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1.
PLoS One ; 18(8): e0288689, 2023.
Article in English | MEDLINE | ID: mdl-37556397

ABSTRACT

Growing evidence is demonstrating the connection between the microbiota gut-brain axis and neurodevelopment. Microbiota colonization occurs before the maturation of many neural systems and is linked to brain health. Because of this it has been hypothesized that the early microbiome interactions along the gut-brain axis evolved to promote advanced cognitive functions and behaviors. Here, we performed a pilot study with a multidisciplinary approach to test if the microbiota composition of infants is associated with measures of early cognitive development, in particular neural rhythm tracking; language (forward speech) versus non-language (backwards speech) discrimination; and social joint attention. Fecal samples were collected from 56 infants between four and six months of age and sequenced by shotgun metagenomic sequencing. Of these, 44 performed the behavioral Point and Gaze test to measure joint attention. Infants were tested on either language discrimination using functional near-infrared spectroscopy (fNIRS; 25 infants had usable data) or neural rhythm tracking using electroencephalogram (EEG; 15 had usable data). Infants who succeeded at the Point and Gaze test tended to have increased Actinobacteria and reduced Firmicutes at the phylum level; and an increase in Bifidobacterium and Eggerthella along with a reduction in Hungatella and Streptococcus at the genus level. Measurements of neural rhythm tracking associated negatively to the abundance of Bifidobacterium and positively to the abundance of Clostridium and Enterococcus for the bacterial abundances, and associated positively to metabolic pathways that can influence neurodevelopment, including branched chain amino acid biosynthesis and pentose phosphate pathways. No associations were found for the fNIRS language discrimination measurements. Although the tests were underpowered due to the small pilot sample sizes, potential associations were identified between the microbiome and measurements of early cognitive development that are worth exploring further.


Subject(s)
Gastrointestinal Microbiome , Microbiota , Humans , Infant , Pilot Projects , Bacteria , Feces/microbiology , Brain
2.
mBio ; 12(1)2021 01 12.
Article in English | MEDLINE | ID: mdl-33436437

ABSTRACT

The gut microbiome is a well-recognized modulator of host immunity, and its compositions differ between geographically separated human populations. Systemic innate immune responses to microbial derivatives also differ between geographically distinct human populations. However, the potential role of the microbiome in mediating geographically varied immune responses is unexplored. We here applied 16S amplicon sequencing to profile the stool microbiome and, in parallel, measured whole-blood innate immune cytokine responses to several pattern recognition receptor (PRR) agonists among 2-year-old children across biogeographically diverse settings. Microbiomes differed mainly between high- and low-resource environments and were not strongly associated with other demographic factors. We found strong correlations between responses to Toll-like receptor 2 (TLR2) and relative abundances of Bacteroides and Prevotella populations, shared among Canadian and Ecuadorean children. Additional correlations between responses to TLR2 and bacterial populations were specific to individual geographic cohorts. As a proof of concept, we gavaged germfree mice with human donor stools and found murine splenocyte responses to TLR stimulation were consistent with responses of the corresponding human donor populations. This study identified differences in immune responses correlating to gut microbiomes across biogeographically diverse settings and evaluated biological plausibility using a mouse model. This insight paves the way to guide optimization of population-specific interventions aimed to improve child health outcomes.IMPORTANCE Both the gut microbiome and innate immunity are known to differ across biogeographically diverse human populations. The gut microbiome has been shown to directly influence systemic immunity in animal models. With this, modulation of the gut microbiome represents an attractive avenue to improve child health outcomes associated with altered immunity using population-specific approaches. However, there are very scarce data available to determine which members of the gut microbiome are associated with specific immune responses and how these differ around the world, creating a substantial barrier to rationally designing such interventions. This study addressed this knowledge gap by identifying relationships between distinct bacterial taxa and cytokine responses to specific microbial agonists across highly diverse settings. Furthermore, we provide evidence that immunomodulatory effects of region-specific stool microbiomes can be partially recapitulated in germfree mice. This is an important contribution toward improving global child health by targeting the gut microbiome.


