (5'-NT) is released following the plasmolysis event triggered by the peptide. Ado accumulation was enhanced in the presence of Co²⁺ ion and inhibited by EDTA, further supporting the involvement of a metallo-phosphatase such as 5’-NT in extracellular AMP conversion into Ado. The comparative analysis of hBD-induced Ado accumulation in different E. coli strains and in Pseudomonas aeruginosa revealed that the response is not correlated to the peptide's effect on cell viability, but indicates it might be dependent on the subcellular distribution of the nucleotidase. Taken together, these data shed light on a yet undescribed mechanism of host-microbial interaction: a human antimicrobial peptide inducing selective release of a bacterial enzyme (E. coli 5'-NT), leading to the formation of a potent immunomodulator metabolite (Ado).

Antimicrobial use in swine production and its effect on the swine gut microbiota and antimicrobial resistance

Antimicrobials have been used in swine production at subtherapeutic levels since the early 1950s to increase feed efficiency and promote growth. In North America, a number of antimicrobials are available for use in swine. However, the continuous administration of subtherapeutic, low concentrations of antimicrobials to pigs also provides selective pressure for antimicrobial-resistant bacteria and resistance determinants. For this reason, subtherapeutic antimicrobial use in livestock remains a source of controversy and concern. The swine gut microbiota demonstrates a number of changes in response to antimicrobial administration depending on the dosage, duration of treatment, age of the pigs, and gut location that is sampled. Both culture-independent and -dependent studies have also shown that the swine gut microbiota contains a large number of antimicrobial resistance determinants even in the absence of antimicrobial exposure. Heavy metals, such as zinc and copper, which are often added at relatively high doses to swine feed, may also play a role in maintaining antimicrobial resistance and in the stability of the swine gut microbiota. This review focuses on the use of antimicrobials in swine production, with an emphasis on the North American regulatory context, and their effect on the swine gut microbiota and on antimicrobial resistance determinants in the gut microbiota.

The Microbiome: The Trillions of Microorganisms That Maintain Health and Cause Disease in Humans and Companion Animals

The microbiome is the complex collection of microorganisms, their genes, and their metabolites, colonizing the human and animal mucosal surfaces, digestive tract, and skin. It is now well known that the microbiome interacts with its host, assisting in digestion and detoxification, supporting immunity, protecting against pathogens, and maintaining health. Studies published to date have demonstrated that healthy individuals are often colonized with different microbiomes than those with disease involving various organ systems. This review covers a brief history of the development of the microbiome field, the main objectives of the Human Microbiome Project, and the most common microbiomes inhabiting the human respiratory tract, companion animal digestive tract, and skin in humans and companion animals. The main changes in the microbiomes in patients with pulmonary, gastrointestinal, and cutaneous lesions are described.

Distal modulation of bacterial cell-cell signalling in a synthetic ecosystem using partitioned microfluidics

The human gut is over a meter in length, liquid residence times span several hours. Recapitulating the human gut microbiome "on chip" holds promise to revolutionize therapeutic strategies for a variety of diseases, as well as for maintaining homeostasis in healthy individuals. A more refined understanding of bacterial-bacterial and bacterial-epithelial cell signalling is envisioned and such a device is a key enabler. Indeed, significant advances in the study of bacterial cell-cell signalling have been reported, including at length and time scales of the cells and their responses. Few reports exist, however, where signalling events that span physiologically relevant time scales are monitored and coordinated. Here, we employ principles of biofabrication to assemble, in situ, cell communities that are (i) spatially adjacent within partitioned microchannels for studying near communication and (ii) distally connected within longitudinal microfluidic networks so as to mimic long distance signalling among intestinal flora. We observed native signalling processes of the bacterial quorum sensing autoinducer-2 (AI-2) system among and between these communities. Cells in an upstream device successfully self-reported their activities and also secreted autoinducers that were carried downstream to the assembled networks of bacteria that reported on their presence. Furthermore, active signal modulation of among distal populations was demonstrated in a "programmed" manner where "enhancer" and "reducer" communities were assembled adjacent to the test population or "reporter" cells. The modulator cells either amplified or attenuated the cell-cell signalling between the distal, already communicating cell populations. Modulation was quantified with a bioassay, and the reaction rates of signal production and consumption were further characterized using a first principles mathematical model. Simulated distribution profiles of signalling molecules in the cell-gel composites agreed well with the observed cellular responses. We believe this simple platform and the ease by which it is assembled can be applied to other cell-cell interaction studies among various species or kingdoms of cells within well-regulated microenvironments.

Culture and molecular-based profiles show shifts in bacterial communities of the upper respiratory tract that occur with age

The upper respiratory tract (URT) is a crucial site for host defense, as it is home to bacterial communities that both modulate host immune defense and serve as a reservoir of potential pathogens. Young children are at high risk of respiratory illness, yet the composition of their URT microbiota is not well understood. Microbial profiling of the respiratory tract has traditionally focused on culturing common respiratory pathogens, whereas recent culture-independent microbiome profiling can only report the relative abundance of bacterial populations. In the current study, we used both molecular profiling of the bacterial 16S rRNA gene and laboratory culture to examine the bacterial diversity from the oropharynx and nasopharynx of 51 healthy children with a median age of 1.1 years (range 1-4.5 years) along with 19 accompanying parents. The resulting profiles suggest that in young children the nasopharyngeal microbiota, much like the gastrointestinal tract microbiome, changes from an immature state, where it is colonized by a few dominant taxa, to a more diverse state as it matures to resemble the adult microbiota. Importantly, this difference in bacterial diversity between adults and children accompanies a change in bacterial load of three orders of magnitude. This indicates that the bacterial communities in the nasopharynx of young children have a fundamentally different structure from those in adults and suggests that maturation of this community occurs sometime during the first few years of life, a period that includes ages at which children are at the highest risk for respiratory disease.

