ORCID Profile
0000-0002-8964-4456
Current Organisations
Monash University
,
La Trobe University
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Microbiology | Infectious Agents | Proteomics and Intermolecular Interactions (excl. Medical Proteomics) | Biochemistry and Cell Biology | Medical Bacteriology | Nanoscale Characterisation | Analytical Biochemistry | Systems Biology | Bacteriology
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in the Chemical Sciences | Human Biological Preventatives (e.g. Vaccines) | Expanding Knowledge in the Agricultural and Veterinary Sciences |
Publisher: The American Association of Immunologists
Date: 15-12-2009
Abstract: Helicobacter pylori rapidly activates MAPKs and transcription factors, NF-κB and AP-1, in gastric epithelial cells following host attachment. Activation of these signal transducers is largely dependent on the cag pathogenicity island (cagPAI)-encoded Type IV Secretion System. H. pylori was shown to translocate peptidoglycan through the Type IV Secretion System, which is recognized by the pathogen recognition molecule, NOD1, thus resulting in NF-κB activation. The mechanisms of H. pylori-induced MAPK and AP-1 activation, however, are less well defined and therefore, we assessed the contribution of NOD1 to their activation. For this, we used gastric epithelial cell lines, stably expressing siRNA to either NOD1 or a control gene. In siNOD1-expressing cells stimulated with cagPAI+ H. pylori, we observed significant reductions in p38 and ERK phosphorylation (p & 0.05), whereas the levels of Jnk phosphorylation remained unchanged. Consistent with a previous report, however, we were able to demonstrate NOD1-dependent Jnk phosphorylation by the invasive pathogen Shigella flexneri, highlighting pathogen-specific host responses to infection. We also show that NOD1 was essential for H. pylori induction of not only NF-κB, but also AP-1 activation, implying that NOD1 induces robust proinflammatory responses, in an attempt to rapidly control infection. Pharmacological inhibition of p38 and ERK activity significantly reduced IL-8 production in response to H. pylori, further emphasizing the importance of MAPKs in innate immune responses to the pathogen. Thus, for the first time we have shown the important role for NOD1 in MAPK and AP-1 activation in response to cagPAI+ H. pylori.
Publisher: Hindawi Limited
Date: 25-09-2016
DOI: 10.1111/CMI.12658
Abstract: Outer membrane vesicles were first described approximately 50 years ago and for many years were considered to be an artifact of bacterial growth. Since that initial discovery, it has become evident that outer membrane vesicles are produced by almost all Gram-negative bacteria as part of their normal growth in addition to driving pathogenesis within the host. More recently, the identification of membrane vesicle (MV) production by some Gram-positive bacteria, parasites, fungi, mycobacteria and infected host cells has significantly broadened the field of MV research and emphasized their importance to pathogenesis. In this review, we will focus on discussing recent advances in the field of bacterial MV biogenesis and the mechanisms whereby they modulate immunity and contribute to pathogenesis. We will highlight findings identifying the contribution of extracellular vesicles produced by Gram-positive bacteria, fungi, parasites, and infected host cells in mediating pathogenesis in addition to the functions of MVs produced by commensal bacteria. Finally, we will discuss recent progress in the development of bacterial MVs as novel vaccines capable of mediating cellular and humoral immune responses.
Publisher: Hindawi Limited
Date: 03-2010
DOI: 10.1111/J.1462-5822.2009.01404.X
Abstract: Gram-negative bacterial peptidoglycan is specifically recognized by the host intracellular sensor NOD1, resulting in the generation of innate immune responses. Although epithelial cells are normally refractory to external stimulation with peptidoglycan, these cells have been shown to respond in a NOD1-dependent manner to Gram-negative pathogens that can either invade or secrete factors into host cells. In the present work, we report that Gram-negative bacteria can deliver peptidoglycan to cytosolic NOD1 in host cells via a novel mechanism involving outer membrane vesicles (OMVs). We purified OMVs from the Gram-negative mucosal pathogens: Helicobacter pylori, Pseudomonas aeruginosa and Neisseria gonorrhoea and demonstrated that these peptidoglycan containing OMVs upregulated NF-kappaB and NOD1-dependent responses in vitro. These OMVs entered epithelial cells through lipid rafts thereby inducing NOD1-dependent responses in vitro. Moreover, OMVs delivered intragastrically to mice-induced innate and adaptive immune responses via a NOD1-dependent but TLR-independent mechanism. Collectively, our findings identify OMVs as a generalized mechanism whereby Gram-negative bacteria deliver peptidoglycan to cytosolic NOD1. We propose that OMVs released by bacteria in vivo may promote inflammation and pathology in infected hosts.
