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Nakamura T, Shimizu T, Ikegaya R, Uda A, Watanabe K, Watarai M. Identification of pyrC gene as an immunosuppressive factor in Francisella novicida infection. Front Cell Infect Microbiol 2022; 12:1027424. [DOI: 10.3389/fcimb.2022.1027424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 10/13/2022] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis, a bacterial causative agent of the zoonosis tularemia, is highly pathogenic to humans. The pathogenicity of this bacterium is characterized by intracellular growth in immune cells, like macrophages, and host immune suppression. However, the detailed mechanism of immune suppression by F. tularensis is still unclear. To identify the key factors causing Francisella-mediated immunosuppression, large-scale screening using a transposon random mutant library containing 3552 mutant strains of F. tularensis subsp. novicida (F. novicida) was performed. Thirteen mutants that caused stronger tumor necrosis factor (TNF)-α production in infected U937 human macrophage cells than the wild-type F. novicida strain were isolated. Sequencing analysis of transposon insertion sites revealed 10 genes, including six novel genes, as immunosuppressive factors of Francisella. Among these, the relationship of the pyrC gene, which encodes dihydroorotase in the pyrimidine biosynthesis pathway, with Francisella-mediated immunosuppression was investigated. The pyrC deletion mutant strain (ΔpyrC) induced higher TNF-α production in U937 host cells than the wild-type F. novicida strain. The ΔpyrC mutant strain was also found to enhance host interleukin-1β and interferon (IFN)-β production. The heat-inactivated ΔpyrC mutant strain could not induce host TNF-α production. Moreover, the production of IFN-β resulting from ΔpyrC infection in U937 cells was repressed upon treatment with the stimulator of interferon genes (STING)-specific inhibitor, H-151. These results suggest that pyrC is related to the immunosuppressive activity and pathogenicity of Francisella via the STING pathway.
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Gavrilin MA, Prather ER, Vompe AD, McAndrew CC, Wewers MD. cAbl Kinase Regulates Inflammasome Activation and Pyroptosis via ASC Phosphorylation. THE JOURNAL OF IMMUNOLOGY 2021; 206:1329-1336. [PMID: 33568399 DOI: 10.4049/jimmunol.2000969] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 01/07/2021] [Indexed: 11/19/2022]
Abstract
Inflammasome activation is regulated in part by the posttranslational modification of inflammasome proteins. Tyrosine phosphorylation is one possible modification. Having previously shown that the protein tyrosine kinase (PTK) inhibitor AG126 greatly inhibits inflammasome activation, we sought to uncover the target kinase. To do this, we screened a commercial tyrosine kinase library for inhibition of inflammasome-dependent IL-18/IL-1β release and pyroptosis. THP-1 cells (human monocyte cell line) were incubated with PTK inhibitors (0.1, 1, and 10 μM) before stimulation with LPS followed by ATP. The PTK inhibitors DCC-2036 (Rebastinib) and GZD824, specific for Bcr-Abl kinase, showed the most severe reduction of IL-18 and lactate dehydrogenase release at all concentrations used. The suggested kinase target, cAbl kinase, was then deleted in THP-1 cells by CRISPR/Cas9 editing and then tested for its role in inflammasome function and potential to phosphorylate the inflammasome adaptor ASC. The cABL knockout not only significantly inhibited inflammasome function but also decreased release of phosphorylated ASC after LPS/ATP stimulation. One predicted target of cAbl kinase is tyrosine 146 in ASC. Complementation of ASC knockout THP-1 cells with mutated Y146A ASC significantly abrogated inflammasome activation and ASC oligomerization as compared with wild-type ASC complementation. Thus, these findings support cAbl kinase as a positive regulator of inflammasome activity and pyroptosis, likely via phosphorylation of ASC.
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Affiliation(s)
- Mikhail A Gavrilin
- Pulmonary, Critical Care, and Sleep Medicine Division, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210; and .,Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210
| | - Evan R Prather
- Pulmonary, Critical Care, and Sleep Medicine Division, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210; and.,Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210
| | - Alex D Vompe
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210
| | - Christian C McAndrew
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210
| | - Mark D Wewers
- Pulmonary, Critical Care, and Sleep Medicine Division, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210; and .,Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210
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Benaoudia S, Martin A, Puig Gamez M, Gay G, Lagrange B, Cornut M, Krasnykov K, Claude J, Bourgeois CF, Hughes S, Gillet B, Allatif O, Corbin A, Ricci R, Henry T. A genome-wide screen identifies IRF2 as a key regulator of caspase-4 in human cells. EMBO Rep 2019; 20:e48235. [PMID: 31353801 PMCID: PMC6727027 DOI: 10.15252/embr.201948235] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 07/01/2019] [Accepted: 07/10/2019] [Indexed: 12/12/2022] Open
Abstract
Caspase-4, the cytosolic LPS sensor, and gasdermin D, its downstream effector, constitute the non-canonical inflammasome, which drives inflammatory responses during Gram-negative bacterial infections. It remains unclear whether other proteins regulate cytosolic LPS sensing, particularly in human cells. Here, we conduct a genome-wide CRISPR/Cas9 screen in a human monocyte cell line to identify genes controlling cytosolic LPS-mediated pyroptosis. We find that the transcription factor, IRF2, is required for pyroptosis following cytosolic LPS delivery and functions by directly regulating caspase-4 levels in human monocytes and iPSC-derived monocytes. CASP4, GSDMD, and IRF2 are the only genes identified with high significance in this screen highlighting the simplicity of the non-canonical inflammasome. Upon IFN-γ priming, IRF1 induction compensates IRF2 deficiency, leading to robust caspase-4 expression. Deficiency in IRF2 results in dampened inflammasome responses upon infection with Gram-negative bacteria. This study emphasizes the central role of IRF family members as specific regulators of the non-canonical inflammasome.
