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Godbold GD, Scholz MB. Annotation of Functions of Sequences of Concern and Its Relevance to the New Biosecurity Regulatory Framework in the United States. APPLIED BIOSAFETY 2024; 29:142-149. [PMID: 39372509 PMCID: PMC11447126 DOI: 10.1089/apb.2023.0030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/08/2024]
Abstract
Introduction Recent regulations from United States Government agencies reshape the screening of synthetic nucleic acids. These take a step away from categorizing hazard on the basis of "bad" taxa and invoke the function of the sequence in pathogenesis or intoxication. Ascertaining functions related to pathogenesis and distinguishing these from other molecular abilities that are unproblematic is not simple. Some have suggested that this information can be readily obtained from existing databases of pathogens. Objectives We evaluate how virulence factors are described in current databases of pathogens and their adequacy for biothreat data science. We discuss limitations of how virulence factors have been conceived and propose using the sequence of concern (SoC) term to distinguish sequences with biothreat from those without. We discuss ways in which databases of SoCs might be implemented for research and regulatory purposes. We describe ongoing work improving functional descriptions of SoCs. Methods We assess the adequacy of descriptions of virulence factors in pathogen databases following extensive engagement with the literature in microbial pathogenesis. Results/Conclusions Descriptions of virulence factors in pathogen databases are inadequate for understanding biothreats. Many are not biothreats and would not be concerning if transferred to another pathogen. New gene ontology terms have been authored, and those specific to pathogenic viral processes are being generalized to make them relevant to other pathogenic taxa. This allows better understanding by humans and better recognition by machines. A database of annotated functions of SoCs could benefit the evolving biosecurity regulatory framework in the United States.
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2
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Burns L, Le Mauff F, Gruenheid S. Direct evidence of host-mediated glycosylation of NleA and its dependence on interaction with the COPII complex. Gut Microbes 2024; 16:2305477. [PMID: 38298145 PMCID: PMC10841024 DOI: 10.1080/19490976.2024.2305477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2024] Open
Abstract
Non-LEE-encoded Effector A (NleA) is a type III secreted effector protein of enterohaemorrhagic and enteropathogenic Escherichia coli as well as the related mouse pathogen Citrobacter rodentium. NleA translocation into host cells is essential for virulence. We previously published several lines of evidence indicating that NleA is modified by host-mediated mucin-type O-linked glycosylation, the first example of a bacterial effector protein modified in this way. In this study, we use lectins to provide direct evidence for the modification of NleA by O-linked glycosylation and determine that the interaction of NleA with the COPII complex is necessary for this modification to occur.
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Affiliation(s)
- Lindsay Burns
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
| | - François Le Mauff
- Infectious Disease and Immunity in Global Health Program, Research Institute of the McGill University Health Centre, Montreal, QC, Canada
- Glyco-NET Integrated Services, Microbial Glycomic Node, Montreal, QC, Canada
- McGill Interdisciplinary Initiative in Infection and Immunity, Montreal, QC, Canada
| | - Samantha Gruenheid
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
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3
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Godbold GD, Hewitt FC, Kappell AD, Scholz MB, Agar SL, Treangen TJ, Ternus KL, Sandbrink JB, Koblentz GD. Improved understanding of biorisk for research involving microbial modification using annotated sequences of concern. Front Bioeng Biotechnol 2023; 11:1124100. [PMID: 37180048 PMCID: PMC10167326 DOI: 10.3389/fbioe.2023.1124100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 04/11/2023] [Indexed: 05/15/2023] Open
Abstract
Regulation of research on microbes that cause disease in humans has historically been focused on taxonomic lists of 'bad bugs'. However, given our increased knowledge of these pathogens through inexpensive genome sequencing, 5 decades of research in microbial pathogenesis, and the burgeoning capacity of synthetic biologists, the limitations of this approach are apparent. With heightened scientific and public attention focused on biosafety and biosecurity, and an ongoing review by US authorities of dual-use research oversight, this article proposes the incorporation of sequences of concern (SoCs) into the biorisk management regime governing genetic engineering of pathogens. SoCs enable pathogenesis in all microbes infecting hosts that are 'of concern' to human civilization. Here we review the functions of SoCs (FunSoCs) and discuss how they might bring clarity to potentially problematic research outcomes involving infectious agents. We believe that annotation of SoCs with FunSoCs has the potential to improve the likelihood that dual use research of concern is recognized by both scientists and regulators before it occurs.
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Affiliation(s)
| | | | | | | | - Stacy L. Agar
- Signature Science, LLC, Charlottesville, VA, United States
| | - Todd J. Treangen
- Department of Computer Science, Rice University, Houston, TX, United States
| | | | - Jonas B. Sandbrink
- Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Gregory D. Koblentz
- Schar School of Policy and Government, George Mason University, Arlington, VA, United States
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4
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Burns L, Giannakopoulou N, Zhu L, Xu YZ, Khan RH, Bekal S, Schurr E, Schmeing TM, Gruenheid S. The bacterial virulence factor NleA undergoes host-mediated O-linked glycosylation. Mol Microbiol 2023; 119:161-173. [PMID: 36196760 DOI: 10.1111/mmi.14989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 09/01/2022] [Accepted: 09/29/2022] [Indexed: 11/28/2022]
Abstract
Enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC) are gastrointestinal pathogens responsible for severe diarrheal illness. EHEC and EPEC form "attaching and effacing" lesions during colonization and, upon adherence, inject proteins directly into host intestinal cells via the type III secretion system (T3SS). Injected bacterial proteins have a variety of functions but generally alter host cell biology to favor survival and/or replication of the pathogen. Non-LEE-encoded effector A (NleA) is a T3SS-injected effector of EHEC, EPEC, and the related mouse pathogen Citrobacter rodentium. Studies in mouse models indicate that NleA has an important role in bacterial virulence. However, the mechanism by which NleA contributes to disease remains unknown. We have determined that the following translocation into host cells, a serine and threonine-rich region of NleA is modified by host-mediated mucin-type O-linked glycosylation. Surprisingly, this region was not present in several clinical EHEC isolates. When expressed in C. rodentium, a non-modifiable variant of NleA was indistinguishable from wildtype NleA in an acute mortality model but conferred a modest increase in persistence over the course of infection in mixed infections in C57BL/6J mice. This is the first known example of a bacterial effector being modified by host-mediated O-linked glycosylation. Our data also suggests that this modification may confer a selective disadvantage to the bacteria during in vivo infection.
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Affiliation(s)
- Lindsay Burns
- McGill Research Centre on Complex Traits and Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada
| | - Natalia Giannakopoulou
- McGill Research Centre on Complex Traits and Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada
| | - Lei Zhu
- McGill Research Centre on Complex Traits and Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada
| | - Yong Zhong Xu
- Program in Infectious Diseases and Global Health, The Research Institute of the McGill University Health Centre and McGill International TB Centre, Department of Medicine, Faculty of Medicine, McGill University, Montréal, Québec, Canada
| | - Rufaida H Khan
- Laboratoire de Santé Publique du Québec, Institut National de Santé Publique du Québec, Sainte-Anne-de-Bellevue, Québec, Canada.,Department of Food Science and Agricultural Chemistry, McGill University, Sainte-Anne-de-Bellevue, Québec, Canada
| | - Sadjia Bekal
- Laboratoire de Santé Publique du Québec, Institut National de Santé Publique du Québec, Sainte-Anne-de-Bellevue, Québec, Canada.,Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montréal, Québec, Canada
| | - Erwin Schurr
- Program in Infectious Diseases and Global Health, The Research Institute of the McGill University Health Centre and McGill International TB Centre, Department of Medicine, Faculty of Medicine, McGill University, Montréal, Québec, Canada.,Department of Biochemistry, Faculty of Medicine, McGill University, Montréal, Québec, Canada
| | - T Martin Schmeing
- Department of Biochemistry, Faculty of Medicine, McGill University, Montréal, Québec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montréal, Québec, Canada
| | - Samantha Gruenheid
- McGill Research Centre on Complex Traits and Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada
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Kautzman AM, Mobulakani JMF, Marrero Cofino G, Quenum AJI, Cayarga AA, Asselin C, Fortier LC, Ilangumaran S, Menendez A, Ramanathan S. Interleukin 15 in murine models of colitis. Anat Rec (Hoboken) 2022; 306:1111-1130. [PMID: 35899872 DOI: 10.1002/ar.25044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 06/28/2022] [Accepted: 07/05/2022] [Indexed: 11/09/2022]
Abstract
Inflammatory bowel diseases (IBDs) are characterized by abnormal, non-antigen specific chronic inflammation of unknown etiology. Genome-wide association studies show that many IBD genetic susceptibility loci map to immune function genes and compelling evidence indicate that environmental factors play a critical role in IBD pathogenesis. Clinical and experimental evidence implicate the pro-inflammatory cytokine IL-15 in the pathogenesis of IBD. IL-15 and IL-15α expression is increased in the inflamed mucosa of IBD patients. IL-15 contributes to the maintenance of different cell subsets in the intestinal mucosa. However, very few studies have addressed the role of IL-15 in pre-clinical models of colitis. In this study, we use three well-characterized models of experimental colitis to determine the contribution of IL-15 to pathological intestinal inflammation.
