scholarly journals Knowledge to Predict Pathogens: Legionella pneumophila Lifecycle Systematic Review Part II Growth within and Egress from a Host Cell

2022 ◽  
Vol 10 (1) ◽  
pp. 141
Author(s):  
Alexis L. Mraz ◽  
Mark H. Weir
Keyword(s):  
Systematic Review ◽  
Host Cell ◽  
Legionella Pneumophila ◽  
Water System ◽  
Severe Pneumonia ◽  
Host Cells ◽  
Premise Plumbing ◽  
Plumbing Systems ◽  
Legionnaires Disease ◽  
Protozoan Cell

Legionella pneumophila (L. pneumophila) is a pathogenic bacterium of increasing concern, due to its ability to cause a severe pneumonia, Legionnaires’ Disease (LD), and the challenges in controlling the bacteria within premise plumbing systems. L. pneumophila can thrive within the biofilm of premise plumbing systems, utilizing protozoan hosts for protection from environmental stressors and to increase its growth rate, which increases the bacteria’s infectivity to human host cells. Typical disinfectant techniques have proven to be inadequate in controlling L. pneumophila in the premise plumbing system, exposing users to LD risks. As the bacteria have limited infectivity to human macrophages without replicating within a host protozoan cell, the replication within, and egress from, a protozoan host cell is an integral part of the bacteria’s lifecycle. While there is a great deal of information regarding how L. pneumophila interacts with protozoa, the ability to use this data in a model to attempt to predict a concentration of L. pneumophila in a water system is not known. This systematic review summarizes the information in the literature regarding L. pneumophila’s growth within and egress from the host cell, summarizes the genes which affect these processes, and calculates how oxidative stress can downregulate those genes.

scholarly journals Prevalence of Infection-Competent Serogroup 6 Legionella pneumophila within Premise Plumbing in Southeast Michigan

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Brenda G. Byrne ◽  
Sarah McColm ◽  
Shawn P. McElmurry ◽  
Paul E. Kilgore ◽  
Joanne Sobeck ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Water System ◽  
Disease Outbreaks ◽  
Clinical Isolates ◽  
Environmental Isolates ◽  
Urinary Antigen ◽  
Clinical Strains ◽  
Municipal Water ◽  
Premise Plumbing ◽  
Legionnaires Disease

ABSTRACTCoinciding with major changes to its municipal water system, Flint, MI, endured Legionnaires’ disease outbreaks in 2014 and 2015. By sampling premise plumbing in Flint in the fall of 2016, we found that 12% of homes harbored legionellae, a frequency similar to that in residences in neighboring areas. To evaluate the genetic diversity ofLegionella pneumophilain Southeast Michigan, we determined the sequence type (ST) and serogroup (SG) of the 18 residential isolates from Flint and Detroit, MI, and the 33 clinical isolates submitted by hospitals in three area counties in 2013 to 2016. Common to one environmental and four clinical samples were strains ofL. pneumophilaSG1 and ST1, the most prevalent ST worldwide. Among the Flint premise plumbing isolates, 14 of 16 strains were of ST367 and ST461, two closely related SG6 strain types isolated previously from patients and corresponding environmental samples. Each of the representative SG1 clinical strains and SG6 environmental isolates from Southeast Michigan infected and survived within macrophage cultures at least as well as a virulent laboratory strain, as judged by microscopy and by enumerating CFU. Likewise, 72 h after infection, the yield of viable-cell counts increased >100-fold for each of the representative SG1 clinical isolates, Flint premise plumbing SG6 ST367 and -461 isolates, and two Detroit residential isolates. We verified by immunostaining that SG1-specific antibody does not cross-react with the SG6L. pneumophilaenvironmental strains. Because the widely used urinary antigen diagnostic test does not readily detect non-SG1L. pneumophila, Legionnaires’ disease caused by SG6L. pneumophilais likely underreported worldwide.IMPORTANCEL. pneumophilais the leading cause of disease outbreaks associated with drinking water in the United States. Compared to what is known of the established risks of colonization within hospitals and hotels, relatively little is known about residential exposure toL. pneumophila. One year after two outbreaks of Legionnaires’ disease in Genesee County, MI, that coincided with damage to the Flint municipal water system, our multidisciplinary team launched an environmental surveillance and laboratory research campaign aimed at informing risk management strategies to provide safe public water supplies. The most prevalentL. pneumophilastrains isolated from residential plumbing were closely related strains of SG6. In laboratory tests of virulence, the SG6 environmental isolates resembled SG1 clinical strains, yet they are not readily detected by the common diagnostic urinary antigen test, which is specific for SG1. Therefore, our study complements the existing epidemiological literature indicating that Legionnaires’ disease due to non-SG1 strains is underreported around the globe.