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Affiliation(s)
- Sacha Benaoudia
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
| | - Amandine Martin
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
| | - Marta Puig Gamez
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC)Centre National de la Recherche Scientifique, UMR 7104Institut National de la Santé et de la Recherche Médicale U964Université de StrasbourgIllkirchFrance
- Laboratoire de Biochimie et de Biologie MoléculaireNouvel Hôpital CivilStrasbourgFrance
- Université de StrasbourgStrasbourgFrance
- INGESTEM National iPSC InfrastructureVillejuifFrance
| | - Gabrielle Gay
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
| | - Brice Lagrange
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
| | - Maxence Cornut
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
| | - Kyrylo Krasnykov
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
| | - Jean‐Baptiste Claude
- LBMC, Laboratoire de Biologie et Modélisation de la celluleUniversité Claude Bernard Lyon 1INSERM U1210, CNRS, UMR5239École Normale Supérieure de LyonUniv LyonLyonFrance
| | - Cyril F Bourgeois
- LBMC, Laboratoire de Biologie et Modélisation de la celluleUniversité Claude Bernard Lyon 1INSERM U1210, CNRS, UMR5239École Normale Supérieure de LyonUniv LyonLyonFrance
| | - Sandrine Hughes
- Sequencing PlatformInstitut de Génomique Fonctionnelle de Lyon (IGFL)Université Claude Bernard Lyon 1, CNRS, UMR5242École Normale Supérieure de LyonUniv LyonLyonFrance
| | - Benjamin Gillet
- Sequencing PlatformInstitut de Génomique Fonctionnelle de Lyon (IGFL)Université Claude Bernard Lyon 1, CNRS, UMR5242École Normale Supérieure de LyonUniv LyonLyonFrance
| | - Omran Allatif
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
- BIBS, Bioinformatic and Biostatic ServicesCIRILyonFrance
| | - Antoine Corbin
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
- BIBS, Bioinformatic and Biostatic ServicesCIRILyonFrance
| | - Romeo Ricci
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC)Centre National de la Recherche Scientifique, UMR 7104Institut National de la Santé et de la Recherche Médicale U964Université de StrasbourgIllkirchFrance
- Laboratoire de Biochimie et de Biologie MoléculaireNouvel Hôpital CivilStrasbourgFrance
- Université de StrasbourgStrasbourgFrance
- INGESTEM National iPSC InfrastructureVillejuifFrance
| | - Thomas Henry
- CIRI, Centre International de Recherche en InfectiologieInserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonUniv LyonLyonFrance
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Kubelkova K, Macela A. Innate Immune Recognition: An Issue More Complex Than Expected. Front Cell Infect Microbiol 2019; 9:241. [PMID: 31334134 PMCID: PMC6616152 DOI: 10.3389/fcimb.2019.00241] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 06/18/2019] [Indexed: 12/11/2022] Open
Abstract
Primary interaction of an intracellular bacterium with its host cell is initiated by activation of multiple signaling pathways in response to bacterium recognition itself or as cellular responses to stress induced by the bacterium. The leading molecules in these processes are cell surface membrane receptors as well as cytosolic pattern recognition receptors recognizing pathogen-associated molecular patterns or damage-associated molecular patterns induced by the invading bacterium. In this review, we demonstrate possible sequences of events leading to recognition of Francisella tularensis, present findings on known mechanisms for manipulating cell responses to protect Francisella from being killed, and discuss newly published data from the perspective of early stages of host-pathogen interaction.
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Affiliation(s)
- Klara Kubelkova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czechia
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Mitra S, Dolvin E, Krishnamurthy K, Wewers MD, Sarkar A. Francisella induced microparticulate caspase-1/gasdermin-D activation is regulated by NLRP3 independent of Pyrin. PLoS One 2018; 13:e0209931. [PMID: 30596757 PMCID: PMC6312237 DOI: 10.1371/journal.pone.0209931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 12/13/2018] [Indexed: 11/18/2022] Open
Abstract
Although the study of pathogen sensing by host defense systems continues to uncover a role for inflammasome components specific to particular pathogens, gaps remain in our knowledge. After internalization, Francisella escapes from the phagosome in mononuclear cells and is thought to be detected by intracellular pathogen-response-receptors pyrin and Aim2 in human and murine models, respectively. However, it remains controversial as to the role of pyrin in detecting Francisella. Our current work aims to study the contribution of inflammasome sensor, Pyrin in regulating microparticulate caspase-1/GSDM-D activation by Francisella. Our findings suggest that NLRP3 is central to the activation/release of active caspase-1/GSDM-D encapsulated in microparticles (MP) by Francisella. We also provide evidence that this regulation is independent of pyrin, implicated in sensing cytosolic Francisella in NLRP3-/- conditions where endogenous Pyrin is present. Absence of NLRP3 completely abrogated Francisella mediated MP caspase-1/GSDM-D activation and release both before and after internalization of the pathogen. However, deletion of pyrin not only enhanced both LPS and Francisella mediated MP active caspase-1/GSDM-D release, but pyrin overexpression resulted in a reduction of inflammasome activation and release; suggesting an inhibitory role of pyrin in LPS and Francisella mediated MP responses. This NLRP3 dependence and inhibitory effect of pyrin correlated with cytokine release as well. These observations also correlated with MPs ability to induce cell death; as LPS and Francisella-induced MPs from pyrin-deficient cells were more potent than wild-type monocytes whereas, NLRP3-/- MPs failed to induce cell death. Taken together, we report that NLPR3 not only mediates Francisella induced cytokine responses, but is also critical for cytokine-independent microparticle-induced inflammasome activation and endothelial cell injury independent of pyrin.
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Affiliation(s)
- Srabani Mitra
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States of America
| | - Erin Dolvin
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States of America
| | - Karthikeyan Krishnamurthy
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States of America
| | - Mark D. Wewers
- Department of Internal Medicine, The Ohio State University, Columbus, OH, United States of America
| | - Anasuya Sarkar
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States of America
- Department of Internal Medicine, The Ohio State University, Columbus, OH, United States of America
- * E-mail:
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6
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Whelan AO, Flick-Smith HC, Homan J, Shen ZT, Carpenter Z, Khoshkenar P, Abraham A, Walker NJ, Levitz SM, Ostroff GR, Oyston PCF. Protection induced by a Francisella tularensis subunit vaccine delivered by glucan particles. PLoS One 2018; 13:e0200213. [PMID: 30296254 PMCID: PMC6175290 DOI: 10.1371/journal.pone.0200213] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 06/21/2018] [Indexed: 01/21/2023] Open
Abstract
Francisella tularensis is an intracellular pathogen causing the disease tularemia, and an organism of concern to biodefence. There is no licensed vaccine available. Subunit approaches have failed to induce protection, which requires both humoral and cellular immune memory responses, and have been hampered by a lack of understanding as to which antigens are immunoprotective. We undertook a preliminary in silico analysis to identify candidate protein antigens. These antigens were then recombinantly expressed and encapsulated into glucan particles (GPs), purified Saccharomyces cerevisiae cell walls composed primarily of β-1,3-glucans. Immunological profiling in the mouse was used to down-selection to seven lead antigens: FTT1043 (Mip), IglC, FTT0814, FTT0438, FTT0071 (GltA), FTT0289, FTT0890 (PilA) prior to transitioning their evaluation to a Fischer 344 rat model for efficacy evaluation. F344 rats were vaccinated with the GP protein antigens co-delivered with GP-loaded with Francisella LPS. Measurement of cell mediated immune responses and computational epitope analysis allowed down-selection to three promising candidates: FTT0438, FTT1043 and FTT0814. Of these, a GP vaccine delivering Francisella LPS and the FTT0814 protein was able to induce protection in rats against an aerosol challenge of F. tularensis SchuS4, and reduced organ colonisation and clinical signs below that which immunisation with a GP-LPS alone vaccine provided. This is the first report of a protein supplementing protection induced by LPS in a Francisella vaccine. This paves the way for developing an effective, safe subunit vaccine for the prevention of inhalational tularemia, and validates the GP platform for vaccine delivery where complex immune responses are required for prevention of infections by intracellular pathogens.