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Affiliation(s)
- Alicia Molina Kautzman
- Department of Immunology and Cell Biology, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | | | - Gisela Marrero Cofino
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | | | - Anny Armas Cayarga
- Department of Immunology and Cell Biology, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Claude Asselin
- Department of Immunology and Cell Biology, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,CRCHUS, Sherbrooke, Quebec, Canada
| | - Louis-Charles Fortier
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,CRCHUS, Sherbrooke, Quebec, Canada
| | - Subburaj Ilangumaran
- Department of Immunology and Cell Biology, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,CRCHUS, Sherbrooke, Quebec, Canada
| | - Alfredo Menendez
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,CRCHUS, Sherbrooke, Quebec, Canada
| | - Sheela Ramanathan
- Department of Immunology and Cell Biology, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,CRCHUS, Sherbrooke, Quebec, Canada
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Categorizing sequences of concern by function to better assess mechanisms of microbial pathogenesis. Infect Immun 2021; 90:e0033421. [PMID: 34780277 PMCID: PMC9119117 DOI: 10.1128/iai.00334-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
To identify sequences with a role in microbial pathogenesis, we assessed the adequacy of their annotation by existing controlled vocabularies and sequence databases. Our goal was to regularize descriptions of microbial pathogenesis for improved integration with bioinformatic applications. Here, we review the challenges of annotating sequences for pathogenic activity. We relate the categorization of more than 2,750 sequences of pathogenic microbes through a controlled vocabulary called Functions of Sequences of Concern (FunSoCs). These allow for an ease of description by both humans and machines. We provide a subset of 220 fully annotated sequences in the supplemental material as examples. The use of this compact (∼30 terms), controlled vocabulary has potential benefits for research in microbial genomics, public health, biosecurity, biosurveillance, and the characterization of new and emerging pathogens.
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Life history and population regulation shape demographic competence and influence the maintenance of endemic disease. Nat Ecol Evol 2020; 5:82-91. [PMID: 33168996 DOI: 10.1038/s41559-020-01333-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 09/23/2020] [Indexed: 11/09/2022]
Abstract
Host life history and demography play important roles in host-pathogen dynamics, by influencing the ability of hosts and their pathogens to coexist. We introduce the concept of demographic competence to describe the ability of host populations to sustain endemic infectious disease. Hosts with high demographic competence are more likely to act as keystone hosts and constitute reservoirs of infection that can spill over into other species. We propose that the pace of host life history will interact with pathogen life history to influence demographic competence. Our models demonstrate that slow-living hosts (with high survival and low recruitment rates) have greater demographic competence than fast-living hosts (with low survival and high recruitment rates) for susceptible-infected disease dynamics, although this difference is reduced when populations of slow hosts are age structured. Demographic competence is generally greater among hosts with populations regulated by survival compared to reproduction, but this difference is smallest among slow life histories and reversed for some pathogens with frequency-dependent transmission. An association between pathogen life history traits and the demographic competence of faster-living hosts also has implications for trade-offs between pathogen virulence and transmissibility. Overall, we demonstrate how host life history traits can help predict wildlife reservoirs of zoonoses and the vulnerability of populations to disease-induced extinction.
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8
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Chen Y, Hammer EE, Richards VP. Phylogenetic signature of lateral exchange of genes for antibiotic production and resistance among bacteria highlights a pattern of global transmission of pathogens between humans and livestock. Mol Phylogenet Evol 2018; 125:255-264. [DOI: 10.1016/j.ympev.2018.03.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 03/27/2018] [Accepted: 03/29/2018] [Indexed: 01/08/2023]
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9
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Garber JJ, Mallick EM, Scanlon KM, Turner JR, Donnenberg MS, Leong JM, Snapper SB. Attaching-and-Effacing Pathogens Exploit Junction Regulatory Activities of N-WASP and SNX9 to Disrupt the Intestinal Barrier. Cell Mol Gastroenterol Hepatol 2017; 5:273-288. [PMID: 29675452 PMCID: PMC5904039 DOI: 10.1016/j.jcmgh.2017.11.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 11/28/2017] [Indexed: 02/05/2023]
Abstract
BACKGROUND & AIMS Neural Wiskott-Aldrich Syndrome protein (N-WASP) is a key regulator of the actin cytoskeleton in epithelial tissues and is poised to mediate cytoskeletal-dependent aspects of apical junction complex (AJC) homeostasis. Attaching-and-effacing (AE) pathogens disrupt this homeostasis through translocation of the effector molecule early secreted antigenic target-6 (ESX)-1 secretion-associated protein F (EspF). Although the mechanisms underlying AJC disruption by EspF are unknown, EspF contains putative binding sites for N-WASP and the endocytic regulator sorting nexin 9 (SNX9). We hypothesized that N-WASP regulates AJC integrity and AE pathogens use EspF to induce junction disassembly through an N-WASP- and SNX9-dependent pathway. METHODS We analyzed mice with intestine-specific N-WASP deletion and generated cell lines with N-WASP and SNX9 depletion for dynamic functional assays. We generated EPEC and Citrobacter rodentium strains complemented with EspF bearing point mutations abolishing N-WASP and SNX9 binding to investigate the requirement for these interactions. RESULTS Mice lacking N-WASP in the intestinal epithelium showed spontaneously increased permeability, abnormal AJC morphology, and mislocalization of occludin. N-WASP depletion in epithelial cell lines led to impaired assembly and disassembly of tight junctions in response to changes in extracellular calcium. Cells lacking N-WASP or SNX9 supported actin pedestals and type III secretion, but were resistant to EPEC-induced AJC disassembly and loss of transepithelial resistance. We found that during in vivo infection with AE pathogens, EspF must bind both N-WASP and SNX9 to disrupt AJCs and induce intestinal barrier dysfunction. CONCLUSIONS Overall, these studies show that N-WASP critically regulates AJC homeostasis, and the AE pathogen effector EspF specifically exploits both N-WASP and SNX9 to disrupt intestinal barrier integrity during infection.
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Key Words
- ADF, actin depolymerization factor
- AE, attaching-and-effacing
- AJ, adherens junction
- AJC, apical junction complex
- Arp, actin-related protein
- CR, Citrobacter rodentium
- Crb, Crumbs
- Cytoskeleton
- DBS100, David B. Schauer 100
- EHEC, enterohemorrhagic Escherichia coli
- EM, electron microscopy
- EPEC, enteropathogenic Escherichia coli
- EcoRI, E. coli RY13 I
- EspF
- EspF, early secreted antigenic target-6 (ESX)-1 secretion-associated protein F
- FITC, fluorescein isothiocyanate
- Junction Regulation
- KO, knockout
- N-WASP
- N-WASP, Neural Wiskott-Aldrich Syndrome protein
- NWKD, Neural Wiskott-Aldrich Syndrome protein knockdown
- PBS, phosphate-buffered saline
- PCR, polymerase chain reaction
- SNX9, sorting nexin 9
- SNX9KD, sorting nexin 9 knockdown
- TER, transepithelial electrical resistance
- TJ, tight junction
- Tir, translocated intimin receptor
- ZO-1, zonula occludens-1
- iNWKO, intestine Neural Wiskott-Aldrich Syndrome protein knockout
- shRNA, short hairpin RNA
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Affiliation(s)
- John J. Garber
- Gastrointestinal Unit, Massachusetts General Hospital, Boston, Massachusetts,Division of Gastroenterology/Nutrition and Center for Inflammatory Bowel Disease Treatment and Research, Boston Children's Hospital, Boston, Massachusetts,Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Emily M. Mallick
- Department of Medicine Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Karen M. Scanlon
- Department of Medicine and Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Jerrold R. Turner
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts,Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Michael S. Donnenberg
- Department of Medicine and Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - John M. Leong
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
| | - Scott B. Snapper
- Division of Gastroenterology/Nutrition and Center for Inflammatory Bowel Disease Treatment and Research, Boston Children's Hospital, Boston, Massachusetts,Division of Gastroenterology and Hepatology, Brigham and Women's Hospital, Boston, Massachusetts,Department of Medicine, Harvard Medical School, Boston, Massachusetts,Correspondence Address correspondence to: Scott B. Snapper, MD, PhD, Division of Gastroenterology/Nutrition, Boston Children’s Hospital, Enders 676, 300 Longwood Avenue, Boston, Massachusetts 02115. fax: (617) 730-0498.
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10
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Moxon R, Kussell E. The impact of bottlenecks on microbial survival, adaptation, and phenotypic switching in host-pathogen interactions. Evolution 2017; 71:2803-2816. [PMID: 28983912 DOI: 10.1111/evo.13370] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Accepted: 09/01/2017] [Indexed: 12/18/2022]
Abstract
Microbial pathogens and viruses can often maintain sufficient population diversity to evade a wide range of host immune responses. However, when populations experience bottlenecks, as occurs frequently during initiation of new infections, pathogens require specialized mechanisms to regenerate diversity. We address the evolution of such mechanisms, known as stochastic phenotype switches, which are prevalent in pathogenic bacteria. We analyze a model of pathogen diversification in a changing host environment that accounts for selective bottlenecks, wherein different phenotypes have distinct transmission probabilities between hosts. We show that under stringent bottlenecks, such that only one phenotype can initiate new infections, there exists a threshold stochastic switching rate below which all pathogen lineages go extinct, and above which survival is a near certainty. We determine how quickly stochastic switching rates can evolve by computing a fitness landscape for the evolutionary dynamics of switching rates, and analyzing its dependence on both the stringency of bottlenecks and the duration of within-host growth periods. We show that increasing the stringency of bottlenecks or decreasing the period of growth results in faster adaptation of switching rates. Our model provides strong theoretical evidence that bottlenecks play a critical role in accelerating the evolutionary dynamics of pathogens.
