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Xie Z, Zhang Y, Huang X. Evidence and speculation: the response of Salmonella confronted by autophagy in macrophages. Future Microbiol 2020; 15:1277-1286. [PMID: 33026883 DOI: 10.2217/fmb-2020-0125] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bacteria of the Salmonella genus cause diseases ranging from self-limited gastroenteritis to typhoid fever. Macrophages are immune cells that engulf and restrict Salmonella. These cells will carry Salmonella into the circulatory system and provoke a systemic infection. Therefore, the interaction between macrophages and intracellular Salmonella is vital for its pathogenicity. As one of the immune responses of macrophages, autophagy, along with the fusion of autophagosomes with lysosomes, occupies an important position in eliminating Salmonella. However, Salmonella that can overcome cellular defensive responses and infect neighboring cells must derive strategies to escape autophagy. This review introduces novel findings on Salmonella and macrophage autophagy as a mechanism against infection and explores the strategies used by Salmonella to escape autophagy.
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Affiliation(s)
- Zhongyi Xie
- Department of Biochemistry & Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China.,International Genome Center, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Ying Zhang
- Department of Biochemistry & Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China
| | - Xinxiang Huang
- Department of Biochemistry & Molecular Biology, Jiangsu University School of Medicine, Zhenjiang, Jiangsu 212013, China
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2
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Bao H, Wang S, Zhao JH, Liu SL. Salmonella secretion systems: Differential roles in pathogen-host interactions. Microbiol Res 2020; 241:126591. [PMID: 32932132 DOI: 10.1016/j.micres.2020.126591] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/24/2020] [Accepted: 08/29/2020] [Indexed: 12/26/2022]
Abstract
The bacterial genus Salmonella includes a large group of food-borne pathogens that cause a variety of gastrointestinal or systemic diseases in hosts. Salmonella use several secretion devices to inject various effectors targeting eukaryotic hosts, or bacteria. In the past few years, considerable progress has been made towards understanding the structural features and molecular mechanisms of the secretion systems of Salmonella, particularly regarding their roles in host-pathogen interactions. In this review, we summarize the current advances about the main characteristics of the Salmonella secretion systems. Clarifying the roles of the secretion systems in the process of infecting various hosts will broaden our understanding of the importance of microbial interactions in maintaining human health and will provide information for developing novel therapeutic approaches.
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Affiliation(s)
- Hongxia Bao
- Genomics Research Center, College of Pharmacy, Harbin Medical University, Harbin, China; HMU-UCCSM Centre for Infection and Genomics, Harbin Medical University, Harbin, China; Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Harbin, China.
| | - Shuang Wang
- Department of Biopharmaceutical Sciences (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China), College of Pharmacy, Harbin Medical University, Harbin, China
| | - Jian-Hua Zhao
- Genomics Research Center, College of Pharmacy, Harbin Medical University, Harbin, China; HMU-UCCSM Centre for Infection and Genomics, Harbin Medical University, Harbin, China; Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Harbin, China
| | - Shu-Lin Liu
- Genomics Research Center, College of Pharmacy, Harbin Medical University, Harbin, China; HMU-UCCSM Centre for Infection and Genomics, Harbin Medical University, Harbin, China; Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences, Harbin, China; Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Canada.
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3
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Jneid B, Rouaix A, Féraudet-Tarisse C, Simon S. SipD and IpaD induce a cross-protection against Shigella and Salmonella infections. PLoS Negl Trop Dis 2020; 14:e0008326. [PMID: 32463817 PMCID: PMC7282677 DOI: 10.1371/journal.pntd.0008326] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 06/09/2020] [Accepted: 04/26/2020] [Indexed: 01/05/2023] Open
Abstract
Salmonella and Shigella species are food- and water-borne pathogens that are responsible for enteric infections in both humans and animals and are still the major cause of morbidity and mortality in the emerging countries. The existence of multiple Salmonella and Shigella serotypes as well as the emergence of strains resistant to antibiotics require the development of broadly protective therapies. Those bacteria utilize a Type III Secretion System (T3SS), necessary for their pathogenicity. The structural proteins composing the T3SS are common to all virulent Salmonella and Shigella spp., particularly the needle-tip proteins SipD (Salmonella) and IpaD (Shigella). We investigated the immunogenicity and protective efficacy of SipD and IpaD administered by intranasal and intragastric routes, in a mouse model of Salmonella enterica serotype Typhimurium (S. Typhimurium) intestinal challenge. Robust IgG (in all immunization routes) and IgA (in intranasal and oral immunization routes) antibody responses were induced against both proteins. Mice immunized with SipD or IpaD were protected against lethal intestinal challenge with S. Typhimurium or Shigella flexneri (100 Lethal Dose 50%). We have shown that SipD and IpaD are able to induce a cross-protection in a murine model of infection by Salmonella and Shigella. We provide the first demonstration that Salmonella and Shigella T3SS SipD and IpaD are promising antigens for the development of a cross-protective Salmonella-Shigella vaccine. These results open the way to the development of cross-protective therapeutic molecules.