Subject(s)
Bacteria/classification , Gastrointestinal Microbiome/immunology , Host Microbial Interactions/immunology , Immune System , Animals , Biodiversity , Canada , Child, Preschool , Cytokines/metabolism , Fecal Microbiota Transplantation , Feces/microbiology , Female , Gastrointestinal Microbiome/physiology , Germ-Free Life , Humans , Immunity, Innate , Infant , Male , Phylogeography , Toll-Like Receptor 2
3.
J Parkinsons Dis ; 11(1): 153-158, 2021.
Article in English | MEDLINE | ID: mdl-33164944

ABSTRACT

The gut microbiome has been increasingly implicated in Parkinson's disease (PD); however, most existing studies employ bacterial-specific sequencing, and have not investigated non-bacterial microbiome constituents. Here, we use fungal-specific internal transcribed spacer (ITS)-2 amplicon sequencing in a cross-sectional PD cohort to investigate associations between the fungal gut microbiome and PD. Fungal load among participants was extremely low, and genera identified were almost exclusively of proposed dietary or environmental origin. We observed significantly lower fungal DNA relative to bacterial DNA among PD patients. No fungi differed in abundance between patients and controls, nor were any associated with motor, cognitive, or gastrointestinal features among patients.


Subject(s)
DNA, Bacterial , DNA, Fungal , Gastrointestinal Microbiome , Mycobiome , Parkinson Disease/microbiology , Aged , Cross-Sectional Studies , Female , High-Throughput Nucleotide Sequencing , Humans , Male , Middle Aged , Sequence Analysis, DNA
4.
Bioessays ; 41(10): e1800257, 2019 10.
Article in English | MEDLINE | ID: mdl-31157928

ABSTRACT

Humans' indigenous microbes strongly influence organ functions in an age- and diet-dependent manner, adding an important dimension to aging biology that remains poorly understood. Although age-related differences in the gut microbiota composition correlate with age-related loss of organ function and diseases, including inflammation and frailty, variation exists among the elderly, especially centenarians and people living in areas of extreme longevity. Studies using short-lived as well as nonsenescent model organisms provide surprising functional insights into factors affecting aging and implicate attenuating effects of microbes as well as a crucial role for certain transcription factors like forkhead box O. The unexpected beneficial effects of microbes on aged animals imply an even more complex interplay between the gut microbiome and the host. The microbiome constitutes the major interface between humans and the environment, is influenced by biosocial stressors and behaviors, and mediates effects on health and aging processes, while being moderated by sex and developmental stages.


Subject(s)
Aging , Microbiota , Animals , Diet , Humans
5.
J Allergy Clin Immunol ; 142(2): 424-434.e10, 2018 08.
Article in English | MEDLINE | ID: mdl-29241587

ABSTRACT

BACKGROUND: Asthma is the most prevalent chronic disease of childhood. Recently, we identified a critical window early in the life of both mice and Canadian infants during which gut microbial changes (dysbiosis) affect asthma development. Given geographic differences in human gut microbiota worldwide, we studied the effects of gut microbial dysbiosis on atopic wheeze in a population living in a distinct developing world environment. OBJECTIVE: We sought to determine whether microbial alterations in early infancy are associated with the development of atopic wheeze in a nonindustrialized setting. METHODS: We conducted a case-control study nested within a birth cohort from rural Ecuador in which we identified 27 children with atopic wheeze and 70 healthy control subjects at 5 years of age. We analyzed bacterial and eukaryotic gut microbiota in stool samples collected at 3 months of age using 16S and 18S sequencing. Bacterial metagenomes were predicted from 16S rRNA data by using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States and categorized by function with Kyoto Encyclopedia of Genes and Genomes ontology. Concentrations of fecal short-chain fatty acids were determined by using gas chromatography. RESULTS: As previously observed in Canadian infants, microbial dysbiosis at 3 months of age was associated with later development of atopic wheeze. However, the dysbiosis in Ecuadorian babies involved different bacterial taxa, was more pronounced, and also involved several fungal taxa. Predicted metagenomic analysis emphasized significant dysbiosis-associated differences in genes involved in carbohydrate and taurine metabolism. Levels of the fecal short-chain fatty acids acetate and caproate were reduced and increased, respectively, in the 3-month stool samples of children who went on to have atopic wheeze. CONCLUSIONS: Our findings support the importance of fungal and bacterial microbiota during the first 100 days of life on the development of atopic wheeze and provide additional support for considering modulation of the gut microbiome as a primary asthma prevention strategy.