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.CYTO.2015.02.018
Abstract: The host has developed an array of systems that enables protection against infection and response to injury, ultimately resulting in the generation of a pro-inflammatory response. The most rapid immune response is mediated via the innate immune system, which is comprised of germ line encoded pathogen recognition receptors (PRRs). This PRR mediated system functions by specifically recognizing conserved structures of microbial molecules or products, known as microbial-associated molecular patterns (MAMPs), ultimately enabling transduction of signaling cascades, gene transcription and the development of a pro-inflammatory innate immune response. The intracellular PRRs nucleotide-binding oligomerization domain protein 1 (NOD1) and NOD2 will be the focus of this review. A brief overview of NOD1 and NOD2 and recent advances in the field regarding the intracellular location and mechanisms of NOD1 signaling will be discussed. These new findings have broadened our understanding of the mechanisms whereby NOD1 signaling results in the induction of the cellular degradation pathway of autophagy and the development of pro-inflammatory responses that activate the adaptive immune system.
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.CHOM.2014.04.001
Abstract: The intracellular innate immune receptor NOD1 detects Gram-negative bacterial peptidoglycan (PG) to induce autophagy and inflammatory responses in host cells. To date, the intracellular compartment in which PG is detected by NOD1 and whether NOD1 directly interacts with PG are two questions that remain to be resolved. To address this, we used outer membrane vesicles (OMVs) from pathogenic bacteria as a physiological mechanism to deliver PG into the host cell cytosol. We report that OMVs induced autophagosome formation and inflammatory IL-8 responses in epithelial cells in a NOD1- and RIP2-dependent manner. PG contained within OMVs colocalized with both NOD1 and RIP2 in EEA1-positive early endosomes. Further, we provide evidence for direct interactions between NOD1 and PG. Collectively, these findings demonstrate that NOD1 detects PG within early endosomes, thereby promoting RIP2-dependent autophagy and inflammatory signaling in response to bacterial infection.
Publisher: Public Library of Science (PLoS)
Date: 27-03-2013
Publisher: Public Library of Science (PLoS)
Date: 04-2010
Publisher: Wiley
Date: 09-02-2015
DOI: 10.1111/HEL.12196
Abstract: Multiple studies have established the importance of the tol-pal gene cluster in bacterial cell membrane integrity and outer membrane vesicle (OMV) formation in Escherichia coli. In contrast, the functions of Tol-Pal proteins in pathogenic organisms, including those of the Epsilonproteobacteria, remain poorly if at all defined. The aim of this study was to characterize the roles of two key components of the Tol-Pal system, TolB and Pal, in OMV formation in the pathogenic bacterium, Helicobacter pylori. H. pylori ΔtolB, Δpal and ΔtolBpal mutants, as well as complemented strains, were generated and assessed for changes in morphology and OMV production by scanning electron microscopy and enzyme-linked immunoassay (ELISA), respectively. The protein content and pro-inflammatory properties of OMVs were determined by mass spectroscopy and interleukin-8 (IL-8) ELISA on culture supernatants from OMV-stimulated cells, respectively. H. pylori ΔtolB and Δpal bacteria exhibited aberrant cell morphology and/or flagella biosynthesis. Importantly, the disruption of H. pylori tolB but not pal resulted in a significant increase in OMV production. The OMVs from H. pylori ΔtolB and Δpal bacteria harbored many of the major outer membrane and virulence proteins observed in wild-type (WT) OMVs. Interestingly, ΔtolB, Δpal and ΔtolBpal OMVs induced significantly higher levels of IL-8 production by host cells, compared with WT OMVs. This work demonstrates that TolB and Pal are important for membrane integrity in H. pylori. Moreover, it shows how H. pylori tolB-pal genes may be manipulated to develop "hypervesiculating" strains for vaccine purposes.
