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Kang S, Dai A, Wang H, Ding PH. Interaction Between Autophagy and Porphyromonas gingivalis-Induced Inflammation. Front Cell Infect Microbiol 2022; 12:892610. [PMID: 35846745 PMCID: PMC9283780 DOI: 10.3389/fcimb.2022.892610] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 06/06/2022] [Indexed: 11/13/2022] Open
Abstract
Autophagy is an immune homeostasis process induced by multiple intracellular and extracellular signals. Inflammation is a protective response to harmful stimuli such as pathogen microbial infection and body tissue damage. Porphyromonas gingivalis infection elicits both autophagy and inflammation, and dysregulation of autophagy and inflammation promotes pathology. This review focuses on the interaction between autophagy and inflammation caused by Porphyromonas gingivalis infection, aiming to elaborate on the possible mechanism involved in the interaction.
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2
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Naseer N, Egan MS, Reyes Ruiz VM, Scott WP, Hunter EN, Demissie T, Rauch I, Brodsky IE, Shin S. Human NAIP/NLRC4 and NLRP3 inflammasomes detect Salmonella type III secretion system activities to restrict intracellular bacterial replication. PLoS Pathog 2022; 18:e1009718. [PMID: 35073381 PMCID: PMC8812861 DOI: 10.1371/journal.ppat.1009718] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 02/03/2022] [Accepted: 12/27/2021] [Indexed: 01/16/2023] Open
Abstract
Salmonella enterica serovar Typhimurium is a Gram-negative pathogen that uses two distinct type III secretion systems (T3SSs), termed Salmonella pathogenicity island (SPI)-1 and SPI-2, to deliver virulence factors into the host cell. The SPI-1 T3SS enables Salmonella to invade host cells, while the SPI-2 T3SS facilitates Salmonella's intracellular survival. In mice, a family of cytosolic immune sensors, including NAIP1, NAIP2, and NAIP5/6, recognizes the SPI-1 T3SS needle, inner rod, and flagellin proteins, respectively. Ligand recognition triggers assembly of the NAIP/NLRC4 inflammasome, which mediates caspase-1 activation, IL-1 family cytokine secretion, and pyroptosis of infected cells. In contrast to mice, humans encode a single NAIP that broadly recognizes all three ligands. The role of NAIP/NLRC4 or other inflammasomes during Salmonella infection of human macrophages is unclear. We find that although the NAIP/NLRC4 inflammasome is essential for detecting T3SS ligands in human macrophages, it is partially required for responses to infection, as Salmonella also activated the NLRP3 and CASP4/5 inflammasomes. Importantly, we demonstrate that combinatorial NAIP/NLRC4 and NLRP3 inflammasome activation restricts Salmonella replication in human macrophages. In contrast to SPI-1, the SPI-2 T3SS inner rod is not sensed by human or murine NAIPs, which is thought to allow Salmonella to evade host recognition and replicate intracellularly. Intriguingly, we find that human NAIP detects the SPI-2 T3SS needle protein. Critically, in the absence of both flagellin and the SPI-1 T3SS, the NAIP/NLRC4 inflammasome still controlled intracellular Salmonella burden. These findings reveal that recognition of Salmonella SPI-1 and SPI-2 T3SSs and engagement of both the NAIP/NLRC4 and NLRP3 inflammasomes control Salmonella infection in human macrophages.
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Affiliation(s)
- Nawar Naseer
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Marisa S. Egan
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Valeria M. Reyes Ruiz
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - William P. Scott
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon
| | - Emma N. Hunter
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Tabitha Demissie
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Isabella Rauch
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon
| | - Igor E. Brodsky
- Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania
| | - Sunny Shin
- Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
- * E-mail:
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Keshavarz Shahbaz S, Koushki K, Ayati SH, Bland AR, Bezsonov EE, Sahebkar A. Inflammasomes and Colorectal Cancer. Cells 2021; 10:2172. [PMID: 34571825 PMCID: PMC8467678 DOI: 10.3390/cells10092172] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/22/2021] [Accepted: 07/29/2021] [Indexed: 02/07/2023] Open
Abstract
Inflammasomes are important intracellular multiprotein signaling complexes that modulate the activation of caspase-1 and induce levels of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 in response to pathogenic microorganisms and molecules that originated from host proteins. Inflammasomes play contradictory roles in the development of inflammation-induced cancers. Based on several findings, inflammasomes can initiate and promote carcinogenesis. On the contrary, inflammasomes also exhibit anticancer effects by triggering pyroptosis and immunoregulatory functions. Herein, we review extant studies delving into different functions of inflammasomes in colorectal cancer development.
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Affiliation(s)
- Sanaz Keshavarz Shahbaz
- Cellular and Molecular Research Center, Research Institute for Prevention of Non-Communicable Disease, Qazvin University of Medical Science, Qazvin 3419759811, Iran;
| | - Khadijeh Koushki
- Department of Immunology, School of Medicine, Mashhad University of Medical Sciences, Mashhad 9177948564, Iran;
| | - Seyed Hassan Ayati
- Immunobiochemistry Lab, Immunology Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad 9177948564, Iran;
| | - Abigail R. Bland
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin 9016, New Zealand;
| | - Evgeny E. Bezsonov
- Laboratory of Angiopathology, Institute of General Pathology and Pathophysiology, 8 Baltiiskaya Street, 125315 Moscow, Russia;
| | - Amirhossein Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad 9177948564, Iran
- Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad 1313199137, Iran
- School of Medicine, The University of Western Australia, Perth 6009, Australia
- School of Pharmacy, Mashhad University of Medical Sciences, Mashhad 9177948564, Iran
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4
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Viewing Legionella pneumophila Pathogenesis through an Immunological Lens. J Mol Biol 2019; 431:4321-4344. [PMID: 31351897 DOI: 10.1016/j.jmb.2019.07.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [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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5
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Ramachandran RA, Lupfer C, Zaki H. The Inflammasome: Regulation of Nitric Oxide and Antimicrobial Host Defence. Adv Microb Physiol 2018; 72:65-115. [PMID: 29778217 DOI: 10.1016/bs.ampbs.2018.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nitric oxide (NO) is a gaseous signalling molecule that plays diverse physiological functions including antimicrobial host defence. During microbial infection, NO is synthesized by inducible NO synthase (iNOS), which is expressed by host immune cells through the recognition of microbial pattern molecules. Therefore, sensing pathogens or their pattern molecules by pattern recognition receptors (PRRs), which are located at the cell surface, endosomal and phagosomal compartment, or in the cytosol, is key in inducing iNOS and eliciting antimicrobial host defence. A group of cytosolic PRRs is involved in inducing NO and other antimicrobial molecules by forming a molecular complex called the inflammasome. Assembled inflammasomes activate inflammatory caspases, such as caspase-1 and caspase-11, which in turn process proinflammatory cytokines IL-1β and IL-18 into their mature forms and induce pyroptotic cell death. IL-1β and IL-18 play a central role in immunity against microbial infection through activation and recruitment of immune cells, induction of inflammatory molecules, and regulation of antimicrobial mediators including NO. Interestingly, NO can also regulate inflammasome activity in an autocrine and paracrine manner. Here, we discuss molecular mechanisms of inflammasome formation and the inflammasome-mediated regulation of host defence responses during microbial infections.
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Affiliation(s)
| | | | - Hasan Zaki
- UT Southwestern Medical Center, Dallas, TX, United States.
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6
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Kajiwara C, Kusaka Y, Kimura S, Yamaguchi T, Nanjo Y, Ishii Y, Udono H, Standiford TJ, Tateda K. Metformin Mediates Protection against Legionella Pneumonia through Activation of AMPK and Mitochondrial Reactive Oxygen Species. THE JOURNAL OF IMMUNOLOGY 2017; 200:623-631. [PMID: 29246951 DOI: 10.4049/jimmunol.1700474] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 11/06/2017] [Indexed: 12/25/2022]
Abstract
In Legionella pneumophila infection, macrophages play a critical role in the host defense response. Metformin, an oral drug for type 2 diabetes, is attracting attention as a new supportive therapy against a variety of diseases, such as cancer and infectious diseases. The novel mechanisms for metformin actions include modulation of the effector functions of macrophages and other host immune cells. In this study, we have examined the effects of metformin on L. pneumophila infection in vitro and in vivo. Metformin treatment suppressed growth of L. pneumophila in a time- and concentration-dependent fashion in bone marrow-derived macrophages, RAW cells (mouse), and U937 cells (human). Metformin induced phosphorylation of AMP-activated protein kinase (AMPK) in L. pneumophila-infected bone marrow-derived macrophages, and the AMPK inhibitor Compound C negated metformin-mediated growth suppression. Also, metformin induced mitochondrial reactive oxygen species but not phagosomal NADPH oxidase-derived reactive oxygen species. Metformin-mediated growth suppression was mitigated in the presence of the reactive oxygen species scavenger glutathione. In a murine L. pneumophila pneumonia model, metformin treatment improved survival of mice, which was associated with a significant reduction in bacterial number in the lung. Similar to in vitro observations, induction of AMPK phosphorylation and mitochondrial ROS was demonstrated in the infected lungs of mice treated with metformin. Finally, glutathione treatment abolished metformin effects on lung bacterial clearance. Collectively, these data suggest that metformin promotes mitochondrial ROS production and AMPK signaling and enhances the bactericidal activity of macrophages, which may contribute to improved survival in L. pneumophila pneumonia.