Subject(s)
Bacteria/genetics , Dysbiosis/epidemiology , Feces/microbiology , Fungi/physiology , Gastrointestinal Microbiome/genetics , Hypersensitivity, Immediate/epidemiology , Carbohydrate Metabolism , Case-Control Studies , Child, Preschool , Cohort Studies , Ecuador/epidemiology , Humans , Infant , RNA, Ribosomal, 16S/genetics , Respiratory Sounds , Rural Population , Taurine/metabolism
6.
Ann Neurol ; 81(3): 369-382, 2017 Mar.
Article in English | MEDLINE | ID: mdl-28220542

ABSTRACT

Almost half the cells and 1% of the unique genes found in our bodies are human, the rest are from microbes, predominantly bacteria, archaea, fungi, and viruses. These microorganisms collectively form the human microbiota, with most colonizing the gut. Recent technological advances, open access data libraries, and application of high-throughput sequencing have allowed these microbes to be identified and their contribution to neurological health to be examined. Emerging evidence links perturbations in the gut microbiota to neurological disease, including disease risk, activity, and progression. This review provides an overview of the recent advances in microbiome research in relation to neuro(auto)immune and neurodegenerative conditions affecting humans, such as multiple sclerosis, neuromyelitis optica spectrum disorders, Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. Study design and terminology used in this rapidly evolving, highly multidisciplinary field are summarized to empower and engage the neurology community in this "newly discovered organ." Ann Neurol 2017;81:369-382.


Subject(s)
Demyelinating Autoimmune Diseases, CNS , Gastrointestinal Microbiome/physiology , Neurodegenerative Diseases , Animals , Demyelinating Autoimmune Diseases, CNS/etiology , Demyelinating Autoimmune Diseases, CNS/immunology , Demyelinating Autoimmune Diseases, CNS/microbiology , Humans , Neurodegenerative Diseases/etiology , Neurodegenerative Diseases/immunology , Neurodegenerative Diseases/microbiology
7.
Transplantation ; 101(1): 74-82, 2017 Jan.
Article in English | MEDLINE | ID: mdl-27681266

ABSTRACT

BACKGROUND: Transplant recipients are treated with immunosuppressive (IS) therapies, which impact host-microbial interactions. We examined the impact of IS drugs on gut microbiota and on the expression of ileal antimicrobial peptides. METHODS: Mice were treated for 14 days with prednisolone, mycophenolate mofetil, tacrolimus, a combination of these 3 drugs, everolimus, or water. Feces were collected before and after treatment initiation. Ileal samples were collected after sacrifice. Fecal and ileal microbiota were analyzed by pyrosequencing of 16S rRNA genes and enumeration of selected bacteria by culture, and C-type lectins were assessed in ileal tissues by reverse transcriptase-quantitative polymerase chain reaction. RESULTS: Prednisolone disrupted fecal microbiota community structure, decreased Bacteroidetes, and increased Firmicutes in the feces. Prednisolone, tacrolimus, and mycophenolate mofetil modified fecal microbiota at the family level in each experimental replicate, but changes were not consistent between the replicates. In ileal samples, the genus Clostridium sensu stricto was dramatically reduced in the prednisolone and combined IS drug groups. These modifications corresponded to an altered ileal expression of C-type lectins Reg3γ and Reg3ß, and of interleukin 22. Interestingly, the combined IS treatment enabled a commensal Escherichia coli to flourish, and dramatically increased colonization by uropathogenic E. coli strain 536. CONCLUSIONS: IS treatment alters innate antimicrobial defenses and disrupts the gut microbiota, which leads to overgrowth of indigenous E. coli and facilitates colonization by opportunistic pathogens.


Subject(s)
Antimicrobial Cationic Peptides/metabolism , Gastrointestinal Microbiome/drug effects , Ileum/drug effects , Immunosuppressive Agents/toxicity , Mycophenolic Acid/toxicity , Prednisolone/toxicity , Tacrolimus/toxicity , Uropathogenic Escherichia coli/growth & development , Animals , Drug Therapy, Combination , Escherichia coli Infections/immunology , Escherichia coli Infections/microbiology , Feces/microbiology , Host-Pathogen Interactions , Ileum/immunology , Ileum/metabolism , Ileum/microbiology , Immunocompromised Host , Lectins, C-Type/genetics , Lectins, C-Type/immunology , Mice, Inbred C57BL , Models, Animal , Opportunistic Infections/immunology , Opportunistic Infections/microbiology , Reverse Transcriptase Polymerase Chain Reaction , Ribotyping , Time Factors , Urinary Tract Infections/immunology , Urinary Tract Infections/microbiology , Uropathogenic Escherichia coli/immunology , Uropathogenic Escherichia coli/pathogenicity
8.
J Infect ; 69 Suppl 1: S53-5, 2014 Nov.
Article in English | MEDLINE | ID: mdl-25264162

