1
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Garrett SR, Mietrach N, Deme J, Bitzer A, Yang Y, Ulhuq FR, Kretschmer D, Heilbronner S, Smith TK, Lea SM, Palmer T. A type VII-secreted lipase toxin with reverse domain arrangement. Nat Commun 2023; 14:8438. [PMID: 38114483 PMCID: PMC10730906 DOI: 10.1038/s41467-023-44221-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 12/05/2023] [Indexed: 12/21/2023] Open
Abstract
The type VII protein secretion system (T7SS) is found in many Gram-positive bacteria and in pathogenic mycobacteria. All T7SS substrate proteins described to date share a common helical domain architecture at the N-terminus that typically interacts with other helical partner proteins, forming a composite signal sequence for targeting to the T7SS. The C-terminal domains are functionally diverse and in Gram-positive bacteria such as Staphylococcus aureus often specify toxic anti-bacterial activity. Here we describe the first example of a class of T7 substrate, TslA, that has a reverse domain organisation. TslA is widely found across Bacillota including Staphylococcus, Enterococcus and Listeria. We show that the S. aureus TslA N-terminal domain is a phospholipase A with anti-staphylococcal activity that is neutralised by the immunity lipoprotein TilA. Two small helical partner proteins, TlaA1 and TlaA2 are essential for T7-dependent secretion of TslA and at least one of these interacts with the TslA C-terminal domain to form a helical stack. Cryo-EM analysis of purified TslA complexes indicate that they share structural similarity with canonical T7 substrates. Our findings suggest that the T7SS has the capacity to recognise a secretion signal present at either end of a substrate.
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Affiliation(s)
- Stephen R Garrett
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Nicole Mietrach
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Justin Deme
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, NIH, Frederick, MD, 21702, USA
| | - Alina Bitzer
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076, Tübingen, Germany
| | - Yaping Yang
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Fatima R Ulhuq
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Dorothee Kretschmer
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076, Tübingen, Germany
| | - Simon Heilbronner
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany
| | - Terry K Smith
- School of Biology, Biomedical Sciences Research Complex, University of St. Andrews, North Haugh, St. Andrews, United Kingdom
| | - Susan M Lea
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, NIH, Frederick, MD, 21702, USA
| | - Tracy Palmer
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
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2
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Slavetinsky J, Lehmann E, Slavetinsky C, Gritsch L, van Dalen R, Kretschmer D, Bleul L, Wolz C, Weidenmaier C, Peschel A. Wall Teichoic Acid Mediates Staphylococcus aureus Binding to Endothelial Cells via the Scavenger Receptor LOX-1. ACS Infect Dis 2023; 9:2133-2140. [PMID: 37910786 DOI: 10.1021/acsinfecdis.3c00252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
The success of Staphylococcus aureus as a major cause for endovascular infections depends on effective interactions with blood-vessel walls. We have previously shown that S. aureus uses its wall teichoic acid (WTA), a surface glycopolymer, to attach to endothelial cells. However, the endothelial WTA receptor remained unknown. We show here that the endothelial oxidized low-density lipoprotein receptor 1 (LOX-1) interacts with S. aureus WTA and permits effective binding of S. aureus to human endothelial cells. Purified LOX-1 bound to isolated S. aureus WTA. Ectopic LOX-1 expression led to increased binding of S. aureus wild type but not of a WTA-deficient mutant to a cell line, and LOX-1 blockage prevented S. aureus binding to endothelial cells. Moreover, WTA and LOX-1 expression levels correlated with the efficacy of the S. aureus-endothelial interaction. Thus, LOX-1 is an endothelial ligand for S. aureus, whose blockage may help to prevent or treat severe endovascular infections.
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Affiliation(s)
- Jessica Slavetinsky
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Esther Lehmann
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Christoph Slavetinsky
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
- Pediatric Surgery and Urology, University Children's Hospital Tübingen, Tübingen 72076, Germany
| | - Lisa Gritsch
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Rob van Dalen
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Dorothee Kretschmer
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Lisa Bleul
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Christiane Wolz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Christopher Weidenmaier
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
| | - Andreas Peschel
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen72076, Germany
- Cluster of Excellence EXC 2124 "Controlling Microbes to Fight Infections", University of Tübingen, Tübingen 72076, Germany
- German Center for Infection Research (DZIF), Partner Site Tübingen, Tübingen 72076 , Germany
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3
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Lebtig M, Scheurer J, Muenkel M, Becker J, Bastounis E, Peschel A, Kretschmer D. Keratinocytes use FPR2 to detect Staphylococcus aureus and initiate antimicrobial skin defense. Front Immunol 2023; 14:1188555. [PMID: 37325619 PMCID: PMC10264695 DOI: 10.3389/fimmu.2023.1188555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/16/2023] [Indexed: 06/17/2023] Open
Abstract
Introduction Keratinocytes form a multilayer barrier that protects the skin from invaders or injuries. The barrier function of keratinocytes is in part mediated by the production of inflammatory modulators that promote immune responses and wound healing. Skin commensals and pathogens such as Staphylococcus aureus secrete high amounts of phenol-soluble modulin (PSM) peptides, agonists of formyl-peptide receptor 2 (FPR2). FPR2 is crucial for the recruitment of neutrophils to the sites of infection, and it can influence inflammation. FPR1 and FPR2 are also expressed by keratinocytes but the consequences of FPR activation in skin cells have remained unknown. Methods Since an inflammatory environment influences S. aureus colonization, e. g. in patients with atopic dermatitis (AD), we hypothesized that interference with FPRs may alter keratinocyte-induced inflammation, proliferation, and bacterial colonization of the skin. To assess this hypothesis, we investigated the effects of FPR activation and inhibition in keratinocytes with respect to chemokine and cytokine release as well as proliferation and skin wound gap closure. Results We observed that FPR activation induces the release of IL-8, IL-1α and promotes keratinocyte proliferation in a FPR-dependent manner. To elucidate the consequence of FPR modulation on skin colonization, we used an AD-simulating S. aureus skin colonization mouse model using wild-type (WT) or Fpr2-/- mice and demonstrate that inflammation enhances the eradication of S. aureus from the skin in a FPR2-dependent way. Consistently, inhibition of FPR2 in the mouse model or in human keratinocytes as well as human skin explants promoted S. aureus colonization. Discussion Our data indicate that FPR2 ligands promote inflammation and keratinocyte proliferation in a FPR2-dependent manner, which is necessary for eliminating S. aureus during skin colonization.
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Affiliation(s)
- Marco Lebtig
- Department first: Infection Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
| | - Jasmin Scheurer
- Department of Dermatology, University of Tübingen, Tübingen, Germany
| | - Marie Muenkel
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Janna Becker
- Department first: Infection Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
| | - Effie Bastounis
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Andreas Peschel
- Department first: Infection Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Department first: Infection Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
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4
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Kengmo Tchoupa A, Kretschmer D, Schittek B, Peschel A. The epidermal lipid barrier in microbiome-skin interaction. Trends Microbiol 2023:S0966-842X(23)00027-6. [PMID: 36822953 DOI: 10.1016/j.tim.2023.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Revised: 01/24/2023] [Accepted: 01/24/2023] [Indexed: 02/25/2023]
Abstract
The corneocyte layers forming the upper surface of mammalian skin are embedded in a lamellar-membrane matrix which repels harmful molecules while retaining solutes from subcutaneous tissues. Only certain bacterial and fungal taxa colonize skin surfaces. They have ways to use epidermal lipids as nutrients while resisting antimicrobial fatty acids. Skin microorganisms release lipophilic microbe-associated molecular pattern (MAMP) molecules which are largely retained by the epidermal lipid barrier. Skin barrier defects, as in atopic dermatitis, impair lamellar-membrane integrity, resulting in altered skin microbiomes, which then include the pathogen Staphylococcus aureus. The resulting increased penetration of MAMPs and toxins promotes skin inflammation. Elucidating how microorganisms manipulate the epidermal lipid barrier will be key for better ways of preventing inflammatory skin disorders.
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Affiliation(s)
- Arnaud Kengmo Tchoupa
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Infection Biology Section, University of Tübingen, Tübingen, Germany; Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany; German Center for Infection Research (DZIF), partner site Tübingen, Germany
| | - Dorothee Kretschmer
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Infection Biology Section, University of Tübingen, Tübingen, Germany; Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany; German Center for Infection Research (DZIF), partner site Tübingen, Germany
| | - Birgit Schittek
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany; Dermatology Department, University Hospital Tübingen, Tübingen, Germany
| | - Andreas Peschel
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, Infection Biology Section, University of Tübingen, Tübingen, Germany; Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany; German Center for Infection Research (DZIF), partner site Tübingen, Germany.