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Affiliation(s)
- Richard Moxon
- University of Oxford Medical Sciences Division, John Radcliffe Hospital, Oxford, United Kingdom
| | - Edo Kussell
- Department of Biology and Center for Genomics and Systems Biology, 12 Waverly Place, New York University, New York, 10003.,Department of Physics, New York University, 726 Broadway, New York, 10003
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11
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Rao S, Schieber AMP, O'Connor CP, Leblanc M, Michel D, Ayres JS. Pathogen-Mediated Inhibition of Anorexia Promotes Host Survival and Transmission. Cell 2017; 168:503-516.e12. [PMID: 28129542 DOI: 10.1016/j.cell.2017.01.006] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 11/21/2016] [Accepted: 01/06/2017] [Indexed: 01/06/2023]
Abstract
Sickness-induced anorexia is a conserved behavior induced during infections. Here, we report that an intestinal pathogen, Salmonella Typhimurium, inhibits anorexia by manipulating the gut-brain axis. Inhibition of inflammasome activation by the S. Typhimurium effector, SlrP, prevented anorexia caused by IL-1β-mediated signaling to the hypothalamus via the vagus nerve. Rather than compromising host defenses, pathogen-mediated inhibition of anorexia increased host survival. SlrP-mediated inhibition of anorexia prevented invasion and systemic infection by wild-type S. Typhimurium, reducing virulence while increasing transmission to new hosts, suggesting that there are trade-offs between transmission and virulence. These results clarify the complex and contextual role of anorexia in host-pathogen interactions and suggest that microbes have evolved mechanisms to modulate sickness-induced behaviors to promote health of their host and their transmission at the expense of virulence.
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Affiliation(s)
- Sheila Rao
- Nomis Center for Immunobiology and Microbial Pathogenesis, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Alexandria M Palaferri Schieber
- Nomis Center for Immunobiology and Microbial Pathogenesis, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Carolyn P O'Connor
- Flow Cytometry Core Facility, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Mathias Leblanc
- Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Daniela Michel
- Nomis Center for Immunobiology and Microbial Pathogenesis, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Janelle S Ayres
- Nomis Center for Immunobiology and Microbial Pathogenesis, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
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12
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Baltrus DA, McCann HC, Guttman DS. Evolution, genomics and epidemiology of Pseudomonas syringae: Challenges in Bacterial Molecular Plant Pathology. MOLECULAR PLANT PATHOLOGY 2017; 18:152-168. [PMID: 27798954 PMCID: PMC6638251 DOI: 10.1111/mpp.12506] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 05/12/2023]
Abstract
A remarkable shift in our understanding of plant-pathogenic bacteria is underway. Until recently, nearly all research on phytopathogenic bacteria was focused on a small number of model strains, which provided a deep, but narrow, perspective on plant-microbe interactions. Advances in genome sequencing technologies have changed this by enabling the incorporation of much greater diversity into comparative and functional research. We are now moving beyond a typological understanding of a select collection of strains to a more generalized appreciation of the breadth and scope of plant-microbe interactions. The study of natural populations and evolution has particularly benefited from the expansion of genomic data. We are beginning to have a much deeper understanding of the natural genetic diversity, niche breadth, ecological constraints and defining characteristics of phytopathogenic species. Given this expanding genomic and ecological knowledge, we believe the time is ripe to evaluate what we know about the evolutionary dynamics of plant pathogens.
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Affiliation(s)
| | - Honour C. McCann
- New Zealand Institute for Advanced StudyMassey UniversityAuckland 0632New Zealand
| | - David S. Guttman
- Department of Cell and Systems BiologyUniversity of TorontoTorontoON M5S 3B2Canada
- Centre for the Analysis of Genome Evolution and FunctionUniversity of TorontoTorontoON M5S 3B2Canada
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13
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Pearson JS, Giogha C, Wong Fok Lung T, Hartland EL. The Genetics of EnteropathogenicEscherichia coliVirulence. Annu Rev Genet 2016; 50:493-513. [DOI: 10.1146/annurev-genet-120215-035138] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jaclyn S. Pearson
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
| | - Cristina Giogha
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
| | - Tania Wong Fok Lung
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
| | - Elizabeth L. Hartland
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria 3010, Australia; , , ,
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14
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Probiotic Enterococcus faecalis Symbioflor® down regulates virulence genes of EHEC in vitro and decrease pathogenicity in a Caenorhabditis elegans model. Arch Microbiol 2016; 199:203-213. [DOI: 10.1007/s00203-016-1291-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 08/30/2016] [Accepted: 09/12/2016] [Indexed: 11/30/2022]
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15
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Smith AD, Yan X, Chen C, Dawson HD, Bhagwat AA. Understanding the host-adapted state of Citrobacter rodentium by transcriptomic analysis. Arch Microbiol 2016; 198:353-62. [PMID: 26837900 DOI: 10.1007/s00203-016-1191-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 12/17/2015] [Accepted: 01/12/2016] [Indexed: 12/18/2022]
Abstract
Citrobacter rodentium (Cr) is a mouse pathogen that mimics many aspects of enteropathogenic Escherichia coli infections including producing attaching and effacing (A/E) lesions. Host-adapted (HA) Cr cells that are shed at the peak of infection have been reported to be hyper-infective. The exact mechanism underlying this phenomenon has remained elusive since the pathogen loses its HA 'status' immediately upon subculturing in laboratory media. We sequenced the entire transcriptome of Cr directly from the feces of infected mice and analyzed the gene expression pattern. We observed that the entire transcriptional machinery as well as several transcriptional regulators to be differentially expressed when compared with the transcriptome of cells grown on laboratory media. Major adhesion and effector genes, tir and eae, were highly expressed in HA along with many genes located on all five loci of enterocyte effacement regions (LEE 1-5). Notable absent among the HA expressed genes were 19 fimbrial operons and non-fimbrial adhesions and several non-LEE encoded effectors. These results demonstrate that host-adapted Cr has a unique transcriptome that is associated with increased host transmission.
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Affiliation(s)
- Allen D Smith
- Diet, Genomics and Immunology Laboratory, Beltsville Human Nutrition Research Center, USDA-ARS, 10300 Baltimore Ave., B307C, Rm. 228, BARC-E, Beltsville, MD, 20705, USA.
| | - Xianghe Yan
- Environmental, Microbial, and Food Safety Laboratory, Beltsville Agriculture Research Center, USDA-ARS, Beltsville, MD, USA
| | - Celine Chen
- Diet, Genomics and Immunology Laboratory, Beltsville Human Nutrition Research Center, USDA-ARS, 10300 Baltimore Ave., B307C, Rm. 228, BARC-E, Beltsville, MD, 20705, USA
| | - Harry D Dawson
- Diet, Genomics and Immunology Laboratory, Beltsville Human Nutrition Research Center, USDA-ARS, 10300 Baltimore Ave., B307C, Rm. 228, BARC-E, Beltsville, MD, 20705, USA
| | - Arvind A Bhagwat
- Environmental, Microbial, and Food Safety Laboratory, Beltsville Agriculture Research Center, USDA-ARS, Beltsville, MD, USA
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Liu PF, Cheng JS, Sy CL, Huang WC, Yang HC, Gallo RL, Huang CM, Shu CW. IsaB Inhibits Autophagic Flux to Promote Host Transmission of Methicillin-Resistant Staphylococcus aureus. J Invest Dermatol 2015; 135:2714-2722. [PMID: 26134948 PMCID: PMC4641007 DOI: 10.1038/jid.2015.254] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Accepted: 06/17/2015] [Indexed: 12/19/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major nosocomial pathogen that is widespread in both health-care facilities and in the community at large, as a result of direct host-to-host transmission. Several virulence factors are associated with pathogen transmission to naive hosts. Immunodominant surface antigen B (IsaB) is a virulence factor that helps Staphylococcus aureus to evade the host defense system. However, the mechanism of IsaB on host transmissibility remains unclear. We found that IsaB expression was elevated in transmissible MRSA. Wild-type isaB strains inhibited autophagic flux to promote bacterial survival and elicit inflammation in THP-1 cells and mouse skin. MRSA isolates with increased IsaB expression showed decreased autophagic flux, and the MRSA isolate with the lowest IsaB expression showed increased autophagic flux. In addition, recombinant IsaB rescued the virulence of the isaB deletion strain and increased the group A streptococcus (GAS) virulence in vivo. Together, these results reveal that IsaB diminishes autophagic flux, thereby allowing MRSA to evade host degradation. These findings suggest that IsaB is a suitable target for preventing or treating MRSA infection.
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Affiliation(s)
- Pei-Feng Liu
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
- Department of Medicine, Division of Dermatology, University of California, San Diego, USA
| | - Jin-Shiung Cheng
- Department of Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Cheng-Len Sy
- Department of Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Wei-Chun Huang
- Cardiovascular Medical Center, Kaohsiung Veterans General Hospital, Kaohsiung City
- School of Medicine, National Yang-Ming University, Taipei City
| | - Hsiu-Chen Yang
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Richard L. Gallo
- Department of Medicine, Division of Dermatology, University of California, San Diego, USA
- VA San Diego Healthcare Center, San Diego, USA
| | - Chun-Ming Huang
- Department of Medicine, Division of Dermatology, University of California, San Diego, USA
| | - Chih-Wen Shu
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
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Luo J, Hu J, Zhang Y, Hu Q, Li S. Hijacking of death receptor signaling by bacterial pathogen effectors. Apoptosis 2015; 20:216-23. [PMID: 25528554 DOI: 10.1007/s10495-014-1068-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Death receptors such as Tumor necrosis factor receptor 1, FAS and TNF-associated apoptosis-inducing ligand-R1/2 play a major role in counteracting with bacterial pathogen infection through regulation of inflammation and programmed cell death. The highly regulated death receptor signaling is frequently targeted by gram-negative bacterial pathogens such as Salmonella, Shigella, enteropathogenic Escherichia coli and enterohamorrhagic Escherichia coli, which harbor a conserved type III secretion system that delivers a repertoire of effector proteins to manipulate host signal transductions for their own benefit. This review focuses on how bacterial gut pathogens hijack death receptor signaling to inhibit host NF-κB and programmed cell death pathways.