ABSTRACT

There is increasing evidence that environmental changes are involved in the sharp increase in asthma incidence, as well as with other immune-mediated diseases. This increase matches the introduction of modern life advances such as antibiotics and caesarean sections. Several epidemiological studies provide convincing evidence that a lack of exposure to microbes early in life is associated with later development of allergic asthma. In addition, animal studies have shown that early life modulation of the intestinal microbiota with antibiotics has profound effects in the immune cellular mechanisms that lead to asthma. By describing some of the most relevant human and animal studies in this field, we explore the concept that significant perturbations of the intestinal and perhaps the lung microbiota are a cause of allergic asthma.


Subject(s)
Asthma/etiology , Intestines/microbiology , Microbiota , Animals , Humans , Intestines/immunology , Microbial Interactions
9.
Front Immunol ; 5: 427, 2014.
Article in English | MEDLINE | ID: mdl-25250028

ABSTRACT

Human microbial colonization begins at birth and continues to develop and modulate in species abundance for about 3 years, until the microbiota becomes adult-like. During the same time period, children experience significant developmental changes that influence their health status as well as their immune system. An ever-expanding number of articles associate several diseases with early-life imbalances of the gut microbiota, also referred to as gut microbial dysbiosis. Whether early-life dysbiosis precedes and plays a role in disease pathogenesis, or simply originates from the disease process itself is a question that is beginning to be answered in a few diseases, including IBD, obesity, and asthma. This review describes the gut microbiome structure and function during the formative first years of life, as well as the environmental factors that determine its composition. It also aims to discuss the recent advances in understanding the role of the early-life gut microbiota in the development of immune-mediated, metabolic, and neurological diseases. A greater understanding of how the early-life gut microbiota impacts our immune development could potentially lead to novel microbial-derived therapies that target disease prevention at an early age.

10.
Cell Res ; 24(1): 5-6, 2014 Jan.
Article in English | MEDLINE | ID: mdl-24165893

ABSTRACT

Antibiotic therapies disrupt the intestinal microbiota and render the host susceptible to enteric infections. A recent report by Ng et al. explores the ability of two intestinal pathogens (Salmonella enterica serovar Typhimurium and Clostridium difficile) to use this disruption to their advantage and consume host carbohydrates that would otherwise be unavailable in the presence of a normal gut microbiota.


Subject(s)
Anti-Bacterial Agents/pharmacology , Carbohydrate Metabolism/drug effects , Clostridioides difficile/physiology , Enterocolitis, Pseudomembranous/microbiology , Intestinal Mucosa/microbiology , Salmonella Infections/microbiology , Salmonella typhimurium/physiology , Animals , Female , Male
11.
Gut Microbes ; 4(2): 158-64, 2013.
Article in English | MEDLINE | ID: mdl-23333861

ABSTRACT

There is convincing evidence from recent human and animal studies that suggests the intestinal microbiota plays an important role in regulating immune responses associated with the development of allergic asthma, particularly during early infancy. Although identifying the mechanistic link between host-microbe interactions in the gut and lung mucosal tissues has proved challenging, several very recent studies are now providing significant insights. We have shown that administering vancomycin to mice early in life shifts resident gut flora and enhances future susceptibility to allergic asthma. This effect was not observed in mice given another antibiotic, streptomycin, nor when either antibiotic was administered to adult mice. In this addendum, we further analyze the link between early life administration of vancomycin and future susceptibility to asthma and describe how specific immune cell populations, which have been implicated in other asthma-related microbiota studies, are affected. We propose that shifts in gut microbiota exacerbate asthma-related immune responses when they occur shortly after birth and before weaning (perinatal period), and suggest that these effects may be mediated, at least in the case of vancomycin, by elevated serum IgE and reduced regulatory T cell populations.