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Affiliation(s)
- Chiaki Kajiwara
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan
| | - Yu Kusaka
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan.,Department of Respiratory Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
| | - Soichiro Kimura
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan
| | - Tetsuo Yamaguchi
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan
| | - Yuta Nanjo
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan.,Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109; and
| | - Yoshikazu Ishii
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan
| | - Heiichiro Udono
- Department of Immunology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Theodore J Standiford
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109; and
| | - Kazuhiro Tateda
- Department of Microbiology and Infectious Diseases, Faculty of Medicine, Toho University School of Medicine, Tokyo 143-8540, Japan;
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7
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Dolasia K, Bisht MK, Pradhan G, Udgata A, Mukhopadhyay S. TLRs/NLRs: Shaping the landscape of host immunity. Int Rev Immunol 2017; 37:3-19. [PMID: 29193992 DOI: 10.1080/08830185.2017.1397656] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Innate immune system provides the first line of defense against pathogenic organisms. It has a varied and large collection of molecules known as pattern recognition receptors (PRRs) which can tackle the pathogens promptly and effectively. Toll-like receptors (TLRs) and NOD-like receptors (NLRs) are members of the PRR family that recognize pathogen associated molecular patterns (PAMPs) and play pivotal roles to mediate defense against infections from bacteria, fungi, virus and various other pathogens. In this review, we discuss the critical roles of TLRs and NLRs in the regulation of host immune-effector functions such as cytokine production, phagosome-lysosome fusion, inflammasome activation, autophagy, antigen presentation, and B and T cell immune responses that are known to be essential for mounting a protective immune response against the pathogens. This review may be helpful to design TLRs/NLRs based immunotherapeutics to control various infections and pathophysiological disorders.
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Affiliation(s)
- Komal Dolasia
- a Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD) , Tuljaguda Complex, Nampally, Hyderabad , India
| | - Manoj K Bisht
- a Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD) , Tuljaguda Complex, Nampally, Hyderabad , India
| | - Gourango Pradhan
- a Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD) , Tuljaguda Complex, Nampally, Hyderabad , India
| | - Atul Udgata
- a Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD) , Tuljaguda Complex, Nampally, Hyderabad , India
| | - Sangita Mukhopadhyay
- a Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD) , Tuljaguda Complex, Nampally, Hyderabad , India
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8
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Naujoks J, Lippmann J, Suttorp N, Opitz B. Innate sensing and cell-autonomous resistance pathways in Legionella pneumophila infection. Int J Med Microbiol 2017; 308:161-167. [PMID: 29097162 DOI: 10.1016/j.ijmm.2017.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 10/20/2017] [Accepted: 10/23/2017] [Indexed: 12/20/2022] Open
Abstract
Legionella pneumophila is a facultative intracellular bacterium which can cause a severe pneumonia called Legionnaires' disease after inhalation of contaminated water droplets and replication in alveolar macrophages. The innate immune system is generally able to sense and -in most cases- control L. pneumophila infection. Comorbidities and genetic risk factors, however, can compromise the immune system and high infection doses might overwhelm its capacity, thereby enabling L. pneumophila to grow and disseminate inside the lung. The innate immune system mediates sensing of L. pneumophila by employing e.g. NOD-like receptors (NLRs), Toll-like receptors (TLRs), as well as the cGAS/STING pathway to stimulate death of infected macrophages as well as production of proinflammatory cytokines and interferons (IFNs). Control of pulmonary L. pneumophila infection is largely mediated by inflammasome-, TNFα- and IFN-dependent macrophage-intrinsic resistance mechanisms. This article summarizes the current knowledge of innate immune responses to L. pneumophila infection in general, and of macrophage-intrinsic defense mechanisms in particular.
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Affiliation(s)
- Jan Naujoks
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Juliane Lippmann
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Norbert Suttorp
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Bastian Opitz
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Augustenburger Platz 1, 13353 Berlin, Germany; German Center for Lung Research (DZL), Germany.
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9
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Deviant Behavior: Tick-Borne Pathogens and Inflammasome Signaling. Vet Sci 2016; 3:vetsci3040027. [PMID: 29056735 PMCID: PMC5606592 DOI: 10.3390/vetsci3040027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/22/2016] [Accepted: 09/23/2016] [Indexed: 12/11/2022] Open
Abstract
In the face of an assault, host cells mount an immediate response orchestrated by innate immunity. Two of the best described innate immune signaling networks are the Toll- and the Nod-like receptor pathways. Extensive work has been done characterizing both signaling cascades with several recent advances on the forefront of inflammasome biology. In this review, we will discuss how more commonly-studied pathogens differ from tick-transmitted microbes in the context of Nod-like receptor signaling and inflammasome formation. Because pathogens transmitted by ticks have unique characteristics, we offer the opinion that these microbes can be used to uncover novel principles of Nod-like receptor biology.
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10
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Shin S. Innate Immunity to Intracellular Pathogens: Lessons Learned from Legionella pneumophila. ADVANCES IN APPLIED MICROBIOLOGY 2016; 79:43-71. [PMID: 22569517 DOI: 10.1016/b978-0-12-394318-7.00003-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intracellular bacterial pathogens have the remarkable ability to manipulate host cell processes in order to establish a replicative niche within the host cell. In response, the host can initiate immune defenses that lead to the eventual restriction and clearance of intracellular infection. The bacterial pathogen Legionella pneumophila has evolved elaborate virulence mechanisms that allow for its survival inside protozoa within a specialized membrane-bound organelle. These strategies also enable L. pneumophila to survive and replicate within alveolar macrophages, and can result in the severe pneumonia Legionnaires' disease. Essential to L. pneumophila's intracellular lifestyle is a specialized type IV secretion system, termed Dot/Icm, that translocates bacterial effector proteins into host cells. The ease with which L. pneumophila can be genetically manipulated has facilitated the comparison of host responses to virulent and isogenic avirulent mutants lacking a functional Dot/Icm system. This has made L. pneumophila an excellent model for understanding how the host discriminates between pathogenic and nonpathogenic bacteria and for systematically dissecting host defense mechanisms against intracellular pathogens. In this chapter, I discuss a few examples demonstrating how the study of immune responses triggered specifically by the L. pneumophila type IV secretion system has provided unique insight into our understanding of host immunity against intracellular bacterial pathogens.
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Affiliation(s)
- Sunny Shin
- Department of Microbiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania, USA.
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11
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Krause K, Amer AO. Caspase Exploitation by Legionella pneumophila. Front Microbiol 2016; 7:515. [PMID: 27148204 PMCID: PMC4829591 DOI: 10.3389/fmicb.2016.00515] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 03/29/2016] [Indexed: 12/21/2022] Open
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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12
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Zhao Y, Shao F. The NAIP-NLRC4 inflammasome in innate immune detection of bacterial flagellin and type III secretion apparatus. Immunol Rev 2016; 265:85-102. [PMID: 25879286 DOI: 10.1111/imr.12293] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Bacterial flagella and type III secretion system (T3SS) are evolutionarily related molecular transport machineries. Flagella mediate bacterial motility; the T3SS delivers virulence effectors to block host defenses. The inflammasome is a cytosolic multi-protein complex that activates caspase-1. Active caspase-1 triggers interleukin-1β (IL-1β)/IL-18 maturation and macrophage pyroptotic death to mount an inflammatory response. Central to the inflammasome is a pattern recognition receptor that activates caspase-1 either directly or through an adapter protein. Studies in the past 10 years have established a NAIP-NLRC4 inflammasome, in which NAIPs are cytosolic receptors for bacterial flagellin and T3SS rod/needle proteins, while NLRC4 acts as an adapter for caspase-1 activation. Given the wide presence of flagella and the T3SS in bacteria, the NAIP-NLRC4 inflammasome plays a critical role in anti-bacteria defenses. Here, we review the discovery of the NAIP-NLRC4 inflammasome and further discuss recent advances related to its biochemical mechanism and biological function as well as its connection to human autoinflammatory disease.