Degradation of Fructans and Production of Propionic Acid by Bacteroides thetaiotaomicron are Enhanced by the Shortage of Amino Acids

Bacteroides thetaiotaomicron is commonly found in the human colon and stabilizes its ecosystem by catabolism of various polysaccharides. A model of cross-talk between the metabolism of amino acids and fructans in B. thetaiotaomicron was proposed. The growth of B. thetaiotaomicron DSM 2079 in two defined media containing mineral salts and vitamins, and supplemented with either 20 or 2 amino acids, was studied in an isothermal microcalorimeter. The polyfructans inulin (from chicory) and levan (synthesized using levansucrase from Pseudomonas syringae), two fructooligosaccharide preparations with different composition, sucrose and fructose were tested as substrates. The calorimetric power-time curves were substrate specific and typically multiauxic. A surplus of amino acids reduced the consumption of longer oligosaccharides (degree of polymerization > 3). Bacterial growth was not detected either in the carbohydrate free medium containing amino acids or in the medium with inulin as a sole carbohydrate. In amino acid-restricted medium, fermentation leading to acetic acid formation was dominant at the beginning of growth (up to 24 h), followed by increased lactic acid production, and mainly propionic and succinic acids were produced at the end of fermentation. In the medium supplemented with 20 amino acids, the highest production of d-lactate (82 ± 33 mmol/gDW) occurred in parallel with extensive consumption (up to 17 mmol/gDW) of amino acids, especially Ser, Thr, and Asp. The production of Ala and Glu was observed at growth on all substrates, and the production was enhanced under amino acid deficiency. The study revealed the influence of amino acids on fructan metabolism in B. thetaiotaomicron and showed that defined growth media are invaluable in elucidating quantitative metabolic profiles of the bacteria. Levan was shown to act as an easily degradable substrate for B. thetaiotaomicron. The effect of levan on balancing or modifying colon microbiota will be studied in further experiments.

The gastrointestinal microbiome - functional interference between stomach and intestine

The gastrointestinal (GI) tract is a complex and dynamic network with interplay between various gut mucosal cells and their defence molecules, the immune system, food particles, and the resident microbiota. This ecosystem acts as a functional unit organized as a semipermeable multi-layer system that allows the absorption of nutrients and macromolecules required for human metabolic processes and, on the other hand, protects the individual from potentially invasive microorganisms. Commensal microbiota and the host are a unique entity in a continuum along the GI tract, every change in one of these players is able to modify the whole homeostasis. In the stomach, Helicobacter pylori is a gram-negative pathogen that is widespread all over the world, infecting more than 50% of the world's population. In this scenario, H. pylori infection is associated with changes in the gastric microenvironment, which in turn affects the gastric microbiota composition, but also might trigger large intestinal microbiota changes. It is able to influence all the vital pathways of human system and also to influence microbiota composition along the GI tract. This can cause a change in the normal functions exerted by intestinal commensal microorganisms leading to a new gastrointestinal physiological balance. This review focuses and speculates on the possible interactions between gastric microorganisms and intestinal microbiota and on the consequences of this interplay in modulating gut health.

Interaction of NPSR1 genotypes and probiotics in the manifestation of atopic eczema in early childhood

BACKGROUND

Neuropeptide S Receptor (NPSR1) gene has been associated with multiple allergic phenotypes in several patient populations.

OBJECTIVE

We analysed the effect of the NPSR1 genotypes in the development of asthma, rhinitis, eczema, or food allergy in children randomly receiving either probiotic or placebo treatment.

METHODS

796 children born to families at high risk for allergic diseases were examined by a paediatrician at the age of three months, six months, two years, and five years. Asthma, rhinitis, eczema, and food allergy were diagnosed according to international guidelines. Treatment with probiotics (double-blinded and placebo controlled) was begun with mothers at 35 weeks of gestation age and continued after the birth of infants up to the age of six months. Association and additive inheritance models were used in genetic analyses.

RESULTS

Distribution of the hopo546333 was suggestive in the group of patients with atopic eczema at two years. The hopo546333_G was found more often in those with eczema in the placebo group (p=0.048, after Bonferroni correction) and the hopo546333_A was found more often in those with eczema and probiotics compared to those with eczema and placebo treatment. None of the NPSR1 tagging SNPs was associated with asthma, IgE-mediated asthma, or sensitisation. Allergic disease in both parents doubled the risk for IgE-mediated allergic disease (OR 2.1).

CONCLUSIONS

The NPSR1 gene SNP hopo546333 showed a suggestive association for high IgE-associated atopic eczema at two years.

Dead bacteria reverse antibiotic-induced host defense impairment in burns

BACKGROUND

Burn patients can incur high rates of hospital-acquired infections. The mechanism of antibiotic exposure on inducing infection vulnerability has not been determined. This study aimed to examine the effects of antibiotic treatment on host defense mechanisms.

STUDY DESIGN

First we treated C57/BL6 mice with combined antibiotic treatment after 30% to 35% total body surface area burn. Animals were sacrificed at 48 hours after sham or thermal injury treatment. Bacterial counts in intestinal lumen and mucosa were measured. Next, we treated animals with or without oral dead Escherichia coli or Staphylococcus aureus supplementation to stimulate Toll-like receptor in the intestinal mucosa. Toll-like receptor 4, antibacterial protein expression, nuclear factor (NF)-κB DNA-binding activity, and bacteria-killing activity in the intestinal mucosa; intestinal permeability; bacterial translocation to mesenteric lymph nodes; Klebsiella pneumoniae translocation; interleukin-6 in the blood; and phagocytic activity of alveolar macrophages, were assessed.

RESULTS

Thermal injury increased microflora and NF-κB DNA-binding activity of the intestine. Systemic antibiotic treatment decreased gut microflora and increased bacterial translocation to mesenteric lymph nodes, intestinal permeability, and interleukin-6 levels in the blood. Antibiotic treatment also decreased bacteria-killing activity in intestinal mucosa and phagocytic activity of alveolar macrophages. Oral dead E coli and S aureus supplementation induced NF-κB DNA-binding activity, Toll-like receptor 4, and antibacterial protein expression of the intestinal mucosa.

CONCLUSIONS

Taken together with the fact that dead bacteria reversed antibiotic-induced K pneumoniae translocation and intestinal and pulmonary defense impairment, we conclude that combined antibiotic treatment results in systemic host defense impairment in burns through the decrease in intestinal flora. We suggest that dead bacteria supplementation could induce nondefensin protein expression and reverse antibiotic-induced gut and lung defense impairment in burn patients.

Teleost microbiomes: the state of the art in their characterization, manipulation and importance in aquaculture and fisheries

Indigenous microbiota play a critical role in the lives of their vertebrate hosts. In human and mouse models it is increasingly clear that innate and adaptive immunity develop in close concert with the commensal microbiome. Furthermore, several aspects of digestion and nutrient metabolism are governed by intestinal microbiota. Research on teleosts has responded relatively slowly to the introduction of massively parallel sequencing procedures in microbiomics. Nonetheless, progress has been made in biotic and gnotobiotic zebrafish models, defining a core microbiome and describing its role in development. However, microbiome research in other teleost species, especially those important from an aquaculture perspective, has been relatively slow. In this review, we examine progress in teleost microbiome research to date. We discuss teleost microbiomes in health and disease, microbiome ontogeny, prospects for successful microbiome manipulation (especially in an aquaculture setting) and attempt to identify important future research themes. We predict an explosion in research in this sector in line with the increasing global demand for fish protein, and the need to find sustainable approaches to improve aquaculture yield. The reduced cost and increasing ease of next generation sequencing technologies provides the technological backing, and the next 10 years will be an exciting time for teleost microbiome research.