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Affiliation(s)
- Bakhos Jneid
- Université Paris Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, Gif-sur-Yvette, France
| | - Audrey Rouaix
- Université Paris Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, Gif-sur-Yvette, France
| | - Cécile Féraudet-Tarisse
- Université Paris Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, Gif-sur-Yvette, France
| | - Stéphanie Simon
- Université Paris Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, Gif-sur-Yvette, France
- * E-mail:
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4
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Intestinal Lamina Propria CD4 + T Cells Promote Bactericidal Activity of Macrophages via Galectin-9 and Tim-3 Interaction during Salmonella enterica Serovar Typhimurium Infection. Infect Immun 2018; 86:IAI.00769-17. [PMID: 29844236 DOI: 10.1128/iai.00769-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 05/21/2018] [Indexed: 12/13/2022] Open
Abstract
The intestinal immune system is crucial for protection from pathogenic infection and maintenance of mucosal homeostasis. We studied the intestinal immune microenvironment in a Salmonella enterica serovar Typhimurium intestinal infection mouse model. Intestinal lamina propria macrophages are the main effector cells in innate resistance to intracellular microbial pathogens. We found that S Typhimurium infection augmented Tim-3 expression on intestinal lamina propria CD4+ T cells and enhanced galectin-9 expression on F4/80+ CD11b+ macrophages. Moreover, CD4+ T cells promoted the activation and bactericidal activity of intestinal F4/80+ CD11b+ macrophages via the Tim-3/galectin-9 interaction during S Typhimurium infection. Blocking the Tim-3/galectin-9 interaction with α-lactose significantly attenuated the bactericidal activity of intracellular S Typhimurium by macrophages. Furthermore, the Tim-3/galectin-9 interaction promoted the formation and activation of inflammasomes, which led to caspase-1 cleavage and interleukin 1β (IL-1β) secretion. The secretion of active IL-1β further improved bactericidal activity of macrophages and galectin-9 expression on macrophages. These results demonstrated the critical role of the cross talk between CD4+ T cells and macrophages, particularly the Tim-3/galectin-9 interaction, in antimicrobial immunity and the control of intestinal pathogenic infections.
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Batan D, Braselmann E, Minson M, Nguyen DMT, Cossart P, Palmer AE. A Multicolor Split-Fluorescent Protein Approach to Visualize Listeria Protein Secretion in Infection. Biophys J 2018; 115:251-262. [PMID: 29653838 PMCID: PMC6050711 DOI: 10.1016/j.bpj.2018.03.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 03/04/2018] [Accepted: 03/20/2018] [Indexed: 12/12/2022] Open
Abstract
Listeria monocytogenes is an intracellular food-borne pathogen that has evolved to enter mammalian host cells, survive within them, spread from cell to cell, and disseminate throughout the body. A series of secreted virulence proteins from Listeria are responsible for manipulation of host-cell defense mechanisms and adaptation to the intracellular lifestyle. Identifying when and where these virulence proteins are located in live cells over the course of Listeria infection can provide valuable information on the roles these proteins play in defining the host-pathogen interface. These dynamics and protein levels may vary from cell to cell, as bacterial infection is a heterogeneous process both temporally and spatially. No assay to visualize virulence proteins over time in infection with Listeria or other Gram-positive bacteria has been developed. Therefore, we adapted a live, long-term tagging system to visualize a model Listeria protein by fluorescence microscopy on a single-cell level in infection. This system leverages split-fluorescent proteins, in which the last strand of a fluorescent protein (a 16-amino-acid peptide) is genetically fused to the virulence protein of interest. The remainder of the fluorescent protein is produced in the mammalian host cell. Both individual components are nonfluorescent and will bind together and reconstitute fluorescence upon virulence-protein secretion into the host cell. We demonstrate accumulation and distribution within the host cell of the model virulence protein InlC in infection over time. A modular expression platform for InlC visualization was developed. We visualized InlC by tagging it with red and green split-fluorescent proteins and compared usage of a strong constitutive promoter versus the endogenous promoter for InlC production. This split-fluorescent protein approach is versatile and may be used to investigate other Listeria virulence proteins for unique mechanistic insights in infection progression.