scholarly journals Bacterial OTU deubiquitinases regulate substrate ubiquitination upon Legionella infection

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Donghyuk Shin ◽  
Anshu Bhattacharya ◽  
Yi-Lin Cheng ◽  
Marta Campos Alonso ◽  
Ahmad Reza Mehdipour ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Severe Pneumonia ◽  
Effector Proteins ◽  
Host Cells ◽  
Catalytic Core ◽  
Polyubiquitin Chains ◽  
Ubiquitin Binding ◽  
Legionnaires Disease ◽  
Ubiquitination System ◽  
Structural Insights

Legionella pneumophila causes a severe pneumonia known as Legionnaires’ disease. During the infection, Legionella injects more than 300 effector proteins into host cells. Among them are enzymes involved in altering the host-ubiquitination system. Here, we identified two LegionellaOTU (ovarian tumor)-like deubiquitinases (LOT-DUBs; LotB [Lpg1621/Ceg23] and LotC [Lpg2529]). The crystal structure of the LotC catalytic core (LotC14-310) was determined at 2.4 Å. Unlike the classical OTU-family, the LOT-family shows an extended helical lobe between the Cys-loop and the variable loop, which defines them as a unique class of OTU-DUBs. LotB has an additional ubiquitin-binding site (S1’), which enables the specific cleavage of Lys63-linked polyubiquitin chains. By contrast, LotC only contains the S1 site and cleaves different species of ubiquitin chains. MS analysis of LotB and LotC identified different categories of host-interacting proteins and substrates. Together, our results provide new structural insights into bacterial OTU-DUBs and indicate distinct roles in host–pathogen interactions.

Adherence of Legionella pneumophila to U-937 cells, guinea-pig alveolar macrophages, and MRC-5 cells by a novel, complement-independent binding mechanism

1994 ◽  
Vol 40 (10) ◽  
pp. 865-872 ◽  
Author(s):  
Frank C. Gibson III ◽  
Arthur O. Tzianabos ◽  
Frank G. Rodgers
Keyword(s):  
Monoclonal Antibodies ◽  
Guinea Pig ◽  
Host Cell ◽  
Alveolar Macrophages ◽  
Legionella Pneumophila ◽  
Cell Receptor ◽  
Host Cells ◽  
Order Kinetic ◽  
Complement Receptors ◽  
Host Cell Receptor

In the absence of serum, Legionella pneumophila demonstrated wash-resistant adherence to U-937 cells, primary guinea-pig alveolar macrophages, and MRC-5 cells. Neither complement nor antibody was required for binding. The dynamics of adherence following inoculation of L. pneumophila at increasing 10-fold multiplicities of infection to each of the three host cell types resulted in a first-order kinetic relationship of binding, indicative of one bacterial adhesin molecule recognized by one host cell receptor moiety. Host cell receptor saturation studies showed that depending on the cell type, 2–8% of the bacterial inoculum adhered to cells under these nonopsonic conditions. Preliminary adhesin and receptor characterization studies were preformed to define the chemical composition of the binding structures on both the organism and the three different host cell surfaces. The adherence phenomenon was investigated using competitive binding assays in the presence of putative adhesin analogs as well as following treatments modifying the microbial and host cell surface membranes. Attachment was evaluated both by viable bacterial cell colony counts and by indirect immunofluorescent assay. With the exception of aldehyde treatments, the various membrane-modifying regimes and the presence of the adhesin analogs were shown to have no effect on organism or host cell viability. Data suggested that the L. pneumophila adhesin responsible for opsonin-independent binding to these host cells was a protein structure with lectin-like properties. Furthermore, this protein would appear to be intimately associated with carbohydrate or lipid structures located on the bacterial outer membrane. The receptor moiety present on all host cells responsible for binding L. pneumophila had properties consistent with a carbohydrate or complex saccharide structure. To evaluate the role of complement receptors as the structures necessary for L. pneumophila infection of macrophages, a battery of monoclonal antibodies were used to block the complement receptor (CR) types 1 (CD35), CR3 (CD 18, CD11b), and CR4 (CD18, CD11c). Blocking studies with CR-specific monoclonal antibodies indicated that CR1 and the integrin receptors CR3 and CR4 were not involved in the opsonin-independent binding of L. pneumophila to macrophage-like cells.Key words: Legionella, opsonin-independent attachment, bacterial adherence, complement receptors, adhesion–receptor interactions.