Gut-targeted immunonutrition boosting natural killer cell activity using Saccharomyces boulardii lysates in immuno-compromised healthy elderly subjects

The aim of this study was to assess the immunomodulatory effect of KC-1317 (a symbiotic mixture containing Saccharomyces boulardii lysate in a cranberry, colostrum-derived lactoferrin, fragaria, and lactose mixture) supplementation in immune-compromised but otherwise healthy elderly subjects. A liquid formulation of KC-1317 was administered in a randomized controlled trial (RCT) fashion to healthy volunteers (65-79 years) previously selected for low natural killer (NK) cell activity, and this parameter was checked at the completion of the study. A significant improvement in NK cell activity of KC-1317 consumers was observed as compared to placebo at the end of 2 months. Although preliminary, these beneficial immune-modulatory effects of KC-1317 in aged individuals might indicate its employment within a wider age-management strategy.

Toll-like receptor stimulation induces nondefensin protein expression and reverses antibiotic-induced gut defense impairment

Prior antibiotic exposure is associated with increased mortality in Gram-negative bacteria-induced sepsis. However, how antibiotic-mediated changes of commensal bacteria promote the spread of enteric pathogenic bacteria in patients remains unclear. In this study, the effects of systemic antibiotic treatment with or without Toll-like receptor (TLR) stimulation on bacterium-killing activity, antibacterial protein expression in the intestinal mucosa, and bacterial translocation were examined in mice receiving antibiotics with or without oral supplementation of dead Escherichia coli or Staphylococcus aureus. We developed a systemic ampicillin, vancomycin, and metronidazole treatment protocol to simulate the clinical use of antibiotics. Antibiotic treatment decreased the total number of bacteria, including aerobic bacteria belonging to the family Enterobacteriaceae and the genus Enterococcus as well as organisms of the anaerobic genera Lactococcus and Bifidobacterium in the intestinal mucosa and lumen. Antibiotic treatment significantly decreased the bacterium-killing activity of the intestinal mucosa and the expression of non-defensin-family proteins, such as RegIIIβ, RegIIIγ, C-reactive protein-ductin, and RELMβ, but not the defensin-family proteins, and increased Klebsiella pneumoniae translocation. TLR stimulation after antibiotic treatment increased NF-κB DNA binding activity, nondefensin protein expression, and bacterium-killing activity in the intestinal mucosa and decreased K. pneumoniae translocation. Moreover, germfree mice showed a significant decrease in nondefensin proteins as well as intestinal defense against pathogen translocation. Since TLR stimulation induced NF-κB DNA binding activity, TLR4 expression, and mucosal bacterium-killing activity in germfree mice, we conclude that the commensal microflora is critical in maintaining intestinal nondefensin protein expression and the intestinal barrier. In turn, we suggest that TLR stimulation induces nondefensin protein expression and reverses antibiotic-induced gut defense impairment.

Systemic immune activation in HIV and potential therapeutic options

CONTEXT

Advancement in HIV treatment has evolved over the last two decades with the discovery of new drugs and approaches. Studies have demonstrated that HIV-infected individuals have elevated immune activation even during effective antiretroviral therapy. Persistently elevated immune activation has been one of the main obstacles against developing an effective approach for curing HIV.

OBJECTIVE

This review examines the mechanism of microbial translocation in HIV-infected individuals and currently investigated potential therapeutic approaches.

METHODS

We searched PubMed and Medline for peer-reviwed articles and recent HIV/AIDS conference abstracts and papers. Narrative review method was used since the objectives of the study were mechanism of microbial translocation and mechanism of action of multiple drugs against it.

RESULTS

Microbial translocation occurs as a result of the disruption of epithelial barrier and immunological dysfunction within the intestinal tract due to defective tight junctions, loss of TH17 type CD4(+) T cells, impaired liver architecture, and depletion of intestinal myelomonocytic cells. Potent and effective way to intervene microbial translocation is to target the mechanism of actions involved in microbial translocation by restoration of beneficial microbiata with supplemental probiotics/prebiotics, increased clearance of microbial products from systemic circulation with targeted antibodies and restoration of intestinal integrity with antibiotics.

CONCLUSIONS

Number of promising drug molecules against microbial translocation are currently under various stages of trials and the results of these trials will hopefully contribute significantly toward effective therapeutic intervention. However, studies also need to explore the effect of combination drugs to abrogate microbial translocation.

Salmonella pathogenicity and host adaptation in chicken-associated serovars

Enteric pathogens such as Salmonella enterica cause significant morbidity and mortality. S. enterica serovars are a diverse group of pathogens that have evolved to survive in a wide range of environments and across multiple hosts. S. enterica serovars such as S. Typhi, S. Dublin, and S. Gallinarum have a restricted host range, in which they are typically associated with one or a few host species, while S. Enteritidis and S. Typhimurium have broad host ranges. This review examines how S. enterica has evolved through adaptation to different host environments, especially as related to the chicken host, and continues to be an important human pathogen. Several factors impact host range, and these include the acquisition of genes via horizontal gene transfer with plasmids, transposons, and phages, which can potentially expand host range, and the loss of genes or their function, which would reduce the range of hosts that the organism can infect. S. Gallinarum, with a limited host range, has a large number of pseudogenes in its genome compared to broader-host-range serovars. S. enterica serovars such as S. Kentucky and S. Heidelberg also often have plasmids that may help them colonize poultry more efficiently. The ability to colonize different hosts also involves interactions with the host's immune system and commensal organisms that are present. Thus, the factors that impact the ability of Salmonella to colonize a particular host species, such as chickens, are complex and multifactorial, involving the host, the pathogen, and extrinsic pressures. It is the interplay of these factors which leads to the differences in host ranges that we observe today.

