scholarly journals Invasion of Eukaryotic Cells byLegionella Pneumophila: A Common Strategy for all Hosts?

1997 ◽  
Vol 8 (3) ◽  
pp. 139-146 ◽  
Author(s):  
Paul S Hoffman
Keyword(s):  
Legionella Pneumophila ◽  
Human Infection ◽  
Host Cells ◽  
Eukaryotic Cells ◽  
Mature Form ◽  
Cellular Processes ◽  
Wide Range ◽  
Common Strategy ◽  
Legionnaires Disease ◽  
Host Parasite

Legionella pneumophilais an environmental micro-organism capable of producing an acute lobar pneumonia, commonly referred to as Legionnaires’ disease, in susceptible humans. Legionellae are ubiquitous in aquatic environments, where they survive in biofilms or intracellularly in various protozoans. Susceptible humans become infected by breathing aerosols laden with the bacteria. The target cell for human infection is the alveolar macrophage, in which the bacteria abrogate phagolysosomal fusion. The remarkable ability ofL pneumophilato infect a wide range of eukaryotic cells suggests a common strategy that exploits very fundamental cellular processes. The bacteria enter host cells via coiling phagocytosis and quickly subvert organelle trafficking events, leading to formation of a replicative phagosome in which the bacteria multiply. Vegetative growth continues for 8 to 10 h, after which the bacteria develop into a short, highly motile form called the ‘mature form’. The mature form exhibits a thickening of the cell wall, stains red with the Gimenez stain, and is between 10 and 100 times more infectious than agar-grown bacteria. Following host cell lysis, the released bacteria infect other host cells, in which the mature form differentiates into a Gimenez-negative vegetative form, and the cycle begins anew. Virulence ofL pneumophilais considered to be multifactorial, and there is growing evidence for both stage specific and sequential gene expression. Thus,L pneumophilamay be a good model system for dissecting events associated with the host-parasite interactions.

scholarly journals Human Lung Tissue Explants Reveal Novel Interactions during Legionella pneumophila Infections

2013 ◽  
Vol 82 (1) ◽  
pp. 275-285 ◽  
Author(s):  
Jens Jäger ◽  
Sebastian Marwitz ◽  
Jana Tiefenau ◽  
Janine Rasch ◽  
Olga Shevchuk ◽  
...  
Keyword(s):  
Lung Tissue ◽  
Legionella Pneumophila ◽  
Human Lung ◽  
Transcriptional Response ◽  
Human Infection ◽  
Bacterial Invasion ◽  
Human Lung Tissue ◽  
Content Type ◽  
Tissue Explants ◽  
Legionnaires Disease

ABSTRACTHistological and clinical investigations describe late stages of Legionnaires' disease but cannot characterize early events of human infection. Cellular or rodent infection models lack the complexity of tissue or have nonhuman backgrounds. Therefore, we developed and applied a novel model forLegionella pneumophilainfection comprising living human lung tissue. We stimulated lung explants withL. pneumophilastrains and outer membrane vesicles (OMVs) to analyze tissue damage, bacterial replication, and localization as well as the transcriptional response of infected tissue. Interestingly, we found that extracellular adhesion ofL. pneumophilato the entire alveolar lining precedes bacterial invasion and replication in recruited macrophages. In contrast, OMVs predominantly bound to alveolar macrophages. Specific damage to septa and epithelia increased over 48 h and was stronger in wild-type-infected and OMV-treated samples than in samples infected with the replication-deficient, type IVB secretion-deficient DotA−strain. Transcriptome analysis of lung tissue explants revealed a differential regulation of 2,499 genes after infection. The transcriptional response included the upregulation of uteroglobin and the downregulation of the macrophage receptor with collagenous structure (MARCO). Immunohistochemistry confirmed the downregulation of MARCO at sites of pathogen-induced tissue destruction. Neither host factor has ever been described in the context ofL. pneumophilainfections. This work demonstrates that the tissue explant model reproduces realistic features of Legionnaires' disease and reveals new functions for bacterial OMVs during infection. Our model allows us to characterize early steps of human infection which otherwise are not feasible for investigations.

scholarly journals Peptidyl-Prolyl-cis/trans-Isomerases Mip and PpiB ofLegionella pneumophilaContribute to Surface Translocation, Growth at Suboptimal Temperature, and Infection

2018 ◽  
Vol 87 (1) ◽  
Author(s):  
J. Rasch ◽  
C. M. Ünal ◽  
A. Klages ◽  
Ü. Karsli ◽  
N. Heinsohn ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Acanthamoeba Castellanii ◽  
Temperature Tolerance ◽  
Lung Damage ◽  
Atypical Pneumonia ◽  
Content Type ◽  
Wide Range ◽  
Legionnaires Disease ◽  
Environmental Fitness ◽  
Sliding Motility