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5
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Zipperer A, Scheurer J, Kretschmer D. Cytotoxicity Assays as Predictors of the Safety and Efficacy of Antimicrobial Agents. Methods Mol Biol 2023; 2601:153-167. [PMID: 36445583 DOI: 10.1007/978-1-0716-2855-3_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The development of safe antimicrobial agents is important for the effective treatment of pathogens. From a multitude of discovered inhibitory compounds, only a few antimicrobial agents are able to enter the market. Many antimicrobials are, on the one hand, quite effective in killing pathogens but, on the other hand, cytotoxic to eukaryotic cells. Cell health can be monitored by various methods. Plasma membrane integrity, DNA synthesis, enzyme activity, and reducing conditions within the cell are known indicators of cell viability and cell death. For a comprehensive overview, methods to analyze cytotoxic and hemolytic effects, e.g., lactate dehydrogenase release, cell proliferation analysis, cell viability analysis based on the activity of different intracellular enzymes, and hemolysis assay of antimicrobial compounds on human cells, are described in this updated chapter.
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Affiliation(s)
- Alexander Zipperer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
| | - Jasmin Scheurer
- Department of Dermatology, Division of Dermatooncology, University of Tübingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.
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6
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Schlatterer K, Peschel A, Kretschmer D. Short-Chain Fatty Acid and FFAR2 Activation - A New Option for Treating Infections? Front Cell Infect Microbiol 2021; 11:785833. [PMID: 34926327 PMCID: PMC8674814 DOI: 10.3389/fcimb.2021.785833] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 11/09/2021] [Indexed: 01/05/2023] Open
Abstract
The human innate immune system is equipped with multiple mechanisms to detect microbe-associated molecular patterns (MAMPs) to fight bacterial infections. The metabolite short-chain fatty acids (SCFAs) acetate, propionate and butyrate are released by multiple bacteria or are food ingredients. SCFA production, especially acetate production, is usually essential for bacteria, and knockout of pathways involved in acetate production strongly impairs bacterial fitness. Because host organisms use SCFAs as MAMPs and alter immune reactions in response to SCFAs, interventions that modulate SCFA levels can be a new strategy for infection control. The interaction between SCFAs and host cells has been primarily investigated in the intestinal lumen because of the high local levels of SCFAs released by bacterial microbiome members. However, members of not only the intestinal microbiome but also the skin microbiome produce SCFAs, which are known ligands of the seven-transmembrane G-protein-coupled receptor FFAR2. In addition to enterocytes, FFAR2 is expressed on other human cell types, including leukocytes, especially neutrophils. This finding is in line with other research that determined that targeted activation of FFAR2 diminishes susceptibility toward various types of infection by bacteria such as Klebsiella pneumonia, Citrobacter rodentium, and Staphylococcus aureus but also by viruses such as respiratory syncytial and influenza viruses. Thus, our immune system appears to be able to use FFAR2-dependent detection of SCFAs for perceiving and even averting severe infections. We summarize recent advances in understanding the role of SCFAs and FFAR2 in various infection types and propose the manipulation of this receptor as an additional therapeutic strategy to fight infections.
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Affiliation(s)
- Katja Schlatterer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence Cluster of Excellence (EXC) 2124 Controlling Microbes to Fight Infections, University of Tuebingen, Tübingen, Germany
| | - Andreas Peschel
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence Cluster of Excellence (EXC) 2124 Controlling Microbes to Fight Infections, University of Tuebingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence Cluster of Excellence (EXC) 2124 Controlling Microbes to Fight Infections, University of Tuebingen, Tübingen, Germany
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7
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Staudenmaier L, Focken J, Schlatterer K, Kretschmer D, Schittek B. Bacterial membrane vesicles shape Staphylococcus aureus skin colonization and induction of innate immune responses. Exp Dermatol 2021; 31:349-361. [PMID: 34679243 DOI: 10.1111/exd.14478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 09/10/2021] [Accepted: 10/17/2021] [Indexed: 11/30/2022]
Abstract
Staphylococcus aureus colonization is abundant on the skin of atopic dermatitis (AD) patients where it contributes to skin inflammation. S. aureus produces virulence factors that distinguish it from commensal skin bacteria such as S. epidermidis and S. lugdunensis. However, it has remained unclear, which of these virulence factors have the strongest impact on AD. Membrane vesicles (MVs) are released by pathogenic bacteria and might play an essential role in the long-distance delivery of bacterial effectors such as virulence factors. We show that MVs are also released by skin commensals in a similar quantity and membrane lipid amount as those from pathogenic S. aureus. Interestingly, MVs from skin commensals can protect against S. aureus skin colonization by conditioning human skin for enhanced defence. In contrast, MVs released by S. aureus are able to induce CXCL8 and TNF-α in primary human keratinocytes, recruit neutrophils and induce neutrophil extracellular traps, which enhance S. aureus skin colonization. CXCL8 induction is TLR2- and NFkB-dependent and the induction level correlates with the membrane lipid and protein A content of the MVs. Interestingly, MVs of S. aureus strains from the lesional skin of AD patients show an enhanced membrane lipid and protein A content compared to the strains from the non-lesional sites and have an enhanced proinflammatory potential. Our data underline the complex interplay in host- and bacterial derived factors in S. aureus skin colonization and the important role of bacterial derived MVs and their membrane lipid and protein A content in skin inflammatory disorders.
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Affiliation(s)
- Lena Staudenmaier
- Department of Dermatology, University of Tübingen, Tübingen, Germany.,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
| | - Jule Focken
- Department of Dermatology, University of Tübingen, Tübingen, Germany.,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
| | - Katja Schlatterer
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany.,Interfaculty Institute of Microbiology and Infection Medicine, Infection Biology, University of Tübingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany.,Interfaculty Institute of Microbiology and Infection Medicine, Infection Biology, University of Tübingen, Tübingen, Germany
| | - Birgit Schittek
- Department of Dermatology, University of Tübingen, Tübingen, Germany.,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
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8
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Kretschmer D, Breitmeyer R, Gekeler C, Lebtig M, Schlatterer K, Nega M, Stahl M, Stapels D, Rooijakkers S, Peschel A. Staphylococcus aureus Depends on Eap Proteins for Preventing Degradation of Its Phenol-Soluble Modulin Toxins by Neutrophil Serine Proteases. Front Immunol 2021; 12:701093. [PMID: 34552584 PMCID: PMC8451722 DOI: 10.3389/fimmu.2021.701093] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 08/18/2021] [Indexed: 11/13/2022] Open
Abstract
Neutrophil granulocytes act as a first line of defense against pathogenic staphylococci. However, Staphylococcus aureus has a remarkable capacity to survive neutrophil killing, which distinguishes it from the less-pathogenic Staphylococcus epidermidis. Both species release phenol-soluble modulin (PSM) toxins, which activate the neutrophil formyl-peptide receptor 2 (FPR2) to promote neutrophil influx and phagocytosis, and which disrupt neutrophils or their phagosomal membranes at high concentrations. We show here that the neutrophil serine proteases (NSPs) neutrophil elastase, cathepsin G and proteinase 3, which are released into the extracellular space or the phagosome upon neutrophil FPR2 stimulation, effectively degrade PSMs thereby preventing their capacity to activate and destroy neutrophils. Notably, S. aureus, but not S. epidermidis, secretes potent NSP-inhibitory proteins, Eap, EapH1, EapH2, which prevented the degradation of PSMs by NSPs. Accordingly, a S. aureus mutant lacking all three NSP inhibitory proteins was less effective in activating and destroying neutrophils and it survived less well in the presence of neutrophils than the parental strain. We show that Eap proteins promote pathology via PSM-mediated FPR2 activation since murine intraperitoneal infection with the S. aureus parental but not with the NSP inhibitors mutant strain, led to a significantly higher bacterial load in the peritoneum and kidneys of mFpr2-/- compared to wild-type mice. These data demonstrate that NSPs can very effectively detoxify some of the most potent staphylococcal toxins and that the prominent human pathogen S. aureus has developed efficient inhibitors to preserve PSM functions. Preventing PSM degradation during infection represents an important survival strategy to ensure FPR2 activation.