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Affiliation(s)
- Dilara Batan
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado
| | - Esther Braselmann
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado; BioFrontiers Institute, University of Colorado, Boulder, Colorado
| | - Michael Minson
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado; BioFrontiers Institute, University of Colorado, Boulder, Colorado
| | | | - Pascale Cossart
- Unité des Interactions Bactéries-Cellules, Département de Biologie Cellulaire et Infection, Institut Pasteur, Paris, France; Inserm U604, Paris, France; French National Institute for Agricultural Research, Unité Sous-Contrat 2020, Paris, France
| | - Amy E Palmer
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado; BioFrontiers Institute, University of Colorado, Boulder, Colorado.
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6
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Hiyoshi H, Tiffany CR, Bronner DN, Bäumler AJ. Typhoidal Salmonella serovars: ecological opportunity and the evolution of a new pathovar. FEMS Microbiol Rev 2018; 42:527-541. [DOI: 10.1093/femsre/fuy024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 05/19/2018] [Indexed: 12/20/2022] Open
Affiliation(s)
- Hirotaka Hiyoshi
- Department of Medial Microbiology and Immunology, School of Medicine, University of California Davis, Davis, CA 95616, USA
| | - Connor R Tiffany
- Department of Medial Microbiology and Immunology, School of Medicine, University of California Davis, Davis, CA 95616, USA
| | - Denise N Bronner
- Department of Medial Microbiology and Immunology, School of Medicine, University of California Davis, Davis, CA 95616, USA
| | - Andreas J Bäumler
- Department of Medial Microbiology and Immunology, School of Medicine, University of California Davis, Davis, CA 95616, USA
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7
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Jneid B, Moreau K, Plaisance M, Rouaix A, Dano J, Simon S. Role of T3SS-1 SipD Protein in Protecting Mice against Non-typhoidal Salmonella Typhimurium. PLoS Negl Trop Dis 2016; 10:e0005207. [PMID: 27992422 PMCID: PMC5167260 DOI: 10.1371/journal.pntd.0005207] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 10/25/2016] [Indexed: 11/24/2022] Open
Abstract
Background Salmonella enterica species are enteric pathogens that cause severe diseases ranging from self-limiting gastroenteritis to enteric fever and sepsis in humans. These infectious diseases are still the major cause of morbidity and mortality in low-income countries, especially in children younger than 5 years and immunocompromised adults. Vaccines targeting typhoidal diseases are already marketed, but none protect against non-typhoidal Salmonella. The existence of multiple non-typhoidal Salmonella serotypes as well as emerging antibiotic resistance highlight the need for development of a broad-spectrum protective vaccine. All Salmonella spp. utilize two type III Secretion Systems (T3SS 1 and 2) to initiate infection, allow replication in phagocytic cells and induce systemic disease. T3SS-1, which is essential to invade epithelial cells and cross the barrier, forms an extracellular needle and syringe necessary to inject effector proteins into the host cell. PrgI and SipD form, respectively, the T3SS-1 needle and the tip complex at the top of the needle. Because they are common and highly conserved in all virulent Salmonella spp., they might be ideal candidate antigens for a subunit-based, broad-spectrum vaccine. Principal Findings We investigated the immunogenicity and protective efficacy of PrgI and SipD administered by subcutaneous, intranasal and oral routes, alone or combined, in a mouse model of Salmonella intestinal challenge. Robust IgG (in all immunization routes) and IgA (in intranasal and oral immunization routes) antibody responses were induced against both proteins, particularly SipD. Mice orally immunized with SipD alone or SipD combined with PrgI were protected against lethal intestinal