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Affiliation(s)
- Jie Luo
- Taihe Hospital, Hubei University of Medicine, #32 Renmin South Rd, Shiyan, 442000, Hubei, China
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18
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The Serine Protease Autotransporter Pic Modulates Citrobacter rodentium Pathogenesis and Its Innate Recognition by the Host. Infect Immun 2015; 83:2636-50. [PMID: 25895966 DOI: 10.1128/iai.00025-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Bacterial pathogens produce a number of autotransporters that possess diverse functions. These include the family of serine protease autotransporters of Enterobacteriaceae (SPATEs) produced by enteric pathogens such as Shigella flexneri and enteroaggregative Escherichia coli. Of these SPATEs, one termed "protein involved in colonization," or Pic, has been shown to possess mucinase activity in vitro, but to date, its role in in vivo enteric pathogenesis is unknown. Testing a pic null (ΔpicC) mutant in Citrobacter rodentium, a natural mouse pathogen, found that the C. rodentium ΔpicC strain was impaired in its ability to degrade mucin in vitro compared to the wild type. Upon infection of mice, the ΔpicC mutant exhibited a hypervirulent phenotype with dramatically heavier pathogen burdens found in intestinal crypts. ΔpicC mutant-infected mice suffered greater barrier disruption and more severe colitis and weight loss, necessitating their euthanization between 10 and 14 days postinfection. Notably, the virulence of the ΔpicC mutant was normalized when the picC gene was restored; however, a PicC point mutant causing loss of mucinase activity did not replicate the ΔpicC phenotype. Exploring other aspects of PicC function, the ΔpicC mutant was found to aggregate to higher levels in vivo than wild-type C. rodentium. Moreover, unlike the wild type, the C. rodentium ΔpicC mutant had a red, dry, and rough (RDAR) morphology in vitro and showed increased activation of the innate receptor Toll-like receptor 2 (TLR2). Interestingly, the C. rodentium ΔpicC mutant caused a degree of pathology similar to that of wild-type C. rodentium when infecting TLR2-deficient mice, showing that despite its mucinase activity, PicC's major role in vivo may be to limit C. rodentium's stimulation of the host's innate immune system.
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Sit B, Crowley SM, Bhullar K, Lai CCL, Tang C, Hooda Y, Calmettes C, Khambati H, Ma C, Brumell JH, Schryvers AB, Vallance BA, Moraes TF. Active Transport of Phosphorylated Carbohydrates Promotes Intestinal Colonization and Transmission of a Bacterial Pathogen. PLoS Pathog 2015; 11:e1005107. [PMID: 26295949 PMCID: PMC4546632 DOI: 10.1371/journal.ppat.1005107] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 07/22/2015] [Indexed: 12/22/2022] Open
Abstract
Efficient acquisition of extracellular nutrients is essential for bacterial pathogenesis, however the identities and mechanisms for transport of many of these substrates remain unclear. Here, we investigate the predicted iron-binding transporter AfuABC and its role in bacterial pathogenesis in vivo. By crystallographic, biophysical and in vivo approaches, we show that AfuABC is in fact a cyclic hexose/heptose-phosphate transporter with high selectivity and specificity for a set of ubiquitous metabolites (glucose-6-phosphate, fructose-6-phosphate and sedoheptulose-7-phosphate). AfuABC is conserved across a wide range of bacterial genera, including the enteric pathogens EHEC O157:H7 and its murine-specific relative Citrobacter rodentium, where it lies adjacent to genes implicated in sugar sensing and acquisition. C. rodentium ΔafuA was significantly impaired in an in vivo murine competitive assay as well as its ability to transmit infection from an afflicted to a naïve murine host. Sugar-phosphates were present in normal and infected intestinal mucus and stool samples, indicating that these metabolites are available within the intestinal lumen for enteric bacteria to import during infection. Our study shows that AfuABC-dependent uptake of sugar-phosphates plays a critical role during enteric bacterial infection and uncovers previously unrecognized roles for these metabolites as important contributors to successful pathogenesis. Essentially all Gram-negative pathogens are reliant on specific transport machineries termed binding protein-dependent transporters (BPDTs) to transport solutes such as amino acids, sugars and metal ions across their membranes. In this study we investigated AfuABC, a predicted iron-transporting BPDT found in many bacterial pathogens. We show by structural and functional approaches that AfuABC is not an iron transporter. Instead, AfuABC is a trio of proteins that bind and transport sugar-phosphates such as glucose-6-phosphate (G6P). In doing so, we present the first structural solution of a G6P-specific transport protein and add to the few known unique machineries for sugar-phosphate uptake by bacteria. Furthermore, we show that AfuABC is required by the intestinal pathogen C. rodentium to effectively transmit between mice and re-establish infection, leading us to propose that the transport of sugar-phosphates is an important part of general bacterial pathogenesis.
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Affiliation(s)
- Brandon Sit
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Shauna M. Crowley
- Department of Pediatrics and the Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kirandeep Bhullar
- Department of Pediatrics and the Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Calvin Tang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Yogesh Hooda
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Charles Calmettes
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Husain Khambati
- Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Caixia Ma
- Department of Pediatrics and the Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - John H. Brumell
- Department of Molecular Genetics and Institute of Medical Science, University of Toronto, Ontario, Canada
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- SickKids Inflammatory Bowel Disease Centre, Toronto, Ontario, Canada
| | - Anthony B. Schryvers
- Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Bruce A. Vallance
- Department of Pediatrics and the Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail: (BAV); (TFM)
| | - Trevor F. Moraes
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (BAV); (TFM)
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20
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Mikonranta L, Mappes J, Laakso J, Ketola T. Within-host evolution decreases virulence in an opportunistic bacterial pathogen. BMC Evol Biol 2015; 15:165. [PMID: 26282271 PMCID: PMC4539714 DOI: 10.1186/s12862-015-0447-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 08/06/2015] [Indexed: 12/15/2022] Open
Abstract
Background Pathogens evolve in a close antagonistic relationship with their hosts. The conventional theory proposes that evolution of virulence is highly dependent on the efficiency of direct host-to-host transmission. Many opportunistic pathogens, however, are not strictly dependent on the hosts due to their ability to reproduce in the free-living environment. Therefore it is likely that conflicting selection pressures for growth and survival outside versus within the host, rather than transmission potential, shape the evolution of virulence in opportunists. We tested the role of within-host selection in evolution of virulence by letting a pathogen Serratia marcescens db11 sequentially infect Drosophila melanogaster hosts and then compared the virulence to strains that evolved only in the outside-host environment. Results We found that the pathogen adapted to both Drosophila melanogaster host and novel outside-host environment, leading to rapid evolutionary changes in the bacterial life-history traits including motility, in vitro growth rate, biomass yield, and secretion of extracellular proteases. Most significantly, selection within the host led to decreased virulence without decreased bacterial load while the selection lines in the outside-host environment maintained the same level of virulence with ancestral bacteria. Conclusions This experimental evidence supports the idea that increased virulence is not an inevitable consequence of within-host adaptation even when the epidemiological restrictions are removed. Evolution of attenuated virulence could occur because of immune evasion within the host. Alternatively, rapid fluctuation between outside-host and within-host environments, which is typical for the life cycle of opportunistic bacterial pathogens, could lead to trade-offs that lower pathogen virulence.
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Affiliation(s)
- Lauri Mikonranta
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.
| | - Johanna Mappes
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.
| | - Jouni Laakso
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland. .,Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Helsinki, University of Helsinki, P.O. Box 65, 00014, Helsinki, Finland.
| | - Tarmo Ketola
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.
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21
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Santos AS, Finlay BB. Bringing down the host: enteropathogenic and enterohaemorrhagic Escherichia coli effector-mediated subversion of host innate immune pathways. Cell Microbiol 2015; 17:318-32. [PMID: 25588886 DOI: 10.1111/cmi.12412] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 12/17/2014] [Accepted: 12/22/2014] [Indexed: 12/14/2022]
Abstract
Enteric bacterial pathogens commonly use a type III secretion system (T3SS) to successfully infect intestinal epithelial cells and survive and proliferate in the host. Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC; EHEC) colonize the human intestinal mucosa, form characteristic histological lesions on the infected epithelium and require the T3SS for full virulence. T3SS effectors injected into host cells subvert cellular pathways to execute a variety of functions within infected host cells. The EPEC and EHEC effectors that subvert innate immune pathways--specifically those involved in phagocytosis, host cell survival, apoptotic cell death and inflammatory signalling--are all required to cause disease. These processes are reviewed within, with a focus on recent work that has provided insights into the functions and host cell targets of these effectors.