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Affiliation(s)
- Dorothee Kretschmer
- Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany
| | - Ricarda Breitmeyer
- Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany
| | - Cordula Gekeler
- Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany
| | - Marco Lebtig
- Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany
| | - Katja Schlatterer
- Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany
| | - Mulugeta Nega
- Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany.,Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Microbial Genetics, University of Tübingen, Tübingen, Germany
| | - Mark Stahl
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen, Germany
| | - Daphne Stapels
- Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Suzan Rooijakkers
- Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Andreas Peschel
- Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany.,German Center for Infection Research, Partner Site Tübingen, Tübingen, Germany.,Cluster of Excellence EXC2124 "Controlling Microbes to Fight Infections", Tübingen, Germany
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9
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Schlatterer K, Beck C, Schoppmeier U, Peschel A, Kretschmer D. Acetate sensing by GPR43 alarms neutrophils and protects from severe sepsis. Commun Biol 2021; 4:928. [PMID: 34330996 PMCID: PMC8324776 DOI: 10.1038/s42003-021-02427-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 06/23/2021] [Indexed: 02/07/2023] Open
Abstract
Bacterial sepsis is a major cause of mortality resulting from inadequate immune responses to systemic infection. Effective immunomodulatory approaches are urgently needed but it has remained elusive, which targets might be suitable for intervention. Increased expression of the G-protein-coupled receptor GPR43, which is known to govern intestinal responses to acetate, has been associated with sepsis patient survival but the mechanisms behind this observation have remained unclear. We show that elevated serum acetate concentrations prime neutrophils in a GPR43-dependent fashion, leading to enhanced neutrophil chemotaxis, oxidative burst, cytokine release and upregulation of phagocytic receptors. Consequently, acetate priming improved the capacity of human neutrophils to eliminate methicillin-resistant Staphylococcus aureus. Acetate administration increased mouse serum acetate concentrations and primed neutrophils. Notably, it rescued wild-type mice from severe S. aureus sepsis and reduced bacterial numbers in peripheral organs by several magnitudes. Acetate treatment improved the sepsis course even when applied several hours after onset of the infection, which recommends GPR43 as a potential target for sepsis therapy. Our study indicates that the severity of sepsis depends on transient neutrophil priming by appropriate blood acetate concentrations. Therapeutic interventions based on GPR43 stimulation could become valuable strategies for reducing sepsis-associated morbidity and mortality.
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Affiliation(s)
- Katja Schlatterer
- grid.10392.390000 0001 2190 1447Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany ,grid.452463.2German Center for Infection Research, partner site Tübingen, Tübingen, Germany ,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, Tübingen, Germany
| | - Christian Beck
- grid.10392.390000 0001 2190 1447Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany ,grid.452463.2German Center for Infection Research, partner site Tübingen, Tübingen, Germany ,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, Tübingen, Germany
| | - Ulrich Schoppmeier
- grid.452463.2German Center for Infection Research, partner site Tübingen, Tübingen, Germany ,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, Tübingen, Germany ,grid.10392.390000 0001 2190 1447Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Andreas Peschel
- grid.10392.390000 0001 2190 1447Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany ,grid.452463.2German Center for Infection Research, partner site Tübingen, Tübingen, Germany ,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, Tübingen, Germany
| | - Dorothee Kretschmer
- grid.10392.390000 0001 2190 1447Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Infection Biology, University of Tübingen, Tübingen, Germany ,grid.452463.2German Center for Infection Research, partner site Tübingen, Tübingen, Germany ,Cluster of Excellence EXC 2124 Controlling Microbes to Fight Infections, Tübingen, Germany
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10
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Weiß E, Schlatterer K, Beck C, Peschel A, Kretschmer D. Formyl-Peptide Receptor Activation Enhances Phagocytosis of Community-Acquired Methicillin-Resistant Staphylococcus aureus. J Infect Dis 2020; 221:668-678. [PMID: 31573600 DOI: 10.1093/infdis/jiz498] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 09/27/2019] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Formyl-peptide receptors (FPRs) are important pattern recognition receptors that sense specific bacterial peptides. Formyl-peptide receptors are highly expressed on neutrophils and monocytes, and their activation promotes the migration of phagocytes to sites of infection. It is currently unknown whether FPRs may also influence subsequent processes such as bacterial phagocytosis and killing. Staphylococcus aureus, especially highly pathogenic community-acquired methicillin-resistant S aureus strains, release high amounts of FPR2 ligands, the phenol-soluble modulins. METHODS We demonstrate that FPR activation leads to upregulation of complement receptors 1 and 3 as well as FCγ receptor I on neutrophils and, consequently, increased opsonic phagocytosis of S aureus and other pathogens. RESULTS Increased phagocytosis promotes killing of S aureus and interleukin-8 release by neutrophils. CONCLUSIONS We show here for the first time that FPRs govern opsonic phagocytosis. Manipulation of FPR2 activation could open new therapeutic opportunities against bacterial pathogens.
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Affiliation(s)
- Elisabeth Weiß
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Katja Schlatterer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Christian Beck
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Andreas Peschel
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
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11
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Liu L, Beck C, Nøhr-Meldgaard K, Peschel A, Kretschmer D, Ingmer H, Vestergaard M. Inhibition of the ATP synthase sensitizes Staphylococcus aureus towards human antimicrobial peptides. Sci Rep 2020; 10:11391. [PMID: 32647350 PMCID: PMC7347559 DOI: 10.1038/s41598-020-68146-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 06/08/2020] [Indexed: 11/09/2022] Open
Abstract
Antimicrobial peptides (AMPs) are an important part of the human innate immune system for protection against bacterial infections, however the AMPs display varying degrees of activity against Staphylococcus aureus. Previously, we showed that inactivation of the ATP synthase sensitizes S. aureus towards the AMP antibiotic class of polymyxins. Here we wondered if the ATP synthase similarly is needed for tolerance towards various human AMPs, including human β-defensins (hBD1-4), LL-37 and histatin 5. Importantly, we find that the ATP synthase mutant (atpA) is more susceptible to killing by hBD4, hBD2, LL-37 and histatin 5 than wild type cells, while no changes in susceptibility was detected for hBD3 and hBD1. Administration of the ATP synthase inhibitor, resveratrol, sensitizes S. aureus towards hBD4-mediated killing. Neutrophils rely on AMPs and reactive oxygen molecules to eliminate bacteria and the atpA mutant is more susceptible to killing by neutrophils than the WT, even when the oxidative burst is inhibited.These results show that the staphylococcal ATP synthase enhance tolerance of S. aureus towards some human AMPs and this indicates that inhibition of the ATP synthase may be explored as a new therapeutic strategy that sensitizes S. aureus to naturally occurring AMPs of the innate immune system.
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Affiliation(s)
- Liping Liu
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark
| | - Christian Beck
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
| | - Katrine Nøhr-Meldgaard
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark
| | - Andreas Peschel
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
| | - Dorothee Kretschmer
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), Cluster of Excellence 'Controlling Microbes to Fight Infections', University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
| | - Hanne Ingmer
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.
| | - Martin Vestergaard
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark
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12
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Tribelli PM, Luqman A, Nguyen MT, Madlung J, Fan SH, Macek B, Sass P, Bitschar K, Schittek B, Kretschmer D, Götz F. Staphylococcus aureus Lpl protein triggers human host cell invasion via activation of Hsp90 receptor. Cell Microbiol 2019; 22:e13111. [PMID: 31515903 DOI: 10.1111/cmi.13111] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/02/2019] [Accepted: 08/26/2019] [Indexed: 12/19/2022]
Abstract
Staphylococcus aureus is a facultative intracellular pathogen. Recently, it has been shown that the protein part of the lipoprotein-like lipoproteins (Lpls), encoded by the lpl cluster comprising of 10 lpls paralogue genes, increases pathogenicity, delays the G2/M phase transition, and also triggers host cell invasion. Here, we show that a recombinant Lpl1 protein without the lipid moiety binds directly to the isoforms of the human heat shock proteins Hsp90α and Hsp90ß. Synthetic peptides covering the Lpl1 sequence caused a twofold to fivefold increase of S. aureus invasion in HaCaT cells. Antibodies against Hsp90 decrease S. aureus invasion in HaCaT cells and in primary human keratinocytes. Additionally, inhibition of ATPase function of Hsp90 or silencing Hsp90α expression by siRNA also decreased the S. aureus invasion in HaCaT cells. Although the Hsp90ß is constitutively expressed, the Hsp90α isoform is heat-inducible and appears to play a major role in Lpl1 interaction. Pre-incubation of HaCaT cells at 39°C increased both the Hsp90α expression and S. aureus invasion. Lpl1-Hsp90 interaction induces F-actin formation, thus, triggering an endocytosis-like internalisation. Here, we uncovered a new host cell invasion principle on the basis of Lpl-Hsp90 interaction.
