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Allen CNS, Banks DA, Shuster M, Vogel SN, O’Connor TJ, Briken V. Legionella pneumophila inhibits type I interferon signaling to avoid cell-intrinsic host cell defense. Infect Immun 2023; 91:e0036523. [PMID: 37843413 PMCID: PMC10652965 DOI: 10.1128/iai.00365-23] [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: 09/08/2023] [Accepted: 09/15/2023] [Indexed: 10/17/2023] Open
Abstract
The host type I interferon (IFN) response protects against Legionella pneumophila infections. Other bacterial pathogens inhibit type I IFN-mediated cell signaling; however, the interaction between this signaling pathway and L. pneumophila has not been well described. Here, we demonstrate that L. pneumophila inhibits the IFN-β signaling pathway but does not inhibit IFN-γ-mediated cell signaling. The addition of IFN-β to L. pneumophila-infected macrophages limited bacterial growth independently of NOS2 and reactive nitrogen species. The type IV secretion system of L. pneumophila is required to inhibit IFN-β-mediated cell signaling. Finally, we show that the inhibition of the IFN-β signaling pathway occurs downstream of STAT1 and STAT2 phosphorylation. In conclusion, our findings describe a novel host cell signaling pathway inhibited by L. pneumophila via its type IV secretion system.
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Affiliation(s)
- Charles N. S. Allen
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Dallas A. Banks
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Michael Shuster
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Stefanie N. Vogel
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Tamara J. O’Connor
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Volker Briken
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
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Maciag K, Raychowdhury R, Smith K, Schneider AM, Coers J, Mumbach MR, Schwartz S, Hacohen N. IRF3 inhibits IFN-γ-mediated restriction of intracellular pathogens in macrophages independently of IFNAR. J Leukoc Biol 2022; 112:257-271. [PMID: 34826345 PMCID: PMC9550582 DOI: 10.1002/jlb.3a0218-069rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [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: 02/18/2018] [Revised: 10/25/2021] [Accepted: 10/30/2021] [Indexed: 01/14/2023] Open
Abstract
Macrophages use an array of innate immune sensors to detect intracellular pathogens and to tailor effective antimicrobial responses. In addition, extrinsic activation with the cytokine IFN-γ is often required as well to tip the scales of the host-pathogen balance toward pathogen restriction. However, little is known about how host-pathogen sensing impacts the antimicrobial IFN-γ-activated state. It was observed that in the absence of IRF3, a key downstream component of pathogen sensing pathways, IFN-γ-primed macrophages more efficiently restricted the intracellular bacterium Legionella pneumophila and the intracellular protozoan parasite Trypanosoma cruzi. This effect did not require IFNAR, the receptor for Type I IFNs known to be induced by IRF3, nor the sensing adaptors MyD88/TRIF, MAVS, or STING. This effect also did not involve differential activation of STAT1, the major signaling protein downstream of both Type 1 and Type 2 IFN receptors. IRF3-deficient macrophages displayed a significantly altered IFN-γ-induced gene expression program, with up-regulation of microbial restriction factors such as Nos2. Finally, we found that IFN-γ-primed but not unprimed macrophages largely excluded the activated form of IRF3 from the nucleus following bacterial infection. These data are consistent with a relationship of mutual inhibition between IRF3 and IFN-γ-activated programs, possibly as a component of a partially reversible mechanism for modulating the activity of potent innate immune effectors (such as Nos2) in the context of intracellular infection.
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Affiliation(s)
- Karolina Maciag
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA,Program in Immunology, Harvard Medical School, Boston, MA 02115, USA,Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Charlestown, MA 02129, USA
| | | | - Karen Smith
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Alexis M. Schneider
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jörn Coers
- Departments of Molecular Genetics and Microbiology and Immunology, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | - Nir Hacohen
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA,Program in Immunology, Harvard Medical School, Boston, MA 02115, USA,Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Charlestown, MA 02129, USA
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Liu X, Shin S. Viewing Legionella pneumophila Pathogenesis through an Immunological Lens. J Mol Biol 2019; 431:4321-44. [PMID: 31351897 DOI: 10.1016/j.jmb.2019.07.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 06/25/2019] [Accepted: 07/13/2019] [Indexed: 12/14/2022]
Abstract
Legionella pneumophila is the causative agent of the severe pneumonia Legionnaires' disease. L. pneumophila is ubiquitously found in freshwater environments, where it replicates within free-living protozoa. Aerosolization of contaminated water supplies allows the bacteria to be inhaled into the human lung, where L. pneumophila can be phagocytosed by alveolar macrophages and replicate intracellularly. The Dot/Icm type IV secretion system (T4SS) is one of the key virulence factors required for intracellular bacterial replication and subsequent disease. The Dot/Icm apparatus translocates more than 300 effector proteins into the host cell cytosol. These effectors interfere with a variety of cellular processes, thus enabling the bacterium to evade phagosome-lysosome fusion and establish an endoplasmic reticulum-derived Legionella-containing vacuole, which facilitates bacterial replication. In turn, the immune system has evolved numerous strategies to recognize intracellular bacteria such as L. pneumophila, leading to potent inflammatory responses that aid in eliminating infection. This review aims to provide an overview of L. pneumophila pathogenesis in the context of the host immune response.