Subject(s)
Anti-Bacterial Agents/administration & dosage , Asthma/immunology , Asthma/microbiology , Gastrointestinal Tract/microbiology , Metagenome/drug effects , Metagenome/immunology , Animals , Immunoglobulin E/blood , Mice , Streptomycin/administration & dosage , T-Lymphocytes, Regulatory/immunology , Vancomycin/administration & dosage
12.
Innate Immun ; 19(3): 315-27, 2013 Jun.
Article in English | MEDLINE | ID: mdl-23109507

ABSTRACT

Innate immunity is triggered by a variety of bacterial molecules, resulting in both protective and potentially harmful pro-inflammatory responses. Further, innate immunity also provides a mechanism for the maintenance of homeostasis between the host immune system and symbiotic or non-pathogenic microorganisms. However, the bacterial factors that mediate these protective effects have been incompletely defined. Here, it was demonstrated that the lantiobiotic nisin Z is able to modulate host immune responses and mediate protective host immunity. Nisin Z induced the secretion of the chemokines MCP-1, IL-8 and Gro-α, and significantly reduced TNF-α induction in response to bacterial LPS in human PBMC. The results correlated with the ability of nisin Z to confer protection against both the Gram-positive organism Staphylococcus aureus, and the Gram-negatives Salmonella enterica sv. Typhimurium and Escherichia coli in murine challenge models. Mechanistic studies revealed that nisin Z modulates host immunity through similar mechanisms as natural host defense peptides, engaging multiple signal transduction pathways and growth factor receptors. The results presented herein demonstrate that, in addition to nisin Z, other bacterial cationic peptides and, in particular, the lantibiotics, could represent a new class of secreted bacterial molecule with immunomodulatory activities.


Subject(s)
Antimicrobial Cationic Peptides/administration & dosage , Escherichia coli/immunology , Nisin/analogs & derivatives , Salmonella enterica/immunology , Staphylococcus aureus/immunology , Animals , Bacterial Load/radiation effects , Cell Line , Chemokines/metabolism , Female , Humans , Immunity, Innate/drug effects , Immunomodulation , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Nisin/administration & dosage , Signal Transduction/drug effects , Tumor Necrosis Factor-alpha/metabolism
13.
Curr Opin Gastroenterol ; 28(6): 563-9, 2012 Nov.
Article in English | MEDLINE | ID: mdl-23010680

ABSTRACT

PURPOSE OF REVIEW: The prevalence of allergic diseases continues to rise globally in developed countries. Since the initial proposal of the hygiene hypothesis, there has been increasing evidence to suggest that the intestinal microbiota, particularly during early infancy, plays a critical role in regulating immune responses associated with the development of atopy. This review evaluates the key epidemiologic and mechanistic data published to date. RECENT FINDINGS: Epidemiological data have provided the framework for animal studies investigating the importance of gut commensals in allergy development. These studies provide new insights about the microbial regulation of mucosal immune responses inside and outside the gut, and how these effects may drive allergic inflammation in susceptible individuals. Specific immune cells have been identified as mediators of these microbiota-regulated allergic responses. SUMMARY: In the last year, technological advances have provided us with a better understanding of the gut microbiome in healthy and allergic individuals. Recent studies have identified the associations between particular gut microbes and different disease phenotypes, as well as identified immune cells and their mediators involved in allergy development. This research has provided a number of host and microbe targets that may be used to develop novel therapies suitable for the treatment or prevention of allergic diseases.


Subject(s)
Hypersensitivity/microbiology , Intestines/microbiology , Metagenome/immunology , Animals , Asthma/epidemiology , Asthma/immunology , Disease Models, Animal , Humans , Hygiene Hypothesis , Hypersensitivity/epidemiology , Hypersensitivity/immunology , Immunity, Mucosal , Intestines/immunology , Mucous Membrane/immunology
15.
EMBO Rep ; 13(5): 440-7, 2012 May 01.
Article in English | MEDLINE | ID: mdl-22422004

ABSTRACT

Allergic asthma rates have increased steadily in developed countries, arguing for an environmental aetiology. To assess the influence of gut microbiota on experimental murine allergic asthma, we treated neonatal mice with clinical doses of two widely used antibiotics--streptomycin and vancomycin--and evaluated resulting shifts in resident flora and subsequent susceptibility to allergic asthma. Streptomycin treatment had little effect on the microbiota and on disease, whereas vancomycin reduced microbial diversity, shifted the composition of the bacterial population and enhanced disease severity. Neither antibiotic had a significant effect when administered to adult mice. Consistent with the 'hygiene hypothesis', our data support a neonatal, microbiota-driven, specific increase in susceptibility to experimental murine allergic asthma.