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Affiliation(s)
- Paula M Tribelli
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.,Departamento de Química Biológica, FCEyN-UBA, Buenos Aires, Argentina.,IQUIBICEN-CONICET, Buenos Aires, Argentina
| | - Arif Luqman
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.,Institut Teknologi Sepuluh Nopember, Biology Department, Surabaya, Indonesia
| | - Minh-Thu Nguyen
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.,Division of Microbiology, Paul-Ehrlich Institute, Langen, Germany
| | - Johannes Madlung
- Proteome Center Tübingen, University of Tübingen, Tübingen, Germany
| | - Sook-Ha Fan
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
| | - Boris Macek
- Proteome Center Tübingen, University of Tübingen, Tübingen, Germany
| | - Peter Sass
- Microbial Bioactive Compounds, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
| | | | - Birgit Schittek
- Department of Dermatology, University of Tübingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
| | - Friedrich Götz
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
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13
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Stoll H, Ost M, Singh A, Mehling R, Neri D, Schäfer I, Velic A, Macek B, Kretschmer D, Weidenmaier C, Hector A, Handgretinger R, Götz F, Peschel A, Hartl D, Rieber N. Staphylococcal Enterotoxins Dose-Dependently Modulate the Generation of Myeloid-Derived Suppressor Cells. Front Cell Infect Microbiol 2018; 8:321. [PMID: 30271756 PMCID: PMC6146041 DOI: 10.3389/fcimb.2018.00321] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/22/2018] [Indexed: 11/13/2022] Open
Abstract
Staphylococcus aureus is one of the major human bacterial pathogens causing a broad spectrum of serious infections. Myeloid-derived suppressor cells (MDSC) represent an innate immune cell subset capable of regulating host-pathogen interactions, yet their role in the pathogenesis of S. aureus infections remains incompletely defined. The aim of this study was to determine the influence of different S. aureus strains and associated virulence factors on human MDSC generation. Using an in vitro MDSC generation assay we demonstrate that low concentrations of supernatants of different S. aureus strains led to an induction of functional MDSC, whereas increased concentrations, conversely, reduced MDSC numbers. The concentration-dependent reduction of MDSC correlated with T cell proliferation and cytotoxicity. Several findings supported a role for staphylococcal enterotoxins in modulating MDSC generation. Staphylococcal enterotoxins recapitulated concentration-dependent MDSC induction and inhibition, T cell proliferation and cytotoxicity, while an enterotoxin-deficient S. aureus strain largely failed to alter MDSC. Taken together, we identified staphylococcal enterotoxins as main modulators of MDSC generation. The inhibition of MDSC generation by staphylococcal enterotoxins might represent a novel therapeutic target in S. aureus infections and beyond in non-infectious conditions, such as cancer.
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Affiliation(s)
- Hartmut Stoll
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | - Michael Ost
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | - Anurag Singh
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | - Roman Mehling
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | - Davide Neri
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | - Iris Schäfer
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | - Ana Velic
- Proteome Center Tuebingen, Interfaculty Institute for Cell Biology, University of Tuebingen, Tuebingen, Germany
| | - Boris Macek
- Proteome Center Tuebingen, Interfaculty Institute for Cell Biology, University of Tuebingen, Tuebingen, Germany
| | - Dorothee Kretschmer
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tuebingen, Tuebingen, Germany
| | - Christopher Weidenmaier
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tuebingen, Tuebingen, Germany
| | - Andreas Hector
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany
| | | | - Friedrich Götz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tuebingen, Tuebingen, Germany
| | - Andreas Peschel
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tuebingen, Tuebingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tuebingen, Tuebingen, Germany
| | - Dominik Hartl
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tuebingen, Tuebingen, Germany
| | - Nikolaus Rieber
- Department of Pediatrics I, University of Tuebingen, Tuebingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tuebingen, Tuebingen, Germany.,Department of Pediatrics, Kinderklinik Muenchen Schwabing, Klinikum Schwabing, StKM GmbH und Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
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14
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Weiß E, Kretschmer D. Formyl-Peptide Receptors in Infection, Inflammation, and Cancer. Trends Immunol 2018; 39:815-829. [PMID: 30195466 DOI: 10.1016/j.it.2018.08.005] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 08/02/2018] [Accepted: 08/12/2018] [Indexed: 12/15/2022]
Abstract
Formyl-peptide receptors (FPRs) recognize bacterial and mitochondrial formylated peptides as well as endogenous non-formylated peptides and even lipids. FPRs are expressed on various host cell types but most strongly on neutrophils and macrophages. After the discovery of FPRs on leukocytes, it was assumed that these receptors predominantly govern a proinflammatory response resulting in chemotaxis, degranulation, and oxidative burst during infection. However, it is clear that the activation of FPRs has more complex consequences and can also promote the resolution of inflammation. Recent studies have highlighted associations between FPR function and inflammatory conditions, including inflammatory disorders, cancer, and infection. In this review we discuss these recent findings.
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Affiliation(s)
- Elisabeth Weiß
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Dorothee Kretschmer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
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15
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Kretschmer D, Hanzelmann D, Peschel A. Lipoprotein immunoproteomics question the potential of Staphylococcus aureus TLR2 agonists as vaccine antigens. Proteomics 2017; 16:2603-2604. [PMID: 27667303 DOI: 10.1002/pmic.201600351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 09/23/2016] [Indexed: 12/27/2022]
Abstract
Toll-like receptor 2 (TLR2) is regarded as the major innate immunity sensor in infections caused by the Gram-positive bacterial pathogen Staphylococcus aureus. However, previous studies on the roles of TLR2 in S. aureus infections have been elusive and in part contradictory. It has remained particularly unclear if bacterial lipoproteins, the major TLR2 ligands, could serve as antigens with intrinsic adjuvant property for the development of protective vaccines. The study by Vu et al. published in this issue of Proteomics analyzed the antibody and T-cell responses in human sera against major S. aureus lipoproteins. Notably, even lipoproteins released to culture filtrates at similar levels as established immunodominant antigens elicited only very weak or no detectable antibody and T-cell responses, indicating that the potent TLR2-stimulating capacity of S. aureus lipoproteins does not promote and may rather impair robust immune responses so lipoprpteins. Among several potential explanations it is tempting to speculate that the role of TLR2 in S. aureus infections may be more complex and more ambiguous than previously thought. The study of Vu et al. may thus provoke more detailed investigations on the roles of lipoproteins and TLR2 in innate and adaptive immunity against bacterial pathogens.
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Affiliation(s)
- Dorothee Kretschmer
- Infection Biology Department, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Dennis Hanzelmann
- Infection Biology Department, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Andreas Peschel
- Infection Biology Department, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany.
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16
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Weiss E, Hanzelmann D, Fehlhaber B, Klos A, von Loewenich FD, Liese J, Peschel A, Kretschmer D. Formyl-peptide receptor 2 governs leukocyte influx in local Staphylococcus aureus infections. FASEB J 2017; 32:26-36. [PMID: 28855276 DOI: 10.1096/fj.201700441r] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 08/07/2017] [Indexed: 01/15/2023]
Abstract
Leukocytes express formyl-peptide receptors (FPRs), which sense microbe-associated molecular pattern (MAMP) molecules, leading to leukocyte chemotaxis and activation. We recently demonstrated that phenol-soluble modulin (PSM) peptides from highly pathogenic Staphylococcus aureus are efficient ligands for the human FPR2. How PSM detection by FPR2 impacts on the course of S. aureus infections has remained unknown. We characterized the specificity of mouse FPR2 (mFpr2) using a receptor-transfected cell line, homeobox b8 (Hoxb8), and primary neutrophils isolated from wild-type (WT) or mFpr2-/- mice. The influx of leukocytes into the peritoneum of WT and mFpr2-/- mice was analyzed. We demonstrate that mFpr2 is specifically activated by PSMs in mice, and they represent the first secreted pathogen-derived ligands for the mFpr2. Intraperitoneal infection with S. aureus led to lower numbers of immigrated leukocytes in mFpr2-/- compared with WT mice at 3 h after infection, and this difference was not observed when mice were infected with an S. aureus PSM mutant. Our data support the hypothesis that the mFpr2 is the functional homolog of the human FPR2 and that a mouse infection model represents a suitable model for analyzing the role of PSMs during infection. PSM recognition by mFpr2 shapes leukocyte influx in local infections, the typical infections caused by S. aureus-Weiss, E., Hanzelmann, D., Fehlhaber, B., Klos, A., von Loewenich, F. D., Liese, J., Peschel, A., Kretschmer, D. Formyl-peptide receptor 2 governs leukocyte influx in local Staphylococcus aureus infections.