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Affiliation(s)
- Andrew S Santos
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada; Michael Smith Laboratories, The University of British Columbia, Vancouver, BC, Canada
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22
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A horizontally acquired transcription factor coordinates Salmonella adaptations to host microenvironments. mBio 2014; 5:e01727-14. [PMID: 25249283 PMCID: PMC4173766 DOI: 10.1128/mbio.01727-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The transcription factors HilA and SsrB activate expression of two type III secretion systems (T3SSs) and cognate effectors that reprogram host cell functions to benefit infecting Salmonella in the host. These transcription factors, the secretion systems, and the effectors are all encoded by horizontally acquired genes. Using quantitative proteomics, we quantified the abundance of 2,149 proteins from hilA or ssrB Salmonella in vitro. Our results suggest that the HilA regulon does not extend significantly beyond proteins known to be involved in direct interactions with intestinal epithelium. On the other hand, SsrB influences the expression of a diverse range of proteins, many of which are ancestral to the acquisition of ssrB. In addition to the known regulon of T3SS-related proteins, we show that, through SodCI and bacterioferritin, SsrB controls resistance to reactive oxygen species and that SsrB down-regulates flagella and motility. This indicates that SsrB-controlled proteins not only redirect host cell membrane traffic to establish a supportive niche within host cells but also have adapted to the chemistry and physical constraints of that niche. Expression of T3SSs typically requires a transcription factor that is linked in a genomic island. Studies of the targets of HilA and SsrB have focused on almost exclusively on T3SS substrates that are either linked or encoded in distinct genomic islands. By broadening our focus, we found that the regulon of SsrB extended considerably beyond T3SS-2 and its substrates, while that of HilA did not. That at least two SsrB-regulated processes streamline existence in the intracellular niche afforded by T3SS-2 seems to be a predictable outcome of evolution and natural selection. However, and importantly, these are the first such functions to be implicated as being SsrB dependent. The concept of T3SS-associated transcription factors coordinating manipulations of host cells together with distinct bacterial processes for increased efficiency has unrealized implications for numerous host-pathogen systems.
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Abstract
Citrobacter rodentium is a mucosal pathogen of mice that shares several pathogenic mechanisms with enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC), which are two clinically important human gastrointestinal pathogens. Thus, C. rodentium has long been used as a model to understand the molecular basis of EPEC and EHEC infection in vivo. In this Review, we discuss recent studies in which C. rodentium has been used to study mucosal immunology, including the deregulation of intestinal inflammatory responses during bacteria-induced colitis and the role of the intestinal microbiota in mediating resistance to colonization by enteric pathogens. These insights should help to elucidate the roles of mucosal inflammatory responses and the microbiota in the virulence of enteric pathogens.
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24
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Giogha C, Lung TWF, Pearson JS, Hartland EL. Inhibition of death receptor signaling by bacterial gut pathogens. Cytokine Growth Factor Rev 2014; 25:235-43. [DOI: 10.1016/j.cytogfr.2013.12.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 12/18/2013] [Indexed: 12/22/2022]
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Molecular characterization of Shiga-toxigenic Escherichia coli isolated from diverse sources from India by multi-locus variable number tandem repeat analysis (MLVA). Epidemiol Infect 2014; 142:2572-82. [PMID: 24534324 DOI: 10.1017/s0950268814000065] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
In a first study from India, a diverse collection of 140 environmental and clinical non-O157 Shiga-toxigenic Escherichia coli strains from a large geographical area in north India was typed by multi-locus variable number tandem repeat analysis (MLVA). The distribution of major virulence genes stx1, stx2 and eae was found to be 78%, 70% and 10%, respectively; 15 isolates were enterohaemorrhagic E. coli (stx1 +/stx2 + and eae +). By MLVA analysis, 44 different alleles were obtained. Dendrogram analysis revealed 104 different genotypes and 19 MLVA-type complexes divided into two main lineages, i.e. mutton and animal stool. Human isolates presented a statistically significant greater odds ratio for clustering with mutton samples compared to animal stool isolates. Five human isolates clustered with animal stool strains suggesting that some of the human infections may be from cattle, perhaps through milk, contact or the environment. Further epidemiological studies are required to explore these sources in context with occurrence of human cases.
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26
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Rolin O, Smallridge W, Henry M, Goodfield L, Place D, Harvill ET. Toll-like receptor 4 limits transmission of Bordetella bronchiseptica. PLoS One 2014; 9:e85229. [PMID: 24497924 PMCID: PMC3907416 DOI: 10.1371/journal.pone.0085229] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 11/25/2013] [Indexed: 02/06/2023] Open
Abstract
Transmission of pathogens has been notoriously difficult to study under laboratory conditions leaving knowledge gaps regarding how bacterial factors and host immune components affect the spread of infections between hosts. We describe the development of a mouse model of transmission of a natural pathogen, Bordetella bronchiseptica, and its use to assess the impact of host immune functions. Although B. bronchiseptica transmits poorly between wild-type mice and mice lacking other immune components, it transmits efficiently between mice deficient in Toll-Like Receptor 4 (TLR4). TLR4-mutant mice were more susceptible to initial colonization, and poorly controlled pathogen growth and shedding. Heavy neutrophil infiltration distinguished TLR4-deficient responses, and neutrophil depletion did not affect respiratory CFU load, but decreased bacterial shedding. The effect of TLR4 response on transmission may explain the extensive variation in TLR4 agonist potency observed among closely related subspecies of Bordetella. This transmission model will enable mechanistic studies of how pathogens spread from one host to another, the defining feature of infectious disease.
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Affiliation(s)
- Olivier Rolin
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Will Smallridge
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Michael Henry
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Laura Goodfield
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - David Place
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Eric T. Harvill
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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27
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Smallridge WE, Rolin OY, Jacobs NT, Harvill ET. Different effects of whole-cell and acellular vaccines on Bordetella transmission. J Infect Dis 2014; 209:1981-8. [PMID: 24443545 DOI: 10.1093/infdis/jiu030] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Vaccine development has largely focused on the ability of vaccines to reduce disease in individual hosts, with less attention to assessing the vaccine's effects on transmission between hosts. Current acellular vaccines against Bordetella pertussis are effective in preventing severe disease but have little effect on less severe coughing illness that can mediate transmission. METHODS Using mice that are natural host's of Bordetella bronchiseptica, we determined the effects of vaccination on shedding and transmission of this pathogen. RESULTS Vaccination with heat-killed whole-cell B. bronchiseptica or B. pertussis inhibited shedding of B. bronchiseptica. Differences in neutrophil and B-cell recruitment distinguished sham-vaccine from whole-cell-----vaccine responses and correlated with shedding output. Both B and T cells were essential for vaccine-induced control of shedding. Adoptive transfer of antibodies was able to limit shedding, while depletion of CD4(+) T cells led to increased shedding in vaccinated mice. Finally, whole-cell vaccination was able to prevent transmission, but an acellular vaccine that effectively controls disease failed to control shedding and transmission. CONCLUSIONS Our results highlight discrepancies between whole-cell and acellular vaccination that could contribute to the increased incidence of B. pertussis infection since the transition to the use of acellular vaccination.
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Affiliation(s)
- William E Smallridge
- Department of Veterinary and Biomedical Sciences Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park
| | - Olivier Y Rolin
- Department of Veterinary and Biomedical Sciences Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park
| | | | - Eric T Harvill
- Department of Veterinary and Biomedical Sciences Graduate Program in Immunology and Infectious Disease, The Pennsylvania State University, University Park
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28
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Pearson JS, Giogha C, Ong SY, Kennedy CL, Kelly M, Robinson KS, Wong T, Mansell A, Riedmaier P, Oates CVL, Zaid A, Mühlen S, Crepin VF, Marches O, Ang CS, Williamson NA, O’Reilly LA, Bankovacki A, Nachbur U, Infusini G, Webb AI, Silke J, Strasser A, Frankel G, Hartland EL. A type III effector antagonizes death receptor signalling during bacterial gut infection. Nature 2013; 501:247-51. [PMID: 24025841 PMCID: PMC3836246 DOI: 10.1038/nature12524] [Citation(s) in RCA: 219] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 08/02/2013] [Indexed: 02/07/2023]
Abstract
Successful infection by enteric bacterial pathogens depends on the ability of the bacteria to colonize the gut, replicate in host tissues and disseminate to other hosts. Pathogens such as Salmonella, Shigella and enteropathogenic and enterohaemorrhagic (EPEC and EHEC, respectively) Escherichia coli use a type III secretion system (T3SS) to deliver virulence effector proteins into host cells during infection that promote colonization and interfere with antimicrobial host responses. Here we report that the T3SS effector NleB1 from EPEC binds to host cell death-domain-containing proteins and thereby inhibits death receptor signalling. Protein interaction studies identified FADD, TRADD and RIPK1 as binding partners of NleB1. NleB1 expressed ectopically or injected by the bacterial T3SS prevented Fas ligand or TNF-induced formation of the canonical death-inducing signalling complex (DISC) and proteolytic activation of caspase-8, an essential step in death-receptor-induced apoptosis. This inhibition depended on the N-acetylglucosamine transferase activity of NleB1, which specifically modified Arg 117 in the death domain of FADD. The importance of the death receptor apoptotic pathway to host defence was demonstrated using mice deficient in the FAS signalling pathway, which showed delayed clearance of the EPEC-like mouse pathogen Citrobacter rodentium and reversion to virulence of an nleB mutant. The activity of NleB suggests that EPEC and other attaching and effacing pathogens antagonize death-receptor-induced apoptosis of infected cells, thereby blocking a major antimicrobial host response.