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Affiliation(s)
- Adam O. Whelan
- CBR Division, Dstl Porton Down, Salisbury, United Kingdom
| | | | - Jane Homan
- ioGenetics LLC, Madison, WI, United States of America
| | - Zu T. Shen
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Zoe Carpenter
- CBR Division, Dstl Porton Down, Salisbury, United Kingdom
| | - Payam Khoshkenar
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Ambily Abraham
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | | | - Stuart M. Levitz
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Gary R. Ostroff
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
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7
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Hoang KV, Rajaram MVS, Curry HM, Gavrilin MA, Wewers MD, Schlesinger LS. Complement Receptor 3-Mediated Inhibition of Inflammasome Priming by Ras GTPase-Activating Protein During Francisella tularensis Phagocytosis by Human Mononuclear Phagocytes. Front Immunol 2018; 9:561. [PMID: 29632532 PMCID: PMC5879101 DOI: 10.3389/fimmu.2018.00561] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 03/06/2018] [Indexed: 01/08/2023] Open
Abstract
Francisella tularensis is a remarkably infectious facultative intracellular bacterium of macrophages that causes tularemia. Early evasion of host immune responses contributes to the success of F. tularensis as a pathogen. F. tularensis entry into human monocytes and macrophages is mediated by the major phagocytic receptor, complement receptor 3 (CR3, CD11b/CD18). We recently determined that despite a significant increase in macrophage uptake following C3 opsonization of the virulent Type A F. tularensis spp. tularensis Schu S4, this phagocytic pathway results in limited pro-inflammatory cytokine production. Notably, MAP kinase/ERK activation is suppressed immediately during C3-opsonized Schu S4-CR3 phagocytosis. A mathematical model of CR3-TLR2 crosstalk predicted early involvement of Ras GTPase-activating protein (RasGAP) in immune suppression by CR3. Here, we link CR3-mediated uptake of opsonized Schu S4 by human monocytes and macrophages with inhibition of early signal 1 inflammasome activation, evidenced by limited caspase-1 cleavage and IL-18 release. This inhibition is due to increased RasGAP activity, leading to a reduction in the Ras-ERK signaling cascade upstream of the early inflammasome activation event. Thus, our data uncover a novel signaling pathway mediated by CR3 following engagement of opsonized virulent F. tularensis to limit inflammasome activation in human phagocytic cells, thereby contributing to evasion of the host innate immune system.
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Affiliation(s)
- Ky V Hoang
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States
| | - Murugesan V S Rajaram
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States
| | - Heather Marie Curry
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States
| | - Mikhail A Gavrilin
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, United States
| | - Mark D Wewers
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, United States
| | - Larry S Schlesinger
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States.,Texas Biomedical Research Institute, San Antonio, TX, United States
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8
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Seveau S, Turner J, Gavrilin MA, Torrelles JB, Hall-Stoodley L, Yount JS, Amer AO. Checks and Balances between Autophagy and Inflammasomes during Infection. J Mol Biol 2017; 430:174-192. [PMID: 29162504 DOI: 10.1016/j.jmb.2017.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 11/05/2017] [Accepted: 11/09/2017] [Indexed: 12/24/2022]
Abstract
Autophagy and inflammasome complex assembly are physiological processes that control homeostasis, inflammation, and immunity. Autophagy is a ubiquitous pathway that degrades cytosolic macromolecules or organelles, as well as intracellular pathogens. Inflammasomes are multi-protein complexes that assemble in the cytosol of cells upon detection of pathogen- or danger-associated molecular patterns. A critical outcome of inflammasome assembly is the activation of the cysteine protease caspase-1, which activates the pro-inflammatory cytokine precursors pro-IL-1β and pro-IL-18. Studies on chronic inflammatory diseases, heart diseases, Alzheimer's disease, and multiple sclerosis revealed that autophagy and inflammasomes intersect and regulate each other. In the context of infectious diseases, however, less is known about the interplay between autophagy and inflammasome assembly, although it is becoming evident that pathogens have evolved multiple strategies to inhibit and/or subvert these pathways and to take advantage of their intricate crosstalk. An improved appreciation of these pathways and their subversion by diverse pathogens is expected to help in the design of anti-infective therapeutic interventions.
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Affiliation(s)
- Stephanie Seveau
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA.
| | - Joanne Turner
- Texas Biomedical Research Institute, San Antonio, TX 78227, USA
| | - Mikhail A Gavrilin
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA; Department of Internal Medicine, College of Medicine, The Ohio State University, Columbus, OH, USA
| | | | - Luanne Hall-Stoodley
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
| | - Jacob S Yount
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
| | - Amal O Amer
- Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA; Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
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Brenz Y, Winther-Larsen HC, Hagedorn M. Expanding Francisella models: Pairing up the soil amoeba Dictyostelium with aquatic Francisella. Int J Med Microbiol 2017; 308:32-40. [PMID: 28843671 DOI: 10.1016/j.ijmm.2017.08.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 07/31/2017] [Accepted: 08/04/2017] [Indexed: 12/19/2022] Open
Abstract
The bacterial genus Francisella comprises highly pathogenic species that infect mammals, arthropods, fish and protists. Understanding virulence and host defense mechanisms of Francisella infection relies on multiple animal and cellular model systems. In this review, we want to summarize the most commonly used Francisella host model platforms and highlight novel, alternative model systems using aquatic Francisella species. Established mouse and macrophage models contributed extensively to our understanding of Francisella infection. However, murine and human cells display significant differences in their response to Francisella infection. The zebrafish and the amoeba Dictyostelium are well-established model systems for host-pathogen interactions and open up opportunities to investigate bacterial virulence and host defense. Comparisons between model systems using human and fish pathogenic Francisella species revealed shared virulence strategies and pathology between them. Hence, zebrafish and Dictyostelium might complement current model systems to find new vaccine candidates and contribute to our understanding of Francisella infection.
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Affiliation(s)
- Yannick Brenz
- Department of Parasitology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Straße 74, 20359 Hamburg, Germany.
| | - Hanne C Winther-Larsen
- Centre for Integrative Microbial Evolution (CIME) and Department of Pharmaceutical Biosciences, University of Oslo, Sem Sælands vei 3, 0371 Oslo, Norway.
| | - Monica Hagedorn
- Department of Life Sciences and Chemistry, Jacobs University, Campus Ring 1, 28759 Bremen, Germany.
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Abstract
Inflammasomes are intracellular multiprotein complexes that comprise part of the
innate immune response. Since their definition, inflammasome disorders have been
linked to an increasing number of diseases. Autoinflammatory diseases refer to
disorders in which local factors lead to the activation of innate immune cells,
causing tissue damage when in the absence of autoantigens and autoantibodies.
Skin symptoms include the main features of monogenic inflammasomopathies, such
as Cryopyrin-Associated Periodic Syndromes (CAPS), Familial Mediterranean Fever
(FMF), Schnitzler Syndrome, Hyper-IgD Syndrome (HIDS), PAPA Syndrome, and
Deficiency of IL-1 Receptor Antagonist (DIRA). Concepts from other pathologies
have also been reviewed in recent years, such as psoriasis, after the
recognition of a combined contribution of innate and adaptive immunity in its
pathogenesis. Inflammasomes are also involved in the response to various
infections, malignancies, such as melanoma, autoimmune diseases, including
vitiligo and lupus erythematosus, atopic and contact dermatitis, acne,
hidradenitis suppurativa, among others. Inhibition of the inflammasome pathway
may be a target for future therapies, as already occurs in the handling of CAPS,
through the introduction of IL-1 inhibitors. This study presents a literature
review focusing on the participation of inflammasomes in skin diseases.