challenge with Salmonella Typhimurium (100 Lethal Dose 50%) depending on antigen, route and adjuvant. Conclusions and Significance Salmonella T3SS SipD is a promising antigen for the development of a protective Salmonella vaccine, and could be developed for vaccination in tropical endemic areas to control infant mortality. Salmonella are bacteria responsible for a high global burden of invasive diseases, especially in South and South-East Asia (mainly enteric fever due to Salmonella Typhi) and sub-Saharan Africa (mainly invasive Non-Typhoidal Salmonella, iNTS). This iNTS disease has emerged as a prominent cause of systemic infection in children and immunocompromised African adults, with an associated case fatality of 20–25%. Because licensed vaccines only protect against enteric fever, there is a crucial need to develop a new broad-spectrum vaccine effective against enteric fever and iNTS that can be administered safely to children under 2 years old. The virulence of Salmonella depends on two type III secretion systems (T3SS-1 and T3SS-2) necessary for invasion, replication, intracellular survival and dissemination of the bacteria. Two structural proteins of T3SS-1 (essential for crossing the epithelial barrier) are highly conserved among Salmonella spp. and might be good candidates for a broad-spectrum vaccine. The current study describes the protective effect elicited by these proteins in a murine model. A specific immune response was generated against our antigens and provided protection against Salmonella Typhimurium oral infection. Such a candidate vaccine offers promising perspectives to control Salmonella diseases.
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Affiliation(s)
- Bakhos Jneid
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Karine Moreau
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Marc Plaisance
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Audrey Rouaix
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Julie Dano
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Stéphanie Simon
- Service de Pharmacologie et Immunoanalyse (SPI), CEA, INRA, Université Paris-Saclay, Gif-sur-Yvette, France
- * E-mail:
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8
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McQuate SE, Young AM, Silva-Herzog E, Bunker E, Hernandez M, de Chaumont F, Liu X, Detweiler CS, Palmer AE. Long-term live-cell imaging reveals new roles for Salmonella effector proteins SseG and SteA. Cell Microbiol 2016; 19. [PMID: 27376507 DOI: 10.1111/cmi.12641] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 06/08/2016] [Accepted: 06/28/2016] [Indexed: 01/18/2023]
Abstract
Salmonella Typhimurium is an intracellular bacterial pathogen that infects both epithelial cells and macrophages. Salmonella effector proteins, which are translocated into the host cell and manipulate host cell components, control the ability to replicate and/or survive in host cells. Due to the complexity and heterogeneity of Salmonella infections, there is growing recognition of the need for single-cell and live-cell imaging approaches to identify and characterize the diversity of cellular phenotypes and how they evolve over time. Here, we establish a pipeline for long-term (17 h) live-cell imaging of infected cells and subsequent image analysis methods. We apply this pipeline to track bacterial replication within the Salmonella-containing vacuole in epithelial cells, quantify vacuolar replication versus survival in macrophages and investigate the role of individual effector proteins in mediating these parameters. This approach revealed that dispersed bacteria can coalesce at later stages of infection, that the effector protein SseG influences the propensity for cytosolic hyper-replication in epithelial cells, and that while SteA only has a subtle effect on vacuolar replication in epithelial cells, it has a profound impact on infection parameters in immunocompetent macrophages, suggesting differential roles for effector proteins in different infection models.