The gastrointestinal microbiome and musculoskeletal diseases: a beneficial role for probiotics and prebiotics

Natural medicines are an attractive option for patients diagnosed with common and debilitating musculoskeletal diseases such as Osteoarthritis (OA) or Rheumatoid Arthritis (RA). The high rate of self-medication with natural products is due to (1) lack of an available cure and (2) serious adverse events associated with chronic use of pharmaceutical medications in particular non-steroidal anti-inflammatory drugs (NSAIDs) and high dose paracetamol. Pharmaceuticals to treat pain may disrupt gastrointestinal (GIT) barrier integrity inducing GIT inflammation and a state of and hyper-permeability. Probiotics and prebiotics may comprise plausible therapeutic options that can restore GIT barrier functionality and down regulate pro-inflammatory mediators by modulating the activity of, for example, Clostridia species known to induce pro-inflammatory mediators. The effect may comprise the rescue of gut barrier physiological function. A postulated requirement has been the abrogation of free radical formation by numerous natural antioxidant molecules in order to improve musculoskeletal health outcomes, this notion in our view, is in error. The production of reactive oxygen species (ROS) in different anatomical environments including the GIT by the epithelial lining and the commensal microbe cohort is a regulated process, leading to the formation of hydrogen peroxide which is now well recognized as an essential second messenger required for normal cellular homeostasis and physiological function. The GIT commensal profile that tolerates the host does so by regulating pro-inflammatory and anti-inflammatory GIT mucosal actions through the activity of ROS signaling thereby controlling the activity of pathogenic bacterial species.

Immune activation and HIV persistence: considerations for novel therapeutic interventions

PURPOSE OF REVIEW

One of the potential barriers to current HIV cure strategies is the persistence of elevated levels of immune activation despite otherwise effective antiretroviral therapy (ART). The purpose of this review is to examine the relationship between immune activation and HIV persistence, and to review the novel therapeutic interventions that are currently being pursued to target immune activation in treated HIV disease.

RECENT FINDINGS

Multiple groups have consistently observed that elevated levels of inflammation, immune activation, and immune dysfunction persist in ART-treated individuals, despite the successful suppression of plasma viremia. Increased immune activation may lead to viral persistence through multiple mechanisms. Several novel interventions aimed at decreasing persistent immune activation are being pursued and include studies aimed at decreasing low-level viral replication, approaches aimed at decreasing microbial translocation, interventions to treat co-infections, and therapies that directly target immune activation.

SUMMARY

There appears to be a clear and consistent relationship between immune activation and viral persistence in treated HIV disease. Whether this relationship is causal or mediated through other mechanisms is still unknown. Small-scale, pathogenesis-oriented interventional studies are necessary to further evaluate this relationship and the effect of potential interventions.

Small intestinal nematode infection of mice is associated with increased enterobacterial loads alongside the intestinal tract

Parasitic nematodes are potent modulators of immune reactivity in mice and men. Intestinal nematodes live in close contact with commensal gut bacteria, provoke biased Th2 immune responses upon infection, and subsequently lead to changes in gut physiology. We hypothesized that murine nematode infection is associated with distinct changes of the intestinal bacterial microbiota composition. We here studied intestinal inflammatory and immune responses in mice following infection with the hookworm Heligmosomoidespolygyrusbakeri and applied cultural and molecular techniques to quantitatively assess intestinal microbiota changes in the ileum, cecum and colon. At day 14 post nematode infection, mice harbored significantly higher numbers of γ-Proteobacteria/Enterobacteriaceae and members of the Bacteroides/Prevotella group in their cecum as compared to uninfected controls. Abundance of Gram-positive species such as Lactobacilli, Clostridia as well as the total bacterial load was not affected by worm infection. The altered microbiota composition was independent of the IL-4/-13 – STAT6 signaling axis, as infected IL-4Rα^-/- mice showed a similar increase in enterobacterial loads. In conclusion, infection with an enteric nematode is accompanied by distinct intestinal microbiota changes towards higher abundance of gram-negative commensal species at the small intestinal site of infection (and inflammation), but also in the parasite-free large intestinal tract. Further studies should unravel the impact of nematode-induced microbiota changes in inflammatory bowel disease to allow for a better understanding of how theses parasites interfere with intestinal inflammation and bacterial communities in men.

Strain differences in the humoral immune response to commensal bacterial antigens in rats

We have investigated the immune response to commensal bacterial species in the two inbred rat strains: Dark Agouti (DA) and Albino Oxford (AO). The predominant Gram-negative aerobe in our rats' intestinal bacterial flora was Escherichia coli, while Proteus mirabilis was isolated only from DA rat strain. We report that sera from both DA and AO rat strains contain specific IgG against predominant intestinal flora. Intramuscular administration of commensal bacterial antigens provoked only Th1-type antibody response in AO rats while DA rats developed mixed Th1- and Th2-type antibody response to E. coli and Th1-type response to P. mirabilis antigens. Weaker antibody production to own E. coli and higher serum levels of natural IgG and IgA P. mirabilis-specific antibodies combined with higher CD3+ cells proliferation was found in AO rats. Strain difference in the pattern of antibody production and differential regulation of immune response to commensal bacteria may contribute to the marked differences in the immune reactivity of AO and DA rats.

Commensal Clostridia: leading players in the maintenance of gut homeostasis

The gastrointestinal tract is a complex and dynamic network where an intricate and mutualistic symbiosis modulates the relationship between the host and the microbiota in order to establish and ensure gut homeostasis. Commensal Clostridia consist of gram-positive, rod-shaped bacteria in the phylum Firmicutes and make up a substantial part of the total bacteria in the gut microbiota. They start to colonize the intestine of breastfed infants during the first month of life and populate a specific region in the intestinal mucosa in close relationship with intestinal cells. This position allows them to participate as crucial factors in modulating physiologic, metabolic and immune processes in the gut during the entire lifespan, by interacting with the other resident microbe populations, but also by providing specific and essential functions. This review focus on what is currently known regarding the role of commensal Clostridia in the maintenance of overall gut function, as well as touch on their potential contribution in the unfavorable alteration of microbiota composition (dysbiosis) that has been implicated in several gastrointestinal disorders. Commensal Clostridia are strongly involved in the maintenance of overall gut function. This leads to important translational implications in regard to the prevention and treatment of dysbiosis, to drug efficacy and toxicity, and to the development of therapies that may modulate the composition of the microflora, capitalizing on the key role of commensal Clostridia, with the end goal of promoting gut health.