Publisher: Frontiers Media SA
Date: 02-07-2018
Publisher: Proceedings of the National Academy of Sciences
Date: 20-01-2015
Abstract: Maintaining physiological balance is vital in the primary response to infectious and other stress stimuli to avert damaging inflammation. Delineation of the cell regulatory processes that control inflammatory processes better enable the development of informed strategies to treat associated pathologies. Toward this end, we identify that the promyelocytic leukemia zinc finger (PLZF) transcription factor limits pathogen-induced inflammation. PLZF stabilizes a repressor complex that encompasses histone deacetylase activity, which modifies the state of chromatin. This activity maintains homeostasis by decreasing the scale of induction of select immune response genes. In the absence of PLZF, the chromatin structure is altered, enabling active transcriptional complexes to immediately assemble on gene promoters, resulting in inordinate production of inflammatory cytokines.
Publisher: Hindawi Limited
Date: 05-2010
DOI: 10.1111/J.1462-5822.2009.01421.X
Abstract: The cytosolic innate immune molecule, NOD1, recognizes peptidoglycan (PG) delivered to epithelial cells via the Helicobacter pylori cag pathogenicity island (cagPAI), and has been implicated in host defence against cagPAI(+)H. pylori bacteria. To further clarify the role of NOD1 in host defence, we investigated NOD1-dependent regulation of human beta-defensins (DEFBs) in two epithelial cell lines. Our findings identify that NOD1 activation, via either cagPAI(+) bacteria or internalized PG, was required for DEFB4 and DEFB103 expression in HEK293 cells. To investigate cell type-specific induction of DEFB4 and DEFB103, we generated stable NOD1'knockdown' (KD) and control AGS cells. Reporter gene assay and RT-PCR analyses revealed that only DEFB4 was induced in an NOD1-/cagPAI-dependent fashion in AGS cells. Moreover, culture supernatants from AGS control, but not AGS NOD1 KD cells, stimulated with cagPAI(+)H. pylori, significantly reduced H. pylori bacterial numbers. siRNA studies confirmed that human beta-defensin 2 (hBD-2), but not hBD-3, contributes to the antimicrobial activity of AGS cell supernatants against H. pylori. This study demonstrates, for the first time, the involvement of NOD1 and hBD-2 in direct killing of H. pylori bacteria by epithelial cells and confirms the importance of NOD1 in host defence mechanisms against cagPAI(+)H. pylori infection.
Publisher: Wiley
Date: 04-2021
DOI: 10.1002/JEV2.12080
Abstract: Gram‐positive bacteria ubiquitously produce membrane vesicles (MVs), and although they contribute to biological functions, our knowledge regarding their composition and immunogenicity remains limited. Here we examine the morphology, contents and immunostimulatory functions of MVs produced by three Staphylococcus aureus strains a methicillin resistant clinical isolate, a methicillin sensitive clinical isolate and a laboratory‐adapted strain. We observed differences in the number and morphology of MVs produced by each strain and showed that they contain microbe‐associated molecular patterns (MAMPs) including protein, nucleic acids and peptidoglycan. Analysis of MV‐derived RNA indicated the presence of small RNA (sRNA). Furthermore, we detected variability in the amount and composition of protein, nucleic acid and peptidoglycan cargo carried by MVs from each S. aureus strain. S. aureus MVs activated Toll‐like receptor (TLR) 2, 7, 8, 9 and nucleotide‐binding oligomerization domain containing protein 2 (NOD2) signalling and promoted cytokine and chemokine release by epithelial cells, thus identifying that MV‐associated MAMPs including DNA, RNA and peptidoglycan are detected by pattern recognition receptors (PRRs). Moreover, S. aureus MVs induced the formation of and colocalized with autophagosomes in epithelial cells, while inhibition of lysosomal acidification using bafilomycin A1 resulted in accumulation of autophagosomal puncta that colocalized with MVs, revealing the ability of the host to degrade MVs via autophagy. This study reveals the ability of DNA, RNA and peptidoglycan associated with MVs to activate PRRs in host epithelial cells, and their intracellular degradation via autophagy. These findings advance our understanding of the immunostimulatory roles of Gram‐positive bacterial MVs in mediating pathogenesis, and their intracellular fate within the host.