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Affiliation(s)
- Elisabeth Weiss
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Dennis Hanzelmann
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Beate Fehlhaber
- Institute of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Hannover, Germany
| | - Andreas Klos
- Institute of Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Hannover, Germany
| | - Friederike D von Loewenich
- Department of Medical Microbiology and Hygiene, Medical Center, University of Mainz, Mainz, Germany; and
| | - Jan Liese
- Medical Microbiology and Hygiene, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
| | - Andreas Peschel
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Dorothee Kretschmer
- Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany;
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17
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Wanner S, Schade J, Keinhörster D, Weller N, George SE, Kull L, Bauer J, Grau T, Winstel V, Stoy H, Kretschmer D, Kolata J, Wolz C, Bröker BM, Weidenmaier C. Wall teichoic acids mediate increased virulence in Staphylococcus aureus. Nat Microbiol 2017; 2:16257. [DOI: 10.1038/nmicrobiol.2016.257] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 11/28/2016] [Indexed: 12/15/2022]
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18
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Abstract
The development of safe antimicrobial agents is important for the effective treatment of pathogens. From a multitude of discovered inhibitory compounds only few antimicrobial agents are able to enter the market. Many antimicrobials are, on the one hand, quite effective in killing pathogens but, on the other hand, cytotoxic to eukaryotic cells. Cell health can be monitored by various methods. Plasma membrane integrity, DNA synthesis, enzyme activity, and reducing conditions within the cell are known indicators of cell viability and cell death. For a comprehensive overview, methods to analyze cytotoxic and hemolytic effects, e.g., lactate dehydrogenase release, cell proliferation analysis, cell viability analysis, and hemolysis assay of antimicrobial compounds on human cells, are described in this chapter.
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Affiliation(s)
- Alexander Zipperer
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen(IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
| | - Dorothee Kretschmer
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen(IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
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19
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Blättner S, Das S, Paprotka K, Eilers U, Krischke M, Kretschmer D, Remmele CW, Dittrich M, Müller T, Schuelein-Voelk C, Hertlein T, Mueller MJ, Huettel B, Reinhardt R, Ohlsen K, Rudel T, Fraunholz MJ. Staphylococcus aureus Exploits a Non-ribosomal Cyclic Dipeptide to Modulate Survival within Epithelial Cells and Phagocytes. PLoS Pathog 2016; 12:e1005857. [PMID: 27632173 PMCID: PMC5025175 DOI: 10.1371/journal.ppat.1005857] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 08/10/2016] [Indexed: 12/21/2022] Open
Abstract
Community-acquired (CA) Staphylococcus aureus cause various diseases even in healthy individuals. Enhanced virulence of CA-strains is partly attributed to increased production of toxins such as phenol-soluble modulins (PSM). The pathogen is internalized efficiently by mammalian host cells and intracellular S. aureus has recently been shown to contribute to disease. Upon internalization, cytotoxic S. aureus strains can disrupt phagosomal membranes and kill host cells in a PSM-dependent manner. However, PSM are not sufficient for these processes. Here we screened for factors required for intracellular S. aureus virulence. We infected escape reporter host cells with strains from an established transposon mutant library and detected phagosomal escape rates using automated microscopy. We thereby, among other factors, identified a non-ribosomal peptide synthetase (NRPS) to be required for efficient phagosomal escape and intracellular survival of S. aureus as well as induction of host cell death. By genetic complementation as well as supplementation with the synthetic NRPS product, the cyclic dipeptide phevalin, wild-type phenotypes were restored. We further demonstrate that the NRPS is contributing to virulence in a mouse pneumonia model. Together, our data illustrate a hitherto unrecognized function of the S. aureus NRPS and its dipeptide product during S. aureus infection.
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Affiliation(s)
- Sebastian Blättner
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
| | - Sudip Das
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
| | - Kerstin Paprotka
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
| | - Ursula Eilers
- Core Unit Functional Genomics, University of Würzburg, Würzburg, Germany
| | - Markus Krischke
- Biocenter, Chair of Pharmaceutical Biology, University of Würzburg, Würzburg, Germany
| | - Dorothee Kretschmer
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University Tübingen, Tübingen, Germany
| | | | - Marcus Dittrich
- Biocenter, Chair of Bioinformatics, University of Würzburg, Würzburg, Germany
- Institute of Human Genetics, University of Würzburg, Würzburg, Germany
| | - Tobias Müller
- Biocenter, Chair of Bioinformatics, University of Würzburg, Würzburg, Germany
| | | | - Tobias Hertlein
- Institute for Molecular Infection Biology, University of Würzburg, Würzburg, Germany
| | - Martin J. Mueller
- Biocenter, Chair of Pharmaceutical Biology, University of Würzburg, Würzburg, Germany
| | | | | | - Knut Ohlsen
- Institute for Molecular Infection Biology, University of Würzburg, Würzburg, Germany
| | - Thomas Rudel
- Biocenter, Chair of Microbiology, University of Würzburg, Würzburg, Germany
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Hanzelmann D, Joo HS, Franz-Wachtel M, Hertlein T, Stevanovic S, Macek B, Wolz C, Götz F, Otto M, Kretschmer D, Peschel A. Toll-like receptor 2 activation depends on lipopeptide shedding by bacterial surfactants. Nat Commun 2016; 7:12304. [PMID: 27470911 PMCID: PMC4974576 DOI: 10.1038/ncomms12304] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 06/21/2016] [Indexed: 12/18/2022] Open
Abstract
Sepsis caused by Gram-positive bacterial pathogens is a major fatal disease but its molecular basis remains elusive. Toll-like receptor 2 (TLR2) has been implicated in the orchestration of inflammation and sepsis but its role appears to vary for different pathogen species and clones. Accordingly, Staphylococcus aureus clinical isolates differ substantially in their capacity to activate TLR2. Here we show that strong TLR2 stimulation depends on high-level production of phenol-soluble modulin (PSM) peptides in response to the global virulence activator Agr. PSMs are required for mobilizing lipoproteins, the TLR2 agonists, from the staphylococcal cytoplasmic membrane. Notably, the course of sepsis caused by PSM-deficient S. aureus is similar in wild-type and TLR2-deficient mice, but TLR2 is required for protection of mice against PSM-producing S. aureus. Thus, a crucial role of TLR2 depends on agonist release by bacterial surfactants. Modulation of this process may lead to new therapeutic strategies against Gram-positive infections. The role played by human protein TLR2 in inflammation and sepsis varies for different bacterial pathogens. Here, Hanzelmann et al. show that the differential abilities of Staphylococcus aureus strains to activate TLR2 depend on their production of peptides that release lipoproteins known to act as TLR2 agonists.
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Affiliation(s)
- Dennis Hanzelmann
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Hwang-Soo Joo
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Mirita Franz-Wachtel
- Proteome Center Tübingen, Interfaculty Institute of Cell Biology, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Tobias Hertlein
- Institute for Molecular Infection Biology, University of Würzburg, Josef-Schneider-Straße 2, Würzburg 97080, Germany
| | - Stefan Stevanovic
- Department of Immunology, Interfaculty Institute for Cell Biology, Eberhard Karls University, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Boris Macek
- Proteome Center Tübingen, Interfaculty Institute of Cell Biology, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Christiane Wolz
- Department of Medical Microbiology and Hygiene, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Elfriede-Aulhorn-Straße 5, 72076 Tübingen, Germany
| | - Friedrich Götz
- Department of Microbial Genetics, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Dorothee Kretschmer
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.,German Center for Infection Research, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Andreas Peschel
- Department of Infection Biology, Interfaculty Institute for Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.,German Center for Infection Research, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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Armbruster NS, Richardson JR, Schreiner J, Klenk J, Günter M, Kretschmer D, Pöschel S, Schenke-Layland K, Kalbacher H, Clark K, Autenrieth SE. PSM Peptides ofStaphylococcus aureusActivate the p38–CREB Pathway in Dendritic Cells, Thereby Modulating Cytokine Production and T Cell Priming. J I 2016; 196:1284-92. [DOI: 10.4049/jimmunol.1502232] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 11/25/2015] [Indexed: 01/07/2023]
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22
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Cheung GYC, Yeh AJ, Kretschmer D, Duong AC, Tuffuor K, Fu CL, Joo HS, Diep BA, Li M, Nakamura Y, Nunez G, Peschel A, Otto M. Functional characteristics of the Staphylococcus aureus δ-toxin allelic variant G10S. Sci Rep 2015; 5:18023. [PMID: 26658455 PMCID: PMC4674873 DOI: 10.1038/srep18023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 11/10/2015] [Indexed: 11/25/2022] Open
Abstract
Staphylococcus aureus δ-toxin is a member of the phenol-soluble modulin (PSM) peptide family. PSMs have multiple functions in staphylococcal pathogenesis; for example, they lyse red and white blood cells and trigger inflammatory responses. Compared to other PSMs, δ-toxin is usually more strongly expressed but has only moderate cytolytic capacities. The amino acid sequences of S. aureus PSMs are well conserved with two exceptions, one of which is the δ-toxin allelic variant G10S. This variant is a characteristic of the subspecies S. argenteus and S. aureus sequence types ST1 and ST59, the latter representing the most frequent cause of community-associated infections in Asia. δ-toxin G10S and strains expressing that variant from plasmids or the genome had significantly reduced cytolytic and pro-inflammatory capacities, including in a strain background with pronounced production of other PSMs. However, in murine infection models, isogenic strains expressing the two δ-toxin variants did not cause measurable differences in disease severity. Our findings indicate that the widespread G10S allelic variation of the δ-toxin locus has a significant impact on key pathogenesis mechanisms, but more potent members of the PSM peptide family may overshadow that impact in vivo.