Stool microbiome and metabolome differences between colorectal cancer patients and healthy adults

In this study we used stool profiling to identify intestinal bacteria and metabolites that are differentially represented in humans with colorectal cancer (CRC) compared to healthy controls to identify how microbial functions may influence CRC development. Stool samples were collected from healthy adults (n = 10) and colorectal cancer patients (n = 11) prior to colon resection surgery at the University of Colorado Health-Poudre Valley Hospital in Fort Collins, CO. The V4 region of the 16s rRNA gene was pyrosequenced and both short chain fatty acids and global stool metabolites were extracted and analyzed utilizing Gas Chromatography-Mass Spectrometry (GC-MS). There were no significant differences in the overall microbial community structure associated with the disease state, but several bacterial genera, particularly butyrate-producing species, were under-represented in the CRC samples, while a mucin-degrading species, Akkermansia muciniphila, was about 4-fold higher in CRC (p<0.01). Proportionately higher amounts of butyrate were seen in stool of healthy individuals while relative concentrations of acetate were higher in stools of CRC patients. GC-MS profiling revealed higher concentrations of amino acids in stool samples from CRC patients and higher poly and monounsaturated fatty acids and ursodeoxycholic acid, a conjugated bile acid in stool samples from healthy adults (p<0.01). Correlative analysis between the combined datasets revealed some potential relationships between stool metabolites and certain bacterial species. These associations could provide insight into microbial functions occurring in a cancer environment and will help direct future mechanistic studies. Using integrated “omics” approaches may prove a useful tool in identifying functional groups of gastrointestinal bacteria and their associated metabolites as novel therapeutic and chemopreventive targets.

Salivary IgA response to probiotic bacteria and mutans streptococci after the use of chewing gum containing Lactobacillus reuteri

We investigated whether ingestion of probiotic bacteria could influence salivary IgA levels, specific anti-mutans streptococci IgA levels and specific antibodies towards the ingested probiotic bacterium. The study was a randomised, double-blind, placebo-controlled trial, where the test group (n = 11) received twice daily chewing of gum containing Lactobacillus reuteri (2 × 10(8)  CFU per dose) and the control group (n = 12) received placebo. Resting saliva was collected before and after 12 weeks of treatment and 4 weeks after end of treatment. Total salivary IgA concentrations were measured by ELISA. Specific IgA reactivity was determined using a whole-cell ELISA. Results were expressed as % IgA per protein in saliva. The level of total IgA% per protein increased significantly between pretreatment levels (13.5%) and follow-up treatment levels (14.4%) within the test group only (P < 0.05). No changes were seen in the control group during the trial. The level of probiotic-reactive antibodies decreased significantly between pre- and post-treatment samples (from 12.2% to 9.0%, P < 0.05) in the test group. Similarly, the level of specific mutans streptococci antibodies decreased significantly between pre- and post-treatment samples (P < 0.05) in the test group only (for Streptococcus mutans from 20.1% to 15.0%; for Streptococcus sobrinus from 7.4% to 5.3%). Ingestion of probiotic bacteria might influence the adaptive immune response of the host.

Expression of Toll-like receptors 2 and 9 in cells of dog jejunum and colon naturally infected with Leishmania infantum

BACKGROUND

Infection with parasite protozoa is a long-term health issue in tropical and subtropical regions throughout the world. The Toll-like receptor (TLR) signaling pathway is one of the first-responding defense systems against Leishmania. The aim of this study was to investigate the expression of TLR2 and TLR9 in jejunum and colon and its correlation with CD11c, CD11b, and CD14 receptors used as markers for dendritic cells and macrophages.

METHODS

Twenty four dogs infected with Leishmania infantum were used in this study. Cytometry was carried out in lamina propria cells from jejunum and colon using markers for TLR2, TLR9, CD11b, CD11c and CD14.

RESULTS

Cellular inflammatory exudate was diffuse in the mucosa and submucosa, predominately comprising mononuclear cells: plasma cells, macrophages, and lymphocytes. Despite the parasite load, microscopy showed no erosion was evident in the epithelial mucosa layers. The colon harbored more parasites than the jejunum. Flow cytometry revealed higher frequency of TLR2+ and CD11c+ dendritic cells in the colon than in the jejunum. Conversely, TLR9-expressing cells were more frequent in jejunum. Moreover, frequency of macrophages (CD11b+ and CD14+) expressing simultaneity TLR9 were lower in the colon than in jejunum, while CD11c+ cells predominated in the colon. Despite of the negative ELISA serum results, IL-10 and TNF-α were higher in jejunum than colon of infected animals. However, IL-4 was higher in colon than jejunum of infected animals. A higher expression these cytokines were demonstrated in infected dogs compared to uninfected dogs.

CONCLUSIONS

There was no correlation between clinical signs and pathological changes and immunological and parasitological findings in the gastrointestinal tract in canine visceral leishmaniasis. However, jejunum showed a lower parasite load with increased frequency and expression of CD11b, TLR9, CD14/CD11b/TLR9 receptors and IL-10 and TNF-α cytokines. Conversely, the colon showed a higher parasite load along with increased frequency and expression of TLR2, CD11c receptors, and IL-4 cytokine. Thus, Leishmania infantum is able to interfere in jejunum increased expression of TLR2, TLR9, CD11b, CD14, CD14/CD11b/TLR9 receptors, IL-10, and TNF-α; and in colon increased expression of CD11c, TLR2, TLR9, CD11b, CD14 e, CD14/CD11b/TLR9 receptors, IL-10, and TNF-α.

Impact on bacterial community in midguts of the Asian corn borer larvae by transgenic Trichoderma strain overexpressing a heterologous chit42 gene with chitin-binding domain

This paper is the first report of the impact on the bacterial community in the midgut of the Asian corn borer (Ostrinia furnacalis) by the chitinase from the transgenic Trichoderma strain. In this study, we detected a change of the bacterial community in the midgut of the fourth instar larvae by using a culture-independent method. Results suggested that Proteobacteria and Firmicutes were the most highly represented phyla, being present in all the midgut bacterial communities. The observed species richness was simple, ranging from four to five of all the 16S rRNA clone libraries. When using Trichoderma fermentation liquids as additives, the percentages of the dominant flora in the total bacterial community in larval midgut changed significantly. The community of the genus Ochrobactrum in the midgut decreased significantly when the larvae were fed with the fermentation liquids of the transgenic Trichoderma strain Mc4. However, the Enterococcus community increased and then occupied the vacated niche of the Ochrobactrum members. Furthermore, the Shannon-Wiener (H) and the Simpson (1-D) indexes of the larval midgut bacterial library treated by feeding fermentation liquids of the transgenic Trichoderma strain Mc4 was the lowest compared with the culture medium, fermentation liquids of the wild type strain T30, and the sterile artificial diet. The Enterococcus sp. strain was isolated and characterized from the healthy larvae midgut of the Asian corn borer. An infection study of the Asian corn borer larvae using Enterococcus sp. ACB-1 revealed that a correlation existed between the increased Enterococcus community in the larval midgut and larval mortality. These results demonstrated that the transgenic Trichoderma strain could affect the composition of the midgut bacterial community. The change of the midgut bacterial community might be viewed as one of the factors resulting in the increased mortality of the Asian corn borer larvae.

Intestinal microecology in rats with ulcerative colitis

AIM: To study the abundance and diversity of the gut flora in rats with dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) to provide new knowledge about the pathogenesis of this disease.