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Affiliation(s)
| | - Cyro Festa
- Universidade de São Paulo (USP) - São Paulo (SP), Brazil
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11
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Chou AY, Kennett NJ, Melillo AA, Elkins KL. Murine survival of infection with Francisella novicida and protection against secondary challenge is critically dependent on B lymphocytes. Microbes Infect 2016; 19:91-100. [PMID: 27965147 DOI: 10.1016/j.micinf.2016.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 10/13/2016] [Accepted: 12/05/2016] [Indexed: 12/18/2022]
Abstract
Respiratory infection of mice with Francisella novicida has recently been used as a model for the highly virulent human pathogen Francisella tularensis. Similar to F. tularensis, even small doses of F. novicida administered by respiratory routes are lethal for inbred laboratory mice. This feature obviously limits study of infection-induced immunity. Parenteral sublethal infections of mice with F. novicida are feasible, but the resulting immune responses are incompletely characterized. Here we use parenteral intradermal (i.d.) and intraperitoneal (i.p.) F. novicida infections of C57BL/6J mice to determine the role of B cells in controlling primary and secondary F. novicida infections. Despite developing comparable levels of F. novicida-primed T cells, B cell knockout mice were much more susceptible to both primary i.d. infection and secondary i.p. challenge than wild type (normal) C57BL/6J mice. Transfer of F. novicida-immune sera to either wild type C57BL/6J mice or to B cell knockout mice did not appreciably impact survival of subsequent lethal F. novicida challenge. However, F. novicida-immune mice that were depleted of T cells after priming but just before challenge survived and cleared secondary i.p. F. novicida challenge. Collectively these results indicate that B cells, if not serum antibodies, play a major role in controlling F. novicida infections in mice.
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Affiliation(s)
- Alicia Y Chou
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Rockville, MD 20852, United States
| | - Nikki J Kennett
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Rockville, MD 20852, United States
| | - Amanda A Melillo
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Rockville, MD 20852, United States
| | - Karen L Elkins
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Rockville, MD 20852, United States.
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12
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Ratner D, Orning MPA, Proulx MK, Wang D, Gavrilin MA, Wewers MD, Alnemri ES, Johnson PF, Lee B, Mecsas J, Kayagaki N, Goguen JD, Lien E. The Yersinia pestis Effector YopM Inhibits Pyrin Inflammasome Activation. PLoS Pathog 2016; 12:e1006035. [PMID: 27911947 PMCID: PMC5135138 DOI: 10.1371/journal.ppat.1006035] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 10/31/2016] [Indexed: 12/25/2022] Open
Abstract
Type III secretion systems (T3SS) are central virulence factors for many pathogenic Gram-negative bacteria, and secreted T3SS effectors can block key aspects of host cell signaling. To counter this, innate immune responses can also sense some T3SS components to initiate anti-bacterial mechanisms. The Yersinia pestis T3SS is particularly effective and sophisticated in manipulating the production of pro-inflammatory cytokines IL-1β and IL-18, which are typically processed into their mature forms by active caspase-1 following inflammasome formation. Some effectors, like Y. pestis YopM, may block inflammasome activation. Here we show that YopM prevents Y. pestis induced activation of the Pyrin inflammasome induced by the RhoA-inhibiting effector YopE, which is a GTPase activating protein. YopM blocks YopE-induced Pyrin-mediated caspase-1 dependent IL-1β/IL-18 production and cell death. We also detected YopM in a complex with Pyrin and kinases RSK1 and PKN1, putative negative regulators of Pyrin. In contrast to wild-type mice, Pyrin deficient mice were also highly susceptible to an attenuated Y. pestis strain lacking YopM, emphasizing the importance of inhibition of Pyrin in vivo. A complex interplay between the Y. pestis T3SS and IL-1β/IL-18 production is evident, involving at least four inflammasome pathways. The secreted effector YopJ triggers caspase-8- dependent IL-1β activation, even when YopM is present. Additionally, the presence of the T3SS needle/translocon activates NLRP3 and NLRC4-dependent IL-1β generation, which is blocked by YopK, but not by YopM. Taken together, the data suggest YopM specificity for obstructing the Pyrin pathway, as the effector does not appear to block Y. pestis-induced NLRP3, NLRC4 or caspase-8 dependent caspase-1 processing. Thus, we identify Y. pestis YopM as a microbial inhibitor of the Pyrin inflammasome. The fact that so many of the Y. pestis T3SS components are participating in regulation of IL-1β/IL-18 release suggests that these effects are essential for maximal control of innate immunity during plague. Many pathogenic Gram-negative bacteria express type III secretion systems (T3SS) that translocate bacterial proteins into host cells with the potential of altering normal cell processes. Yersinia pestis, the causative agent of plague, harbors a T3SS which is particularly effective in suppressing innate immunity and release of pro-inflammatory cytokines IL-1β and IL-18, potent triggers of anti-bacterial responses. These cytokines are produced via processing by active caspase-1 in inflammasome complexes. Pyrin is an inflammasome component that recognizes alterations in certain host cell signals. Here we show that the T3SS effector protein YopM inhibits effector YopE-mediated Pyrin-induced caspase-1 activation, IL-1β, IL-18 and cell death triggered by Y. pestis. We also found that blocking the Pyrin pathway is important for disease development in a mouse model of bubonic plague. Thus, YopM is a microbial molecule blocking Pyrin inflammasomes.
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Affiliation(s)
- Dmitry Ratner
- UMass Medical School, Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, Worcester, Massachusetts, United States of America
| | - M. Pontus A. Orning
- UMass Medical School, Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, Worcester, Massachusetts, United States of America
- Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Megan K. Proulx
- UMass Medical School, Department of Microbiology and Physiological Systems, Worcester, Massachusetts, United States of America
| | - Donghai Wang
- UMass Medical School, Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, Worcester, Massachusetts, United States of America
- Department of Medicine, School of Medicine, Duke University, Durham, North Carolina, United States of America
| | - Mikhail A. Gavrilin
- Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Wexner Medical Center, The Ohio State University, Columbus, Ohio, United States of America
| | - Mark D. Wewers
- Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, Wexner Medical Center, The Ohio State University, Columbus, Ohio, United States of America
| | - Emad S. Alnemri
- Department of Biochemistry and Molecular Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Peter F. Johnson
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Bettina Lee
- Department of Physiological Chemistry, Genentech, Inc., South San Francisco, California, United States of America
| | - Joan Mecsas
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Nobuhiko Kayagaki
- Department of Physiological Chemistry, Genentech, Inc., South San Francisco, California, United States of America
| | - Jon D. Goguen
- UMass Medical School, Department of Microbiology and Physiological Systems, Worcester, Massachusetts, United States of America
| | - Egil Lien
- UMass Medical School, Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, Worcester, Massachusetts, United States of America
- Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- * E-mail:
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13
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Duffy EB, Periasamy S, Hunt D, Drake JR, Harton JA. FcγR mediates TLR2- and Syk-dependent NLRP3 inflammasome activation by inactivated Francisella tularensis LVS immune complexes. J Leukoc Biol 2016; 100:1335-1347. [PMID: 27365531 PMCID: PMC5110000 DOI: 10.1189/jlb.2a1215-555rr] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 06/09/2016] [Accepted: 06/15/2016] [Indexed: 01/08/2023] Open
Abstract
IgG (mAb)-opsonized, inactivated Francisella tularensis LVS (iFt-mAb) enhances TLR2-dependent IL-6 production by macrophages via Fcγ receptors (FcγR). In mice, vaccination with iFt-mAb provides IgA-dependent protection against lethal challenge with Ft LVS. Because inflammasome maturation of IL-1β is thought important for antibody-mediated immunity, we considered the possibility that iFt-mAb elicits an FcγR-dependent myeloid cell inflammasome response. Herein, we find that iFt-mAb enhances macrophage and dendritic cell IL-1β responses in a TLR2- and FcγR-dependent fashion. Although iFt-mAb complexes bind FcγR and are internalized, sensing of cytosolic DNA by absent in melanoma 2 (AIM2) is not required for the IL-1β response. In contrast, ASC, caspase-1, and NLR family pyrin domain-containing 3 (NLRP3) are indispensable. Further, FcγR-mediated spleen tyrosine kinase (Syk) signaling is required for this NLRP3-dependent IL-1β response, but the alternative IL-1β convertase caspase-8 is insufficient. Finally, iFt-mAb-vaccinated wild-type mice exhibit a significant delay in time to death, but IL-1R1- or Nlrp3-deficient mice vaccinated in this way are not protected and lack appreciable Francisella-specific antibodies. This study demonstrates that FcγR-mediated Syk activation leads to NLRP3 inflammasome-dependent IL-1β production in macrophages and suggests that an Nlrp3- and IL-1R-dependent process contributes to the IgA response important for protection against Ft LVS. These findings extend our understanding of cellular responses to inactivated pathogen-opsonized vaccine, establish FcγR-elicited Syk kinase-mediated NLRP3 inflammasome activation, and provide additional insight toward understanding crosstalk between TLR and FcγR signals.