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Affiliation(s)
- Yue Zhao
- National Institute of Biological Sciences, Beijing, China
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13
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Schell U, Simon S, Hilbi H. Inflammasome Recognition and Regulation of the Legionella Flagellum. Curr Top Microbiol Immunol 2016; 397:161-81. [PMID: 27460809 DOI: 10.1007/978-3-319-41171-2_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The Gram-negative bacterium Legionella pneumophila colonizes extracellular environmental niches and infects free-living protozoa. Upon inhalation into the human lung, the opportunistic pathogen grows in macrophages and causes a fulminant pneumonia termed Legionnaires' disease. L. pneumophila employs a biphasic life cycle, comprising a replicative, non-virulent, and a stationary, virulent form. In the latter phase, the pathogen produces a plethora of so-called effector proteins, which are injected into host cells, where they subvert pivotal processes and promote the formation of a distinct membrane-bound compartment, the Legionella-containing vacuole. In the stationary phase, the bacteria also produce a single monopolar flagellum and become motile. L. pneumophila flagellin is recognized by and triggers the host's NAIP5 (Birc1e)/NLRC4 (Ipaf) inflammasome, which leads to caspase-1 activation, pore formation, and pyroptosis. The production of L. pneumophila flagellin and pathogen-host interactions are controlled by a complex stationary phase regulatory network, detecting nutrient availability as well as the Legionella quorum sensing (Lqs) signaling compound LAI-1 (3-hydroxypentadecane-4-one). Thus, the small molecule LAI-1 coordinates L. pneumophila flagellin production and motility, inflammasome activation, and virulence.
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Affiliation(s)
- Ursula Schell
- Max von Pettenkofer Institute, Ludwig-Maximilians University, Pettenkoferstraße 9a, 80336, Munich, Germany
| | - Sylvia Simon
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30/32, 8006, Zürich, Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 30/32, 8006, Zürich, Switzerland.
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14
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Abstract
Eukaryotes have evolved strategies to detect microbial intrusion and instruct immune responses to limit damage from infection. Recognition of microbes and cellular damage relies on the detection of microbe-associated molecular patterns (MAMPs, also called PAMPS, or pathogen-associated molecular patterns) and so-called "danger signals" by various families of host pattern recognition receptors (PRRs). Members of the recently identified protein family of nucleotide-binding domain andleucine-rich-repeat-containing proteins (NLR), including Nod1, Nod2, NLRP3, and NLRC4, have been shown to detect specific microbial motifs and danger signals for regulating host inflammatory responses. Moreover, with the discovery that polymorphisms in NOD1, NOD2, NLRP1, and NLRP3 are associated with susceptibility to chronic inflammatory disorders, the view has emerged that NLRs act not only as sensors butalso can serve as signaling platforms for instructing and balancing host immune responses. In this chapter, we explore the functions of these intracellular innate immune receptors and examine their implication in inflammatory diseases.
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15
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Simon S, Hilbi H. Subversion of Cell-Autonomous Immunity and Cell Migration by Legionella pneumophila Effectors. Front Immunol 2015; 6:447. [PMID: 26441958 PMCID: PMC4568765 DOI: 10.3389/fimmu.2015.00447] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/17/2015] [Indexed: 12/14/2022] Open
Abstract
Bacteria trigger host defense and inflammatory processes, such as cytokine production, pyroptosis, and the chemotactic migration of immune cells toward the source of infection. However, a number of pathogens interfere with these immune functions by producing specific so-called “effector” proteins, which are delivered to host cells via dedicated secretion systems. Air-borne Legionella pneumophila bacteria trigger an acute and potential fatal inflammation in the lung termed Legionnaires’ disease. The opportunistic pathogen L. pneumophila is a natural parasite of free-living amoebae, but also replicates in alveolar macrophages and accidentally infects humans. The bacteria employ the intracellular multiplication/defective for organelle trafficking (Icm/Dot) type IV secretion system and as many as 300 different effector proteins to govern host–cell interactions and establish in phagocytes an intracellular replication niche, the Legionella-containing vacuole. Some Icm/Dot-translocated effector proteins target cell-autonomous immunity or cell migration, i.e., they interfere with (i) endocytic, secretory, or retrograde vesicle trafficking pathways, (ii) organelle or cell motility, (iii) the inflammasome and programed cell death, or (iv) the transcription factor NF-κB. Here, we review recent mechanistic insights into the subversion of cellular immune functions by L. pneumophila.
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Affiliation(s)
- Sylvia Simon
- Institute of Medical Microbiology, University of Zürich , Zürich , Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology, University of Zürich , Zürich , Switzerland ; Max von Pettenkofer Institute, Ludwig-Maximilians University , Munich , Germany
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16
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Sellin ME, Maslowski KM, Maloy KJ, Hardt WD. Inflammasomes of the intestinal epithelium. Trends Immunol 2015; 36:442-50. [PMID: 26166583 DOI: 10.1016/j.it.2015.06.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 06/16/2015] [Accepted: 06/16/2015] [Indexed: 02/08/2023]
Abstract
While the functional importance of inflammasomes in blood-derived cell types is well established, it remains poorly understood how inflammasomes in nonhematopoietic cells contribute to mucosal immunity. Recent studies have revealed functional roles of inflammasomes - particularly NAIP/NLRC4, NLRP6, and noncanonical caspase-4 (caspase-11) - within epithelial cells of the gut in mucosal immune defense, inflammation, and tumorigenesis. Here, we review and discuss these findings in the broader context of tissue compartment-specific mucosal immunity. We propose several models whereby activities of the intestinal epithelial inflammasomes converge on mechanisms to remove compromised epithelial cells, maintain host-microbiota mutualism, and communicate with immune cells of the underlying lamina propria.
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Affiliation(s)
- Mikael E Sellin
- Institute of Microbiology, ETH Zürich, 8093 Zürich, Switzerland.
| | - Kendle M Maslowski
- Laboratory for Intestinal Ecosystem, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan
| | - Kevin J Maloy
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
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17
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Lage SL, Longo C, Branco LM, da Costa TB, Buzzo CDL, Bortoluci KR. Emerging Concepts about NAIP/NLRC4 Inflammasomes. Front Immunol 2014; 5:309. [PMID: 25071770 PMCID: PMC4078251 DOI: 10.3389/fimmu.2014.00309] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 06/17/2014] [Indexed: 12/14/2022] Open
Abstract
Neuronal apoptosis inhibitory protein (NAIP)/NOD-like receptor (NLR) containing a caspase activating and recruitment domain (CARD) 4 (NLRC4) inflammasome complexes are activated in response to proteins from virulent bacteria that reach the cell cytosol. Specific NAIP proteins bind to the agonists and then physically associate with NLRC4 to form an inflammasome complex able to recruit and activate pro-caspase-1. NAIP5 and NAIP6 sense flagellin, component of flagella from motile bacteria, whereas NAIP1 and NAIP2 detect needle and rod components from bacterial type III secretion systems, respectively. Active caspase-1 mediates the maturation and secretion of the pro-inflammatory cytokines, IL-1β and IL-18, and is responsible for the induction of pyroptosis, a pro-inflammatory form of cell death. In addition to these well-known effector mechanisms, novel roles have been described for NAIP/NLRC4 inflammasomes, such as phagosomal maturation, activation of inducible nitric oxide synthase, regulation of autophagy, secretion of inflammatory mediators, antibody production, activation of T cells, among others. These effector mechanisms mediated by NAIP/NLRC4 inflammasomes have been extensively studied in the context of resistance of infections and the potential of their agonists has been exploited in therapeutic strategies to non-infectious pathologies, such as tumor protection. Thus, this review will discuss current knowledge about the activation of NAIP/NLRC4 inflammasomes and their effector mechanisms.
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Affiliation(s)
- Silvia Lucena Lage
- Centro de Terapia Celular e Molecular (CTC-Mol), Universidade Federal de São Paulo , São Paulo , Brazil
| | - Carla Longo
- Centro de Terapia Celular e Molecular (CTC-Mol), Universidade Federal de São Paulo , São Paulo , Brazil ; Departamento de Ciências Biológicas, Universidade Federal de São Paulo , São Paulo , Brazil
| | - Laura Migliari Branco
- Centro de Terapia Celular e Molecular (CTC-Mol), Universidade Federal de São Paulo , São Paulo , Brazil
| | - Thaís Boccia da Costa
- Centro de Terapia Celular e Molecular (CTC-Mol), Universidade Federal de São Paulo , São Paulo , Brazil
| | - Carina de Lima Buzzo
- Centro de Terapia Celular e Molecular (CTC-Mol), Universidade Federal de São Paulo , São Paulo , Brazil
| | - Karina Ramalho Bortoluci
- Centro de Terapia Celular e Molecular (CTC-Mol), Universidade Federal de São Paulo , São Paulo , Brazil ; Departamento de Ciências Biológicas, Universidade Federal de São Paulo , São Paulo , Brazil
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18
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Casson CN, Shin S. Inflammasome-mediated cell death in response to bacterial pathogens that access the host cell cytosol: lessons from legionella pneumophila. Front Cell Infect Microbiol 2013; 3:111. [PMID: 24409420 PMCID: PMC3873505 DOI: 10.3389/fcimb.2013.00111] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 12/16/2013] [Indexed: 11/25/2022] Open
Abstract
Cell death can be critical for host defense against intracellular pathogens because it eliminates a crucial replicative niche, and pro-inflammatory cell death can alert neighboring cells to the presence of pathogenic organisms and enhance downstream immune responses. Pyroptosis is a pro-inflammatory form of cell death triggered by the inflammasome, a multi-protein complex that assembles in the cytosol to activate caspase-1. Inflammasome activation by pathogens hinges upon violation of the host cell cytosol by activities such as the use of pore-forming toxins, the use of specialized secretion systems, or the cytosolic presence of the pathogen itself. Recently, a non-canonical inflammasome has been described that activates caspase-11 and also leads to pro-inflammatory cell death. Caspase-11 is activated rapidly and robustly in response to violation of the cytosol by bacterial pathogens as well. In this mini-review, we describe the canonical and non-canonical inflammasome pathways that are critical for host defense against a model intracellular bacterial pathogen that accesses the host cytosol—Legionella pneumophila.