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Affiliation(s)
- Gordon Y C Cheung
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Anthony J Yeh
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Dorothee Kretschmer
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen 72076, Germany
| | - Anthony C Duong
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Kwame Tuffuor
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Chih-Lung Fu
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Hwang-Soo Joo
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Binh A Diep
- Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, United States of America
| | - Min Li
- Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200127, China
| | - Yuumi Nakamura
- Department of Dermatology, Chiba University Graduate School of Medicine, Chiba 2608670, Japan
| | - Gabriel Nunez
- Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America
| | - Andreas Peschel
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen 72076, Germany
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, MD 20892, United States of America
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Kretschmer D, Rautenberg M, Linke D, Peschel A. Peptide length and folding state govern the capacity of staphylococcal β-type phenol-soluble modulins to activate human formyl-peptide receptors 1 or 2. J Leukoc Biol 2015; 97:689-97. [PMID: 25724390 DOI: 10.1189/jlb.2a0514-275r] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Most staphylococci produce short α-type PSMs and about twice as long β-type PSMs that are potent leukocyte attractants and toxins. PSMs are usually secreted with the N-terminal formyl group but are only weak agonists for the leukocyte FPR1. Instead, the FPR1-related FPR2 senses PSMs efficiently and is crucial for leukocyte recruitment in infection. Which structural features distinguish FPR1 from FPR2 ligands has remained elusive. To analyze which peptide properties may govern the capacities of β-type PSMs to activate FPRs, full-length and truncated variants of such peptides from Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus lugdunensis were synthesized. FPR2 activation was observed even for short N- or C-terminal β-type PSM variants once they were longer than 18 aa, and this activity increased with length. In contrast, the shortest tested peptides were potent FPR1 agonists, and this property declined with increasing peptide length. Whereas full-length β-type PSMs formed α-helices and exhibited no FPR1-specific activity, the truncated peptides had less-stable secondary structures, were weak agonists for FPR1, and required N-terminal formyl-methionine residues to be FPR2 agonists. Together, these data suggest that FPR1 and FPR2 have opposed ligand preferences. Short, flexible PSM structures may favor FPR1 but not FPR2 activation, whereas longer peptides with α-helical, amphipathic properties are strong FPR2 but only weak FPR1 agonists. These findings should help to unravel the ligand specificities of 2 critical human PRRs, and they may be important for new, anti-infective and anti-inflammatory strategies.
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Affiliation(s)
- Dorothee Kretschmer
- *Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Division, University of Tübingen, Germany; and Max Planck Institute for Developmental Biology, Department I, Tübingen, Germany
| | - Maren Rautenberg
- *Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Division, University of Tübingen, Germany; and Max Planck Institute for Developmental Biology, Department I, Tübingen, Germany
| | - Dirk Linke
- *Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Division, University of Tübingen, Germany; and Max Planck Institute for Developmental Biology, Department I, Tübingen, Germany
| | - Andreas Peschel
- *Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Division, University of Tübingen, Germany; and Max Planck Institute for Developmental Biology, Department I, Tübingen, Germany
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Abstract
The innate immune system recognizes conserved microorganism-associated molecular patterns (MAMPs), some of which are sensed by G protein-coupled receptors (GPCRs), and this leads to chemotactic leukocyte influx. Recent studies have indicated that these processes are crucial for host defence and rely on a larger set of chemotactic MAMPs and corresponding GPCRs than was previously thought. Agonists, such as bacterial formyl peptides, enterococcal pheromone peptides, staphylococcal peptide toxins, bacterial fermentation products and the Helicobacter pylori peptide HP(2-20), stimulate specific GPCRs. The importance of leukocyte chemotaxis in host defence is highlighted by the fact that some bacterial pathogens produce chemotaxis inhibitors. How the various chemoattractants, receptors and antagonists shape antibacterial host defence represents an important topic for future research.
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Affiliation(s)
- Dominik Alexander Bloes
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen 72076, Germany
| | - Dorothee Kretschmer
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen 72076, Germany
| | - Andreas Peschel
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen 72076, Germany
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25
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Cheung GYC, Kretschmer D, Duong AC, Yeh AJ, Ho TV, Chen Y, Joo HS, Kreiswirth BN, Peschel A, Otto M. Production of an attenuated phenol-soluble modulin variant unique to the MRSA clonal complex 30 increases severity of bloodstream infection. PLoS Pathog 2014; 10:e1004298. [PMID: 25144687 PMCID: PMC4140855 DOI: 10.1371/journal.ppat.1004298] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 06/20/2014] [Indexed: 12/19/2022] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of morbidity and death. Phenol-soluble modulins (PSMs) are recently-discovered toxins with a key impact on the development of Staphylococcus aureus infections. Allelic variants of PSMs and their potential impact on pathogen success during infection have not yet been described. Here we show that the clonal complex (CC) 30 lineage, a major cause of hospital-associated sepsis and hematogenous complications, expresses an allelic variant of the PSMα3 peptide. We found that this variant, PSMα3N22Y, is characteristic of CC30 strains and has significantly reduced cytolytic and pro-inflammatory potential. Notably, CC30 strains showed reduced cytolytic and chemotactic potential toward human neutrophils, and increased hematogenous seeding in a bacteremia model, compared to strains in which the genome was altered to express non-CC30 PSMα3. Our findings describe a molecular mechanism contributing to attenuated pro-inflammatory potential in a main MRSA lineage. They suggest that reduced pathogen recognition via PSMs allows the bacteria to evade elimination by innate host defenses during bloodstream infections. Furthermore, they underscore the role of point mutations in key S. aureus toxin genes in that adaptation and the pivotal importance PSMs have in defining key S. aureus immune evasion and virulence mechanisms. Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of morbidity and mortality and a great concern for public health. The CC30 MRSA lineage is especially notorious for causing bloodstream infections with complications such as seeding into organs. In our study, we show that this lineage produces an attenuated form of a key S. aureus toxin with decreased pro-inflammatory features. Our results suggest that attenuation of this toxin allows the bacteria to evade recognition and subsequent elimination by host defenses, thereby increasing pathogen success during blood infection.
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Affiliation(s)
- Gordon Y. C. Cheung
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
| | - Dorothee Kretschmer
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Anthony C. Duong
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
| | - Anthony J. Yeh
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
| | - Trung V. Ho
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
| | - Yan Chen
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hwang-Soo Joo
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
| | - Barry N. Kreiswirth
- Public Health Research Institute Tuberculosis Center, New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America
| | - Andreas Peschel
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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26
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Cheung GYC, Kretschmer D, Queck SY, Joo HS, Wang R, Duong AC, Nguyen TH, Bach THL, Porter AR, DeLeo FR, Peschel A, Otto M. Insight into structure-function relationship in phenol-soluble modulins using an alanine screen of the phenol-soluble modulin (PSM) α3 peptide. FASEB J 2013; 28:153-61. [PMID: 24008753 DOI: 10.1096/fj.13-232041] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Phenol-soluble modulins (PSMs) are a family of peptides with multiple functions in staphylococcal pathogenesis. To gain insight into the structural features affecting PSM functions, we analyzed an alanine substitution library of PSMα3, a strongly cytolytic and proinflammatory PSM of Staphylococcus aureus with a significant contribution to S. aureus virulence. Lysine residues were essential for both receptor-dependent proinflammatory and receptor-independent cytolytic activities. Both phenotypes also required additional structural features, with the C terminus being crucial for receptor activation. Biofilm formation was affected mostly by hydrophobic amino acid positions, suggesting that the capacity to disrupt hydrophobic interactions is responsible for the effect of PSMs on biofilm structure. Antimicrobial activity, absent from natural PSMα3, could be created by the exchange of large hydrophobic side chains, indicating that PSMα3 has evolved to exhibit cytolytic rather than antimicrobial activity. In addition to gaining insight into the structure-function relationship in PSMs, our study identifies nontoxic PSMα3 derivatives for active vaccination strategies and lays the foundation for future efforts aimed to understand the biological role of PSM recognition by innate host defense.