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Affiliation(s)
- Ellen B Duffy
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA
| | - Sivakumar Periasamy
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA
| | - Danielle Hunt
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA
| | - James R Drake
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA
| | - Jonathan A Harton
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA
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14
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Ratner D, Orning MPA, Lien E. Bacterial secretion systems and regulation of inflammasome activation. J Leukoc Biol 2016; 101:165-181. [PMID: 27810946 DOI: 10.1189/jlb.4mr0716-330r] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/19/2016] [Accepted: 09/20/2016] [Indexed: 01/03/2023] Open
Abstract
Innate immunity is critical for host defenses against pathogens, but many bacteria display complex ways of interacting with innate immune signaling, as they may both activate and evade certain pathways. Gram-negative bacteria can exhibit specialized nanomachine secretion systems for delivery of effector proteins into mammalian cells. Bacterial types III, IV, and VI secretion systems (T3SS, T4SS, and T6SS) are known for their impact on caspase-1-activating inflammasomes, necessary for producing bioactive inflammatory cytokines IL-1β and IL-18, key participants of anti-bacterial responses. Here, we discuss how these secretion systems can mediate triggering and inhibition of inflammasome signaling. We propose that a fine balance between secretion system-mediated activation and inhibition can determine net activation of inflammasome activity and control inflammation, clearance, or spread of the infection.
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Affiliation(s)
- Dmitry Ratner
- Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; and
| | - M Pontus A Orning
- Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; and.,Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norges Teknisk-Naturvitenskapelige Universitet, Trondheim, Norway
| | - Egil Lien
- Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; and .,Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norges Teknisk-Naturvitenskapelige Universitet, Trondheim, Norway
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15
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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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16
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Ozanic M, Gobin I, Brezovec M, Marecic V, Trobonjaca Z, Abu Kwaik Y, Santic M. F. novicida-Infected A. castellanii Does Not Enhance Bacterial Virulence in Mice. Front Cell Infect Microbiol 2016; 6:56. [PMID: 27242974 PMCID: PMC4870235 DOI: 10.3389/fcimb.2016.00056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 05/03/2016] [Indexed: 01/02/2023] Open
Abstract
Francisella tularensis is a facultative intracellular bacterium that causes tularemia in humans and animals. Epidemiology of tularemia worldwide is often associated with water-borne transmission, which includes mosquitoes and amoebae as the potential host reservoirs of the bacteria in water environment. In vitro studies showed intracellular replication of F. tularensis within Acanthamoeba castellanii and Hartmanella vermiformis cells. While infection of amoeba by Legionella pneumophila has been shown to enhance infectivity of L. pneumophila the role of F. tularensis-infected protozoa in the pathogenesis of tularemia is not known. We used 6 h coculture of A. castellanii and F. novicida for investigation of the effect of inhaled amoeba on the pathogenesis of tularemia on in vivo model. Balb/c mice were infected intratracheally with F. novicida or with F. novicida-infected A. castellanii. Surprisingly, infection with F. novicida-infected A. castellanii did not lead to bronchopneumonia in Balb/c mice, and Francisella did not disseminate into the liver and spleen. Upon inhalation, F. novicida infects a variety of host cells, though neutrophils are the predominant cells early during infection in the lung infiltrates of pulmonary tularemia. The numbers of neutrophils in the lungs of Balb/c mice were significantly lower in the infection of mice with F. novicida-infected A. castellanii in comparison to group of mice infected only with F. novicida. These results demonstrate that following inoculation of mice with F. novicida-infected A. castellanii, mice did not develop tularemia.
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Affiliation(s)
- Mateja Ozanic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Ivana Gobin
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Martin Brezovec
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Valentina Marecic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Zlatko Trobonjaca
- Department of Physiology and Immunology, Faculty of Medicine, University of RijekaRijeka, Croatia
| | - Yousef Abu Kwaik
- Department of Microbiology and Immunology and Center for Predictive Medicine, College of Medicine, University of LouisvilleLouisville, KY, USA
| | - Marina Santic
- Department of Microbiology and Parasitology, Faculty of Medicine, University of RijekaRijeka, Croatia
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Shaw DK, Kotsyfakis M, Pedra JHF. For Whom the Bell Tolls (and Nods): Spit-acular Saliva. CURRENT TROPICAL MEDICINE REPORTS 2016; 3:40-50. [PMID: 27547699 DOI: 10.1007/s40475-016-0072-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Having emerged during the early part of the Cretaceous period, ticks are an ancient group of hematophagous ectoparasites with significant veterinary and public health importance worldwide. The success of their life strategy can be attributed, in part, to saliva. As we enter into a scientific era where the collection of massive data sets and structures for biological application is possible, we suggest that understanding the molecular mechanisms that govern the life cycle of ticks is within grasp. With this in mind, we discuss what is currently known regarding the manipulation of Toll-like (TLR) and Nod-like (NLR) receptor signaling pathways by tick salivary proteins, and how these molecules impact pathogen transmission.
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Affiliation(s)
- Dana K Shaw
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
| | - Michail Kotsyfakis
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Budweis, Czech Republic
| | - Joao H F Pedra
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
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18
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The cytoskeleton in cell-autonomous immunity: structural determinants of host defence. Nat Rev Immunol 2015; 15:559-73. [PMID: 26292640 DOI: 10.1038/nri3877] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Host cells use antimicrobial proteins, pathogen-restrictive compartmentalization and cell death in their defence against intracellular pathogens. Recent work has revealed that four components of the cytoskeleton--actin, microtubules, intermediate filaments and septins, which are well known for their roles in cell division, shape and movement--have important functions in innate immunity and cellular self-defence. Investigations using cellular and animal models have shown that these cytoskeletal proteins are crucial for sensing bacteria and for mobilizing effector mechanisms to eliminate them. In this Review, we highlight the emerging roles of the cytoskeleton as a structural determinant of cell-autonomous host defence.