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Affiliation(s)
- Cierra N Casson
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
| | - Sunny Shin
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
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19
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Hoffmann C, Harrison CF, Hilbi H. The natural alternative: protozoa as cellular models forLegionellainfection. Cell Microbiol 2013; 16:15-26. [DOI: 10.1111/cmi.12235] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/02/2013] [Accepted: 09/04/2013] [Indexed: 12/22/2022]
Affiliation(s)
- Christine Hoffmann
- Max von Pettenkofer Institute; Department of Medicine; Ludwig-Maximilians University Munich; 80336 Munich Germany
| | - Christopher F. Harrison
- Max von Pettenkofer Institute; Department of Medicine; Ludwig-Maximilians University Munich; 80336 Munich Germany
| | - Hubert Hilbi
- Max von Pettenkofer Institute; Department of Medicine; Ludwig-Maximilians University Munich; 80336 Munich Germany
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20
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Chaput C, Sander LE, Suttorp N, Opitz B. NOD-Like Receptors in Lung Diseases. Front Immunol 2013; 4:393. [PMID: 24312100 PMCID: PMC3836004 DOI: 10.3389/fimmu.2013.00393] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 11/07/2013] [Indexed: 12/15/2022] Open
Abstract
The lung is a particularly vulnerable organ at the interface of the body and the exterior environment. It is constantly exposed to microbes and particles by inhalation. The innate immune system needs to react promptly and adequately to potential dangers posed by these microbes and particles, while at the same time avoiding extensive tissue damage. Nucleotide-binding oligomerization domain-like receptors (NLRs) represent a group of key sensors for microbes and damage in the lung. As such they are important players in various infectious as well as acute and chronic sterile inflammatory diseases, such as pneumonia, chronic obstructive pulmonary disease (COPD), acute lung injury/acute respiratory distress syndrome, pneumoconiosis, and asthma. Activation of most known NLRs leads to the production and release of pro-inflammatory cytokines, and/or to the induction of cell death. We will review NLR functions in the lung during infection and sterile inflammation.
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Affiliation(s)
- Catherine Chaput
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité - Universitätsmedizin Berlin , Berlin , Germany
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21
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Abstract
UNLABELLED When microbes contaminate the macrophage cytoplasm, leukocytes undergo a proinflammatory death that is initiated by nucleotide-binding-domain-, leucine-rich-repeat-containing proteins (NLR proteins) that bind and activate caspase-1. We report that these inflammasome components also regulate autophagy, a vesicular pathway to eliminate cytosolic debris. In response to infection with flagellate Legionella pneumophila, C57BL/6J mouse macrophages equipped with caspase-1 and the NLR proteins NAIP5 and NLRC4 stimulated autophagosome turnover. A second trigger of inflammasome assembly, K(+) efflux, also rapidly activated autophagy in macrophages that produced caspase-1. Autophagy protects infected macrophages from pyroptosis, since caspase-1-dependent cell death occurred more frequently when autophagy was dampened pharmacologically by either 3-methyladenine or an inhibitor of the Atg4 protease. Accordingly, in addition to coordinating pyroptosis, both (pro-) caspase-1 protein and NLR components of inflammasomes equip macrophages to recruit autophagy, a disposal pathway that raises the threshold of contaminants necessary to trigger proinflammatory leukocyte death. IMPORTANCE An exciting development in the innate-immunity field is the recognition that macrophages enlist autophagy to protect their cytoplasm from infection. Nutrient deprivation has long been known to induce autophagy; how infection triggers this disposal pathway is an active area of research. Autophagy is encountered by many of the intracellular pathogens that are known to trigger pyroptosis, an inflammatory cell death initiated when nucleotide-binding-domain-, leucine-rich-repeat-containing proteins (NLR proteins) activate caspase-1 within inflammasome complexes. Therefore, we tested the hypothesis that NLR proteins and caspase-1 also coordinate autophagy as a barrier to cytosolic infection. By exploiting classical bacterial and mouse genetics and kinetic assays of autophagy, we demonstrate for the first time that, when confronted with cytosolic contamination, primary mouse macrophages rely not only on the NLR proteins NAIP5 and NLRC4 but also on (pro-)caspase-1 protein to mount a rapid autophagic response that wards off proinflammatory cell death.
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22
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Richards AL, Jackson WT. Intracellular vesicle acidification promotes maturation of infectious poliovirus particles. PLoS Pathog 2012; 8:e1003046. [PMID: 23209416 PMCID: PMC3510256 DOI: 10.1371/journal.ppat.1003046] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 10/06/2012] [Indexed: 12/30/2022] Open
Abstract
The autophagic pathway acts as part of the immune response against a variety of pathogens. However, several pathogens subvert autophagic signaling to promote their own replication. In many cases it has been demonstrated that these pathogens inhibit or delay the degradative aspect of autophagy. Here, using poliovirus as a model virus, we report for the first time bona fide autophagic degradation occurring during infection with a virus whose replication is promoted by autophagy. We found that this degradation is not required to promote poliovirus replication. However, vesicular acidification, which in the case of autophagy precedes delivery of cargo to lysosomes, is required for normal levels of virus production. We show that blocking autophagosome formation inhibits viral RNA synthesis and subsequent steps in the virus cycle, while inhibiting vesicle acidification only inhibits the final maturation cleavage of virus particles. We suggest that particle assembly, genome encapsidation, and virion maturation may occur in a cellular compartment, and we propose the acidic mature autophagosome as a candidate vesicle. We discuss the implications of our findings in understanding the late stages of poliovirus replication, including the formation and maturation of virions and egress of infectious virus from cells. The autophagic degradation pathway is a well-known agent of innate immunity. Several pathogens, including poliovirus (PV), a model for several medically important RNA viruses, subvert this pathway for their own benefit. In doing so, pathogens often inhibit the degradative portion of the pathway, presumably to prevent their own destruction. We show here that, surprisingly, PV infection results in high levels of degradative autophagy. However, we find that autophagic degradation is dispensable for PV replication. Inhibiting the formation of autophagosomes inhibits virus RNA replication and subsequent steps in virus production. Inhibiting the acidification of vesicles, which in the case of autophagosomes precedes fusion with lysosomes and autophagic degradation, inhibits a much later step in virus production. Our data suggest an important role for an acidic compartment of the cell in the final maturation step, cleaving a capsid protein to generate infectious virus. Importantly, these data also call into question the long-standing hypothesis that all steps in the production of infectious poliovirus are cytosolic.
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Affiliation(s)
| | - William T. Jackson
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- * E-mail:
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23
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Mantegazza AR, Magalhaes JG, Amigorena S, Marks MS. Presentation of phagocytosed antigens by MHC class I and II. Traffic 2012; 14:135-52. [PMID: 23127154 DOI: 10.1111/tra.12026] [Citation(s) in RCA: 145] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 11/01/2012] [Accepted: 11/06/2012] [Indexed: 12/15/2022]
Abstract
Phagocytosis provides innate immune cells with a mechanism to take up and destroy pathogenic bacteria, apoptotic cells and other large particles. In some cases, however, peptide antigens from these particles are preserved for presentation in association with major histocompatibility complex (MHC) class I or class II molecules in order to stimulate antigen-specific T cells. Processing and presentation of antigens from phagosomes presents a number of distinct challenges relative to antigens internalized by other means; while bacterial antigens were among the first discovered to be presented to T cells, analyses of the cellular mechanisms by which peptides from phagocytosed antigens assemble with MHC molecules and by which these complexes are then expressed at the plasma membrane have lagged behind those of conventional model soluble antigens. In this review, we cover recent advances in our understanding of these processes, including the unique cross-presentation of phagocytosed antigens by MHC class I molecules, and in their control by signaling modalities in phagocytic cells.