Subject(s)
Anti-Bacterial Agents/adverse effects , Asthma/chemically induced , Computational Biology/methods , Disease Susceptibility/chemically induced , Metagenome/drug effects , Streptomycin/adverse effects , Vancomycin/adverse effects , Animals , Asthma/microbiology , Female , Flow Cytometry , Mice , Mice, Inbred C57BL
16.
J Infect Dis ; 204(8): 1237-45, 2011 Oct 15.
Article in English | MEDLINE | ID: mdl-21917897

ABSTRACT

BACKGROUND: Invasive nontyphoid Salmonella (iNTS) disease is common and severe in adults with human immunodeficiency virus (HIV) infection in Africa. We previously observed that ex vivo macrophages from HIV-infected subjects challenged with Salmonella Typhimurium exhibit dysregulated proinflammatory cytokine responses. METHODS: We studied the transcriptional response in whole blood from HIV-positive patients during acute and convalescent iNTS disease compared to other invasive bacterial diseases, and to HIV-positive and -negative controls. RESULTS: During iNTS disease, there was a remarkable lack of a coordinated inflammatory or innate immune signaling response. Few interferon γ (IFNγ)-induced genes or Toll-like receptor/transcription factor nuclear factor κB (TLR/NFκB) gene pathways were upregulated in expression. Ex vivo lipopolysacharide (LPS) or flagellin stimulation of whole blood, however, showed that convalescent iNTS subjects and controls were competent to mount prominent TLR/NFκB-associated patterns of mRNA expression. In contrast, HIV-positive patients with other invasive bacterial infections (Escherichia coli and Streptococcus pneumoniae) displayed a pronounced proinflammatory innate immune transcriptional response. There was also upregulated mRNA expression in cell cycle, DNA replication, translation and repair, and viral replication pathways during iNTS. These patterns persisted for up to 2 months into convalescence. CONCLUSIONS: Attenuation of NFκB-mediated inflammation and dysregulation of cell cycle and DNA-function gene pathway expression are key features of the interplay between iNTS and HIV.


Subject(s)
HIV Infections/genetics , HIV Infections/microbiology , HIV/immunology , NF-kappa B/immunology , Salmonella Infections/genetics , Salmonella Infections/virology , Salmonella/immunology , Adult , Africa South of the Sahara , Cluster Analysis , Female , HIV Infections/immunology , HIV Infections/virology , Humans , Leukocytes, Mononuclear/immunology , Male , NF-kappa B/genetics , RNA, Messenger/chemistry , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction , Salmonella Infections/immunology , Salmonella Infections/microbiology , Transcriptome
17.
PLoS One ; 6(5): e20024, 2011.
Article in English | MEDLINE | ID: mdl-21625519

ABSTRACT

To establish a successful infection within the host, a pathogen must closely regulate multiple virulence traits to ensure their accurate temporal and spatial expression. As a highly adapted intracellular pathogen, Salmonella enterica has acquired during its evolution various virulence genes via numerous lateral transfer events, including the acquisition of the Salmonella Pathogenicity Island 2 (SPI-2) and its associated effectors. Beneficial use of horizontally acquired genes requires that their expression is effectively coordinated with the already existing virulence programs and the regulatory set-up in the bacterium. As an example for such a mechanism, we show here that the ancestral PhoPQ system of Salmonella enterica is able to regulate directly the SPI-2 effector gene sseL (encoding a secreted deubiquitinase) in an SsrB-independent manner and that PhoP plays a part in a feed-forward regulatory loop, which fine-tunes the cellular level of SseL. Additionally, we demonstrate the presence of conserved cis regulatory elements in the promoter region of sseL and show direct binding of purified PhoP to this region. Interestingly, in contrast to the S. enterica PhoP, an ortholog regulator from a S. bongori SARC 12 strain was found to be impaired in promoting transcription of sseL and other genes from the PhoP regulon. These findings have led to the identification of a previously uncharacterized residue in the DNA-binding domain of PhoP, which is required for the transcriptional activation of PhoP regulated genes in Salmonella spp. Collectively our data demonstrate an interesting interface between the acquired SsrB regulon and the ancestral PhoPQ regulatory circuit, provide novel insights into the function of PhoP, and highlight a mechanism of regulatory integration of horizontally acquired genes into the virulence network of Salmonella enterica.