ABSTRACTThe gammaproteobacteriumLegionella pneumophilais the causative agent of Legionnaires’ disease, an atypical pneumonia that manifests itself with severe lung damage.L. pneumophila, a common inhabitant of freshwater environments, replicates in free-living amoebae and persists in biofilms in natural and man-made water systems. Its environmental versatility is reflected in its ability to survive and grow within a broad temperature range as well as its capability to colonize and infect a wide range of hosts, including protozoa and humans. Peptidyl-prolyl-cis/trans-isomerases (PPIases) are multifunctional proteins that are mainly involved in protein folding and secretion in bacteria. InL. pneumophilathe surface-associated PPIase Mip was shown to facilitate the establishment of the intracellular infection cycle in its early stages. The cytoplasmic PpiB was shown to promote cold tolerance. Here, we set out to analyze the interrelationship of these two relevant PPIases in the context of environmental fitness and infection. We demonstrate that the PPIases Mip and PpiB are important for surfactant-dependent sliding motility and adaptation to suboptimal temperatures, features that contribute to the environmental fitness ofL. pneumophila. Furthermore, they contribute to infection of the natural hostAcanthamoeba castellaniias well as human macrophages and human explanted lung tissue. These effects were additive in the case of sliding motility or synergistic in the case of temperature tolerance and infection, as assessed by the behavior of the double mutant. Accordingly, we propose that Mip and PpiB are virulence modulators ofL. pneumophilawith compensatory action and pleiotropic effects.

The Legionella pneumophila effector RavY contributes to a replication-permissive vacuolar environment during infection

2021 ◽  
Author(s):  
Luying Liu ◽  
Craig R. Roy
Keyword(s):  
Legionella Pneumophila ◽  
Effector Proteins ◽  
Type Iv Secretion ◽  
Host Cells ◽  
Effector Protein ◽  
Intracellular Replication ◽  
Phagocytic Cells ◽  
Host Molecules ◽  
Type Iv ◽  
Legionnaires Disease

Legionella pneumophila is the causative agent of Legionnaires’ Disease and is capable replicating inside phagocytic cells such as mammalian macrophages. The Dot/Icm type IV secretion system is a L. pneumophila virulence factor that is essential for successful intracellular replication. During infection, L. pneumophila builds a replication permissive vacuole by recruiting multiple host molecules and hijacking host cellular signaling pathways, a process mediated by the coordinated functions of multiple Dot/Icm effector proteins. RavY is a predicted Dot/Icm effector protein found to be important for optimal L. pneumophila replication inside host cells. Here, we demonstrate that RavY is a Dot/Icm-translocated effector protein that is dispensable for axenic replication of L. pneumophila , but critical for optimal intracellular replication of the bacteria. RavY is not required for avoidance of endosomal maturation, nor does RavY contribute to the recruitment of host molecules found on replication-permissive vacuoles, such as ubiquitin, RAB1a, and RTN4. Vacuoles containing L. pneumophila ravY mutants promote intracellular survival but limit replication. The replication defect of the L. pneumophila ravY mutant was complemented when the mutant was in the same vacuole as wild type L. pneumophila . Thus, RavY is an effector that is essential for promoting intracellular replication of L. pneumophila once the specialized vacuole has been established.

scholarly journals Flagellum of Legionella pneumophilaPositively Affects the Early Phase of Infection of Eukaryotic Host Cells

2001 ◽  
Vol 69 (4) ◽  
pp. 2116-2122 ◽  
Author(s):  
Claudia Dietrich ◽  
Klaus Heuner ◽  
Bettina C. Brand ◽  
Jörg Hacker ◽  
Michael Steinert
Keyword(s):  
Electron Microscopy ◽  
Legionella Pneumophila ◽  
Kanamycin Resistance ◽  
Etiologic Agent ◽  
Polyclonal Antiserum ◽  
Host Cells ◽  
Kanamycin Resistance Cassette ◽  
Legionnaires Disease ◽  
Invasion Capacity

ABSTRACT Legionella pneumophila, the etiologic agent of Legionnaires' disease, contains a single, monopolar flagellum which is composed of one major subunit, the FlaA protein. To evaluate the role of the flagellum in the pathogenesis and ecology ofLegionella, the flaA gene of L. pneumophila Corby was mutagenized by introduction of a kanamycin resistance cassette. Immunoblots with antiflagellin-specific polyclonal antiserum, electron microscopy, and motility assays confirmed that the specific flagellar mutant L. pneumophila Corby KH3 was nonflagellated. The redelivery of the intact flaA gene into the chromosome (L. pneumophila Corby CD10) completely restored flagellation and motility. Coculture studies showed that the invasion efficiency of the flaA mutant was moderately reduced in amoebae and severely reduced in HL-60 cells. In contrast, adhesion and the intracellular rate of replication remained unaffected. Taking these results together, we have demonstrated that the flagellum of L. pneumophila positively affects the establishment of infection by facilitating the encounter of the host cell as well as by enhancing the invasion capacity.