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Affiliation(s)
- Adriana R Mantegazza
- Department of Pathology & Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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24
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von Moltke J, Ayres JS, Kofoed EM, Chavarría-Smith J, Vance RE. Recognition of bacteria by inflammasomes. Annu Rev Immunol 2012; 31:73-106. [PMID: 23215645 DOI: 10.1146/annurev-immunol-032712-095944] [Citation(s) in RCA: 322] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Inflammasomes are cytosolic multiprotein complexes that assemble in response to a variety of infectious and noxious insults. Inflammasomes play a critical role in the initiation of innate immune responses, primarily by serving as platforms for the activation of inflammatory caspase proteases. One such caspase, CASPASE-1 (CASP1), initiates innate immune responses by cleaving pro-IL-1β and pro-IL-18, leading to their activation and release. CASP1 and another inflammatory caspase termed CASP11 can also initiate a rapid and inflammatory form of cell death termed pyroptosis. Several distinct inflammasomes have been described, each of which contains a unique sensor protein of the NLR (nucleotide-binding domain, leucine-rich repeat-containing) superfamily or the PYHIN (PYRIN and HIN-200 domain-containing) superfamily. Here we describe the surprisingly diverse mechanisms by which NLR/PYHIN proteins sense bacteria and initiate innate immune responses. We conclude that inflammasomes represent a highly adaptable scaffold ideally suited for detecting and initiating rapid innate responses to diverse and rapidly evolving bacteria.
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Affiliation(s)
- Jakob von Moltke
- Department of Molecular & Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, California 94720, USA
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25
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Affiliation(s)
- Mohamed Lamkanfi
- Department of Biochemistry, Ghent University, Ghent 9000, Belgium
- Department of Medical Protein Research, VIB, Ghent 9000, Belgium;
| | - Vishva M. Dixit
- Department of Physiological Chemistry, Genentech, South San Francisco, California 94080;
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26
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Thi EP, Lambertz U, Reiner NE. Class IA phosphatidylinositol 3-kinase p110α regulates phagosome maturation. PLoS One 2012; 7:e43668. [PMID: 22928013 PMCID: PMC3425514 DOI: 10.1371/journal.pone.0043668] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 07/24/2012] [Indexed: 12/31/2022] Open
Abstract
Of the various phosphatidylinositol 3- kinases (PI3Ks), only the class III enzyme Vps34 has been shown to regulate phagosome maturation. During studies of phagosome maturation in THP-1 cells deficient in class IA PI3K p110α, we discovered that this PI3K isoform is required for vacuole maturation to progress beyond acquisition of Rab7 leading to delivery of lysosomal markers. Bead phagosomes from THP-1 cells acquired p110α and contained PI3P and PI(3,4,5)P3; however, p110α and PI(3,4,5)P3 levels in phagosomes from p110α knockdown cells were decreased. Phagosomes from p110α knock down cells showed normal acquisition of both Rab5 and EEA-1, but were markedly deficient in the lysosomal markers LAMP-1 and LAMP-2, and the lysosomal hydrolase, β-galactosidase. Phagosomes from p110α deficient cells also displayed impaired fusion with Texas Red dextran-loaded lysosomes. Despite lacking lysosomal components, phagosomes from p110α deficient cells recruited normal levels of Rab7, Rab-interacting lysosomal protein (RILP) and homotypic vacuole fusion and protein sorting (HOPs) components Vps41 and Vps16. The latter observations demonstrated that phagosomal Rab7 was active and capable of recruiting effectors involved in membrane fusion. Nevertheless, active Rab7 was not sufficient to bring about the delivery of lysosomal proteins to the maturing vacuole, which is shown for the first time to be dependent on a class I PI3K.
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Affiliation(s)
- Emily P. Thi
- Departments of Medicine, Experimental Medicine Program, Division of Infectious Diseases, University of British Columbia and the Immunity and Infection Research Centre, Vancouver Coastal Health Research Institute, Vancouver, B.C., Canada
| | - Ulrike Lambertz
- Departments of Medicine, Experimental Medicine Program, Division of Infectious Diseases, University of British Columbia and the Immunity and Infection Research Centre, Vancouver Coastal Health Research Institute, Vancouver, B.C., Canada
| | - Neil E. Reiner
- Departments of Medicine, Experimental Medicine Program, Division of Infectious Diseases, University of British Columbia and the Immunity and Infection Research Centre, Vancouver Coastal Health Research Institute, Vancouver, B.C., Canada
- Microbiology and Immunology, University of British Columbia and the Immunity and Infection Research Centre, Vancouver Coastal Health Research Institute, Vancouver, B.C., Canada
- * E-mail:
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27
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Kofoed EM, Vance RE. NAIPs: building an innate immune barrier against bacterial pathogens. NAIPs function as sensors that initiate innate immunity by detection of bacterial proteins in the host cell cytosol. Bioessays 2012; 34:589-98. [PMID: 22513803 DOI: 10.1002/bies.201200013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The innate immune system of mammals encodes several families of immune detector proteins that monitor the cytosol for signs of pathogen invasion. One important but poorly understood family of cytosolic immunosurveillance proteins is the NLR (nucleotide-binding domain, leucine-rich repeat containing) proteins. Recent work has demonstrated that one subfamily of NLRs, the NAIPs (NLR family, apoptosis inhibitory proteins), are activated by specific interaction with bacterial ligands, such as flagellin. NAIP activation leads to assembly of a large multiprotein complex called the inflammasome, which initiates innate immune responses by activation of the Caspase-1 protease. NAIPs therefore appear to detect pathogen molecules via a simple and direct receptor-ligand mechanism. Interestingly, other NLR family members appear to detect pathogens indirectly, perhaps by responding to host cell "stress" caused by the pathogen. Thus, the NLR family may have evolved surprisingly diverse mechanisms for detecting pathogens.
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Affiliation(s)
- Eric M Kofoed
- UC Berkeley-MCB, Life Sciences Addition, University of California-Berkeley, CA, USA.
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28
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Gong YN, Shao F. Sensing bacterial infections by NAIP receptors in NLRC4 inflammasome activation. Protein Cell 2012; 3:98-105. [PMID: 22426978 DOI: 10.1007/s13238-012-2028-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 02/08/2012] [Indexed: 12/16/2022] Open
Abstract
The inflammasome is an emerging new pathway in innate immune defense against microbial infection or endogenous danger signals. The inflammasome stimulates activation of inflammatory caspases, mainly caspase-1. Caspase-1 activation is responsible for processing and secretion of IL-1β and IL-18 as well as for inducing macrophage pyroptotic death. Assembly of the large cytoplasmic inflammasome complex is thought to be mediated by members of NOD-like receptor (NLR) family. While functions of most of the NLR proteins remain to be defined, several NLR proteins including NLRC4 have been shown to assemble distinct inflammasome complexes. These inflammasome pathways, particularly the NLRC4 inflammasome, play a critical role in sensing and restricting diverse types of bacterial infections. Here we review recent advances in defining the exact bacterial ligands and the ligand-binding receptors involved in NLRC4 inflammasome activation. Implications of the discovery of the NAIP family of inflammasome receptors for bacterial flagellin and type III secretion apparatus on future inflammasome and bacterial infection studies are also discussed.
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Affiliation(s)
- Yi-Nan Gong
- National Institute of Biological Sciences, Beijing, 102206, China
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29
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Pereira MSF, Morgantetti GF, Massis LM, Horta CV, Hori JI, Zamboni DS. Activation of NLRC4 by flagellated bacteria triggers caspase-1-dependent and -independent responses to restrict Legionella pneumophila replication in macrophages and in vivo. THE JOURNAL OF IMMUNOLOGY 2011; 187:6447-55. [PMID: 22079982 DOI: 10.4049/jimmunol.1003784] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Although NLRC4/IPAF activation by flagellin has been extensively investigated, the downstream signaling pathways and the mechanisms responsible for infection clearance remain unclear. In this study, we used mice deficient for the inflammasome components in addition to wild-type (WT) Legionella pneumophila or bacteria deficient for flagellin (flaA) or motility (fliI) to assess the pathways responsible for NLRC4-dependent growth restriction in vivo and ex vivo. By comparing infections with WT L. pneumophila, fliI, and flaA, we found that flagellin and motility are important for the colonization of the protozoan host Acanthamoeba castellanii. However, in macrophages and mammalian lungs, flagellin expression abrogated bacterial replication. The flagellin-mediated growth restriction was dependent on NLRC4, and although it was recently demonstrated that NLRC4 is able to recognize bacteria independent of flagellin, we found that the NLRC4-dependent restriction of L. pneumophila multiplication was fully dependent on flagellin. By examining infected caspase-1(-/-) mice and macrophages with flaA, fliI, and WT L. pneumophila, we could detect greater replication of flaA, which suggests that caspase-1 only partially accounted for flagellin-dependent growth restriction. Conversely, WT L. pneumophila multiplied better in macrophages and mice deficient for NLRC4 compared with that in macrophages and mice deficient for caspase-1, supporting the existence of a novel caspase-1-independent response downstream of NLRC4. This response operated early after macrophage infection and accounted for the restriction of bacterial replication within bacteria-containing vacuoles. Collectively, our data indicate that flagellin is required for NLRC4-dependent responses to L. pneumophila and that NLRC4 triggers caspase-1-dependent and -independent responses for bacterial growth restriction in macrophages and in vivo.