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Affiliation(s)
- Sarah E McQuate
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
| | - Alexandra M Young
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
| | - Eugenia Silva-Herzog
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
| | - Eric Bunker
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
| | - Mateo Hernandez
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
| | | | - Xuedong Liu
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
| | - Corrella S Detweiler
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, Boulder, CO, USA
| | - Amy E Palmer
- Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado at Boulder, Boulder, CO, USA
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Silva-Herzog E, McDonald EM, Crooks AL, Detweiler CS. Physiologic Stresses Reveal a Salmonella Persister State and TA Family Toxins Modulate Tolerance to These Stresses. PLoS One 2015; 10:e0141343. [PMID: 26633172 PMCID: PMC4669091 DOI: 10.1371/journal.pone.0141343] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 10/07/2015] [Indexed: 11/18/2022] Open
Abstract
Bacterial persister cells are considered a basis for chronic infections and relapse caused by bacterial pathogens. Persisters are phenotypic variants characterized by low metabolic activity and slow or no replication. This low metabolic state increases pathogen tolerance to antibiotics and host immune defenses that target actively growing cells. In this study we demonstrate that within a population of Salmonella enterica serotype Typhimurium, a small percentage of bacteria are reversibly tolerant to specific stressors that mimic the macrophage host environment. Numerous studies show that Toxin-Antitoxin (TA) systems contribute to persister states, based on toxin inhibition of bacterial metabolism or growth. To identify toxins that may promote a persister state in response to host-associated stressors, we analyzed the six TA loci specific to S. enterica serotypes that cause systemic infection in mammals, including five RelBE family members and one VapBC member. Deletion of TA loci increased or decreased tolerance depending on the stress conditions. Similarly, exogenous expression of toxins had mixed effects on bacterial survival in response to stress. In macrophages, S. Typhimurium induced expression of three of the toxins examined. These observations indicate that distinct toxin family members have protective capabilities for specific stressors but also suggest that TA loci have both positive and negative effects on tolerance.
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Affiliation(s)
- Eugenia Silva-Herzog
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Erin M. McDonald
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Amy L. Crooks
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Corrella S. Detweiler
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
- * E-mail:
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10
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Bacterial Stimulation of Toll-Like Receptor 4 Drives Macrophages To Hemophagocytose. Infect Immun 2015; 84:47-55. [PMID: 26459510 DOI: 10.1128/iai.01149-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 10/07/2015] [Indexed: 01/25/2023] Open
Abstract
During acute infection with bacteria, viruses or parasites, a fraction of macrophages engulf large numbers of red and white blood cells, a process called hemophagocytosis. Hemophagocytes persist into the chronic stage of infection and have an anti-inflammatory phenotype. Salmonella enterica serovar Typhimurium infection of immunocompetent mice results in acute followed by chronic infection, with the accumulation of hemophagocytes. The mechanism(s) that triggers a macrophage to become hemophagocytic is unknown, but it has been reported that the proinflammatory cytokine gamma interferon (IFN-γ) is responsible. We show that primary macrophages become hemophagocytic in the absence or presence of IFN-γ upon infection with Gram-negative bacterial pathogens or prolonged exposure to heat-killed Salmonella enterica, the Gram-positive bacterium Bacillus subtilis, or Mycobacterium marinum. Moreover, conserved microbe-associated molecular patterns are sufficient to stimulate macrophages to hemophagocytose. Purified bacterial lipopolysaccharide (LPS) induced hemophagocytosis in resting and IFN-γ-pretreated macrophages, whereas lipoteichoic acid and synthetic unmethylated deoxycytidine-deoxyguanosine dinucleotides, which mimic bacterial DNA, induced hemophagocytosis only in IFN-γ-pretreated macrophages. Chemical inhibition or genetic deletion of Toll-like receptor 4, a pattern recognition receptor responsive to LPS, prevented both Salmonella- and LPS-stimulated hemophagocytosis. Inhibition of NF-κB also prevented hemophagocytosis. These results indicate that recognition of microbial products by Toll-like receptors stimulates hemophagocytosis, a novel outcome of prolonged Toll-like receptor signaling, suggesting hemophagocytosis is a highly conserved innate immune response.