METHODS: Twenty-six healthy male SD rats were randomly divided into a control group and a model group. UC was induced by giving 40g/L of DSS for 7 days. Fecal samples were collected from the rats and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was employed to analyze the composition and diversity of gut flora. The specific bands were recovered and sequenced, and data were analyzed using Quantity-one, Chromas, SIMCA-P+, MGAE5 and SPSS18.0.

RESULTS: After 7 days of treatment with DSS, rats showed typical symptoms and characteristics of UC. DGGE results showed that gut floras in both group mainly belonged to Bacteroidetes, Firmicutes and Proteobacteria. Compared to the control group, the numbers of Lactobacillus sp. and Lachnospiraceae bacterium significantly decreased and the number of Clostridium bifermentans increased significantly in the model group (all P < 0.05).

CONCLUSION: The abundance and diversity of the intestinal floras obviously decrease in rats with UC. The numbers of Lactobacillus sp., Lachnospiraceae bacterium and Clostridium bifermentans change significantly in the intestinal tract of rats with UC.

Genomic variation landscape of the human gut microbiome

While large-scale efforts have rapidly advanced the understanding and practical impact of human genomic variation, the latter is largely unexplored in the human microbiome. We therefore developed a framework for metagenomic variation analysis and applied it to 252 fecal metagenomes of 207 individuals from Europe and North America. Using 7.4 billion reads aligned to 101 reference species, we detected 10.3 million single nucleotide polymorphisms (SNPs), 107,991 short indels, and 1,051 structural variants. The average ratio of non-synonymous to synonymous polymorphism rates of 0.11 was more variable between gut microbial species than across human hosts. Subjects sampled at varying time intervals exhibited individuality and temporal stability of SNP variation patterns, despite considerable composition changes of their gut microbiota. This implies that individual-specific strains are not easily replaced and that an individual might have a unique metagenomic genotype, which may be exploitable for personalized diet or drug intake.

Bifidobacteria may be beneficial to intestinal microbiota and reduction of bacterial translocation in mice following ischaemia and reperfusion injury

The aim of the present study was to determine the effect of peroral bifidobacteria on the intestinal microbiota, barrier function and bacterial translocation (BT) in a mouse model of ischaemia and reperfusion (I/R) injury. A total of twenty-four male BALB/c mice were randomly allocated into three groups: (1) sham-operated, (2) I/R and (3) I/R injury and bifidobacteria pretreatment (109 colony-forming units/d). Bifidobacteria were administered daily intragastrically for 2 weeks before induction of I/R. Subsequently, samples of caecal content, intestinal mucosa, ileal segments, blood, mesenteric lymph nodes (MLN) and distant organs (liver, spleen and kidney) were prepared for examination. In the I/R model, barrier dysfunction (caecal microbiota dysbiosis, disruption of tight junction (TJ), increased epithelial cell apoptosis, disruption of mucosa and multiple erosions) in the intestine was observed, associated with increased BT to extraintestinal sites. The ratio of BT to MLN and distant organs in mice exposed to I/R injury was 62·5 %, which was significantly higher than the sham-operated group. However, pretreatment of animals with bifidobacteria prevented I/R-induced BT, reduced pro-inflammatory cytokine release, the levels of endotoxin, intestinal epithelial cell apoptosis, disruption of TJ and increased the concentration of SCFA, resulting in recovered microbiota and mucosal integrity. Bifidobacteria may be beneficial in reducing BT in I/R injury of mice. Therefore, peroral administration of bifidobacteria is a potential strategy to prevent I/R-induced BT and intestinal barrier dysfunction.

Host Defence against Bacterial Biofilms: “Mission Impossible”?

Bacteria living as biofilms have been recognised as the ultimate cause of persistent and destructive inflammatory processes. Biofilm formation is a well-organised, genetically-driven process, which is well characterised for numerous bacteria species. In contrast, the host response to bacterial biofilms is less well analysed, and there is the general believe that bacteria in biofilms escape recognition or eradication by the immune defence. In this review the host response to bacterial biofilms is discussed with particular focus on the role of neutrophils because these phagocytic cells are the first to infiltrate areas of bacterial infection, and because neutrophils are equipped with a wide arsenal of bactericidal and toxic entities. I come to the conclusion that bacterial biofilms are not inherently protected against the attack by neutrophils, but that control of biofilm formation is possible depending on a timely and sufficient host response.

Gut microbial activity, implications for health and disease: the potential role of metabolite analysis

Microbial metabolism of proteins and amino acids by human gut bacteria generates a variety of compounds including phenol, indole, and sulfur compounds and branched chain fatty acids, many of which have been shown to elicit a toxic effect on the lumen. Bacterial fermentation of amino acids and proteins occurs mainly in the distal colon, a site that is often fraught with symptoms from disorders including ulcerative colitis (UC) and colorectal cancer (CRC). In contrast to carbohydrate metabolism by the gut microbiota, proteolysis is less extensively researched. Many metabolites are low molecular weight, volatile compounds. This review will summarize the use of analytical methods to detect and identify compounds in order to elucidate the relationship between specific dietary proteinaceous substrates, their corresponding metabolites, and implications for gastrointestinal health.

Safety and tolerance of Bacteroides xylanisolvens DSM 23964 in healthy adults

We recently presented the strain Bacteroides xylanisolvens DSM 23964 to be safe for use in food. In order to confirm the tolerance of healthy humans to a regular oral intake of the strain B. xylanisolvens DSM 23964, we here report on the safety data of two successive human studies: a randomised and double-blind parallel group-controlled pilot study with 41 volunteers receiving a daily dose of a pasteurised fermented milk product containing up to 8.5×1011B. xylanisolvens DSM 23964 cells for 3 weeks, and a randomised and placebo-controlled double-blind major study with 140 volunteers receiving the same product but spray-dried and containing up to 1012 cells for 6 weeks. In both studies no persistent side effects of any kind were reported. The measured haematological parameters, and the serum concentrations of immunoglobulin and of inflammatory markers (IL-6, CRP, IFN-γ) were unaffected by the supplementation in both studies. A small decrease in the phagocytic activity of granulocytes and a small increase of TNF-α detected in the pilot study were both invalidated by the major study. This study further revealed that the supplementation induced no modification in natural killer cell activity and in liver enzyme values (gamma-glutamyl-transferase, glutamate-oxalacetate transaminase, glutamate-pyruvate transaminase). Our results definitively demonstrate that the pasteurised B. xylanisolvens DSM 23964 strain is safe and well tolerated by healthy human individuals.