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Affiliation(s)
- Marcelo S F Pereira
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil
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30
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The NLRC4 inflammasome receptors for bacterial flagellin and type III secretion apparatus. Nature 2011; 477:596-600. [PMID: 21918512 DOI: 10.1038/nature10510] [Citation(s) in RCA: 958] [Impact Index Per Article: 73.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 08/30/2011] [Indexed: 01/16/2023]
Abstract
Inflammasomes are large cytoplasmic complexes that sense microbial infections/danger molecules and induce caspase-1 activation-dependent cytokine production and macrophage inflammatory death. The inflammasome assembled by the NOD-like receptor (NLR) protein NLRC4 responds to bacterial flagellin and a conserved type III secretion system (TTSS) rod component. How the NLRC4 inflammasome detects the two bacterial products and the molecular mechanism of NLRC4 inflammasome activation are not understood. Here we show that NAIP5, a BIR-domain NLR protein required for Legionella pneumophila replication in mouse macrophages, is a universal component of the flagellin-NLRC4 pathway. NAIP5 directly and specifically interacted with flagellin, which determined the inflammasome-stimulation activities of different bacterial flagellins. NAIP5 engagement by flagellin promoted a physical NAIP5-NLRC4 association, rendering full reconstitution of a flagellin-responsive NLRC4 inflammasome in non-macrophage cells. The related NAIP2 functioned analogously to NAIP5, serving as a specific inflammasome receptor for TTSS rod proteins such as Salmonella PrgJ and Burkholderia BsaK. Genetic analysis of Chromobacterium violaceum infection revealed that the TTSS needle protein CprI can stimulate NLRC4 inflammasome activation in human macrophages. Similarly, CprI is specifically recognized by human NAIP, the sole NAIP family member in human. The finding that NAIP proteins are inflammasome receptors for bacterial flagellin and TTSS apparatus components further predicts that the remaining NAIP family members may recognize other unidentified microbial products to activate NLRC4 inflammasome-mediated innate immunity.
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31
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Lippmann J, Müller HC, Naujoks J, Tabeling C, Shin S, Witzenrath M, Hellwig K, Kirschning CJ, Taylor GA, Barchet W, Bauer S, Suttorp N, Roy CR, Opitz B. Dissection of a type I interferon pathway in controlling bacterial intracellular infection in mice. Cell Microbiol 2011; 13:1668-82. [PMID: 21790939 DOI: 10.1111/j.1462-5822.2011.01646.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Defence mechanisms against intracellular bacterial pathogens are incompletely understood. Our study characterizes a type I IFN-dependent cell-autonomous defence pathway directed against Legionella pneumophila, an intracellular model organism and frequent cause of pneumonia. We show that macrophages infected with L. pneumophila produced IFNβ in a STING- and IRF3- dependent manner. Paracrine type I IFNs stimulated upregulation of IFN-stimulated genes and a cell-autonomous defence pathway acting on replicating and non-replicating Legionella within their specialized vacuole. Our infection experiments in mice lacking receptors for type I and/or II IFNs show that type I IFNs contribute to expression of IFN-stimulated genes and to bacterial clearance as well as resistance in L. pneumophila pneumonia in addition to type II IFN. Overall, our study shows that paracrine type I IFNs mediate defence against L. pneumophila, and demonstrates a protective role of type I IFNs in in vivo infections with intracellular bacteria.
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Affiliation(s)
- Juliane Lippmann
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
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32
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Global cellular changes induced by Legionella pneumophila infection of bone marrow-derived macrophages. Immunobiology 2011; 216:1274-85. [PMID: 21794945 DOI: 10.1016/j.imbio.2011.06.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 06/23/2011] [Indexed: 12/23/2022]
Abstract
The nucleotide-binding oligomerization domain (Nod)-like receptor (NLR) family member Naip5 plays an essential role in restricting Legionella pneumophila growth inside primary macrophages. Upon interaction with bacterial flagellin, the intracellular receptor Naip5 forms a multi-protein complex, the inflammasome, which activation has a protective role against infection. The A/J mouse strain carries a Naip5 allele (Naip5(A/J)), which renders its macrophages susceptible to Legionella infection. However, Naip5(A/J) is still competent for inflammasome activation suggesting that an as yet unidentified signaling pathway located downstream of Naip5 and defective in Naip5(A/J) macrophages regulates macrophage defenses against Legionella. Therefore, transcriptional profiling experiments with macrophages from C57BL/6J mice (B6), and from congenic mice (BcA75) carrying the partial loss-of-function A/J-derived allele (Naip5(A/J)) on a B6 background, infected or not with wild-type L. pneumophila or flagellin-deficient mutant were carried out to identify genes regulated by flagellin and by Naip5. Both the Legionella infection per se and the presence of flagellin had very strong effects on transcriptional responses of macrophages, 4h following infection, including modulation of cellular pathways associated with inflammatory response and cell survival. On the other hand, the presence of wild type or partial loss of function allele (Naip5(A/J)) at Naip5 did not cause large effects on transcriptional responses of macrophages to infection. We also examined in L. pneumophila infected macrophages, the effect of Naip5 alleles on expression and phosphorylation of 524 phosphoproteins, kinases and phosphatases involved in cell proliferation, immune response, stress and apoptosis. Naip5 alleles had an effect on the TLR-Il1R signaling pathway, the cell cycle and the caveolin-mediated response to pathogen. The results of transcriptome and proteome analyses were organized into cellular pathways in macrophages that are modulated in response to Legionella infection.
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Joshi AD, Swanson MS. Secrets of a successful pathogen: legionella resistance to progression along the autophagic pathway. Front Microbiol 2011; 2:138. [PMID: 21743811 PMCID: PMC3127087 DOI: 10.3389/fmicb.2011.00138] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 06/13/2011] [Indexed: 11/22/2022] Open
Abstract
To proliferate within phagocytes, Legionella pneumophila relies on Type IV secretion to modulate host cellular pathways. Autophagy is an evolutionarily conserved degradative pathway that captures and transfers a variety of microbes to lysosomes. Biogenesis of L. pneumophila-containing vacuoles and autophagosomes share several features, including endoplasmic reticulum (ER)-derived membranes, contributions by the host GTPases Rab1, Arf1 and Sar1, and a final destiny in lysosomes. We discuss morphological, molecular genetic, and immunological data that support the model that, although A/J mouse macrophages efficiently engulf L. pneumophila within autophagosomal membranes, the Type IV effector proteins DrrA/SidM, LidA, and RalF prolong association with the ER. By inhibiting immediately delivery to lysosomes, the bacteria persist in immature autophagosomal vacuoles for a period sufficient to differentiate into an acid-resistant, replicative form. Subsequent secretion of the Type IV effector LepB releases the block to autophagosome maturation, and the adapted progeny continue to replicate within autophagolysosomes. Accordingly, L. pneumophila can be exploited as a genetic tool to analyze the recruitment and function of the macrophage autophagy pathway.
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Affiliation(s)
- Amrita D Joshi
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
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Massis LM, Zamboni DS. Innate immunity to legionella pneumophila. Front Microbiol 2011; 2:109. [PMID: 21833338 PMCID: PMC3153058 DOI: 10.3389/fmicb.2011.00109] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 05/03/2011] [Indexed: 01/16/2023] Open
Abstract
Innate immune cells, such as macrophages, are highly adapted to rapidly recognize infections by distinct pathogens, including viruses, bacteria, fungi, and protozoa. This recognition is mediated by pattern recognition receptors (PRRs), which are found in host cell surface membranes and the host cell cytoplasm. PRRs include protein families such as the toll-like receptors, nod-like receptors, RIG-I-like receptors, and sensors of cytosolic DNA. The activation of these PRRs by pathogen-associated molecular patterns leads to transcriptional responses and specific forms of cell death. These processes effectively contribute to host resistance to infection either via cell-autonomous processes that lead to the intracellular restriction of microbial replication and/or by activating pathogen-specific adaptive immune responses. Legionella pneumophila, the causative agent of Legionnaires’ disease, is a Gram-negative bacterium that triggers responses by multiple PRRs. Here, we review a set of studies that have contributed to our specific understanding of the molecular mechanisms by which innate immune cells recognize and respond to L. pneumophila and the importance of these processes to the outcome of infection.
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Affiliation(s)
- Liliana M Massis
- Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo Ribeirão Preto, SP, Brazil
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Gruenheid S, Gros P. Forward genetic dissection of innate response to infection in inbred mouse strains: selected success stories. Clin Exp Immunol 2011; 162:393-401. [PMID: 21070206 DOI: 10.1111/j.1365-2249.2010.04249.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mouse genetics is a powerful tool for the dissection of genes, proteins, and pathways important in biological processes. Application of this approach to study the host response to infection has been a rich source of discoveries that have increased our understanding of the early innate pathways involved in responding to microbial infections. Here we review some of the key discoveries that have arisen from pinpointing the genetic defect in mouse strains with unusual or extreme response to infection and have led to insights into pathogen sensing pathways and downstream effector functions of the early innate immune response.