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Abstract
Hemophagocytes are cells of the monocyte lineage that have engulfed erythrocytes and leukocytes. Hemophagocytes frequently accumulate in patients with severe acute bacterial infections, such as those caused by Salmonella enterica, Brucella abortus, and Mycobacterium tuberculosis. The relationship between hemophagocytosis and infection is not well understood. In the murine liver, S. enterica serovar Typhimurium resides within hemophagocytic macrophages containing leukocytes. Here we show that S. Typhimurium also resides within hemophagocytes containing erythrocytes. In cell culture, S. Typhimurium benefits from residence within hemophagocytes by accessing iron, but why macrophages hemophagocytose is unknown. We show that treatment of macrophages with a cocktail of the proinflammatory cytokine interferon gamma (IFN-γ) and lipopolysaccharide (LPS) stimulates engulfment of nonsenescent erythrocytes. Exposure of resting or IFN-γ-treated macrophages to live, but not to heat-killed, S. Typhimurium cells also stimulates erythrocyte engulfment. Single-cell analyses show that S. Typhimurium-infected macrophages are more likely to erythrophagocytose and that infected macrophages engulf more erythrocytes than uninfected macrophages within the same culture well. In addition, macrophages containing erythrocytes harbor more bacteria. However, S. Typhimurium does not promote macrophage engulfment of polystyrene beads, suggesting a role for a ligand on the target cell. Finally, neither of the two S. Typhimurium type 3 secretion systems, T3SS1 or T3SS2, is fully required for hemophagocytosis. These results indicate that infection of macrophages with live S. Typhimurium cells stimulates hemophagocytosis. Macrophages are white blood cells (leukocytes) that engulf and destroy pathogens. Hemophagocytes, a subset of macrophages, are characteristic of severe acute infection in patients with, for instance, typhoid fever, brucellosis, tuberculosis, and leishmaniasis. Each of these diseases has the potential to become chronic. Hemophagocytes (blood-eating cells) engulf and degrade red and white blood cells for unknown reasons. The bacterial pathogen Salmonella acquires the essential nutrient iron from murine hemophagocytes. We report that Salmonella stimulates macrophages to engulf blood cells, indicating that cells of this bacterium actively promote the formation of a specialized cellular niche in which they can acquire nutrients, evade killing by the host immune system, and potentially transition to chronic infection.
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12
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Nagy TA, Moreland SM, Detweiler CS. Salmonella acquires ferrous iron from haemophagocytic macrophages. Mol Microbiol 2014; 93:1314-26. [PMID: 25081030 DOI: 10.1111/mmi.12739] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2014] [Indexed: 01/21/2023]
Abstract
Bacteria harbour both ferrous and ferric iron transporters. We now report that infection of macrophages and mice with a Salmonella enterica Typhimurium strain containing an inactivated feoB-encoded ferrous iron transporter results in increased bacterial replication, compared to infection with wild type. Inactivation of other cation transporters, SitABCD or MntH, did not increase bacterial replication. The feoB mutant strain does not have an intrinsically faster growth rate. Instead, increased replication correlated with increased expression in macrophages of the fepB-encoded bacterial ferric iron transporter and also required siderophores, which capture ferric iron. Co-infection of mice with wild type and a feoB mutant strain yielded a different outcome: FeoB is clearly required for tissue colonization. In co-infected primary mouse macrophages, FeoB is required for S. Typhimurium replication if the macrophages were IFNγ treated and contain phagocytosed erythrocytes, a model for haemophagocytosis. Haemophagocytes are macrophages that have engulfed erythrocytes and/or leucocytes and can harbour Salmonella in mice. These observations suggest that Salmonella acquires ferrous iron from haemophagocytic macrophages.
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Affiliation(s)
- Toni A Nagy
- Department of Molecular, Cellular and Developmental Biology, University of Colorado-Boulder, Boulder, CO, USA
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13
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Zhou M, Guo Z, Duan Q, Hardwidge PR, Zhu G. Escherichia coli type III secretion system 2: a new kind of T3SS? Vet Res 2014; 45:32. [PMID: 24641581 PMCID: PMC3977695 DOI: 10.1186/1297-9716-45-32] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 03/07/2014] [Indexed: 01/16/2023] Open
Abstract
Type III secretion systems (T3SSs) are employed by Gram-negative bacteria to deliver effector proteins into the cytoplasm of infected host cells. Enteropathogenic Escherichia coli use a T3SS to deliver effector proteins that result in the creation of the attaching and effacing lesions. The genome sequence of the Escherichia coli pathotype O157:H7 revealed the existence of a gene cluster encoding components of a second type III secretion system, the E. coli type III secretion system 2 (ETT2). Researchers have revealed that, although ETT2 may not be a functional secretion system in most (or all) strains, it still plays an important role in bacterial virulence. This article summarizes current knowledge regarding the E. coli ETT2, including its genetic characteristics, prevalence, function, association with virulence, and prospects for future work.