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Abstract
Legionella pneumophila remains a major health concern, especially for hospitalized patients. L. pneumophila in the environment can survive extracellular or as protozoan parasite within amoeba. After human infection it efficiently replicates in alveolar macrophages without activating inflammasome assembly and cleavage of caspase-1. In contrast murine macrophages actively recognize intracellular L. pneumophila via inflammasome components which initiate pro-inflammatory cytokine secretion, phagosomal maturation and pyroptotic cell death thereby leading to bacterial restriction. During this process flagellin-dependent and -independent signaling pathways trigger the canonical as well as the non-canonical inflammasome. This review describes the current knowledge about L. pneumophila-induced inflammasome pathways in permissive and restrictive host cells.
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Affiliation(s)
- Kathrin Krause
- Department of Microbial Infection and Immunity, The Ohio State University Columbus, OH, USA
| | - Amal O Amer
- Department of Microbial Infection and Immunity, The Ohio State University Columbus, OH, USA
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Abdul-Sater AA, Majoros A, Plumlee CR, Perry S, Gu AD, Lee C, Shresta S, Decker T, Schindler C. Different STAT Transcription Complexes Drive Early and Delayed Responses to Type I IFNs. J Immunol 2015; 195:210-216. [PMID: 26019270 DOI: 10.4049/jimmunol.1401139] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 04/24/2015] [Indexed: 01/12/2023]
Abstract
IFNs, which transduce pivotal signals through Stat1 and Stat2, effectively suppress the replication of Legionella pneumophila in primary murine macrophages. Although the ability of IFN-γ to impede L. pneumophila growth is fully dependent on Stat1, IFN-αβ unexpectedly suppresses L. pneumophila growth in both Stat1- and Stat2-deficient macrophages. New studies demonstrating that the robust response to IFN-αβ is lost in Stat1-Stat2 double-knockout macrophages suggest that Stat1 and Stat2 are functionally redundant in their ability to direct an innate response toward L. pneumophila. Because the ability of IFN-αβ to signal through Stat1-dependent complexes (i.e., Stat1-Stat1 and Stat1-Stat2 dimers) has been well characterized, the current studies focus on how Stat2 is able to direct a potent response to IFN-αβ in the absence of Stat1. These studies reveal that IFN-αβ is able to drive the formation of a Stat2 and IFN regulatory factor 9 complex that drives the expression of a subset of IFN-stimulated genes, but with substantially delayed kinetics. These observations raise the possibility that this pathway evolved in response to microbes that have devised strategies to subvert Stat1-dependent responses.
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Affiliation(s)
- Ali A Abdul-Sater
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Andrea Majoros
- Department of Microbiology, Immunology & Genetics, University of Vienna, Vienna A-1030 Austria
| | - Courtney R Plumlee
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Stuart Perry
- Division of Vaccine Discovery, La Jolla Inst. for Allergy and Immunology, La Jolla, CA 92037 USA
| | - Ai Di Gu
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Carolyn Lee
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA
| | - Sujan Shresta
- Division of Vaccine Discovery, La Jolla Inst. for Allergy and Immunology, La Jolla, CA 92037 USA
| | - Thomas Decker
- Department of Microbiology, Immunology & Genetics, University of Vienna, Vienna A-1030 Austria
| | - Christian Schindler
- Department of Microbiology & Immunology, Columbia University, New York, NY 10032 USA.,Department of Medicine, Columbia University, New York, NY 10032 USA
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Plumlee CR, Lee C, Beg AA, Decker T, Shuman HA, Schindler C. Interferons direct an effective innate response to Legionella pneumophila infection. J Biol Chem 2009; 284:30058-66. [PMID: 19720834 DOI: 10.1074/jbc.m109.018283] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Legionella pneumophila remains an important opportunistic pathogen of human macrophages. Its more limited ability to replicate in murine macrophages has been attributed to redundant innate sensor systems that detect and effectively respond to this infection. The current studies evaluate the role of one of these innate response systems, the type I interferon (IFN-I) autocrine loop. The ability of L. pneumophila to induce IFN-I expression was found to be dependent on IRF-3, but not NF-kappaB. Secreted IFN-Is then in turn suppress the intracellular replication of L. pneumophila. Surprisingly, this suppression is mediated by a pathway that is independent of Stat1, Stat2, Stat3, but correlates with the polarization of macrophages toward the M1 or classically activated phenotype.