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Affiliation(s)
- Gordon Y C Cheung
- 3National Institute of Allergy and Infectious Diseases, 9000 Rockville Pike, Bldg. 33 1W10, Bethesda, MD 20892, USA.
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27
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Schreiner J, Kretschmer D, Klenk J, Otto M, Bühring HJ, Stevanovic S, Wang JM, Beer-Hammer S, Peschel A, Autenrieth SE. Staphylococcus aureus phenol-soluble modulin peptides modulate dendritic cell functions and increase in vitro priming of regulatory T cells. J Immunol 2013; 190:3417-26. [PMID: 23460735 DOI: 10.4049/jimmunol.1202563] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The major human pathogen Staphylococcus aureus has very efficient strategies to subvert the human immune system. Virulence of the emerging community-associated methicillin-resistant S. aureus depends on phenol-soluble modulin (PSM) peptide toxins, which are known to attract and lyse neutrophils. However, their influences on other immune cells remain elusive. In this study, we analyzed the impact of PSMs on dendritic cells (DCs) playing an essential role in linking innate and adaptive immunity. In human neutrophils, PSMs exert their function by binding to the formyl peptide receptor (FPR) 2. We show that mouse DCs express the FPR2 homolog mFPR2 as well as its paralog mFPR1 and that PSMs are chemoattractants for DCs at noncytotoxic concentrations. PSMs reduced clathrin-mediated endocytosis and inhibited TLR2 ligand-induced secretion of the proinflammatory cytokines TNF, IL-12, and IL-6, while inducing IL-10 secretion by DCs. As a consequence, treatment with PSMs impaired the capacity of DCs to induce activation and proliferation of CD4(+) T cells, characterized by reduced Th1 but increased frequency of FOXP3(+) regulatory T cells. These regulatory T cells secreted high amounts of IL-10, and their suppression capacity was dependent on IL-10 and TGF-β. Interestingly, the induction of tolerogenic DCs by PSMs appeared to be independent of mFPRs, as shown by experiments with mice lacking mFPR2 (mFPR2(-/-)) and the cognate G protein (p110γ(-/-)). Thus, PSMs from highly virulent pathogens affect DC functions, thereby modulating the adaptive immune response and probably increasing the tolerance toward the pathogen.
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Affiliation(s)
- Jens Schreiner
- Interfaculty Institute for Cell Biology, Eberhard Karls University, 72076 Tübingen, Germany
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28
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Bloes DA, Otto M, Peschel A, Kretschmer D. Enterococcus faecium stimulates human neutrophils via the formyl-peptide receptor 2. PLoS One 2012; 7:e39910. [PMID: 22768166 PMCID: PMC3386911 DOI: 10.1371/journal.pone.0039910] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 06/02/2012] [Indexed: 01/23/2023] Open
Abstract
The human formyl-peptide receptor 2 (FPR2/ALX) senses phenol-soluble modulin (PSM) peptide toxins produced by pathogenic staphylococcal species and plays a crucial role in directing neutrophil influx during staphylococcal infection. However, it has remained unclear if FPR2 responds also to molecules from other bacterial pathogens. Here we analyzed a variety of Gram-positive and Gram-negative pathogens and found that apart from staphylococci only certain enterococcal strains have the capacity to stimulate FPR2/ALX. Most of the analyzed Enterococcus faecium but only sporadic Enterococcus faecalis strains released FPR2/ALX-stimulating molecules leading to neutrophil calcium ion fluxes, chemotaxis, and complement receptor upregulation. Among ten test strains vancomycin-resistant E. faecium had a significantly higher capacity to stimulate FPR2/ALX than vancomycin-susceptible strains, suggesting an association of strong FPR2/ALX activation with health-care associated strains. The enterococcal FPR2/ALX agonists were found to be peptides or proteins, which appear, however, to be unrelated to staphylococcal PSMs in sequence and physicochemical properties. Enterococci are among the most frequent invasive bacterial pathogens but the basis of enterococcal virulence and immune activation has remained incompletely understood. Our study indicates that previously unrecognized proteinaceous agonists contribute to Enterococcus-host interaction and underscores the importance of FPR2/ALX in host defense against major endogenous bacterial pathogens.
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Affiliation(s)
- Dominik Alexander Bloes
- Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Section, University of Tübingen, Tübingen, Germany
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, U.S. National Institutes of Health, Bethesda, Maryland, United States of America
| | - Andreas Peschel
- Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Section, University of Tübingen, Tübingen, Germany
- * E-mail:
| | - Dorothee Kretschmer
- Interfaculty Institute of Microbiology and Infection Medicine, Cellular and Molecular Microbiology Section, University of Tübingen, Tübingen, Germany
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Blume KE, Soeroes S, Keppeler H, Stevanovic S, Kretschmer D, Rautenberg M, Wesselborg S, Lauber K. Cleavage of annexin A1 by ADAM10 during secondary necrosis generates a monocytic "find-me" signal. J Immunol 2011; 188:135-45. [PMID: 22116825 DOI: 10.4049/jimmunol.1004073] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Annexin A1 is an intracellular calcium/phospholipid-binding protein that is involved in membrane organization and the regulation of the immune system. It has been attributed an anti-inflammatory role at various control levels, and recently we could show that annexin A1 externalization during secondary necrosis provides an important fail-safe mechanism counteracting inflammatory responses when the timely clearance of apoptotic cells has failed. As such, annexin A1 promotes the engulfment of dying cells and dampens the postphagocytic production of proinflammatory cytokines. In our current follow-up study, we report that exposure of annexin A1 during secondary necrosis coincided with proteolytic processing within its unique N-terminal domain by ADAM10. Most importantly, we demonstrate that the released peptide and culture supernatants of secondary necrotic, annexin A1-externalizing cells induced chemoattraction of monocytes, which was clearly reduced in annexin A1- or ADAM10-knockdown cells. Thus, altogether our findings indicate that annexin A1 externalization and its proteolytic processing into a chemotactic peptide represent final events during apoptosis, which after the transition to secondary necrosis contribute to the recruitment of monocytes and the prevention of inflammation.
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Affiliation(s)
- Karin E Blume
- Department of Internal Medicine I, Eberhard Karls University, Tuebingen, Germany
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30
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Kretschmer D, Nikola N, Dürr M, Otto M, Peschel A. The virulence regulator Agr controls the staphylococcal capacity to activate human neutrophils via the formyl peptide receptor 2. J Innate Immun 2011; 4:201-12. [PMID: 22067547 DOI: 10.1159/000332142] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 08/25/2011] [Indexed: 12/20/2022] Open
Abstract
The Agr quorum-sensing system represents the master regulator for staphylococcal virulence factors and is known to have a strong impact on the release of pathogen-associated molecular pattern (PAMP) molecules. Among the various staphylococcal PAMPs, phenol-soluble modulin (PSM) peptides have attracted increasing interest because they are crucial for staphylococcal virulence and have neutrophil-recruiting properties. The latter depend on recognition of PSMs by the neutrophil formyl peptide receptor 2 (FPR2/ALX), for which PSMs are highly efficient agonists. We demonstrate that Agr inactivation in Staphylococcus aureus or S. epidermidis leads to strongly reduced neutrophil responses, which is in agreement with the previously reported strict control of PSM expression by Agr. Agr had a distinct and profound impact on activation of FPR2/ALX but not of the related FPR1 receptor that senses bacterial formylated peptides. S. epidermidis PSMs had similar FPR2/ALX-activating properties but differed in their dependence on N-terminal formylation compared to S. aureus PSMs. Moreover, S. aureus and S. epidermidis PSMs upregulated the neutrophil complement receptor CD11b via FPR2/ALX stimulation in an Agr-dependent fashion. Hence, Agr controls the capacity of staphylococcal pathogens to activate FPR2/ALX-dependent neutrophil responses, underscoring the crucial role of FPR2/ALX and PSMs in staphylococcus-host interaction.