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Affiliation(s)
- S Gruenheid
- Complex Traits Program, McGill University, Montreal, Canada.
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Skeldon A, Saleh M. The inflammasomes: molecular effectors of host resistance against bacterial, viral, parasitic, and fungal infections. Front Microbiol 2011; 2:15. [PMID: 21716947 PMCID: PMC3109312 DOI: 10.3389/fmicb.2011.00015] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 01/20/2011] [Indexed: 01/01/2023] Open
Abstract
The inflammasomes are large multi-protein complexes scaffolded by cytosolic pattern recognition receptors (PRRs) that form an important part of the innate immune system. They are activated following the recognition of microbial-associated molecular patterns or host-derived danger signals (danger-associated molecular patterns) by PRRs. This recognition results in the recruitment and activation of the pro-inflammatory protease caspase-1, which cleaves its preferred substrates pro-interleukin-1β (IL-1β) and pro-IL-18 into their mature biologically active cytokine forms. Through processing of a number of other cellular substrates, caspase-1 is also required for the release of “alarmins” and the induction and execution of an inflammatory form of cell death termed pyroptosis. A growing spectrum of inflammasomes have been identified in the host defense against a variety of pathogens. Reciprocally, pathogens have evolved effector strategies to antagonize the inflammasome pathway. In this review we discuss recent developments in the understanding of inflammasome-mediated recognition of bacterial, viral, parasitic, and fungal infections and the beneficial or detrimental effects of inflammasome signaling in host resistance.
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Abstract
Introduction It has been proposed that the innate immune system might discriminate living and virulent pathogens from dead or harmless microbes, but the molecular mechanisms by which this discrimination could occur remain unclear. Although studies of model antigens and adjuvants have illuminated important principles underlying immune responses, the specific immune responses made to living, virulent pathogens can only be discovered by studies of the living, virulent pathogens themselves. Methods and Findings Here, I review what one particular bacterium, Legionella pneumophila, has taught us about the innate immune response. Pathogens differ greatly in the mechanisms they use to invade, replicate within, and transmit among their hosts. However, a theme that emerges is that the pathogenic activities sensed by host cells are conserved among multiple pathogenic bacteria. Conclusion Thus, immunology taught by L. pneumophila may lead to a more general understanding of the host response to infection.
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Amer AO. Modulation of caspases and their non-apoptotic functions byLegionella pneumophila. Cell Microbiol 2010; 12:140-7. [DOI: 10.1111/j.1462-5822.2009.01401.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shobuike T, Katagiri N, Miyamoto H. [Control of intracellular Legionella pneumophila growth--with special reference to the Lgn1/Naip5/Birc1e gene--]. Nihon Saikingaku Zasshi 2009; 64:319-330. [PMID: 19628930 DOI: 10.3412/jsb.64.319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Affiliation(s)
- Takeo Shobuike
- Division of Microbiology, Department of Pathology and Microbiology Faculty of Medicine, Saga University, Saga, Japan
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Restriction of Legionella pneumophila replication in macrophages requires concerted action of the transcriptional regulators Irf1 and Irf8 and nod-like receptors Naip5 and Nlrc4. Infect Immun 2009; 77:4794-805. [PMID: 19720760 DOI: 10.1128/iai.01546-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The unique permissiveness of A/J mouse macrophages for replication of Legionella pneumophila is caused by a deficiency in the Nod-like receptor (NLR) protein and intracellular sensor for L. pneumophila flagellin (Naip5). The signaling pathways and proteins activated by Naip5 sensing in macrophages were investigated. Transcript profiling of macrophages from susceptible A/J mice and from resistant A/J mice harboring a transgenic wild-type copy of Naip5 at 4 h following L. pneumophila infection suggested that two members of the Irf transcriptional regulator family, Irf1 and Irf8, are regulated in response to Naip5 sensing of L. pneumophila. We show that macrophages having defective alleles of either Irf1 (Irf1-/-) or its heterodimerization partner gene Irf8 (Irf8R294C) become permissive for L. pneumophila replication, indicating that both the Irf1 and Irf8 proteins are essential for macrophage defense against L. pneumophila. Moreover, macrophages doubly heterozygous (Naip5AJ/WT Irf8R294C/WT or Nlrc4-/+ Irf8R294C/WT) for combined loss-of-function mutations in Irf8 and in either Naip5 or Nlrc4 are highly susceptible to L. pneumophila, indicating that there is a strong genetic interaction between Irf8 and the NLR protein family in the macrophage response to L. pneumophila. Legionella-containing phagosomes (LCPs) formed in permissive Irf1-/- or Irf8R294C macrophages behave like LCPs formed in Naip5-insufficient and Nlrc4-deficient macrophages which fail to acidify. These results suggest that, in addition to Naip5 and Nlrc4, Irf1 and Irf8 play a critical role in the early response of macrophages to infection with L. pneumophila, including antagonizing the ability of L. pneumophila to block phagosome acidification. They also suggest that flagellin sensing by the NLR proteins Naip5 and Nlrc4 may be coupled to Irf1-Irf8-mediated transcriptional activation of key effector genes essential for macrophage resistance to L. pneumophila infection.
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Abstract
The innate immune system is critical in recognizing bacterial and viral infections to evoke a proper immune response. Certain members of the intracellular nucleotide-binding and oligomerization domain (NOD)-like receptor (NLR) family detect microbial components in the cytosol and trigger the assembly of large caspase-1-activating complexes termed inflammasomes. Autoproteolytic maturation of caspase-1 zymogens within these inflammasomes leads to maturation and secretion of the pro-inflammatory cytokines interleukin-1 beta (IL-1 beta) and IL-18. The NLR proteins ICE protease-activating factor (IPAF), NALP1b (NACHT domain-, leucine-rich repeat-, and PYD-containing protein 1b), and cryopyrin/NALP3 assemble caspase-1-activating inflammasomes in a stimulus-dependent manner. Bacterial flagellin is sensed by IPAF, whereas mouse NALP1b detects anthrax lethal toxin. Cryopyrin/NALP3 mediates caspase-1 activation in response to a wide variety of microbial components and in response to crystalline substances such as the endogenous danger signal uric acid. Genetic variations in Nalp1 and cryopyrin/Nalp3 are associated with autoinflammatory disorders and increased susceptibility to microbial infection. Further understanding of inflammasomes and their role in innate immunity should provide new insights into the mechanisms of host defense and the pathogenesis of autoimmune diseases.
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Affiliation(s)
- Mohamed Lamkanfi
- Department of Physiological Chemistry, Genentech, South San Francisco, CA 94080, USA
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42
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Chen G, Shaw MH, Kim YG, Nuñez G. NOD-like receptors: role in innate immunity and inflammatory disease. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2009; 4:365-98. [PMID: 18928408 DOI: 10.1146/annurev.pathol.4.110807.092239] [Citation(s) in RCA: 541] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The NOD-like receptors (NLRs) are a specialized group of intracellular receptors that represent a key component of the host innate immune system. Since the discovery of the first NLR almost 10 years ago, the study of this special class of microbial sensors has burgeoned; consequently, a better understanding of the mechanism by which these receptors recognize microbes and other danger signals and of how they activate inflammatory signaling pathways has emerged. Moreover, in addition to their primary role in host defense against invading pathogens, their ability to regulate nuclear factor-kappa B (NF-kappaB) signaling, interleukin-1-beta (IL-1beta) production, and cell death indicates that they are crucial to the pathogenesis of a variety of inflammatory human diseases.
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Affiliation(s)
- Grace Chen
- Departments of Pathology and Internal Medicine and the Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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Abstract
The gram-negative rod Burkholderia pseudomallei is the causative agent of melioidosis, a potentially fatal disease which is endemic in tropical and subtropical areas. The bacterium multiplies intracellularly within the cytosol, induces the formation of actin tails, and can spread directly from cell to cell. Recently, it has been shown that B. pseudomallei can induce caspase-1-dependent cell death in macrophages. The aim of the present study was to further elucidate the role of caspase-1 during B. pseudomallei infection. In vivo experiments with caspase-1(-/-) mice revealed a high susceptibility to B. pseudomallei challenge. This phenotype was associated with a significantly higher bacterial burden 2 days after infection and decreased gamma interferon (IFN-gamma) and interleukin-18 cytokine levels 24 h after infection compared to control animals. caspase-1(-/-) bone marrow-derived macrophages (BMM) exhibited strong caspase-3 expression and reduced cell damage compared to wild-type (WT) cells during early B. pseudomallei infection, indicating "classical" apoptosis, whereas WT BMM showed signs of rapid caspase-1-dependent cell death. Moreover, we found that caspase-1(-/-) BMM had a strongly increased bacterial burden compared to WT cells 3 h after infection under conditions where no difference in cell death could be observed between both cell populations at this time point. We therefore suggest that caspase-1-dependent rapid cell death might contribute to resistance by reducing the intracellular niche for B. pseudomallei, but, in addition, caspase-1 might also have a role in controlling intracellular replication of B. pseudomallei in macrophages. Moreover, caspase-1-dependent IFN-gamma production is likely to contribute to resistance in murine melioidosis.