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Ghonime MG, Mitra S, Eldomany RA, Wewers MD, Gavrilin MA. Inflammasome priming is similar for francisella species that differentially induce inflammasome activation. PLoS One 2015; 10:e0127278. [PMID: 25993107 PMCID: PMC4436270 DOI: 10.1371/journal.pone.0127278] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 04/13/2015] [Indexed: 01/15/2023] Open
Abstract
Inflammasome activation is a two-step process where step one, priming, prepares the inflammasome for its subsequent activation, by step two. Classically step one can be induced by LPS priming followed by step two, high dose ATP. Furthermore, when IL-18 processing is used as the inflammasome readout, priming occurs before new protein synthesis. In this context, how intracellular pathogens such as Francisella activate the inflammasome is incompletely understood, particularly regarding the relative importance of priming versus activation steps. To better understand these events we compared Francisella strains that differ in virulence and ability to induce inflammasome activation for their relative effects on step one vs. step two. When using the rapid priming model, i.e., 30 min priming by live or heat killed Francisella strains (step 1), followed by ATP (step 2), we found no difference in IL-18 release, p20 caspase-1 release and ASC oligomerization between Francisella strains (F. novicida, F. holarctica -LVS and F. tularensis Schu S4). This priming is fast, independent of bacteria viability, internalization and phagosome escape, but requires TLR2-mediated ERK phosphorylation. In contrast to their efficient priming capacity, Francisella strains LVS and Schu S4 were impaired in inflammasome triggering compared to F. novicida. Thus, observed differences in inflammasome activation by F. novicida, LVS and Schu S4 depend not on differences in priming but rather on their propensity to trigger the primed inflammasome.
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Affiliation(s)
- Mohammed G. Ghonime
- Davis Heart & Lung Research Institute and Pulmonary Allergy Critical Care and Sleep Medicine Division, The Ohio State University, Columbus, OH, 43210, United States of America
- Microbiology and Immunology Department, Faculty of Pharmacy, Helwan University, Cairo, Egypt
| | - Srabani Mitra
- Davis Heart & Lung Research Institute and Pulmonary Allergy Critical Care and Sleep Medicine Division, The Ohio State University, Columbus, OH, 43210, United States of America
| | - Ramadan A. Eldomany
- Microbiology and Immunology Department, Faculty of Pharmacy, Helwan University, Cairo, Egypt
| | - Mark D. Wewers
- Davis Heart & Lung Research Institute and Pulmonary Allergy Critical Care and Sleep Medicine Division, The Ohio State University, Columbus, OH, 43210, United States of America
- * E-mail: and
| | - Mikhail A. Gavrilin
- Davis Heart & Lung Research Institute and Pulmonary Allergy Critical Care and Sleep Medicine Division, The Ohio State University, Columbus, OH, 43210, United States of America
- * E-mail: and
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20
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Gillette DD, Curry HM, Cremer T, Ravneberg D, Fatehchand K, Shah PA, Wewers MD, Schlesinger LS, Butchar JP, Tridandapani S, Gavrilin MA. Virulent Type A Francisella tularensis actively suppresses cytokine responses in human monocytes. Front Cell Infect Microbiol 2014; 4:45. [PMID: 24783062 PMCID: PMC3988375 DOI: 10.3389/fcimb.2014.00045] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 03/27/2014] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Human monocyte inflammatory responses differ between virulent and attenuated Francisella infection. RESULTS A mixed infection model showed that the virulent F. tularensis Schu S4 can attenuate inflammatory cytokine responses to the less virulent F. novicida in human monocytes. CONCLUSION F. tularensis dampens inflammatory response by an active process. SIGNIFICANCE This suppression may contribute to enhanced pathogenicity of F. tularensis. Francisella tularensis is a Gram-negative facultative bacterium that can cause the disease tularemia, even upon exposure to low numbers of bacteria. One critical characteristic of Francisella is its ability to dampen or subvert the host immune response. Previous work has shown that monocytes infected with highly virulent F. tularensis subsp. tularensis strain Schu S4 responded with a general pattern of quantitatively reduced pro-inflammatory signaling pathway genes and cytokine production in comparison to those infected with the less virulent related F. novicida. However, it has been unclear whether the virulent Schu S4 was merely evading or actively suppressing monocyte responses. By using mixed infection assays with F. tularensis and F. novicida, we show that F. tularensis actively suppresses monocyte pro-inflammatory responses. Additional experiments show that this suppression occurs in a dose-dependent manner and is dependent upon the viability of F. tularensis. Importantly, F. tularensis was able to suppress pro-inflammatory responses to earlier infections with F. novicida. These results lend support that F. tularensis actively dampens human monocyte responses and this likely contributes to its enhanced pathogenicity.
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Affiliation(s)
- Devyn D Gillette
- Integrated Biomedical Graduate Program, The Ohio State University Columbus, OH, USA
| | - Heather M Curry
- Department of Microbial Infection and Immunity, The Ohio State University Columbus, OH, USA ; Center for Microbial Interface Biology, The Ohio State University Columbus, OH, USA
| | - Thomas Cremer
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - David Ravneberg
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - Kavin Fatehchand
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - Prexy A Shah
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - Mark D Wewers
- Center for Microbial Interface Biology, The Ohio State University Columbus, OH, USA ; Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - Larry S Schlesinger
- Department of Microbial Infection and Immunity, The Ohio State University Columbus, OH, USA ; Center for Microbial Interface Biology, The Ohio State University Columbus, OH, USA
| | - Jonathan P Butchar
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - Susheela Tridandapani
- Center for Microbial Interface Biology, The Ohio State University Columbus, OH, USA ; Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
| | - Mikhail A Gavrilin
- Center for Microbial Interface Biology, The Ohio State University Columbus, OH, USA ; Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University Columbus, OH, USA
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21
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Malireddi RKS, Kanneganti TD. Role of type I interferons in inflammasome activation, cell death, and disease during microbial infection. Front Cell Infect Microbiol 2013; 3:77. [PMID: 24273750 PMCID: PMC3824101 DOI: 10.3389/fcimb.2013.00077] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 10/24/2013] [Indexed: 12/17/2022] Open
Abstract
Interferons (IFNs) were discovered over a half-century ago as antiviral factors. The role of type I IFNs has been studied in the pathogenesis of both acute and chronic microbial infections. Deregulated type I IFN production results in a damaging cascade of cell death, inflammation, and immunological host responses that can lead to tissue injury and disease progression. Here, we summarize the role of type I IFNs in the regulation of cell death and disease during different microbial infections, ranging from viruses and bacteria to fungal pathogens. Understanding the specific mechanisms driving type I IFN-mediated cell death and disease could aid in the development of targeted therapies.