Publisher: Hindawi Limited
Date: 22-07-2010
DOI: 10.1002/HUMU.21321
Abstract: Human Toll-like receptors (TLRs) TLR7, TLR8, and TLR9 are important immune sensors of foreign nucleic acids encountered by phagocytes. Although there is growing evidence implicating TLR7 and TLR9 in the detection of intracellular pathogenic bacteria, characterization of such a role for TLR8 is currently lacking. A recent genetic study has correlated the presence of a TLR8 single nucleotide polymorphism (SNP) (rs3764880:A>G p.Met1Val) with the development of active tuberculosis, suggesting a role for TLR8 in the detection of phagosomal bacteria. Here we provide the first direct evidence that TLR8 sensing is activated in human monocytic cells following Helicobacter pylori phagocytosis. In addition, we show that rs3764880 fine tunes translation of the two TLR8 main isoforms, without affecting protein function. Although we show that TLR8 variant 2 (TLR8v2) is the prevalent form of TLR8 contributing to TLR8 function, we also uncover a role for the TLR8 long isoform (TLR8v1) in the positive regulation of TLR8 function in CD16(+)CD14(+) differentiated monocytes. Thus, TLR8 sensing can be activated following bacterial phagocytosis, and rs3764880 may play a role in the modulation of TLR8-dependent microbicidal response of infected macrophages.
Publisher: American Society for Microbiology
Date: 02-2007
DOI: 10.1128/AEM.01675-06
Abstract: We examined the impact of Helicobacter pylori infection on the murine gastric microbiota by culture and terminal-restriction fragment length polymorphism and found that neither acute nor chronic H. pylori infection substantially affected the gastric microbial composition. Interestingly, the total H. pylori burden detected by real-time PCR was significantly higher than that revealed by viable counts, suggesting that the antigenic load sustaining H. pylori -induced gastritis could be considerably higher than previously believed.
Publisher: Oxford University Press (OUP)
Date: 07-06-2012
DOI: 10.1093/NAR/GKS521
Publisher: Wiley
Date: 03-01-2012
DOI: 10.1111/J.1523-5378.2011.00914.X
Abstract: Growth of Helicobacter pyloriin vitro depends on supplementation of the medium with blood or serum. However, these supplements often require frozen storage and can show batch-to-batch variation, resulting in differences in bacterial growth. In this study, we introduce the use of a commercially available, lipid-rich supplement called AlbuMAX II(®) (Gibco BRL, Grand Island, NY, USA) for use as a serum/blood replacement for H. pylori culture. The growth of H. pylori on solid and liquid media was examined by comparing growth after supplementation with horse blood, fetal calf serum, β-cyclodextrin or AlbuMAX II(®) (Gibco BRL). Human gastric adenocarcinoma (AGS) cellular responses to H. pylori were measured by NF-κB luciferase assays and IL-8 ELISA. We show that the growth of H. pylori on both solid and liquid media containing AlbuMAX II(®) (Gibco BRL) were comparable to levels obtained on blood agar or liquid media supplemented with serum. Growth was consistently higher in media supplemented with AlbuMAX II(®) (Gibco BRL) than media containing β-cyclodextrin. Furthermore, bacteria grown in AlbuMAX II(®) (Gibco BRL) induced proinflammatory responses in AGS cells. AlbuMAX II(®) (Gibco BRL) can be used as a serum/blood replacement for the cultivation of H. pylori in solid and liquid media. This medium could be useful for an improved understanding of H. pylori metabolism or for antigen production. Furthermore, AlbuMAX II(®) (Gibco BRL) may be suitable for use in remote locations, particularly in areas where frozen storage of serum may be a problem.
Publisher: Springer Science and Business Media LLC
Date: 15-05-2015
DOI: 10.1038/NRI3837
Abstract: Gram-negative bacteria shed extracellular outer membrane vesicles (OMVs) during their normal growth both in vitro and in vivo. OMVs are spherical, bilayered membrane nanostructures that contain many components found within the parent bacterium. Until recently, OMVs were dismissed as a by-product of bacterial growth however, findings within the past decade have revealed that both pathogenic and commensal bacteria can use OMVs to manipulate the host immune response. In this Review, we describe the mechanisms through which OMVs induce host pathology or immune tolerance, and we discuss the development of OMVs as innovative nanotechnologies.