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A hemidominant Naip5 allele in mouse strain MOLF/Ei-derived macrophages restricts Legionella pneumophila intracellular growth. Infect Immun 2008; 77:196-204. [PMID: 18981241 DOI: 10.1128/iai.01011-08] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Mouse-derived macrophages have the unique ability to restrict or permit Legionella pneumophila intracellular growth. The common inbred mouse strain C57BL/6J (B6) restricts L. pneumophila growth, whereas macrophages derived from A/J mice allow >10(3)-fold bacterial growth within three days. This phenotypic difference was mapped to the mouse Naip5 allele. The B6 restrictive Naip5 allele is dominant, and six amino acid changes in its product were predicted to control permissiveness. By using the wild-derived mouse strain MOLF/Ei, we found that MOLF/Ei-derived macrophages also restrict L. pneumophila growth, yet the Naip5 protein is identical to the A/J Naip5 at the six-amino-acid signature. The MOLF/Ei restrictive trait, unlike that of B6-derived macrophages, was not dominant over the A/J trait. In spite of this phenotypic difference, the L. pneumophila growth restriction in MOLF/Ei macrophages was mapped to the Naip5 region as well, indicating that the originally predicted change in the A/J Naip5 allele may not be critical for restriction. In the product of the A/J Naip5 permissive allele, there are four unique amino acid changes that map to a NACHT-like domain. Similar misregulating mutations have been identified in the NACHT domains of Nod-like receptor (NLR) proteins. Therefore, one of these mutations may be critical for restriction of L. pneumophila intracellular growth, and this parallels results found with human NLR variants with defects in the innate immune response.
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Lightfield KL, Persson J, Brubaker SW, Witte CE, von Moltke J, Dunipace EA, Henry T, Sun YH, Cado D, Dietrich WF, Monack DM, Tsolis RM, Vance RE. Critical function for Naip5 in inflammasome activation by a conserved carboxy-terminal domain of flagellin. Nat Immunol 2008; 9:1171-8. [PMID: 18724372 DOI: 10.1038/ni.1646] [Citation(s) in RCA: 373] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Accepted: 07/22/2008] [Indexed: 02/07/2023]
Abstract
Inflammasomes are cytosolic multiprotein complexes that sense microbial infection and trigger cytokine production and cell death. However, the molecular components of inflammasomes and what they sense remain poorly defined. Here we demonstrate that 35 amino acids of the carboxyl terminus of flagellin triggered inflammasome activation in the absence of bacterial contaminants or secretion systems. To further elucidate the host flagellin-sensing pathway, we generated mice deficient in the intracellular sensor Naip5. These mice failed to activate the inflammasome in response to the 35 amino acids of flagellin or in response to Legionella pneumophila infection. Our data clarify the molecular basis for the cytosolic response to flagellin.
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Affiliation(s)
- Karla L Lightfield
- School of Public Health, University of California, Berkeley, CA 94720, USA
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46
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Vidal SM, Malo D, Marquis JF, Gros P. Forward genetic dissection of immunity to infection in the mouse. Annu Rev Immunol 2008; 26:81-132. [PMID: 17953509 DOI: 10.1146/annurev.immunol.26.021607.090304] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Forward genetics is an experimental approach in which gene mapping and positional cloning are used to elucidate the molecular mechanisms underlying phenotypic differences between two individuals for a given trait. This strategy has been highly successful for the study of inbred mouse strains that show differences in innate susceptibility to bacterial, parasitic, fungal, and viral infections. Over the past 20 years, these studies have led to the identification of a number of cell populations and critical biochemical pathways and proteins that are essential for the early detection of and response to invading pathogens. Strikingly, the macrophage is the point of convergence for many of these genetic studies. This has led to the identification of diverse pathways involved in extracellular and intracellular pathogen recognition, modification of the properties and content of phagosomes, transcriptional response, and signal transduction for activation of adaptive immune mechanisms. In models of viral infections, elegant genetic studies highlighted the pivotal role of natural killer cells in the detection and destruction of infected cells.
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Affiliation(s)
- S M Vidal
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada H3G 1Y6
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47
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Shin S, Roy CR. Host cell processes that influence the intracellular survival of Legionella pneumophila. Cell Microbiol 2008; 10:1209-20. [PMID: 18363881 DOI: 10.1111/j.1462-5822.2008.01145.x] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Key to the pathogenesis of intracellular pathogens is their ability to manipulate host cell processes, permitting the establishment of an intracellular replicative niche. In turn, the host cell deploys defence mechanisms that limit intracellular infection. The bacterial pathogen Legionella pneumophila, the aetiological agent of Legionnaire's Disease, has evolved virulence mechanisms that allow it to replicate within protozoa, its natural host. Many of these tactics also enable L. pneumophila's survival and replication inside macrophages within a membrane-bound compartment known as the Legionella-containing vacuole. One of the virulence factors indispensable for L. pneumophila's intracellular survival is a type IV secretion system, which translocates a large repertoire of bacterial effectors into the host cell. These effectors modulate multiple host cell processes and in particular, redirect trafficking of the L. pneumophila phagosome and mediate its conversion into an ER-derived organelle competent for intracellular bacterial replication. In this review, we discuss how L. pneumophila manipulates host cells, as well as host cell processes that either facilitate or impede its intracellular survival.
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Affiliation(s)
- Sunny Shin
- Section of Microbial Pathogenesis, Yale University School of Medicine, 295 Congress Avenue, Room 345, New Haven, CT 06536, USA.
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Sirard JC, Vignal C, Dessein R, Chamaillard M. Nod-like receptors: cytosolic watchdogs for immunity against pathogens. PLoS Pathog 2008; 3:e152. [PMID: 18166077 PMCID: PMC2156082 DOI: 10.1371/journal.ppat.0030152] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In mammals, tissue-specific sets of pattern-recognition molecules, including Nod-like receptors (NLR), enable concomitant and sequential detection of microbial-associated molecular patterns from both the extracellular and intracellular microenvironment. Repressing and de-repressing the cytosolic surveillance machinery contributes to vital immune homeostasis and protective responses within specific tissues. Conversely, defective biology of NLR drives the development of recurrent infectious, autoimmune and/or inflammatory diseases by failing to mount barrier functions against pathogens, to tolerate commensals, and/or to instruct the adaptive immune response against microbes. Better decoding microbial strategies that are evolved to circumvent NLR sensing will provide clues for the development of rational therapies aimed at curing and/or preventing common and emerging immunopathologies.
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Marquis JF, Gros P. Genetic analysis of resistance to infections in mice: A/J meets C57BL/6J. Curr Top Microbiol Immunol 2008; 321:27-57. [PMID: 18727486 DOI: 10.1007/978-3-540-75203-5_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Susceptibility to infectious diseases has long been known to have a genetic component in human populations. This genetic effect is often complex and difficult to study as it is further modified by environmental factors including the disease-causing pathogen itself. The laboratory mouse has proved a useful alternative to implement a genetic approach to study host defenses against infections. Our laboratory has used genetic analysis and positional cloning to characterize single and multi-gene effects regulating inter-strain differences in the susceptibility of A/J and C57BL/6J mice to infection with several bacterial and parasitic pathogens. This has led to the identification of several proteins including Nrampl (Slc11a1), Birc1e, Icsbp, C5a, and others that play critical roles in the antimicrobial defenses of macrophages against intracellular pathogens. The use of AcB/BcA recombinant congenic strains has further facilitated the characterization of single gene effects in complex traits such as susceptibility to malaria. The genetic identification of erythrocyte pyruvate kinase (Pklr) and myeloid pantetheinase enzymes (Vnn1/3) as key regulators of blood-stage parasitemia has suggested that cellular redox potential may be a key biochemical determinant of Plasmodium parasite replication. Expanding these types of studies to additional inbred strains and to emerging stocks of mutagenized mice will undoubtedly continue to unravel the molecular basis of host defense against infections.
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Affiliation(s)
- J-F Marquis
- Department of Biochemistry, McGill University, McIntyre Medical Building, Montreal, QC H3G 1Y6, Canada
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50
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Abstract
Electron microscopy (EM) is the only technique that can combine sensitive protein-detection methods with detailed information on the substructure of cellular compartments. The purpose of this chapter is to describe some of the methods at the EM level that can be used to analyze the spatial organization of cell organelles with respect to phagosomes or vacuoles in which pathogens are sequestered, characterize the compartment in which pathogens are harbored, ie immature phagosomes, phagolysosomes, autophagosomes, and ER-derived vacuoles, to cite a few, and decipher the molecular mechanisms involved in survival of pathogens within infected host cells.
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