Subject(s)
Bacterial Proteins/metabolism , Gene Transfer, Horizontal , Genes, Bacterial , Salmonella enterica/metabolism , Base Sequence , Molecular Sequence Data , Promoter Regions, Genetic , Salmonella enterica/genetics , Sequence Homology, Nucleic Acid , Transcription, Genetic
19.
J Transl Med ; 8: 6, 2010 Jan 27.
Article in English | MEDLINE | ID: mdl-20105294

ABSTRACT

BACKGROUND: Activation of Toll-like receptors (TLRs) is widely accepted as an essential event for defence against infection. Many TLRs utilize a common signalling pathway that relies on activation of the kinase IRAK4 and the transcription factor NFkappaB for the rapid expression of immunity genes. METHODS: 21 K DNA microarray technology was used to evaluate LPS-induced (TLR4) gene responses in blood monocytes from a child with an IRAK4-deficiency. In vitro responsiveness to LPS was confirmed by real-time PCR and ELISA and compared to the clinical predisposition of the child and IRAK4-deficient mice to Gram negative infection. RESULTS: We demonstrated that the vast majority of LPS-responsive genes in IRAK4-deficient monocytes were greatly suppressed, an observation that is consistent with the described role for IRAK4 as an essential component of TLR4 signalling. The severely impaired response to LPS, however, is inconsistent with a remarkably low incidence of Gram negative infections observed in this child and other children with IRAK4-deficiency. This unpredicted clinical phenotype was validated by demonstrating that IRAK4-deficient mice had a similar resistance to infection with Gram negative S. typhimurium as wildtype mice. A number of immunity genes, such as chemokines, were expressed at normal levels in human IRAK4-deficient monocytes, indicating that particular IRAK4-independent elements within the repertoire of TLR4-induced responses are expressed. CONCLUSIONS: Sufficient defence to Gram negative immunity does not require IRAK4 or a robust, 'classic' inflammatory and immune response.


Subject(s)
Gene Expression Regulation , Immunity , Interleukin-1 Receptor-Associated Kinases/immunology , Signal Transduction/immunology , Toll-Like Receptor 4 , Animals , Chemokines/immunology , Child , Cytokines/immunology , Gene Expression Profiling , Gene Expression Regulation/immunology , Humans , Immunity/genetics , Immunity/immunology , Interleukin-1 Receptor-Associated Kinases/genetics , Lipopolysaccharides/immunology , Lipopolysaccharides/pharmacology , Mice , Mice, Inbred C57BL , Monocytes/cytology , Monocytes/drug effects , Monocytes/immunology , NF-kappa B/immunology , Oligonucleotide Array Sequence Analysis , Polymerase Chain Reaction/methods , Salmonella typhimurium/immunology , Salmonella typhimurium/pathogenicity , Toll-Like Receptor 4/genetics , Toll-Like Receptor 4/immunology
20.
Gut Microbes ; 1(1): 30-41, 2010 Jan.
Article in English | MEDLINE | ID: mdl-21327114

ABSTRACT

Gastrointestinal infections involve an interactive tripartite relationship between the invading pathogen, the host, and the host's resident intestinal microbiota. To characterize the host inflammatory response and microbiota alterations during enteric salmonellosis, C57BL/6 mice were pre-treated with a low dose of streptomycin (LD model) and then infected with S. typhimurium strains, including mutants in the two Type III secretion systems, SPI-1 and SPI-2 (invAmut and ssaRmut, respectively). Cecal colonization and inflammation in the LD model were evaluated to assess infection success and progression, and compared to the traditional high dose (HD) model. Perturbations to the microbial community in the LD model were assessed via evaluation of total microbial numbers, the proportion of intestinal γ-Proteobacteria and tRFLP analysis. In the LD model, consistently high colonization by the parental strain (WT) and invAmut S. typhimurium was associated with significant intestinal pathology. However, microbial community profiles were more similar both in numbers and composition between mice infected with the mutant strains, than with the WT strain. Consequently, significant infection-induced inflammation did not always produce similar microbiota perturbations. Large numbers of luminal neutrophils were observed in the ceca of WT-infected, but not in invAmut or ssaRmut infected mice. Neutrophils were thus implicated as a potential mediator of microbiota perturbations during WT enteric salmonellosis. These studies offer a new model of S. typhimurium-induced intestinal disease that retains the three participants of the disease process and further defines the role of virulence factors, the host microbiota, and inflammation in S. typhimurium-induced intestinal disease.

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