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Affiliation(s)
| | | | | | | | - Guoqiang Zhu
- College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China.
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Nagy TA, Moreland SM, Andrews-Polymenis H, Detweiler CS. The ferric enterobactin transporter Fep is required for persistent Salmonella enterica serovar typhimurium infection. Infect Immun 2013; 81:4063-70. [PMID: 23959718 PMCID: PMC3811836 DOI: 10.1128/iai.00412-13] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 08/10/2013] [Indexed: 01/24/2023] Open
Abstract
Most bacterial pathogens require iron to grow and colonize host tissues. The Gram-negative bacterium Salmonella enterica serovar Typhimurium causes a natural systemic infection of mice that models acute and chronic human typhoid fever. S. Typhimurium resides in tissues within cells of the monocyte lineage, which limit pathogen access to iron, a mechanism of nutritional immunity. The primary ferric iron import system encoded by Salmonella is the siderophore ABC transporter FepBDGC. The Fep system has a known role in acute infection, but it is unclear whether ferric iron uptake or the ferric iron binding siderophores enterobactin and salmochelin are required for persistent infection. We defined the role of the Fep iron transporter and siderophores in the replication of Salmonella in macrophages and in mice that develop acute followed by persistent infections. Replication of wild-type and iron transporter mutant Salmonella strains was quantified in cultured macrophages, fecal pellets, and host tissues in mixed- and single-infection experiments. We show that deletion of fepB attenuated Salmonella replication and colonization within macrophages and mice. Additionally, the genes required to produce and transport enterobactin and salmochelin across the outer membrane receptors, fepA and iroN, are needed for colonization of all tissues examined. However, salmochelin appears to be more important than enterobactin in the colonization of the spleen and liver, both sites of dissemination. Thus, the FepBDGC ferric iron transporter and the siderophores enterobactin and salmochelin are required by Salmonella to evade nutritional immunity in macrophages and cause persistent infection in mice.
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Affiliation(s)
- Toni A. Nagy
- Department of Molecular, Cellular and Developmental Biology, University of Colorado—Boulder, Boulder, Colorado, USA
| | - Sarah M. Moreland
- Department of Molecular, Cellular and Developmental Biology, University of Colorado—Boulder, Boulder, Colorado, USA
| | | | - Corrella S. Detweiler
- Department of Molecular, Cellular and Developmental Biology, University of Colorado—Boulder, Boulder, Colorado, USA
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Moest TP, Méresse S. Salmonella T3SSs: successful mission of the secret(ion) agents. Curr Opin Microbiol 2013; 16:38-44. [DOI: 10.1016/j.mib.2012.11.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 11/15/2012] [Accepted: 11/26/2012] [Indexed: 10/27/2022]
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16
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Salmonella Pathogenicity Island 1(SPI-1) at Work. Curr Microbiol 2013; 66:582-7. [DOI: 10.1007/s00284-013-0307-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 01/08/2013] [Indexed: 10/27/2022]
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Ruby T, McLaughlin L, Gopinath S, Monack D. Salmonella's long-term relationship with its host. FEMS Microbiol Rev 2012; 36:600-15. [PMID: 22335190 DOI: 10.1111/j.1574-6976.2012.00332.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 01/30/2012] [Accepted: 02/07/2012] [Indexed: 12/23/2022] Open
Abstract
Host-adapted strains of Salmonella enterica cause systemic infections and have the ability to persist systemically for long periods of time and pose significant public-health problems. Multidrug-resistant S. enterica serovar Typhi (S. Typhi) and nontyphoidal Salmonella (NTS) are on the increase and are often associated with HIV infection. Chronically infected hosts are often asymptomatic and transmit disease to naïve hosts via fecal shedding of bacteria, thereby serving as a critical reservoir for disease. Salmonella utilizes multiple ways to evade and modulate host innate and adaptive immune responses in order to persist in the presence of a robust immune response. Survival in macrophages and modulation of immune cells migration allow Salmonella to evade various immune responses. The ability of Salmonella to persist depends on a balance between immune responses that lead to the clearance of the pathogen and avoidance of damage to host tissues.