Atomic force microscopy-based molecular studies on the recognition of immunogenic chlorinated ovalbumin by macrophage receptors

This report presents simple and reliable approach developed to study the specific recognition events between chlorinated ovalbumin (OVA) and macrophages using atomic force microscopy (AFM). Thanks to the elimination of nonspecific adhesion, the interactions of the native and chlorinated OVA with a membrane of macrophages could be quantified using exclusively the so-called adhesion frequency (AF). The proposed system not only enabled the application of AFM-based force measurements for such poorly defined ligand-receptor pairs but also significantly improved both the acquisition and the processing of the data. The proteins were immobilized on the gold-coated AFM tips from the aqueous solutions containing charged thiol adsorbates. Such surface dilution of the proteins ensured the presence of single or just a few macromolecules at the tip-surface contact. The formation of negatively charged monolayer on the tip dramatically limited its nonspecific interactions with the macrophage surface. In such systems, AF was used as a measure of the recognition events even if the interaction forces varied significantly for sets of measurements. The system with the native OVA, a weak immunogen, showed only negligible AF compared with 85% measured for the immunogenic chlorinated OVA. The AF values varied with the tip-macrophage contact time and loading velocity. Blocking of the receptors by the chlorinated OVA was also confirmed. The developed approach can be also used to study other ligand-receptor interactions in poorly defined biological systems with intrinsically broad distribution of the rupture forces, thus opening new fields for AFM-based recognition on molecular level.

Changes in the gut microbiome of the sea lamprey during metamorphosis

Vertebrate metamorphosis is often marked by dramatic morphological and physiological changes of the alimentary tract, along with major shifts in diet following development from larva to adult. Little is known about how these developmental changes impact the gut microbiome of the host organism. The metamorphosis of the sea lamprey (Petromyzon marinus) from a sedentary filter-feeding larva to a free-swimming sanguivorous parasite is characterized by major physiological and morphological changes to all organ systems. The transformation of the alimentary canal includes closure of the larval esophagus and the physical isolation of the pharynx from the remainder of the gut, which results in a nonfeeding period that can last up to 8 months. To determine how the gut microbiome is affected by metamorphosis, the microbial communities of feeding and nonfeeding larval and parasitic sea lamprey were surveyed using both culture-dependent and -independent methods. Our results show that the gut of the filter-feeding larva contains a greater diversity of bacteria than that of the blood-feeding parasite, with the parasite gut being dominated by Aeromonas and, to a lesser extent, Citrobacter and Shewanella. Phylogenetic analysis of the culturable Aeromonas from both the larval and parasitic gut revealed that at least five distinct species were represented. Phenotypic characterization of these isolates revealed that over half were capable of sheep red blood cell hemolysis, but all were capable of trout red blood cell hemolysis. This suggests that the enrichment of Aeromonas that accompanies metamorphosis is likely related to the sanguivorous lifestyle of the parasitic sea lamprey.

Immune disorders and its correlation with gut microbiome

Allergic disorders such as atopic dermatitis and asthma are common hyper-immune disorders in industrialized countries. Along with genetic association, environmental factors and gut microbiota have been suggested as major triggering factors for the development of atopic dermatitis. Numerous studies support the association of hygiene hypothesis in allergic immune disorders that a lack of early childhood exposure to diverse microorganism increases susceptibility to allergic diseases. Among the symbiotic microorganisms (e.g. gut flora or probiotics), probiotics confer health benefits through multiple action mechanisms including modification of immune response in gut associated lymphoid tissue (GALT). Although many human clinical trials and mouse studies demonstrated the beneficial effects of probiotics in diverse immune disorders, this effect is strain specific and needs to apply specific probiotics for specific allergic diseases. Herein, we briefly review the diverse functions and regulation mechanisms of probiotics in diverse disorders.

Impact of nutritional factors on the proteome of intestinal Escherichia coli: induction of OxyR-dependent proteins AhpF and Dps by a lactose-rich diet

To study the impact of nutritional factors on protein expression of intestinal bacteria, gnotobiotic mice monoassociated with Escherichia coli K-12 were fed three different diets: a diet rich in starch, a diet rich in nondigestible lactose, and a diet rich in casein. Two-dimensional gel electrophoresis and electrospray-tandem mass spectrometry were used to identify differentially expressed proteins of bacteria recovered from small intestine and cecum. Oxidative stress response proteins such as AhpF, Dps, and Fur, all of which belong to the oxyR regulon, were upregulated in E. coli isolates from mice fed the lactose-rich diet. Luciferase reporter gene assays demonstrated that osmotic stress caused by carbohydrates led to the expression of ahpCF and dps, which was not observed in an E. coli ΔoxyR mutant. Growth of ahpCF and oxyR deletion mutants was strongly impaired when nondigestible sucrose was present in the medium. The wild-type phenotype could be restored by complementation of the deletions with plasmids containing the corresponding genes and promoters. The results indicate that some OxyR-dependent proteins play a major role in the adaptation of E. coli to osmotic stress. We conclude that there is an overlap of osmotic and oxidative stress responses. Mice fed the lactose-rich diet possibly had a higher intestinal osmolality, leading to the upregulation of OxyR-dependent proteins, which enable intestinal E. coli to better cope with diet-induced osmotic stress.

Divergent pro-inflammatory profile of human dendritic cells in response to commensal and pathogenic bacteria associated with the airway microbiota

Recent studies using culture-independent methods have characterized the human airway microbiota and report microbial communities distinct from other body sites. Changes in these airway bacterial communities appear to be associated with inflammatory lung disease, yet the pro-inflammatory properties of individual bacterial species are unknown. In this study, we compared the immune stimulatory capacity on human monocyte-derived dendritic cells (DCs) of selected airway commensal and pathogenic bacteria predominantly associated with lungs of asthma or COPD patients (pathogenic Haemophillus spp. and Moraxella spp.), healthy lungs (commensal Prevotella spp.) or both (commensal Veillonella spp. and Actinomyces spp.). All bacteria were found to induce activation of DCs as demonstrated by similar induction of CD83, CD40 and CD86 surface expression. However, asthma and COPD-associated pathogenic bacteria provoked a 3-5 fold higher production of IL-23, IL-12p70 and IL-10 cytokines compared to the commensal bacteria. Based on the differential cytokine production profiles, the studied airway bacteria could be segregated into three groups (Haemophilus spp. and Moraxella spp. vs. Prevotella spp. and Veillonella spp. vs. Actinomyces spp.) reflecting their pro-inflammatory effects on DCs. Co-culture experiments found that Prevotella spp. were able to reduce Haemophillus influenzae-induced IL-12p70 in DCs, whereas no effect was observed on IL-23 and IL-10 production. This study demonstrates intrinsic differences in DC stimulating properties of bacteria associated with the airway microbiota.