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Affiliation(s)
- Jaclyn S Pearson
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Cristina Giogha
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Sze Ying Ong
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Catherine L Kennedy
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Michelle Kelly
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Keith S Robinson
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, SW7 2AZ, UK
| | - Tania Wong
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Ashley Mansell
- Centre for Innate Immunity and Infectious Diseases, Monash Institute of Medical Research, Victoria 3010, Australia
| | - Patrice Riedmaier
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Clare VL Oates
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Ali Zaid
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Sabrina Mühlen
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
| | - Valerie F Crepin
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, SW7 2AZ, UK
| | - Olivier Marches
- Centre for Immunology and Infectious Disease, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK
| | - Ching-Seng Ang
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria 3010, Australia
| | - Nicholas A Williamson
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria 3010, Australia
| | - Lorraine A O’Reilly
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- Department of Medical Biology, University of Melbourne, Victoria 3010, Australia
| | - Aleksandra Bankovacki
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Ueli Nachbur
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Giuseppe Infusini
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Andrew I Webb
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- Department of Medical Biology, University of Melbourne, Victoria 3010, Australia
| | - John Silke
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- Department of Medical Biology, University of Melbourne, Victoria 3010, Australia
| | - Andreas Strasser
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- Department of Medical Biology, University of Melbourne, Victoria 3010, Australia
| | - Gad Frankel
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, SW7 2AZ, UK
| | - Elizabeth L Hartland
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia
- Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, Victoria 3052, Australia
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29
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Lawley TD, Walker AW. Intestinal colonization resistance. Immunology 2013; 138:1-11. [PMID: 23240815 DOI: 10.1111/j.1365-2567.2012.03616.x] [Citation(s) in RCA: 398] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 06/12/2012] [Accepted: 06/13/2012] [Indexed: 12/16/2022] Open
Abstract
Dense, complex microbial communities, collectively termed the microbiota, occupy a diverse array of niches along the length of the mammalian intestinal tract. During health and in the absence of antibiotic exposure the microbiota can effectively inhibit colonization and overgrowth by invading microbes such as pathogens. This phenomenon is called 'colonization resistance' and is associated with a stable and diverse microbiota in tandem with a controlled lack of inflammation, and involves specific interactions between the mucosal immune system and the microbiota. Here we overview the microbial ecology of the healthy mammalian intestinal tract and highlight the microbe-microbe and microbe-host interactions that promote colonization resistance. Emerging themes highlight immunological (T helper type 17/regulatory T-cell balance), microbiota (diverse and abundant) and metabolic (short-chain fatty acid) signatures of intestinal health and colonization resistance. Intestinal pathogens use specific virulence factors or exploit antibiotic use to subvert colonization resistance for their own benefit by triggering inflammation to disrupt the harmony of the intestinal ecosystem. A holistic view that incorporates immunological and microbiological facets of the intestinal ecosystem should facilitate the development of immunomodulatory and microbe-modulatory therapies that promote intestinal homeostasis and colonization resistance.
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Affiliation(s)
- Trevor D Lawley
- Bacterial Pathogenesis Laboratory, Wellcome Trust Sanger Institute, Hinxton, UK.
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31
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Increased bursting glutamatergic neurotransmission in an auditory forebrain area of the zebra finch (Taenopygia guttata) induced by auditory stimulation. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2012; 198:705-16. [PMID: 22752655 DOI: 10.1007/s00359-012-0741-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 06/14/2012] [Accepted: 06/16/2012] [Indexed: 12/23/2022]
Abstract
The caudomedial nidopallium (NCM) is a telencephalic area involved in auditory processing and memorization in songbirds, but the synaptic mechanisms associated with auditory processing in NCM are largely unknown. To identify potential changes in synaptic transmission induced by auditory stimulation in NCM, we used a slice preparation for path-clamp recordings of synaptic currents in the NCM of adult zebra finches (Taenopygia guttata) sacrificed after sound isolation followed by exposure to conspecific song or silence. Although post-synaptic GABAergic and glutamatergic currents in the NCM of control and song-exposed birds did not present any differences regarding their frequency, amplitude and duration after song exposure, we observed a higher probability of generation of bursting glutamatergic currents after blockade of GABAergic transmission in song-exposed birds as compared to controls. Both song-exposed males and females presented an increase in the probability of the expression of bursting glutamatergic currents, however bursting was more commonly seen in males where they appeared even without blocking GABAergic transmission. Our data show that song exposure changes the excitability of the glutamatergic neuronal network, increasing the probability of the generation of bursts of glutamatergic currents, but does not affect basic parameters of glutamatergic and GABAergic synaptic currents.
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32
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Bryner SF, Rigling D. Virulence not only costs but also benefits the transmission of a fungal virus. Evolution 2012; 66:2540-50. [PMID: 22834751 DOI: 10.1111/j.1558-5646.2012.01637.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Current theory suggests that cost-benefit relationships govern the evolution of parasite virulence. The cost of virulence is expected to be high for fungal viruses, which are obligate parasites and completely dependent on their hosts. The majority of fungal viruses infect their hosts without any apparent symptoms. Cryphonectria hypovirus 1 (CHV-1), in contrast, is virulent and debilitates its host, Cryphonectria parasitica. However, the virulence of CHV-1 is associated with high costs for virus transmission, such as an attenuated fungal growth and reduced production of the fungal spores spreading the virus. In this study, we tested the hypothesis that virulence may not only have costs but also benefits for transmitting CHV-1 across vegetative incompatibility barriers between fungi. We investigated viruses with low, medium, and high virulence, and determined their transmission rate per host-to-host contact (transmissibility). The average transmission rate across all combinations tested was 53% for the most virulent virus, 37% for the virus with intermediate virulence, and 20% for the virus with lowest virulence. These results showed that increased virulence was strongly correlated with increased transmissibility, potentially counterbalancing virulence costs. This association of virulence and transmissibility may explain why CHV-1 spread widely and evolved higher virulence than most other fungal viruses.
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33
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Brown NF, Finlay BB. Potential origins and horizontal transfer of type III secretion systems and effectors. Mob Genet Elements 2011; 1:118-121. [PMID: 22016859 DOI: 10.4161/mge.1.2.16733] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 05/31/2011] [Accepted: 06/01/2011] [Indexed: 11/19/2022] Open
Abstract
A major virulence mechanism used by pathogenic Gram-negative bacteria is the delivery of effector proteins from the bacterial cytoplasm into host cells by type III secretion. Typically, genes encoding type III secretion systems (T3SS) and effectors have been horizontally acquired by the bacteria that employ them. In proteobacteria, and especially Salmonella, and attaching and effacing (A/E) pathogens, the genetic structure of these systems presents as a large locus encoding a T3SS with a small number of effectors, plus numerous small unlinked loci encoding additional individual effectors. We discuss the generation of novel effectors, and the evolution of G+C content following acquisition. We also consider the currently held view that each locus has been acquired individually, as well as propose an alternative where recombination may have redistributed and broken up clusters of effectors. It is clear that the evolution of this virulence strategy is highly complex and challenging to analyze.
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Affiliation(s)
- Nat F Brown
- Department of Microbiology and Immunology; University of Melbourne; Melbourne, VIC Australia
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34
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Coombes BK, Gilmour MW, Goodman CD. The evolution of virulence in non-o157 shiga toxin-producing Escherichia coli. Front Microbiol 2011; 2:90. [PMID: 21833329 PMCID: PMC3153049 DOI: 10.3389/fmicb.2011.00090] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 04/14/2011] [Indexed: 12/30/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) are zoonotic foodborne and waterborne pathogens that are a serious public health concern because they cause outbreaks and the potentially fatal hemolytic uremic syndrome (HUS). The most common STEC serotype associated with human disease is O157:H7, but there is a growing recognition of over 100 non-O157 serotypes that also may result in human illness. Some of these non-O157 STEC strains cause outbreaks and severe disease such as HUS and hemorrhagic colitis, whereas others are associated with only mild diarrhea or with no human disease at all. The relative scarceness of whole genome sequence data for non-O157 STEC has limited the scientific discovery into the genetic basis of these differences in virulence. Uncovering the scope of genetic diversity and phylogeny of the non-O157 STEC through targeting sequencing of clinically relevant isolates will offer new biological insight to the pathogenic behavior of these emerging pathogens. These approaches would also enable molecular risk assessment strategies to rapidly identify and respond to emerging non-O157 STEC that pose a serious public health risk to humans.
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Affiliation(s)
- Brian K Coombes
- Department of Biochemistry and Biomedical Sciences, The Michael G. DeGroote Institute for Infectious Disease Research, McMaster University Hamilton, ON, Canada
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35
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Salmonella phage ST64B encodes a member of the SseK/NleB effector family. PLoS One 2011; 6:e17824. [PMID: 21445262 PMCID: PMC3060822 DOI: 10.1371/journal.pone.0017824] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 02/11/2011] [Indexed: 11/19/2022] Open
Abstract
Salmonella enterica is a species of bacteria that is a major cause of enteritis across the globe, while certain serovars cause typhoid, a more serious disease associated with a significant mortality rate. Type III secreted effectors are major contributors to the pathogenesis of Salmonella infections. Genes encoding effectors are acquired via horizontal gene transfer, and a subset are encoded within active phage lysogens. Because the acquisition of effectors is in flux, the complement of effectors possessed by various Salmonella strains frequently differs. By comparing the genome sequences of S. enterica serovar Typhimurium strain SL1344 with LT2, we identified a gene with significant similarity to SseK/NleB type III secreted effector proteins within a phage ST64B lysogen that is absent from LT2. We have named this gene sseK3. SseK3 was co-regulated with the SPI-2 type III secretion system in vitro and inside host cells, and was also injected into infected host cells. While no role for SseK3 in virulence could be identified, a role for the other family members in murine typhoid was found. SseK3 and other phage-encoded effectors were found to have a significant but sparse distribution in the available Salmonella genome sequences, indicating the potential for more uncharacterised effectors to be present in less studied serovars. These phage-encoded effectors may be principle subjects of contemporary selective processes shaping Salmonella-host interactions.