Publisher: Public Library of Science (PLoS)
Date: 29-04-2009
Publisher: Frontiers Media SA
Date: 20-09-2022
DOI: 10.3389/FIMMU.2022.970725
Abstract: The release of bacterial membrane vesicles (BMVs) has become recognized as a key mechanism used by both pathogenic and commensal bacteria to activate innate immune responses in the host and mediate immunity. Outer membrane vesicles (OMVs) produced by Gram-negative bacteria can harbor various immunogenic cargo that includes proteins, nucleic acids and peptidoglycan, and the composition of OMVs strongly influences their ability to activate host innate immune receptors. Although various Gram-negative pathogens can produce OMVs that are enriched in immunogenic cargo compared to their parent bacteria, the ability of OMVs produced by commensal organisms to be enriched with immunostimulatory contents is only recently becoming known. In this study, we investigated the cargo associated with OMVs produced by the intestinal commensal Bacteroides fragilis and determined their ability to activate host innate immune receptors. Analysis of B. fragilis OMVs revealed that they packaged various biological cargo including proteins, DNA, RNA, lipopolysaccharides (LPS) and peptidoglycan, and that this cargo could be enriched in OMVs compared to their parent bacteria. We visualized the entry of B. fragilis OMVs into intestinal epithelial cells, in addition to the ability of B. fragilis OMVs to transport bacterial RNA and peptidoglycan cargo into Caco-2 epithelial cells. Using HEK-Blue reporter cell lines, we identified that B. fragilis OMVs could activate host Toll-like receptors (TLR)-2, TLR4, TLR7 and nucleotide-binding oligomerization domain-containing protein 1 (NOD1), whereas B. fragilis bacteria could only induce the activation of TLR2. Overall, our data demonstrates that B. fragilis OMVs activate a broader range of host innate immune receptors compared to their parent bacteria due to their enrichment of biological cargo and their ability to transport this cargo directly into host epithelial cells. These findings indicate that the secretion of OMVs by B. fragilis may facilitate immune crosstalk with host epithelial cells at the gastrointestinal surface and suggests that OMVs produced by commensal bacteria may preferentially activate host innate immune receptors at the mucosal gastrointestinal tract.
Publisher: American Society for Microbiology
Date: 31-08-2010
Abstract: Despite recent advances in our understanding of how Helicobacter pylori causes disease, the factors that allow this pathogen to persist in the stomach have not yet been fully characterized. To identify new virulence factors in H. pylori , we generated low-infectivity variants of a mouse-colonizing H. pylori strain using the classical technique of in vitro attenuation. The resulting variants and their highly infectious progenitor bacteria were then analyzed by global gene expression profiling. The gene expression levels of five open reading frames (ORFs) were significantly reduced in low-infectivity variants, with the most significant changes observed for ORFs HP1583 and HP1582. These ORFs were annotated as encoding homologs of the Escherichia coli vitamin B 6 biosynthesis enzymes PdxA and PdxJ. Functional complementation studies with E. coli confirmed H. pylori PdxA and PdxJ to be bona fide homologs of vitamin B 6 biosynthesis enzymes. Importantly, H. pylori PdxA was required for optimal growth in vitro and was shown to be essential for chronic colonization in mice. In addition to having a well-known metabolic role, vitamin B 6 is necessary for the synthesis of glycosylated flagella and for flagellum-based motility in H. pylori . Thus, for the first time, we identify vitamin B 6 biosynthesis enzymes as novel virulence factors in bacteria. Interestingly, pdxA and pdxJ orthologs are present in a number of human pathogens, but not in mammalian cells. We therefore propose that PdxA/J enzymes may represent ideal candidates for therapeutic targets against bacterial pathogens. IMPORTANCE Approximately half of the world’s population is infected with H. pylori , yet how H. pylori bacteria establish chronic infections in human hosts remains elusive. From gene array studies, we identified two genes as representing potentially novel colonization factors for H. pylori . These genes encoded enzymes involved in the synthesis of vitamin B 6 , an important molecule for many metabolic reactions in living organisms. Little is currently known regarding vitamin B 6 biosynthesis in human pathogens. We showed that mutant H. pylori bacteria lacking an enzyme involved in de novo vitamin B 6 biosynthesis, PdxA, were unable to synthesize motility appendages (flagella) and were unable to establish chronic colonization in mice. Thus, this work identifies vitamin B 6 biosynthesis enzymes as novel virulence factors for bacterial pathogens. Interestingly, a number of human pathogens, but not their mammalian hosts, possess these genes, which suggests that Pdx enzymes may represent ideal candidates for new therapeutic targets.