scholarly journals Legionella pneumophila Entry GenertxA Is Involved in Virulence

2001 ◽  
Vol 69 (1) ◽  
pp. 508-517 ◽  
Author(s):  
Suat L. G. Cirillo ◽  
Luiz E. Bermudez ◽  
Sahar H. El-Etr ◽  
Gerald E. Duhamel ◽  
Jeffrey D. Cirillo
Keyword(s):  
Legionella Pneumophila ◽  
Bacterial Species ◽  
Host Cells ◽  
Intracellular Pathogen ◽  
Wild Type ◽  
Integrin Receptors ◽  
Legionnaires Disease ◽  
Cell Spread ◽  
Gain Access

ABSTRACT Successful parasitism of host cells by intracellular pathogens involves adherence, entry, survival, intracellular replication, and cell-to-cell spread. Our laboratory has been examining the role of early events, adherence and entry, in the pathogenesis of the facultative intracellular pathogen Legionella pneumophila. Currently, the mechanisms used by L. pneumophila to gain access to the intracellular environment are not well understood. We have recently isolated three loci, designated enh1,enh2, and enh3, that are involved in the ability of L. pneumophila to enter host cells. One of the genes present in the enh1 locus, rtxA, is homologous to repeats in structural toxin genes (RTX) found in many bacterial pathogens. RTX proteins from other bacterial species are commonly cytotoxic, and some of them have been shown to bind to β2 integrin receptors. In the current study, we demonstrate that the L. pneumophila rtxA gene is involved in adherence, cytotoxicity, and pore formation in addition to its role in entry. Furthermore, an rtxA mutant does not replicate as well as wild-type L. pneumophila in monocytes and is less virulent in mice. Thus, we conclude that the entry genertxA is an important virulence determinant in L. pneumophila and is likely to be critical for the production of Legionnaires' disease in humans.

Creating a customized intracellular niche: subversion of host cell signaling byLegionellatype IV secretion system effectors

2015 ◽  
Vol 61 (9) ◽  
pp. 617-635 ◽  
Author(s):  
Ernest C. So ◽  
Corinna Mattheis ◽  
Edward W. Tate ◽  
Gad Frankel ◽  
Gunnar N. Schroeder
Keyword(s):  
Host Cell ◽  
Legionella Pneumophila ◽  
Current Knowledge ◽  
Secretion System ◽  
Effector Proteins ◽  
Cellular Processes ◽  
Type Iv ◽  
Open Questions ◽  
Exact Function ◽  
Wide Range

The Gram-negative facultative intracellular pathogen Legionella pneumophila infects a wide range of different protozoa in the environment and also human alveolar macrophages upon inhalation of contaminated aerosols. Inside its hosts, it creates a defined and unique compartment, termed the Legionella-containing vacuole (LCV), for survival and replication. To establish the LCV, L. pneumophila uses its Dot/Icm type IV secretion system (T4SS) to translocate more than 300 effector proteins into the host cell. Although it has become apparent in the past years that these effectors subvert a multitude of cellular processes and allow Legionella to take control of host cell vesicle trafficking, transcription, and translation, the exact function of the vast majority of effectors still remains unknown. This is partly due to high functional redundancy among the effectors, which renders conventional genetic approaches to elucidate their role ineffective. Here, we review the current knowledge about Legionella T4SS effectors, highlight open questions, and discuss new methods that promise to facilitate the characterization of T4SS effector functions in the future.

scholarly journals Who's really in control: microbial regulation of protein trafficking in the epithelium

2014 ◽  
Vol 306 (3) ◽  
pp. C187-C197 ◽  
Author(s):  
Matthew R. Hendricks ◽  
Jennifer M. Bomberger
Keyword(s):  
Epithelial Cell ◽  
Protein Trafficking ◽  
Host Cells ◽  
Eukaryotic Cells ◽  
Cell Physiology ◽  
Cellular Physiology ◽  
Cellular Processes ◽  
Complex Interactions ◽  
Host Pathogen ◽  
Host Tissues

Due to evolutionary pressure, there are many complex interactions at the interface between pathogens and eukaryotic host cells wherein host cells attempt to clear invading microorganisms and pathogens counter these mechanisms to colonize and invade host tissues. One striking observation from studies focused on this interface is that pathogens have multiple mechanisms to modulate and disrupt normal cellular physiology to establish replication niches and avoid clearance. The precision by which pathogens exert their effects on host cells makes them excellent tools to answer questions about cell physiology of eukaryotic cells. Furthermore, an understanding of these mechanisms at the host-pathogen interface will benefit our understanding of how pathogens cause disease. In this review, we describe a few examples of how pathogens disrupt normal cellular physiology and protein trafficking at epithelial cell barriers to underscore how pathogens modulate cellular processes to cause disease and how this knowledge has been utilized to learn about cellular physiology.