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36
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Pearson JS, Riedmaier P, Marchès O, Frankel G, Hartland EL. A type III effector protease NleC from enteropathogenic Escherichia coli targets NF-κB for degradation. Mol Microbiol 2011; 80:219-30. [PMID: 21306441 PMCID: PMC3178796 DOI: 10.1111/j.1365-2958.2011.07568.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Many bacterial pathogens utilize a type III secretion system (T3SS) to inject virulence effector proteins into host cells during infection. Previously, we found that enteropathogenic Escherichia coli (EPEC) uses the type III effector, NleE, to block the inflammatory response by inhibiting IκB degradation and nuclear translocation of the p65 subunit of NF-κB. Here we screened further effectors with unknown function for their capacity to prevent p65 nuclear translocation. We observed that ectopic expression of GFP–NleC in HeLa cells led to the degradation of p65. Delivery of NleC by the T3SS of EPEC also induced degradation of p65 in infected cells as well as other NF-κB components, c-Rel and p50. Recombinant His6-NleC induced p65 and p50 cleavage in HeLa cell lysates and mutation of a consensus zinc metalloprotease motif, HEIIH, abrogated NleC proteolytic activity. NleC inhibited IL-8 production during prolonged EPEC infection of HeLa cells in a protease activity-dependent manner. A double nleE/nleC mutant was further impaired for its ability to inhibit IL-8 secretion than either a single nleE or a single nleC mutant. We conclude that NleC is a type III effector protease that degrades NF-κB thereby contributing the arsenal of bacterial effectors that inhibit innate immune activation.
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Affiliation(s)
- Jaclyn S Pearson
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Vic. 3010, Australia
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37
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Virus driven evolution: a probable explanation for "Similia Similibus Curantur" philosophy. INFECTION GENETICS AND EVOLUTION 2011; 11:798-802. [PMID: 21345381 DOI: 10.1016/j.meegid.2011.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 02/07/2011] [Accepted: 02/14/2011] [Indexed: 12/27/2022]
Abstract
Despite the advances in biomedical knowledge, there remain many challenging and significant unsolved problems among which are included viral pathogenesis and antiviral therapy, as main topics in human health. On this respect, for instance, our knowledge about human immunodeficiency virus and AIDS is still insufficient to deal with problems of immense significance, such as the possible "natural cure" for a chronic infection or the induction of protective immunity against this agent. At the same time, new viral diseases of humans and animals continue to emerge or re-emerge, due to changes in host susceptibility and/or in virus virulence as well as to re-introduction of a virus that had disappeared from a defined population. These changes, at least in part, may appear as a consequence of antiviral therapies and lead to the selection of viral mutants. Moreover, taking into account that viruses have been studied as causative agents of conspicuous diseases a broad spectrum of uncertainty is still present when unapparent persistent infections are considered. Based on Hippocrates (460-357 b.C.E) natural philosophy, "Natura Morborum Medicatrix" which represents the natural healing force, i.e.: "Nature cures diseases"; and "Similia Similibus Curantur" which means "like cure like", we propose the use of natural compounds with chemical structures similar to cellular membrane components. On this approach, sulfated polysaccharides obtained from marine algae may act as a driving force for the emergence of attenuated viruses, enabling this way a practical approach for preventive therapies for herpes simplex virus infection. At the same time, viruses would be creative tools and their contribution by adding new genetic identity to their host are set points of genesis in the growth of the tree of life.
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38
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Identification and characterization of Cri1, a locus controlling mortality during Citrobacter rodentium infection in mice. Genes Immun 2011; 12:280-90. [PMID: 21326319 DOI: 10.1038/gene.2010.76] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Infection of inbred mouse strains with Citrobacter rodentium represents an ideal model to reveal the genetic factors controlling host resistance to noninvasive enteric bacterial pathogens. We have chosen a positional cloning approach to identify putative gene(s) that control the known difference in survival between resistant C57BL/6J and susceptible C3H/HeJ and C3H/HeOuJ mice. Our work has identified one major locus within proximal chromosome 15 that is responsible for the marked susceptibility of both C3H strains, and we formally exclude Tlr4 from control of survival to this pathogen. We have named this new host resistance locus Cri1 (Citrobacter rodentium infection 1). The Cri1 genetic interval currently spans ∼16 Mb and it confers survival to the infection in a recessive manner. Transfer of the Cri1 locus from the surviving B6 mice into a congenic mouse with a C3Ou genetic background confirms its overall chromosomal localization and its highly significant effect on host survival. The C3Ou.B6-Cri1 mice thus produced have also enabled us to dissociate the control of mouse survival from the control of bacterial load early in the infection as well as from control of colonic hyperplasia.
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39
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Winter SE, Keestra AM, Tsolis RM, Bäumler AJ. The blessings and curses of intestinal inflammation. Cell Host Microbe 2010; 8:36-43. [PMID: 20638640 DOI: 10.1016/j.chom.2010.06.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 04/10/2010] [Accepted: 06/07/2010] [Indexed: 12/19/2022]
Abstract
The intestinal immune system has to strike a delicate balance between initiating inflammatory responses against invading bacterial pathogens and avoiding their induction against microbiota colonizing the lumen. Adequate inflammatory responses against bacterial invasion result in the lumenal secretion of antimicrobial peptides, as well as the release of cytokines in tissue that recruit and activate phagocytes. However, pathogens have evolved to utilize these environmental changes in the inflamed intestine to promote colonization. This review focuses on the costs and benefits of intestinal inflammation and the fine interplay between the host, its microbiota, and enteric pathogens.
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Affiliation(s)
- Sebastian E Winter
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA
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40
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Thanabalasuriar A, Koutsouris A, Hecht G, Gruenheid S. The bacterial virulence factor NleA's involvement in intestinal tight junction disruption during enteropathogenic E. coli infection is independent of its putative PDZ binding domain. Gut Microbes 2010; 1:114-118. [PMID: 21326920 PMCID: PMC3023590 DOI: 10.4161/gmic.1.2.11685] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 02/23/2010] [Accepted: 03/03/2010] [Indexed: 02/06/2023] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is an enteric pathogen able to cause severe diarrhea. Once adhered to the small intestine, EPEC disrupts tight junctions that are important for intestinal barrier function. This disruption is dependent on the bacterial type III secretion system, as well as the translocated effectors EspF and Map. Recently we have shown that a third type III translocated bacterial effector protein, NleA, is also involved in tight junction disruption during EPEC infection. NleA has a predicted PDZ-binding domain at its C-terminus which is proposed to be involved in protein interactions with PDZ domain containing proteins. Since several PDZ-domain-containing proteins localize to tight junctions, we hypothesized that the PDZ-binding domain of NleA might be important for its role in tight junction disruption. However, here we show that a molecular variant of NleA lacking the PDZ-binding domain behaves indistinguishably from the wild-type protein with respect to disruption of tight junctions.
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Affiliation(s)
- Ajitha Thanabalasuriar
- Department of Microbiology and Immunology; and The McGill Life Sciences Complex; Montreal, QC Canada
| | - Athanasia Koutsouris
- Department of Medicine; Digestive Diseases and Nutrition; University of Illinois; Chicago, IL USA
| | - Gail Hecht
- Department of Medicine; Digestive Diseases and Nutrition; University of Illinois; Chicago, IL USA
| | - Samantha Gruenheid
- Department of Microbiology and Immunology; and The McGill Life Sciences Complex; Montreal, QC Canada
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41
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Genetic diversity of O157:H7 and non-O157 verocytotoxigenic Escherichia coli from Argentina inferred from multiple-locus variable-number tandem repeat analysis (MLVA). Int J Med Microbiol 2009; 300:212-7. [PMID: 19850517 DOI: 10.1016/j.ijmm.2009.08.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 07/20/2009] [Accepted: 08/20/2009] [Indexed: 01/29/2023] Open
Abstract
Although serotype O157:H7 has been implicated in most cases of haemolytic-uraemic syndrome (HUS), there is growing concern about non-O157 serotypes of verocytotoxigenic Escherichia coli (VTEC). Multiple-locus variable-number tandem repeat analysis (MLVA) has been focused on the specific typing of O157:H7 isolates, but recently, a generic MLVA assay for E. coli and Shigella has been developed. We performed a study of the polymorphism in 7 generic VNTR loci both in VTEC O157:H7 and non-O157 isolates from Argentina, in order to asses the ability of the method to type this group of isolates and to get insight into their genetic diversity. Sixty-four isolates from cattle, patients with diarrhoea, and contaminated food belonging to 8 different serotypes were studied. All of them could be typed by this method and revealed 41 different MLVA genotypes. The MLVA dendrogram showed 2 main clusters which corresponded to O157:H7 and non-O157, respectively. Our results confirm the suitability of this MLVA method for analyzing VTEC isolates belonging to several serotypes, both O157:H7 as well as non-O157, highlight the genetic variability of the O157:H7 serotype and the need of additional research in order to find more VNTR loci that could allow a higher discrimination among non-O157 VTEC.
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42
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Thanabalasuriar A, Koutsouris A, Weflen A, Mimee M, Hecht G, Gruenheid S. The bacterial virulence factor NleA is required for the disruption of intestinal tight junctions by enteropathogenic Escherichia coli. Cell Microbiol 2009; 12:31-41. [PMID: 19712078 DOI: 10.1111/j.1462-5822.2009.01376.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Enteropathogenic Escherichia coli (EPEC) is a diarrhoeal pathogen that adheres to epithelial cells of the small intestine and uses a type III secretion system to inject effector proteins into host cells. EPEC infection leads to disruption of host intestinal tight junctions that are important for maintaining intestinal barrier function. This disruption is dependent on the bacterial type III secretion system, as well as the translocated effectors EspF and Map. Here we show that a third type III translocated bacterial effector protein, NleA, is also involved in tight junction disruption during EPEC infection. Using the drug Brefeldin A, we demonstrate that the effect of NleA on tight junction integrity is related to its inhibition of host cell protein trafficking through COPII-dependent pathways. These results suggest that NleA's striking effect on virulence is mediated, at least in part, via its role in disruption of intestinal barrier function.