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Affiliation(s)
- Thomas Ruby
- Department of Microbiology and Immunology, Stanford University, Stanford, CA, USA
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Pilonieta MC, Nagy TA, Jorgensen DR, Detweiler CS. A glycine betaine importer limits Salmonella stress resistance and tissue colonization by reducing trehalose production. Mol Microbiol 2012; 84:296-309. [PMID: 22375627 DOI: 10.1111/j.1365-2958.2012.08022.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mechanisms by which Salmonella establish chronic infections are not well understood. Microbes respond to stress by importing or producing compatible solutes, small molecules that stabilize proteins and lipids. The Salmonella locus opuABCD (also called OpuC) encodes a predicted importer of the compatible solute glycine betaine. Under stress conditions, if glycine betaine cannot be imported, Salmonella enterica produce the disaccharide trehalose, a highly effective compatible solute. We demonstrate that strains lacking opuABCD accumulate more trehalose under stress conditions than wild-type strains. ΔopuABCD mutant strains are more resistant to high-salt, low-pH and -hydrogen peroxide, conditions that mimic aspects of innate immunity, in a trehalose-dependent manner. In addition, ΔopuABCD mutant strains require the trehalose production genes to out-compete wild-type strains in mice and macrophages. These data suggest that in the absence of opuABCD, trehalose accumulation increases bacterial resistance to stress in broth and mice. Thus, opuABCD reduces bacterial colonization via a mechanism that limits trehalose production. Mechanisms by which microbes limit disease may reveal novel pathways as therapeutic targets.
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Affiliation(s)
- M Carolina Pilonieta
- Department of Molecular Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
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How to become a top model: impact of animal experimentation on human Salmonella disease research. Infect Immun 2011; 79:1806-14. [PMID: 21343352 DOI: 10.1128/iai.01369-10] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Salmonella serotypes are a major cause of human morbidity and mortality worldwide. Over the past decades, a series of animal models have been developed to advance vaccine development, provide insights into immunity to infection, and study the pathogenesis of human Salmonella disease. The successive introduction of new animal models, each suited to interrogate previously neglected aspects of Salmonella disease, has ushered in important conceptual advances that continue to have a strong and sustained influence on the ideas driving research on Salmonella serotypes. This article reviews important milestones in the use of animal models to study human Salmonella disease and identify research needs to guide future work.
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Fur negatively regulates hns and is required for the expression of HilA and virulence in Salmonella enterica serovar Typhimurium. J Bacteriol 2010; 193:497-505. [PMID: 21075923 DOI: 10.1128/jb.00942-10] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Iron is an essential element for the survival of living cells. However, excess iron is toxic, and its uptake is exquisitely regulated by the ferric uptake regulator, Fur. In Salmonella, the Salmonella pathogenicity island 1 (SPI-1) encodes a type three secretion system, which is required for invasion of host epithelial cells in the small intestine. A major activator of SPI-1 is HilA, which is encoded within SPI-1. One known regulator of hilA is Fur. The mechanism of hilA regulation by Fur is unknown. We report here that Fur is required for virulence in Salmonella enterica serovar Typhimurium and that Fur is required for the activation of hilA, as well as of other HilA-dependent genes, invF and sipC. The Fur-dependent regulation of hilA was independent of PhoP, a known repressor of hilA. Instead, the expression of the gene coding for the histone-like protein, hns, was significantly derepressed in the fur mutant. Indeed, the activation of hilA by Fur was dependent on 28 nucleotides located upstream of hns. Moreover, we used chromatin immunoprecipitation to show that Fur bound, in vivo, to the upstream region of hns in a metal-dependent fashion. Finally, deletion of fur in an hns mutant resulted in Fur-independent activation of hilA. In conclusion, Fur activates hilA by repressing the expression of hns.
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