Bifidobacterial surface-exopolysaccharide facilitates commensal-host interaction through immune modulation and pathogen protection

Bifidobacteria comprise a significant proportion of the human gut microbiota. Several bifidobacterial strains are currently used as therapeutic interventions, claiming various health benefits by acting as probiotics. However, the precise mechanisms by which they maintain habitation within their host and consequently provide these benefits are not fully understood. Here we show that Bifidobacterium breve UCC2003 produces a cell surface-associated exopolysaccharide (EPS), the biosynthesis of which is directed by either half of a bidirectional gene cluster, thus leading to production of one of two possible EPSs. Alternate transcription of the two opposing halves of this cluster appears to be the result of promoter reorientation. Surface EPS provided stress tolerance and promoted in vivo persistence, but not initial colonization. Marked differences were observed in host immune response: strains producing surface EPS (EPS(+)) failed to elicit a strong immune response compared with EPS-deficient variants. Specifically, EPS production was shown to be linked to the evasion of adaptive B-cell responses. Furthermore, presence of EPS(+) B. breve reduced colonization levels of the gut pathogen Citrobacter rodentium. Our data thus assigns a pivotal and beneficial role for EPS in modulating various aspects of bifidobacterial-host interaction, including the ability of commensal bacteria to remain immunologically silent and in turn provide pathogen protection. This finding enforces the probiotic concept and provides mechanistic insights into health-promoting benefits for both animal and human hosts.

Alternative glycosylation modulates function of IgG and other proteins - implications on evolution and disease

BACKGROUND

Nearly all membrane and secreted proteins, as well as numerous intracellular proteins are glycosylated. However, contrary to proteins which are defined by their individual genetic templates, glycans are encoded in a complex dynamic network of hundreds of genes which participate in the complex biosynthetic pathway of protein glycosylation.

SCOPE OF REVIEW

This review summarizes present knowledge about the importance of alternative glycosylation of IgG and other proteins.

MAJOR CONCLUSIONS

Numerous proteins depend on correct glycosylation for proper function. Very good example for this is the alternative glycosylation of IgG whose effector functions can be completely changed by the addition or removal of a single monosaccharide residue from its glycans.

GENERAL SIGNIFICANCE

The change in the structure of a protein requires mutations in DNA and subsequent selection in the next generation, while even slight alterations in activity or intracellular localization of one or more biosynthetic enzymes are sufficient for the creation of novel glycan structures, which can then perform new functions. Glycome composition varies significantly between individuals, which makes them slightly or even significantly different in their ability to execute specific molecular pathways with numerous implications for development and progression of various diseases. This article is part of a Special Issue entitled Glycoproteomics.

Epigenetic modulation of the HeLa cell membrane N-glycome

BACKGROUND

Epigenetic changes play a role in all major events during tumorigenesis and changes in glycan structures are hallmarks of virtually every cancer. Also, proper N-glycosylation of membrane receptors is important in cell to cell and cell-environment communication. To study how modulation of epigenetic information can affect N-glycan expression we analyzed effects of epigenetic inhibitors on HeLa cell membrane N-glycome.

METHODS

HeLa cells were treated with DNA methylation (zebularin and 5-aza-2-deoxycytidine) and histone deacetylation (trichostatin A and Na-butyrate) inhibitors. The effects on HeLa cell membrane N-glycome were analyzed by hydrophilic interaction high performance liquid chromatography (HILIC).

RESULTS

Each of the four epigenetic inhibitors induced changes in the expression of HeLa cell membrane N-glycans that were seen either as an increase or a decrease of individual glycans in the total N-glycome. Compared to DNA methylation inhibitors, histone deacetylation inhibitors showed more moderate changes, probably due to their higher gene target selectivity.

CONCLUSIONS

The results clearly show that composition of HeLa cell membrane N-glycome can be specifically altered by epigenetic inhibitors.

GENERAL SIGNIFICANCE

Glycans on the cell membrane are essential elements of tumor cell's metastatic potential and are also an entry point for nearly all pathogenic microorganisms. Since epigenetic inhibitors used in this work are registered drugs, our results provide a new line of research in the application of these drugs as anticancer and antimicrobial agents. This article is part of a Special Issue entitled Glycoproteomics.

The genital econiche: focus on microbiota and bacterial vaginosis

Ecological and evolutionary forces shaping the normal and abnormal microflora of the genital econiche are discussed, in particular those related to bacterial vaginosis, which worldwide is the most common vaginal infection, with numerous obstetrical and gynecological complications, including acquisition and transmission of HIV and other sexually transmitted infections (STIs). Characterized by a heavy overgrowth of Gram-negative and Gram-positive anaerobes with no signs of inflammation, bacterial vaginosis has been regarded a microbiological and immunological enigma. Immune tolerance to both normal and abnormal vaginal microbiota, mainly derived from gut microflora, as a result of coevolution with humans might explain the absence of inflammation, supported by short-chain fatty acids, known to modulate immune responses, that are produced in large quantities by anaerobes. Recent studies have implicated the development of a vaginal biofilm with Gardnerella vaginalis and Atopobium vaginae as main players in the pathogenesis of bacterial vaginosis. Supporting this conclusion are data such as those demonstrating heavy growth of G. vaginalis and diversified anaerobes with numerous "clue cells" that are sloughing off from the biofilm. Gardnerella and Atopobium organisms attached to these clue cells can be demonstrated in the male genital econiche, likely reflecting a heterosexual transmission of the disorder.

Aberrant structures of fecal bacterial community in allergic infants profiled by 16S rRNA gene pyrosequencing

We investigated the correlation between fecal bacteria composition in early infancy and the prevalence of allergic diseases in late infancy. The fecal microbiota in the first 2 months was profiled using the 16S rRNA V6 short-tag sequences in the community and statistically compared between two groups of subjects who did and did not show allergic symptoms in the first 2 years (n = 11 vs. 11). In the allergic group, genus Bacteroides at 1 month and genera Propionibacterium and Klebsiella at 2 months were more abundant, and genera Acinetobacter and Clostridium at 1 month were less abundant than in the nonallergic group. Allergic infants who showed high colonization of Bacteroides and/or Klebsiella showed less colonization of Clostridium perfringens/butyricum, suggesting antagonism between these bacterial groups in the gastrointestinal tract. It was also remarkable that the relative abundance of total Proteobacteria, excluding genus Klebsiella, was significantly lower in the allergic than in the nonallergic group at the age of 1 month. These results indicate that pyrosequence-based 16S rRNA gene profiling is valid to find the intestinal microbiotal disorder that correlates with allergy development in later life.