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Affiliation(s)
- Ajitha Thanabalasuriar
- Department of Microbiology and Immunology, The McGill Life Sciences Complex, Montreal, Quebec, Canada
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43
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Best A, White A, Boots M. Resistance is futile but tolerance can explain why parasites do not always castrate their hosts. Evolution 2009; 64:348-57. [PMID: 19686267 DOI: 10.1111/j.1558-5646.2009.00819.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The disease caused by parasites and pathogens often causes sublethal effects that reduce host fecundity. Theory suggests that if parasites can "target" the detrimental effects of their growth on either host mortality or fecundity, they should always fully sterilize. This is because a reduction in host fecundity does not reduce the infectious period and is therefore neutral to a horizontally transmitted infectious organism. However, in nature fully castrating parasites are relatively rare, no doubt in part because of defense mechanisms in the host. Here, we examine in detail the evolution of host defense to the sterilizing effects of parasites and show that intermediate levels of sterility tolerance are found to evolve for a wide range of cost structures. Our key result arises when the host and parasite coevolve. Investment in tolerance by the host may prevent castration, but if host defense is through resistance (by controlling the parasite's growth rate) coevolution by the parasite results in the complete loss of infected host fecundity. Resistance is therefore a waste of resources, but tolerance can explain why parasites do not castrate their hosts. Our results further emphasize the importance of tolerance as opposed to resistance to parasites.
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Affiliation(s)
- Alex Best
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, England, United Kingdom.
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44
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Brodsky IE, Medzhitov R. Targeting of immune signalling networks by bacterial pathogens. Nat Cell Biol 2009; 11:521-6. [PMID: 19404331 DOI: 10.1038/ncb0509-521] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Host defence against microbial pathogens requires appropriate coordination of multiple signalling pathways. These pathways are triggered by innate immune recognition of conserved microbial molecules, and initiate an inflammatory cascade that involves recruitment of leukocytes to the site of infection, activation of antimicrobial effector mechanisms and induction of an adaptive immune response that promotes clearance of infection and long-term immune memory. Microbial pathogens possess specialized proteins termed virulence factors, which interfere with host defence at several levels. Many virulence factors from diverse pathogens have been identified in recent years and their functions linked to disruption of essential processes of immune defence, from signalling to phagocytosis. Although the diversity of pathogens and virulence factors is immense, common themes have emerged with regard to how microbial pathogens interfere with immune responses. Here we discuss recent advances in our understanding of how virulence factors target innate and adaptive immune responses, focusing on bacterial pathogens. We also propose that pathogens responsible for causing acute infection tend to target central components (hubs) of cellular signalling pathways, causing global disruption of the host response. By contrast, pathogens that cause chronic or persistent infections tend to target more peripheral signalling network components (nodes) to promote pathogen persistence.
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Affiliation(s)
- Igor E Brodsky
- Section of Immunobiology, Yale University School of Medicine New Haven, CT 06520, USA
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45
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Alizon S, Hurford A, Mideo N, Van Baalen M. Virulence evolution and the trade-off hypothesis: history, current state of affairs and the future. J Evol Biol 2009; 22:245-59. [PMID: 19196383 DOI: 10.1111/j.1420-9101.2008.01658.x] [Citation(s) in RCA: 586] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
It has been more than two decades since the formulation of the so-called 'trade-off' hypothesis as an alternative to the then commonly accepted idea that parasites should always evolve towards avirulence (the 'avirulence hypothesis'). The trade-off hypothesis states that virulence is an unavoidable consequence of parasite transmission; however, since the 1990s, this hypothesis has been increasingly challenged. We discuss the history of the study of virulence evolution and the development of theories towards the trade-off hypothesis in order to illustrate the context of the debate. We investigate the arguments raised against the trade-off hypothesis and argue that trade-offs exist, but may not be of the simple form that is usually assumed, involving other mechanisms (and life-history traits) than those originally considered. Many processes such as pathogen adaptation to within-host competition, interactions with the immune system and shifting transmission routes, will all be interrelated making sweeping evolutionary predictions harder to obtain. We argue that this is the heart of the current debate in the field and while species-specific models may be better predictive tools, the trade-off hypothesis and its basic extensions are necessary to assess the qualitative impacts of virulence management strategies.
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Affiliation(s)
- S Alizon
- Department of Mathematics and Statistics, Queen's University, Kingston, Canada.
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46
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Coombes BK. Type III secretion systems in symbiotic adaptation of pathogenic and non-pathogenic bacteria. Trends Microbiol 2009; 17:89-94. [PMID: 19217298 DOI: 10.1016/j.tim.2008.11.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 11/06/2008] [Accepted: 11/26/2008] [Indexed: 12/19/2022]
Abstract
The emergence of multi-drug resistance and bacteria with increased virulence is a familiar refrain to the contemporary microbiologist. Although intense research over the past decade has ascribed much molecular detail to these processes, more esoteric questions remain: for example, why are some bacteria evolving increased virulence towards humans, what are the genes underpinning this virulence potential and what are the selective pressures that favor these traits? A holistic approach that considers the organismal biology of bacteria with their diverse hosts seems appropriate to begin to tackle such issues. As it happens, the type III secretion system is turning out to be a central player in the adaptation of both parasites and mutualists to diverse hosts. With this in mind, human interventions in agriculture, animal husbandry and even drug discovery that could influence the selection of bacteria with improved type III secretion system function should be critically appraised.
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Affiliation(s)
- Brian K Coombes
- Michael DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada.
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47
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LeBlanc PM, Yeretssian G, Rutherford N, Doiron K, Nadiri A, Zhu L, Green DR, Gruenheid S, Saleh M. Caspase-12 modulates NOD signaling and regulates antimicrobial peptide production and mucosal immunity. Cell Host Microbe 2008; 3:146-57. [PMID: 18329614 DOI: 10.1016/j.chom.2008.02.004] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 11/13/2007] [Accepted: 02/07/2008] [Indexed: 12/22/2022]
Abstract
Bacterial sensing by intracellular Nod proteins and other Nod-like receptors (NLRs) activates signaling pathways that mediate inflammation and pathogen clearance. Nod1 and Nod2 associate with the kinase Rip2 to stimulate NF-kappaB signaling. Other cytosolic NLRs assemble caspase-1-activating multiprotein complexes termed inflammasomes. Caspase-12 modulates the caspase-1 inflammasome, but unlike other NLRs, Nod1 and Nod2 have not been linked to caspases, and mechanisms regulating the Nod-Rip2 complex are less clear. We report that caspase-12 dampens mucosal immunity to bacterial infection independent of its effects on caspase-1. Caspase-12 deficiency enhances production of antimicrobial peptides, cytokines, and chemokines to entric pathogens, an effect dependent on bacterial type III secretion and the Nod pathway. Mechanistically, caspase-12 binds to Rip2, displacing Traf6 from the signaling complex, inhibiting its ubiquitin ligase activity, and blunting NF-kappaB activation. Nod activation and resulting antimicrobial peptide production constitute an early innate defense mechanism, and caspase-12 inhibits this mucosal antimicrobial response.
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Affiliation(s)
- Philippe M LeBlanc
- Department of Medicine, Division of Critical Care, and Centre for Study of Host Resistance, McGill University, Montreal H3A 1A1, Canada
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Molecular analysis as an aid to assess the public health risk of non-O157 Shiga toxin-producing Escherichia coli strains. Appl Environ Microbiol 2008; 74:2153-60. [PMID: 18245257 DOI: 10.1128/aem.02566-07] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) strains are commensal bacteria in cattle with high potential for environmental and zoonotic transmission to humans. Although O157:H7 is the most common STEC serotype, there is growing concern over the emergence of more than 200 highly virulent non-O157 STEC serotypes that are globally distributed, several of which are associated with outbreaks and/or severe human illness such as hemolytic-uremic syndrome (HUS) and hemorrhagic colitis. At present, the underlying genetic basis of virulence potential in non-O157 STEC is unknown, although horizontal gene transfer and the acquisition of new pathogenicity islands are an expected origin. We used seropathotype classification as a framework to identify genetic elements that distinguish non-O157 STEC strains posing a serious risk to humans from STEC strains that are not associated with severe and epidemic disease. We report the identification of three genomic islands encoding non-LEE effector (nle) genes and 14 individual nle genes in non-O157 STEC strains that correlate independently with outbreak and HUS potential in humans. The implications for transmissible zoonotic spread and public health are discussed. These results and methods offer a molecular risk assessment strategy to rapidly recognize and respond to non-O157 STEC strains from environmental and animal sources that might pose serious public health risks to humans.
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Abstract
The microbial communities of humans are characteristic and complex mixtures of microorganisms that have co-evolved with their human hosts. The species that make up these communities vary between hosts as a result of restricted migration of microorganisms between hosts and strong ecological interactions within hosts, as well as host variability in terms of diet, genotype and colonization history. The shared evolutionary fate of humans and their symbiotic bacteria has selected for mutualistic interactions that are essential for human health, and ecological or genetic changes that uncouple this shared fate can result in disease. In this way, looking to ecological and evolutionary principles might provide new strategies for restoring and maintaining human health.
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50
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Bhavsar AP, Guttman JA, Finlay BB. Manipulation of host-cell pathways by bacterial pathogens. Nature 2007; 449:827-34. [DOI: 10.1038/nature06247] [Citation(s) in RCA: 403] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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