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22
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Newly described pattern recognition receptors team up against intracellular pathogens. Nat Rev Immunol 2013; 13:551-65. [DOI: 10.1038/nri3479] [Citation(s) in RCA: 325] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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23
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Disruption of Francisella tularensis Schu S4 iglI, iglJ, and pdpC genes results in attenuation for growth in human macrophages and in vivo virulence in mice and reveals a unique phenotype for pdpC. Infect Immun 2012; 81:850-61. [PMID: 23275090 DOI: 10.1128/iai.00822-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Francisella tularensis is a facultative intracellular bacterial pathogen and the causative agent of tularemia. After infection of macrophages, the organism escapes from its phagosome and replicates to high density in the cytosol, but the bacterial factors required for these aspects of virulence are incompletely defined. Here, we describe the isolation and characterization of Francisella tularensis subsp. tularensis strain Schu S4 mutants that lack functional iglI, iglJ, or pdpC, three genes of the Francisella pathogenicity island. Our data demonstrate that these mutants were defective for replication in primary human monocyte-derived macrophages and murine J774 cells yet exhibited two distinct phenotypes. The iglI and iglJ mutants were similar to one another, exhibited profound defects in phagosome escape and intracellular growth, and appeared to be trapped in cathepsin D-positive phagolysosomes. Conversely, the pdpC mutant avoided trafficking to lysosomes, phagosome escape was diminished but not ablated, and these organisms replicated in a small subset of infected macrophages. The phenotype of each mutant strain was reversed by trans complementation. In vivo virulence was assessed by intranasal infection of BALB/c mice. The mutants appeared avirulent, as all mice survived infection with 10(8) CFU iglJ- or pdpC-deficient bacteria. Nevertheless, the pdpC mutant disseminated to the liver and spleen before being eliminated, whereas the iglJ mutant did not. Taken together, our data demonstrate that the pathogenicity island genes tested are essential for F. tularensis Schu S4 virulence and further suggest that pdpC may play a unique role in this process, as indicated by its distinct intermediate phenotype.
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Sharma M, Mohapatra J, Acharya A, Deshpande SS, Chatterjee A, Jain MR. Blockade of tumor necrosis factor-α converting enzyme (TACE) enhances IL-1β and IFN-γ via caspase-1 activation: a probable cause for loss of efficacy of TACE inhibitors in humans? Eur J Pharmacol 2012; 701:106-13. [PMID: 23266381 DOI: 10.1016/j.ejphar.2012.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 12/01/2012] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
Abstract
TNF-α converting enzyme (TACE) is a member of the ADAM (a disintegrin and metalloproteinase) family and is known as ADAM17, which processes precursor TNF-α in order to release soluble TNF-α (sTNF-α). Inhibition of TACE has been effective as a strategy to inhibit arthritis in animal models; however, it has not been translated in the clinic due to lack of efficacy or toxicity. We hypothesized that inhibition of TACE may activate a different pro-inflammatory pathway in human. To investigate this, we studied the effect of TACE inhibitor DPC-333 on cytokine levels in concanavalin A (Con A) activated human peripheral blood mononuclear cells (hPBMC). We have also studied the effects of DPC-333 on Con A induced cytokine levels in mice in vivo or in vitro in whole blood assay. DPC-333 treatment significantly up-regulated IL-1β and IFN-γ in Con A activated hPBMC. In contrast, pre-treatment with DPC-333 effectively suppressed IL-1β and IFN-γ in mice in vivo or in vitro. Interestingly, DPC-333 was found to up-regulate mRNA expression of caspase-1 in hPBMC in a dose dependent fashion and selective caspase-1 inhibitor completely restored DPC-333 induced IL-1β and IFN-γ. Furthermore, selective IL-1β receptor antagonist (anakinra) prevented DPC-333 induced IFN-γ. In conclusion, our data demonstrates that blockade of TACE enhances IL-1β in a caspase-1 dependent manner in vitro in hPBMC and the elevation of IFN-γ is secondarily mediated via IL-1β. This novel finding might explain the possible cause behind the loss of efficacy of TACE inhibitors in human.
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Affiliation(s)
- Manoranjan Sharma
- Department of Pharmacology, Zydus Research Centre, Moraiya, Ahmedabad, Gujarat, India
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Chen CC, Tsai SH, Lu CC, Hu ST, Wu TS, Huang TT, Saïd-Sadier N, Ojcius DM, Lai HC. Activation of an NLRP3 inflammasome restricts Mycobacterium kansasii infection. PLoS One 2012; 7:e36292. [PMID: 22558425 PMCID: PMC3340363 DOI: 10.1371/journal.pone.0036292] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Accepted: 03/29/2012] [Indexed: 11/19/2022] Open
Abstract
Mycobacterium kansasii has emerged as an important nontuberculous mycobacterium pathogen, whose incidence and prevalence have been increasing in the last decade. M. kansasii can cause pulmonary tuberculosis clinically and radiographically indistinguishable from that caused by Mycobacterium tuberculosis infection. Unlike the widely-studied M. tuberculosis, little is known about the innate immune response against M. kansasii infection. Although inflammasome activation plays an important role in host defense against bacterial infection, its role against atypical mycobacteria remains poorly understood. In this report, the role of inflammasome activity in THP-1 macrophages against M. kansasii infection was studied. Results indicated that viable, but not heat-killed, M. kansasii induced caspase-1-dependent IL-1β secretion in macrophages. The underlying mechanism was found to be through activation of an inflammasome containing the NLR (Nod-like receptor) family member NLRP3 and the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD). Further, potassium efflux, lysosomal acidification, ROS production and cathepsin B release played a role in M. kansasii-induced inflammasome activation. Finally, the secreted IL-1β derived from caspase-1 activation was shown to restrict intracellular M. kansasii. These findings demonstrate a biological role for the NLRP3 inflammasome in host defense against M. kansasii.
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Affiliation(s)
- Chang-Chieh Chen
- Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu, Taiwan, Republic of China
| | - Sheng-Hui Tsai
- Institute of Microbiology and Immunology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Chia-Chen Lu
- Department of Respiratory Therapy, Fu Jen Catholic University, Taipei, Taiwan, Republic of China
| | - Shiau-Ting Hu
- Institute of Microbiology and Immunology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, Republic of China
- Department of Microbiology and Immunology, School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Ting-Shu Wu
- Department of Internal Medicine, Chang Gung Memorial Hospital and Graduate Institute of Clinical Medical Sciences, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
| | - Tsung-Teng Huang
- Center for Molecular and Clinical Immunology, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- Department of Medical Biotechnology and Laboratory Sciences, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- Laboratory of Nanomaterials, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- Research Center of Bacterial Pathogenesis, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
| | - Najwane Saïd-Sadier
- Health Sciences Research Institute and School of Natural Sciences, University of California Merced, Merced, California, United States of America
| | - David M. Ojcius
- Center for Molecular and Clinical Immunology, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- Health Sciences Research Institute and School of Natural Sciences, University of California Merced, Merced, California, United States of America
| | - Hsin-Chih Lai
- Center for Molecular and Clinical Immunology, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- Department of Medical Biotechnology and Laboratory Sciences, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- Research Center of Bacterial Pathogenesis, Chang Gung University, Kweishan, Taoyuan, Taiwan, Republic of China
- * E-mail:
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Gavrilin MA, Abdelaziz DHA, Mostafa M, Abdulrahman BA, Grandhi J, Akhter A, Abu Khweek A, Aubert DF, Valvano MA, Wewers MD, Amer AO. Activation of the pyrin inflammasome by intracellular Burkholderia cenocepacia. THE JOURNAL OF IMMUNOLOGY 2012; 188:3469-77. [PMID: 22368275 DOI: 10.4049/jimmunol.1102272] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Burkholderia cenocepacia is an opportunistic pathogen that causes chronic infection and induces progressive respiratory inflammation in cystic fibrosis patients. Recognition of bacteria by mononuclear cells generally results in the activation of caspase-1 and processing of IL-1β, a major proinflammatory cytokine. In this study, we report that human pyrin is required to detect intracellular B. cenocepacia leading to IL-1β processing and release. This inflammatory response involves the host adapter molecule ASC and the bacterial type VI secretion system (T6SS). Human monocytes and THP-1 cells stably expressing either small interfering RNA against pyrin or YFP-pyrin and ASC (YFP-ASC) were infected with B. cenocepacia and analyzed for inflammasome activation. B. cenocepacia efficiently activates the inflammasome and IL-1β release in monocytes and THP-1. Suppression of pyrin levels in monocytes and THP-1 cells reduced caspase-1 activation and IL-1β release in response to B. cenocepacia challenge. In contrast, overexpression of pyrin or ASC induced a robust IL-1β response to B. cenocepacia, which correlated with enhanced host cell death. Inflammasome activation was significantly reduced in cells infected with T6SS-defective mutants of B. cenocepacia, suggesting that the inflammatory reaction is likely induced by an as yet uncharacterized effector(s) of the T6SS. Together, we show for the first time, to our knowledge, that in human mononuclear cells infected with B. cenocepacia, pyrin associates with caspase-1 and ASC forming an inflammasome that upregulates mononuclear cell IL-1β processing and release.