Publisher: Elsevier BV
Date: 06-2021
Publisher: MDPI AG
Date: 16-06-2017
DOI: 10.3390/IJMS18061287
Publisher: Springer US
Date: 2022
DOI: 10.1007/978-1-0716-2449-4_4
Abstract: Bacterial membrane vesicles (BMVs) released by Gram-negative and Gram-positive bacteria are a bona fide secretion system that enable the dissemination of bacterial effector molecules, and can trigger a range of responses in the host. The study of BMV production, composition, and functions can give insights into their roles in mediating bacterial survival, pathogenesis, and disease. Furthermore, BMVs can be harnessed to develop cutting-edge nano-therapeutics including targeted chemotherapy delivery, antimicrobials, and novel vaccines. Here we describe routine methods that can be used for small- or large-scale production, isolation, and purification of outer membrane vesicles produced by Gram-negative bacteria, and membrane vesicles produced by Gram-positive bacteria, which we collectively refer to as BMVs. We discuss methods that can be used to visualize BMVs by electron microscopy, and to quantify their DNA, RNA, and protein cargo. We outline a method for the fluorescent labeling of BMVs that can be applied to examine their ability to interact with and enter host cells using a range of in vitro and in vivo biological assays. Finally, we provide a cell culture-based method that can be used to examine a range of immunogenic properties of BMVs, including their cytotoxicity, ability to activate pathogen-recognition receptors (PRRs), induce autophagy and cytokine responses, and modulate cellular pathways.
Publisher: Public Library of Science (PLoS)
Date: 15-10-2013
Publisher: Springer US
Date: 2022
DOI: 10.1007/978-1-0716-2449-4_1
Abstract: Detection of microbes by the host is essential to restrict microbial colonization, to clear pathogens, and to mount adapted defense reactions, and thus is the key function of the innate immune systems of plants and mammals. Here we provide an introduction into pathogen recognition by the innate immune system of both plants and animals. We will particularly focus on the concept of effector-triggered immunity, and similarities and differences in its function between plants and animals.
Publisher: American Society for Microbiology
Date: 22-12-2021
DOI: 10.1128/SPECTRUM.01273-21
Abstract: Recent years have seen a surge in interest in the roles of BMVs in host-microbe interactions and interbacterial communication. As a result of such rapid growth in the field, there is a lack of uniformity in BMV enumeration.
Publisher: American Society for Microbiology
Date: 06-2006
DOI: 10.1128/IAI.01314-05
Abstract: Gastric Helicobacter spp. induce chronic gastritis that may lead to ulceration and dysplasia. The host elicits a T helper 1 (Th1) response that is fundamental to the pathogenesis of these bacteria. We analyzed immune responses in Helicobacter -infected, normal mice depleted of CD4 + CD25 + T cells to investigate the in vivo role of regulatory T cells (Tregs) in the modulation of Helicobacter immunopathology. BALB/c and transgenic mice were depleted of CD4 + CD25 + T cells by administration of an anti-CD25 antibody either at the time of infection with Helicobacter or during chronic infection and gastritis. Depletion of CD25 + Tregs prior to and during infection of mice with Helicobacter spp. did not affect either bacterial colonization or severity of gastritis. Depletion of CD25 + Tregs was associated with increased Helicobacter -specific antibody levels and an altered isotype distribution. Paragastric lymph node cells from CD25 + Treg-depleted and control infected mice showed similar proliferation to Helicobacter antigens, but only cells from anti-CD25-treated animals secreted Th2 cytokines. CD25 + Tregs do not control the level of gastritis induced by gastric Helicobacter spp. in normal, thymus-intact BALB/c mice. However, CD25 + Tregs influence the cytokine and antibody responses induced by infection. Autoimmune gastritis is not induced in Helicobacter -infected mice depleted of CD25 + Tregs but is induced in CD25 + Treg-depleted mice, which have a higher frequency of autoreactive T cells.
Publisher: Frontiers Media SA
Date: 06-06-2017
Publisher: MDPI AG
Date: 20-10-2023
Publisher: Springer International Publishing
Date: 2020
Publisher: Springer Science and Business Media LLC
Date: 26-06-2023
DOI: 10.1038/S41467-023-39487-1
Abstract: The interleukin-1 family members, IL-1β and IL-18, are processed into their biologically active forms by multi-protein complexes, known as inflammasomes. Although the inflammasome pathways that mediate IL-1β processing in myeloid cells have been defined, those involved in IL-18 processing, particularly in non-myeloid cells, are still not well understood. Here we report that the host defence molecule NOD1 regulates IL-18 processing in mouse epithelial cells in response to the mucosal pathogen, Helicobacter pylori . Specifically, NOD1 in epithelial cells mediates IL-18 processing and maturation via interactions with caspase-1, instead of the canonical inflammasome pathway involving RIPK2, NF-κB, NLRP3 and ASC. NOD1 activation and IL-18 then help maintain epithelial homoeostasis to mediate protection against pre-neoplastic changes induced by gastric H. pylori infection in vivo. Our findings thus demonstrate a function for NOD1 in epithelial cell production of bioactive IL-18 and protection against H. pylori -induced pathology.