scholarly journals Aerosol infection of animals with strains ofLegionella pneumophilaof different virulence: comparison with intraperitoneal and intranasal routes of infection

1983 ◽  
Vol 90 (1) ◽  
pp. 81-89 ◽  
Author(s):  
R. B. Fitzgeorge ◽  
A. Baskerville ◽  
M. Broster ◽  
P. Hambleton ◽  
P. J. Dennis
Keyword(s):  
Legionella Pneumophila ◽  
Small Particle ◽  
Guinea Pigs ◽  
Rhesus Monkeys ◽  
Type Strain ◽  
Wide Range ◽  
Strain Nctc ◽  
Legionnaires Disease ◽  
Aerosol Infection ◽  
Intranasal Instillation

SUMMARYInfection of guinea-pigs by intranasal (i.n.) instillation of 109viable organisms of two newly isolated strains ofLegionella pneumophila(74/81, serogroup 1; 166/81, serogroup 3) did not induce disease, but 104organisms administered as a small particle aerosol (< 5 μm diameter) produced a fatal widespread bronchopneumonia within 3 days. Milder illness and less extensive bronchopneumonia were also produced in rhesus monkeys and marmosets by one of these two strains (74/81). Mice were resistant to induction of disease by aerosols of both these two strains, though organisms did persist in the lungs for at least 4 days. Both of theseL. pneumophilastrains were pathogenic for guinea-pigs by aerosol infection over a wide range of doses but the serogroup 1 type strain (NCTC 11192) was not. There was no mortality after infection of guinea-pigs by intranasal instillation of any of these strains but all proved to be fatal after intraperitoneal (i.p.) injection of large doses. Guinea-pigs, rhesus monkeys and marmosets exposed to aerosol infection withL. pneumophilaprovide relevant models for studying the pathogenesis of Legionnaires' disease.

scholarly journals Polar targeting and assembly of theLegionellaDot/Icm type IV secretion system (T4SS) by T6SS-related components

2018 ◽  
Author(s):  
KwangCheol C. Jeong ◽  
Jacob Gyore ◽  
Lin Teng ◽  
Debnath Ghosal ◽  
Grant J. Jensen ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Host Cells ◽  
Type Iv Secretion System ◽  
Membrane Complex ◽  
Type Iv ◽  
Legionnaires Disease ◽  
Type Ivb Secretion ◽  
Type Ivb Secretion System

SummaryLegionella pneumophila, the causative agent of Legionnaires’ disease, survives and replicates inside amoebae and macrophages by injecting a large number of protein effectors into the host cells’ cytoplasm via the Dot/Icm type IVB secretion system (T4BSS). Previously, we showed that the Dot/Icm T4BSS is localized to both poles of the bacterium and that polar secretion is necessary for the proper targeting of theLegionellacontaining vacuole (LCV). Here we show that polar targeting of the Dot/Icm core-transmembrane subcomplex (DotC, DotD, DotF, DotG and DotH) is mediated by two Dot/Icm proteins, DotU and IcmF, which are able to localize to the poles ofL. pneumophilaby themselves. Interestingly, DotU and IcmF are homologs of the T6SS components TssL and TssM, which are part of the T6SS membrane complex (MC). We propose thatLegionellaco-opted these T6SS components to a novel function that mediates subcellular localization and assembly of this T4SS. Finally, in depth examination of the biogenesis pathway revealed that polar targeting and assembly of theLegionellaT4BSS apparatus is mediated by an innovative “outside-inside” mechanism.

scholarly journals Transfection types, methods and strategies: a technical review

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11165
Author(s):  
Zhi Xiong Chong ◽  
Swee Keong Yeap ◽  
Wan Yong Ho
Keyword(s):  
Decision Making ◽  
Nucleic Acids ◽  
Molecular Mechanism ◽  
Transfection Efficiency ◽  
Host Cells ◽  
Eukaryotic Cells ◽  
Powerful Method ◽  
Broad Application ◽  
Cellular Processes ◽  
Transfection Protocol

Transfection is a modern and powerful method used to insert foreign nucleic acids into eukaryotic cells. The ability to modify host cells’ genetic content enables the broad application of this process in studying normal cellular processes, disease molecular mechanism and gene therapeutic effect. In this review, we summarized and compared the findings from various reported literature on the characteristics, strengths, and limitations of various transfection methods, type of transfected nucleic acids, transfection controls and approaches to assess transfection efficiency. With the vast choices of approaches available, we hope that this review will help researchers, especially those new to the field, in their decision making over the transfection protocol or strategy appropriate for their experimental aims.

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