scholarly journals Lessons From an Outbreak of Legionnaires’ Disease on a Hematology-Oncology Unit

2016 ◽  
Vol 38 (3) ◽  
pp. 306-313 ◽  
Author(s):  
Louise K. Francois Watkins ◽  
Karrie-Ann E. Toews ◽  
Aaron M. Harris ◽  
Sherri Davidson ◽  
Stephanie Ayers-Millsap ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Potable Water ◽  
Single Case ◽  
Healthcare Providers ◽  
Water System ◽  
Positive Sequence ◽  
Environmental Isolates ◽  
Legionnaires Disease ◽  
Oncology Unit ◽  
Healthcare Associated

OBJECTIVESTo define the scope of an outbreak of Legionnaires’ disease (LD), to identify the source, and to stop transmission.DESIGN AND SETTINGEpidemiologic investigation of an LD outbreak among patients and a visitor exposed to a newly constructed hematology-oncology unit.METHODSAn LD case was defined as radiographically confirmed pneumonia in a person with positive urinary antigen testing and/or respiratory culture forLegionellaand exposure to the hematology-oncology unit after February 20, 2014. Cases were classified as definitely or probably healthcare-associated based on whether they were exposed to the unit for all or part of the incubation period (2–10 days). We conducted an environmental assessment and collected water samples for culture. Clinical and environmental isolates were compared by monoclonal antibody (MAb) and sequence-based typing.RESULTSOver a 12-week period, 10 cases were identified, including 6 definite and 4 probable cases. Environmental sampling revealedLegionella pneumophilaserogroup 1 (Lp1) in the potable water at 9 of 10 unit sites (90%), including all patient rooms tested. The 3 clinical isolates were identical to environmental isolates from the unit (MAb2-positive, sequence type ST36). No cases occurred with exposure after the implementation of water restrictions followed by point-of-use filters.CONCLUSIONSContamination of the unit’s potable water system with Lp1 strain ST36 was the likely source of this outbreak. Healthcare providers should routinely test patients who develop pneumonia at least 2 days after hospital admission for LD. A single case of LD that is definitely healthcare associated should prompt a full investigation.Infect Control Hosp Epidemiol2017;38:306–313

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 Divergent Evolution of Legionella RCC1 Repeat Effectors Defines the Range of Ran GTPase Cycle Targets

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
A. Leoni Swart ◽  
Bernhard Steiner ◽  
Laura Gomez-Valero ◽  
Sabina Schütz ◽  
Mandy Hannemann ◽  
...  
Keyword(s):  
Host Cell ◽  
Legionella Pneumophila ◽  
Small Gtpase ◽  
Effector Proteins ◽  
Host Cells ◽  
Divergent Evolution ◽  
Ran Gtpase ◽  
Content Type ◽  
Gtpase Cycle ◽  
Gtpase Ran

ABSTRACT Legionella pneumophila governs its interactions with host cells by secreting >300 different “effector” proteins. Some of these effectors contain eukaryotic domains such as the RCC1 (regulator of chromosome condensation 1) repeats promoting the activation of the small GTPase Ran. In this report, we reveal a conserved pattern of L. pneumophila RCC1 repeat genes, which are distributed in two main clusters of strains. Accordingly, strain Philadelphia-1 contains two RCC1 genes implicated in bacterial virulence, legG1 (Legionella eukaryotic gene 1), and ppgA, while strain Paris contains only one, pieG. The RCC1 repeat effectors localize to different cellular compartments and bind distinct components of the Ran GTPase cycle, including Ran modulators and the small GTPase itself, and yet they all promote the activation of Ran. The pieG gene spans the corresponding open reading frames of legG1 and a separate adjacent upstream gene, lpg1975. legG1 and lpg1975 are fused upon addition of a single nucleotide to encode a protein that adopts the binding specificity of PieG. Thus, a point mutation in pieG splits the gene, altering the effector target. These results indicate that divergent evolution of RCC1 repeat effectors defines the Ran GTPase cycle targets and that modulation of different components of the cycle might fine-tune Ran activation during Legionella infection. IMPORTANCE Legionella pneumophila is a ubiquitous environmental bacterium which, upon inhalation, causes a life-threatening pneumonia termed Legionnaires’ disease. The opportunistic pathogen grows in amoebae and macrophages by employing a “type IV” secretion system, which secretes more than 300 different “effector” proteins into the host cell, where they subvert pivotal processes. The function of many of these effector proteins is unknown, and their evolution has not been studied. L. pneumophila RCC1 repeat effectors target the small GTPase Ran, a molecular switch implicated in different cellular processes such as nucleocytoplasmic transport and microtubule cytoskeleton dynamics. We provide evidence that one or more RCC1 repeat genes are distributed in two main clusters of L. pneumophila strains and have divergently evolved to target different components of the Ran GTPase activation cycle at different subcellular sites. Thus, L. pneumophila employs a sophisticated strategy to subvert host cell Ran GTPase during infection.