Publisher: Wiley
Date: 17-12-2018
Abstract: Gram-negative bacteria release outer membrane vesicles (OMVs) as part of their normal growth that contain a range of cargo from their parent bacterium, including DNA, RNA, and proteins. The protein content of OMVs is suggested to be similar in composition to various sub-cellular locations of their parent bacterium. However, very little is known regarding the effect of bacterial growth stage on the size, content, and selective packaging of proteins into OMVs. In this study, the global proteome of Helicobacter pylori and their OMVs throughout bacterial growth are examined to determine if bacterial growth stage affected OMV cargo composition. Analysis of OMVs produced by H. pylori reveals that bacterial growth stage affects the size, composition, and selection of protein cargo into OMVs. Proteomic analysis identifies that the proteome of H. pylori OMVs is vastly different throughout bacterial growth and that OMVs contain a range of proteins compared to their parent bacteria. In addition, bacterial growth stage affects the ability of OMVs to induce the production of IL-8 by human epithelial cells. Therefore, the findings identify that the size, proteome, and immunogenicity of OMVs produced during various stages of bacterial growth is not comparable. Collectively, these findings highlight the importance of considering the bacterial growth stage from which OMVs are isolated, as this will impact their size, protein composition, and ultimately their biological functions.
Publisher: Springer Science and Business Media LLC
Date: 06-02-2009
Abstract: Enteropathogenic Escherichia coli (EPEC) is an attaching and effacing (A/E) pathogen that possesses a type III secretion system (T3SS) encoded within the locus of enterocyte effacement (LEE). The LEE is essential for A/E lesion formation and directs the secretion and translocation of multiple LEE-encoded and non-LEE encoded effector proteins into the cytosol of infected cells. In this study we used proteomics to compare proteins exported to the culture supernatant by wild type EPEC E2348/69, a Δ espADB mutant and a Δ escF T3SS mutant. We observed that flagellin was consistently and strongly present in the secretome of wild type EPEC and the Δ espADB mutant but present only weakly in the secretome of the Δ escF mutant. Given the ancestral relationship between the flagella export apparatus and virulence associated T3SSs, we investigated whether FliC could utilise the LEE-encoded T3SS for export. In the absence of a functional flagella export apparatus, we showed that FliC could be secreted by the LEE-encoded T3SS and stimulate (Toll-like receptor 5) TLR5 signalling but could not confer motility. Since the secretion of FliC during A/E lesion formation would presumably be disadvantageous for the pathogen, we propose that virulence associated T3SSs and flagella T3SSs have evolved through a system of chaperones and complex regulatory pathways to be functional at different times to ensure that FliC secretion does not occur during T3SS effector translocation.
Publisher: American Society for Microbiology
Date: 13-04-2023
DOI: 10.1128/SPECTRUM.05179-22
Abstract: Bacterial membrane vesicles (BMVs) mediate interbacterial communication, and their ability to package DNA specifically contributes to biofilm formation, antibiotic resistance, and HGT between bacteria. However, the ability of P. aeruginosa OMVs to mediate HGT has not yet been demonstrated.
Publisher: Springer New York
Date: 2013
Publisher: Wiley
Date: 08-2007
Abstract: Eukaryotic organisms of the plant and animal kingdoms have developed evolutionarily conserved systems of defence against microbial pathogens. These systems depend on the specific recognition of microbial products or structures by molecules of the host innate immune system. The first mammalian molecules shown to be involved in innate immune recognition of, and defence against, microbial pathogens were the Toll-like receptors (TLRs). These proteins are predominantly but not exclusively located in the transmembrane region of host cells. Interestingly, mammalian hosts were subsequently found to also harbour cytosolic proteins with analogous structures and functions to plant defence molecules. The members of this protein family exhibit a tripartite domain structure and are characterized by a central nucleotide-binding oligomerization domain (NOD). Moreover, in common with TLRs, most NOD proteins possess a C-terminal leucine-rich repeat (LRR) domain, which is required for the sensing of microbial products and structures. Recently, the name 'nucleotide-binding domain and LRR' (NLR) was coined to describe this family of proteins. It is now clear that NLR proteins play key roles in the cytoplasmic recognition of whole bacteria or their products. Moreover, it has been demonstrated in animal studies that NLRs are important for host defence against bacterial infection. This review will particularly focus on two subfamilies of NLR proteins, the NODs and 'NALPs', which specifically recognize bacterial products, including cell wall peptidoglycan and flagellin. We will discuss the downstream signalling events and host cell responses to NLR recognition of such products, as well as the strategies that bacterial pathogens employ to trigger NLR signalling in host cells. Cytosolic recognition of microbial factors by NLR proteins appears to be one mechanism whereby the innate immune system is able to discriminate between pathogenic bacteria ('foe') and commensal ('friendly') members of the host microflora.