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Affiliation(s)
- Courtney R Plumlee
- Department of Biological Sciences, Columbia University, New York, New York 10032, USA
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Abstract
Legionella pneumonia typically presents as lobar pneumonia with multiple-lobe involvement, but Legionella lung abscess is rare. To identify the predisposing factors for Legionella abscess, we analyzed 62 of the 79 case reports on Legionella abscess found in literature; 28 (45.2%) were of hospital-acquired infection and 28 (45.2%), community-acquired infection. Seventeen patients (27.4%) died. L. pneumophila serogroup 1 was the most common, but other serogroups of L. pneumophila, L. micdadei, L. bozemanii, L. dumoffii, and L. maceachernii were also isolated from the abscess. Corticosteroids were administered for underlying diseases to 43 (69.4%) patients. Peripheral neutrophil counts were higher in patients with abscess than in those with only pulmonary infiltration. In certain cases, Legionella abscess developed during neutropenia recovery. However, lymphocyte counts were low in most cases. Clinical factors like corticosteroid treatment, which causes impaired cellular immunity and subsequent neutrophil accumulation in the lesion, might function as predisposing factors for Legionella abscess.
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Affiliation(s)
- Hui Yu
- Department of Medicine and Therapeutics, Control and Prevention of Infectious Diseases (First Department of Internal Medicine), Faculty of Medicine, University of the Ryukyus, Okinawa, China
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Vinzing M, Eitel J, Lippmann J, Hocke AC, Zahlten J, Slevogt H, N'guessan PD, Günther S, Schmeck B, Hippenstiel S, Flieger A, Suttorp N, Opitz B. NAIP and Ipaf control Legionella pneumophila replication in human cells. J Immunol 2008; 180:6808-15. [PMID: 18453601 DOI: 10.4049/jimmunol.180.10.6808] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [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
In mice, different alleles of the mNAIP5 (murine neuronal apoptosis inhibitory protein-5)/mBirc1e gene determine whether macrophages restrict or support intracellular replication of Legionella pneumophila, and whether a mouse is resistant or (moderately) susceptible to Legionella infection. In the resistant mice strains, the nucleotide-binding oligomerization domain (Nod)-like receptor (NLR) family member mNAIP5/mBirc1e, as well as the NLR protein mIpaf (murine ICE protease-activating factor), are involved in recognition of Legionella flagellin and in restriction of bacterial replication. Human macrophages and lung epithelial cells support L. pneumophila growth, and humans can develop severe pneumonia (Legionnaires disease) after Legionella infection. The role of human orthologs to mNAIP5/mBirc1e and mIpaf in this bacterial infection has not been elucidated. Herein we demonstrate that flagellin-deficient L. pneumophila replicate more efficiently in human THP-1 macrophages, primary monocyte-derived macrophages, and alveolar macrophages, and in A549 lung epithelial cells compared with wild-type bacteria. Additionally, we note expression of the mNAIP5 ortholog hNAIP in all cell types examined, and expression of hIpaf in human macrophages. Gene silencing of hNAIP or hIpaf in macrophages or of hNAIP in lung epithelial cells leads to an enhanced bacterial growth, and overexpression of both molecules strongly reduces Legionella replication. In contrast to experiments with wild-type L. pneumophila, hNAIP or hIpaf knock-down affects the (enhanced) replication of flagellin-deficient Legionella only marginally. In conclusion, hNAIP and hIpaf mediate innate intracellular defense against flagellated Legionella in human cells.
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Affiliation(s)
- Maya Vinzing
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité Universitätsmedizin Berlin, Berlin, Germany
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Miao EA, Andersen-Nissen E, Warren SE, Aderem A. TLR5 and Ipaf: dual sensors of bacterial flagellin in the innate immune system. Semin Immunopathol 2007; 29:275-88. [PMID: 17690885 DOI: 10.1007/s00281-007-0078-z] [Citation(s) in RCA: 218] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Accepted: 06/21/2007] [Indexed: 12/26/2022]
Abstract
The innate immune system precisely modulates the intensity of immune activation in response to infection. Flagellin is a microbe-associated molecular pattern that is present on both pathogenic and nonpathogenic bacteria. Macrophages and dendritic cells are able to determine the virulence of flagellated bacteria by sensing whether flagellin remains outside the mammalian cell, or if it gains access to the cytosol. Extracellular flagellin is detected by TLR5, which induces expression of proinflammatory cytokines, while flagellin within the cytosol of macrophages is detected through the Nod-like receptor (NLR) Ipaf, which activates caspase-1. In macrophages infected with Salmonella typhimurium or Legionella pneumophila, Ipaf becomes activated in response to flagellin that appears to be delivered to the cytosol via specific virulence factor transport systems (the SPI1 type III secretion system (T3SS) and the Dot/Icm type IV secretion system (T4SS), respectively). Thus, TLR5 responds more generally to flagellated bacteria, while Ipaf responds to bacteria that express both flagellin and virulence factors.
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Affiliation(s)
- Edward A Miao
- Institute for Systems Biology, Seattle, WA 98103, USA
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