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Affiliation(s)
- Dorothee Kretschmer
- Cellular and Molecular Microbiology Division, Interfaculty Institute for Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
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Kretschmer D, Gleske AK, Rautenberg M, Wang R, Köberle M, Bohn E, Schöneberg T, Rabiet MJ, Boulay F, Klebanoff SJ, van Kessel KA, van Strijp JA, Otto M, Peschel A. Human formyl peptide receptor 2 senses highly pathogenic Staphylococcus aureus. Cell Host Microbe 2010; 7:463-73. [PMID: 20542250 DOI: 10.1016/j.chom.2010.05.012] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 04/09/2010] [Accepted: 05/10/2010] [Indexed: 11/17/2022]
Abstract
Virulence of emerging community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and other highly pathogenic S. aureus strains depends on their production of phenol-soluble modulin (PSM) peptide toxins, which combine the capacities to attract and lyse neutrophils. The molecular basis of PSM-stimulated neutrophil recruitment has remained unclear. Here, we demonstrate that the human formyl peptide receptor 2 (FPR2/ALX), which has previously been implicated in control of endogenous inflammatory processes, senses PSMs at nanomolar concentrations and initiates proinflammatory neutrophil responses to CA-MRSA. Specific blocking of FPR2/ALX or deletion of PSM genes in CA-MRSA severely diminished neutrophil detection of CA-MRSA. Furthermore, a specific inhibitor of FPR2/ALX and of its functional mouse counterpart blocked PSM-mediated leukocyte infiltration in vivo in a mouse model. Thus, the innate immune system uses a distinct FPR2/ALX-dependent mechanism to specifically sense bacterial peptide toxins and detect highly virulent bacterial pathogens. FPR2/ALX represents an attractive target for new anti-infective or anti-inflammatory strategies.
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Affiliation(s)
- Dorothee Kretschmer
- Cellular and Molecular Microbiology Division, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany
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Queck SY, Khan BA, Wang R, Bach THL, Kretschmer D, Chen L, Kreiswirth BN, Peschel A, DeLeo FR, Otto M. Mobile genetic element-encoded cytolysin connects virulence to methicillin resistance in MRSA. PLoS Pathog 2009; 5:e1000533. [PMID: 19649313 PMCID: PMC2712073 DOI: 10.1371/journal.ppat.1000533] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 07/08/2009] [Indexed: 12/15/2022] Open
Abstract
Bacterial virulence and antibiotic resistance have a significant influence on disease severity and treatment options during bacterial infections. Frequently, the underlying genetic determinants are encoded on mobile genetic elements (MGEs). In the leading human pathogen Staphylococcus aureus, MGEs that contain antibiotic resistance genes commonly do not contain genes for virulence determinants. The phenol-soluble modulins (PSMs) are staphylococcal cytolytic toxins with a crucial role in immune evasion. While all known PSMs are core genome-encoded, we here describe a previously unidentified psm gene, psm-mec, within the staphylococcal methicillin resistance-encoding MGE SCCmec. PSM-mec was strongly expressed in many strains and showed the physico-chemical, pro-inflammatory, and cytolytic characteristics typical of PSMs. Notably, in an S. aureus strain with low production of core genome-encoded PSMs, expression of PSM-mec had a significant impact on immune evasion and disease. In addition to providing high-level resistance to methicillin, acquisition of SCCmec elements encoding PSM-mec by horizontal gene transfer may therefore contribute to staphylococcal virulence by substituting for the lack of expression of core genome-encoded PSMs. Thus, our study reveals a previously unknown role of methicillin resistance clusters in staphylococcal pathogenesis and shows that important virulence and antibiotic resistance determinants may be combined in staphylococcal MGEs. The extreme danger associated with Staphylococcus aureus infections is due to the combination of frequent antibiotic resistance, which prevents efficient treatment, with extraordinary virulence, which determines the severity of disease. S. aureus is known to exchange antibiotic resistance and virulence determinants between different strains, thereby spreading the capacity to cause serious infections in the S. aureus population. The genetic information for these determinants is usually found on so-called mobile genetic elements. It has been noted that such exchangeable elements carry genes for either virulence or antibiotic resistance, but not both. Here, we identified and characterized a potent toxin, whose gene is located within an element that encodes resistance to the important antibiotic methicillin. The toxin had strong capacity to kill human white and red blood cells and significantly affected the capacity of MRSA to cause disease. Our study shows that acquisition of methicillin resistance may be combined with gaining possession of potent toxins by a single event of genetic exchange, which likely represents an important feature accelerating the evolution of MRSA virulence.
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Affiliation(s)
- Shu Y. Queck
- Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, and Hamilton, Montana, United States of America
| | - Burhan A. Khan
- Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, and Hamilton, Montana, United States of America
| | - Rong Wang
- Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, and Hamilton, Montana, United States of America
| | - Thanh-Huy L. Bach
- Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, and Hamilton, Montana, United States of America
| | - Dorothee Kretschmer
- Cellular and Molecular Microbiology Unit, Medical Microbiology and Hygiene Department, University of Tübingen, Tübingen, Germany
| | - Liang Chen
- Public Health Research Institute, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
| | - Barry N. Kreiswirth
- Public Health Research Institute, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
| | - Andreas Peschel
- Cellular and Molecular Microbiology Unit, Medical Microbiology and Hygiene Department, University of Tübingen, Tübingen, Germany
| | - Frank R. DeLeo
- Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, and Hamilton, Montana, United States of America
| | - Michael Otto
- Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, and Hamilton, Montana, United States of America
- * E-mail:
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Wang R, Braughton KR, Kretschmer D, Bach THL, Queck SY, Li M, Kennedy AD, Dorward DW, Klebanoff SJ, Peschel A, DeLeo FR, Otto M. Identification of novel cytolytic peptides as key virulence determinants for community-associated MRSA. Nat Med 2007; 13:1510-4. [PMID: 17994102 DOI: 10.1038/nm1656] [Citation(s) in RCA: 781] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 08/21/2007] [Indexed: 12/16/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) remains a major human pathogen. Traditionally, MRSA infections occurred exclusively in hospitals and were limited to immunocompromised patients or individuals with predisposing risk factors. However, recently there has been an alarming epidemic caused by community-associated (CA)-MRSA strains, which can cause severe infections that can result in necrotizing fasciitis or even death in otherwise healthy adults outside of healthcare settings. In the US, CA-MRSA is now the cause of the majority of infections that result in trips to the emergency room. It is unclear what makes CA-MRSA strains more successful in causing human disease compared with their hospital-associated counterparts. Here we describe a class of secreted staphylococcal peptides that have a remarkable ability to recruit, activate and subsequently lyse human neutrophils, thus eliminating the main cellular defense against S. aureus infection. These peptides are produced at high concentrations by standard CA-MRSA strains and contribute significantly to the strains' ability to cause disease in animal models of infection. Our study reveals a previously uncharacterized set of S. aureus virulence factors that account at least in part for the enhanced virulence of CA-MRSA.
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Affiliation(s)
- Rong Wang
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, US National Institutes of Health, 903 South 4th Street, Hamilton, Montana 59840, USA
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Abstract
In order to model a practical combustion system successfully, it is necessary to develop one or more reaction rate equations which will describe performance over a wide range of conditions. The equations should be kept as simple as possible and commensurate with the accuracy needed. In this paper a bimolecular reaction is assumed, based upon a simple mass balance. Temperatures derived from the latter are related to measured practical ones such that, if required, an evaluation of the partly burned product composition can be made. A convenient reaction rate equation is given which describes a wide range of blow-out data for spherical reactors at weak mixture conditions. NVP2φ={1.29×1010(m+1)[5(1−yε)]φ[φ−yε]φe−C/(Ti+εΔT)}/{0.082062φyε[5(m+1)+φ+yε]2φ[Ti+εΔT]2φ−0.5} Analysis of the components used in the above equation (especially the variation of activation energy) clearly shows its empirical nature but does not detract from its engineering value. Rich mixtures are considered also, but lack of data precludes a reliable analysis. One of the major results obtained is the variation of the reaction order (n) with equivalence ratio (φ): weak mixtures, n = 2φ; rich mixtures, n = 2/φ. Some support for this variation has been noticed in published literature of other workers.
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Affiliation(s)
- D. Kretschmer
- Mechanical Engineering Department, Laval University, Quebec, Canada
| | - J. Odgers
- Mechanical Engineering Department, Laval University, Quebec, Canada
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