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.

scholarly journals Involvement of Fractalkine/CX3CL1 Expression by Dendritic Cells in the Enhancement of Host Immunity against Legionella pneumophila

2005 ◽  
Vol 73 (9) ◽  
pp. 5350-5357 ◽  
Author(s):  
Toshiaki Kikuchi ◽  
Sita Andarini ◽  
Hong Xin ◽  
Kazunori Gomi ◽  
Yutaka Tokue ◽  
...  
Keyword(s):  
T Cells ◽  
Immune Responses ◽  
Host Defense ◽  
Legionella Pneumophila ◽  
Recombinant Adenovirus ◽  
Severe Pneumonia ◽  
Adenovirus Vector ◽  
Recombinant Adenovirus Vector ◽  
Legionnaires Disease

ABSTRACT Legionnaires' disease is clinically manifested as severe pneumonia caused by Legionella pneumophila. However, the dendritic cell (DC)-centered immunological framework of the host defense against L. pneumophila has not been fully delineated. For this study, we focused on a potent chemoattractant for lymphocytes, fractalkine/CX3CL1, and observed that the fractalkine expression of DCs was somewhat up-regulated when they encountered L. pneumophila. We therefore hypothesized that fractalkine expressed by Legionella-capturing DCs is involved in the induction of T-cell-mediated immune responses against Legionella, which would be enhanced by a genetic modulation of DCs to overexpress fractalkine. In vivo immunization-challenge experiments demonstrated that DCs modified with a recombinant adenovirus vector to overexpress fractalkine (AdFKN) and pulsed with heat-killed Legionella protected immunized mice from a lethal Legionella infection and that the generation of in vivo protective immunity depended on the host lymphocyte subsets, including CD4+ T cells, CD8+ T cells, and B cells. Consistent with this, immunization with AdFKN/Legionella/DC induced significantly higher levels of serum anti-Legionella antibodies of several isotypes than those induced by control immunizations. Further analysis of spleen cells from the immunized mice indicated that the AdFKN/Legionella/DC immunization elicited Th1-dominated immune responses to L. pneumophila. These observations suggest that fractalkine may play an important role in the DC-mediated host defense against intracellular pathogens such as L. pneumophila.

scholarly journals MultipleLegionella pneumophilaeffector virulence phenotypes revealed through high-throughput analysis of targeted mutant libraries

2017 ◽  
Vol 114 (48) ◽  
pp. E10446-E10454 ◽  
Author(s):  
Stephanie R. Shames ◽  
Luying Liu ◽  
James C. Havey ◽  
Whitman B. Schofield ◽  
Andrew L. Goodman ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Severe Pneumonia ◽  
Effector Proteins ◽  
Host Cells ◽  
Limiting Factor ◽  
Effector Protein ◽  
Host Immune System ◽  
Loss Of Function ◽  
High Throughput Analysis ◽  
Single Strain

Legionella pneumophilais the causative agent of a severe pneumonia called Legionnaires’ disease. A single strain ofL. pneumophilaencodes a repertoire of over 300 different effector proteins that are delivered into host cells by the Dot/Icm type IV secretion system during infection. The large number ofL. pneumophilaeffectors has been a limiting factor in assessing the importance of individual effectors for virulence. Here, a transposon insertion sequencing technology called INSeq was used to analyze replication of a pool of effector mutants in parallel both in a mouse model of infection and in cultured host cells. Loss-of-function mutations in genes encoding effector proteins resulted in host-specific or broad virulence phenotypes. Screen results were validated for several effector mutants displaying different virulence phenotypes using genetic complementation studies and infection assays. Specifically, loss-of-function mutations in the gene encoding LegC4 resulted in enhancedL. pneumophilain the lungs of infected mice but not within cultured host cells, which indicates LegC4 augments bacterial clearance by the host immune system. The effector proteins RavY and Lpg2505 were important for efficient replication within both mammalian and protozoan hosts. Further analysis of Lpg2505 revealed that this protein functions as a metaeffector that counteracts host cytotoxicity displayed by the effector protein SidI. Thus, this study identified a large cohort of effectors that contribute toL. pneumophilavirulence positively or negatively and has demonstrated regulation of effector protein activities by cognate metaeffectors as being critical for host pathogenesis.

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