Publisher: Springer International Publishing
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 17-03-2023
Publisher: American Society for Microbiology
Date: 11-2010
DOI: 10.1128/IAI.00439-10
Abstract: Infection with Helicobacter pylori cag pathogenicity island ( cag PAI)-positive strains is associated with more destructive tissue damage and an increased risk of severe disease. The cag PAI encodes a type IV secretion system (TFSS) that delivers the bacterial effector molecules CagA and peptidoglycan into the host cell cytoplasm, thereby inducing responses in host cells. It was previously shown that interactions between CagL, present on the TFSS pilus, and host α 5 β 1 integrin molecules were critical for CagA translocation and the induction of cytoskeletal rearrangements in epithelial cells. As the α 5 β 1 integrin is found in cholesterol-rich microdomains (known as lipid rafts), we hypothesized that these domains may also be involved in the induction of proinflammatory responses mediated by NOD1 recognition of H. pylori peptidoglycan. Indeed, not only did methyl-β-cyclodextrin depletion of cholesterol from cultured epithelial cells have a significant effect on the levels of NF-κB and interleukin-8 (IL-8) responses induced by H. pylori bacteria with an intact TFSS ( P 0.05), but it also interfered with TFSS-mediated peptidoglycan delivery to cells. Both of these effects could be restored by cholesterol replenishment of the cells. Furthermore, we demonstrated for the first time the involvement of α 5 β 1 integrin in the induction of proinflammatory responses by H. pylori. Taking the results together, we propose that α 5 β 1 integrin, which is associated with cholesterol-rich microdomains at the host cell surface, is required for NOD1 recognition of peptidoglycan and subsequent induction of NF-κB-dependent responses to H. pylori . These data implicate cholesterol-rich microdomains as a novel platform for TFSS-dependent delivery of bacterial products to cytosolic pathogen recognition molecules.
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1053/J.GASTRO.2007.07.003
Abstract: The MUC1 mucin is expressed on the cell surface of epithelial cells lining the gastric mucosa. Epidemiologic studies suggest that functional allelic variations in the MUC1 gene may play a role in human susceptibility to Helicobacter pylori-associated pathologies, including gastric adenocarcinoma. We have evaluated the impact of Muc1 expression on the colonization and pathogenesis of gastric Helicobacter infections. Wild-type and Muc1-deficient mice were infected with H pylori and colonization and gastritis levels determined. Primary gastric cells were used to examine the impact of Muc1 expression on bacterial adherence. Mice lacking Muc1 were colonized by 5-fold more H pylori within 1 day of infection, and this difference was maintained for at least 2 months postinfection. Mice heterozygous for the null Muc1 allele developed intermediate bacterial colonization. Although wild-type mice developed only a mild gastritis when infected for 2 months with H pylori, Muc1(-/-) mice developed an atrophic gastritis marked by loss of parietal cells. We demonstrate H pylori adhesion to purified MUC1 and significantly increased adhesion to cultured murine Muc1 null gastric epithelial cells, suggesting that Muc1 acts as a decoy limiting binding to the cell surface. Muc1 provides a protective barrier, which limits both acute and chronic colonization by H pylori, as well as playing a major role in limiting the inflammation induced by Helicobacter infection. We propose that Muc1 restricts access of H pylori to the epithelial surface, hence reducing exposure of the host to proinflammatory bacterial products.
Publisher: Informa UK Limited
Date: 02-01-2016
Start Date: 2019
End Date: 12-2023
Amount: $375,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2011
End Date: 12-2013
Amount: $240,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2020
End Date: 12-2020
Amount: $1,275,000.00
Funder: Australian Research Council
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