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Affiliation(s)
- Mikhail A Gavrilin
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
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Atianand MK, Duffy EB, Shah A, Kar S, Malik M, Harton JA. Francisella tularensis reveals a disparity between human and mouse NLRP3 inflammasome activation. J Biol Chem 2011; 286:39033-42. [PMID: 21930705 PMCID: PMC3234728 DOI: 10.1074/jbc.m111.244079] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 08/29/2011] [Indexed: 11/06/2022] Open
Abstract
Pathogen-triggered activation of the inflammasome complex leading to caspase-1 activation and IL-1β production involves similar sensor proteins between mouse and human. However, the specific sensors used may differ between infectious agents and host species. In mice, Francisella infection leads to seemingly exclusive activation of the Aim2 inflammasome with no apparent role for Nlrp3. Here we examine the IL-1β response of human cells to Francisella infection. Francisella strains exhibit differences in IL-1β production by influencing induction of IL-1β and ASC transcripts. Unexpectedly, our results demonstrate that Francisella activates the NLRP3 inflammasome in human cells. Francisella infection of THP-1 cells elicits IL-1β production, which is reduced by siRNA targeting of NLRP3. Moreover, in reconstituted 293T cells, Francisella triggers assembly of the NLRP3 inflammasome complex. In addition, inhibitors of reactive oxygen species, cathepsin B, and K(+) efflux pathways, known to specifically influence NLRP3, substantially but not completely impair the Francisella-elicited IL-1β response, suggesting the involvement of another inflammasome pathway. Finally, shRNA targeting of NLRP3 and AIM2 reveals that both pathways contribute to the inflammasome response. Together these results establish NLRP3 as a cytosolic sensor for Francisella in human cells, a role not observed in mouse.
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Affiliation(s)
- Maninjay K. Atianand
- From the Center for Immunology and Microbial Disease, Albany Medical College and
| | - Ellen B. Duffy
- From the Center for Immunology and Microbial Disease, Albany Medical College and
| | - Aaloki Shah
- From the Center for Immunology and Microbial Disease, Albany Medical College and
| | - Supriya Kar
- From the Center for Immunology and Microbial Disease, Albany Medical College and
| | - Meenakshi Malik
- From the Center for Immunology and Microbial Disease, Albany Medical College and
- the Department of Arts and Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208
| | - Jonathan A. Harton
- From the Center for Immunology and Microbial Disease, Albany Medical College and
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IglG and IglI of the Francisella pathogenicity island are important virulence determinants of Francisella tularensis LVS. Infect Immun 2011; 79:3683-96. [PMID: 21690239 DOI: 10.1128/iai.01344-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The Gram-negative bacterium Francisella tularensis is the causative agent of tularemia, a disease intimately associated with the multiplication of the bacterium within host macrophages. This in turn requires the expression of Francisella pathogenicity island (FPI) genes, believed to encode a type VI secretion system. While the exact functions of many of the components have yet to be revealed, some have been found to contribute to the ability of Francisella to cause systemic infection in mice as well as to prevent phagolysosomal fusion and facilitate escape into the host cytosol. Upon reaching this compartment, the bacterium rapidly multiplies, inhibits activation of the inflammasome, and ultimately causes apoptosis of the host cell. In this study, we analyzed the contribution of the FPI-encoded proteins IglG, IglI, and PdpE to the aforementioned processes in F. tularensis LVS. The ΔpdpE mutant behaved similarly to the parental strain in all investigated assays. In contrast, ΔiglG and ΔiglI mutants, although they were efficiently replicating in J774A.1 cells, both exhibited delayed phagosomal escape, conferred a delayed activation of the inflammasome, and exhibited reduced cytopathogenicity as well as marked attenuation in the mouse model. Thus, IglG and IglI play key roles for modulation of the intracellular host response and also for the virulence of F. tularensis.
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Santic M, Ozanic M, Semic V, Pavokovic G, Mrvcic V, Kwaik YA. Intra-Vacuolar Proliferation of F. Novicida within H. Vermiformis. Front Microbiol 2011; 2:78. [PMID: 21747796 PMCID: PMC3128938 DOI: 10.3389/fmicb.2011.00078] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Accepted: 04/04/2011] [Indexed: 01/11/2023] Open
Abstract
Francisella tularensis is a gram negative facultative intracellular bacterium that causes the zoonotic disease tularemia. Free-living amebae, such as Acanthamoeba and Hartmannella, are environmental hosts of several intracellular pathogens. Epidemiology of F. tularensis in various parts of the world is associated with water-borne transmission, which includes mosquitoes and amebae as the potential host reservoirs of the bacteria in water resources. In vitro studies showed intracellular replication of F. tularensis within A. castellanii cells. Whether ameba is a biological reservoir for Francisella in the environment is not known. We used Hartmannella vermiformis as an amebal model system to study the intracellular life of F. novicida. For the first time we show that F. novicida survives and replicates within H. vermiformis. The iglC mutant strain of F. novicida is defective for survival and replication not only within A. castellanii but also in H. vermiformis cells. In contrast to mammalian cells, where bacteria replicate in the cytosol, F. novicida resides and replicates within membrane-bound vacuoles within the trophozoites of H. vermiformis. In contrast to the transient residence of F. novicida within acidic vacuoles prior to escaping to the cytosol of mammalian cells, F. novicida does not reside transiently or permanently in an acidic compartment within H. vermiformis when examined 30 min after initiation of the infection. We conclude that F. tularensis does not replicate within acidified vacuoles and does not escape into the cytosol of H. vermiformis. The Francisella pathogenicity island locus iglC is essential for intra-vacuolar proliferation of F. novicida within H. vermiformis. Our data show a distinct intracellular lifestyle for F. novicida within H. vermiformis compared to mammalian cells.
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Affiliation(s)
- Marina Santic
- Department of Microbiology and Parasitology, Medical Faculty, University of Rijeka Rijeka, Croatia
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