Cytotoxicity of extracellular Legionella pneumophila

Husmann, L K; Johnson, William M.

doi:10.1128/iai.62.5.2111-2114.1994

Cited by 51 publications

(45 citation statements)

References 17 publications

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“…Interestingly, the pore-forming activity of extracellular L. pneumophila does not induce a rapid cytolytic effect on A. polyphaga, different from its action on mammalian cells that are completely killed within 1 h after infection at an MOI of 500 (Husmann and Johnson, 1994;Kirby et al, 1998). It is possible that the pore-forming activity of L. pneumophila is not translocated or is not properly assembled in the outer lea¯et of the plasma membrane of the protozoan cells.…”

Section: Discussionmentioning

confidence: 96%

“…First, infection at this MOI may ensure that most of the cells were infected by L. pneumophila and allow better examination of whether the rib mutants were defective in exiting the protozoan host. Secondly, it has recently been shown that extracellular L. pneumophila induces rapid necrotic killing of mammalian cells within 20±180 min at an MOI of 500 (Husmann and Johnson, 1994;Kirby et al, 1998). At 4 h after infection, there was no detectable staining with PI.…”

Section: Pneumophila Kills a Polyphaga Preferentially By Inductiomentioning

confidence: 96%

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The mechanism of killing and exiting the protozoan host Acanthamoeba polyphaga by Legionella pneumophila

Gao

Kwaik

2000

Environmental Microbiology

103

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The ability of Legionella pneumophila to cause legionnaires' disease is dependent on its capacity to replicate within cells in the alveolar spaces. The bacteria kill mammalian cells in two phases: induction of apoptosis during the early stages of infection, followed by an independent and rapid necrosis during later stages of the infection, mediated by a pore-forming activity. In the environment, L. pneumophila is a parasite of protozoa. The molecular mechanisms by which L. pneumophila kills the protozoan cells, after their exploitation for intracellular proliferation, are not known. In an effort to decipher these mechanisms, we have examined induction of both apoptosis and necrosis in the protozoan Acanthamoeba polyphaga upon infection by L. pneumophila. Our data show that, although A. polyphaga undergoes apoptosis following treatment with actinomycin D, L. pneumophila does not induce apoptosis in these cells. Instead, intracellular L. pneumophila induces necrotic death in A. polyphaga, which is mediated by the pore-forming activity. Mutants of L. pneumophila defective in expression of the pore-forming activity are indistinguishable from the parental strain in intracellular replication within A. polyphaga. The parental strain bacteria cause necrosis-mediated lysis of all the A. polyphaga cells within 48 h after infection, and all the intracellular bacteria are released into the tissue culture medium. In contrast, all cells infected by the mutants remain intact, and the intracellular bacteria are 'trapped' within A. polyphaga after the termination of intracellular replication. Failure to exit the host cell after termination of intracellular replication results in a gradual decline in the viability of the mutant strain bacteria within A. polyphaga starting 48h after infection. Our data show that the pore-forming activity of L. pneumophila is not required for intracellular bacterial replication within A. polyphaga but is required for killing and exiting the protozoan host upon termination of intracellular replication.

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Section: Discussionmentioning

confidence: 96%

Section: Pneumophila Kills a Polyphaga Preferentially By Inductiomentioning

confidence: 96%

The mechanism of killing and exiting the protozoan host Acanthamoeba polyphaga by Legionella pneumophila

Gao

Kwaik

2000

Environmental Microbiology

103

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“…The importance of an intact functional cytoskeleton was demonstrated by Elliott and Winn (7) who observed that L. pneumophila could not grow in guinea pig and rat macrophage cultures in which phagocytic activity, but not bacterial attachment to the macrophage surface, was inhibited by cytochalasin D, an inhibitor of actin filament polymerisation. Yamamoto et al (36) and Husmann and Johnson (18) used cytochalasin D in order to block the phagocytosis of L. pneumophila by murine and guinea pig macrophages, respectively. It has also been shown that cytochalasin D inhibited intracellular multiplication of L. pneumophila in the U937 monocyte model, but had no effect on the intracellular multiplication of legionellas in the axenic amoeba Hartmannella vermiformis (20).…”

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confidence: 99%

Multiplication of Legionella pneumophila in HeLa Cells in the Presence of Cytoskeleton and Metabolic Inhibitors

Goldoni

Cattani

Carrara

et al. 1998

Microbiology and Immunology

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A study has been carried out on the action of cytoskeleton and metabolic inhibitors on intracellular multiplication in HeLa cells of a virulent strain of Legionella pneumophila serogroup 6. The effects of the substances were separately tested on both penetration and intracellular multiplication of L. pneumophila. Only cytochalasin A and 2-deoxy-D-glucose (2dG) affected bacterial internalisation, whereas intracellular multiplication was inhibited by cytochalasins A, B, C, D and J (D being the most active) and by 2dG with a dose-response effect. The action of 2dG was counteracted by 50 mm glucose. Experiments carried out with cytochalasin D and a rhodamine-phalloidin conjugate showed the involvement of cytoskeletal elements in intracellular multiplication of Legionella; compounds acting on microtubules had no effect.

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“…This indicates that L. pneumophila may have a killing mechanism which is independent of its ability to survive and multiply within Ms. This killing ability, which seems to be present only when large numbers of L. pneumophila organisms are incubated with M-like cells, may be due to a reported cytotoxin of L. pneumophila (13,24).…”

Section: Discussionmentioning

confidence: 99%

Early Events in Phagosome Establishment Are Required for Intracellular Survival of Legionella pneumophila

Wiater¹,

Dunn

Maxfield

et al. 1998

Infect. Immun.

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During infection, the Legionnaires' disease bacterium, Legionella pneumophila, survives and multiplies within a specialized phagosome that is near neutral pH and does not fuse with host lysosomes. In order to understand the molecular basis of this organism's ability to control its intracellular fate, we have isolated and characterized a group of transposon-generated mutants which were unable to kill macrophages and were subsequently found to be defective in intracellular multiplication. These mutations define a set of 20 genes (19 icm [for intracellular multiplication] genes and dotA [for defect in organelle trafficking]). In this report, we describe a quantitative assay for phagosome-lysosome fusion (PLF) and its use to measure the levels of PLF in cells that have been infected with either wild-type L. pneumophila or one of several mutants defective in different icm genes or dotA. By using quantitative confocal fluorescence microscopy, PLF could be scored on a per-bacterium basis by determining the extent to which fluorescein-labeled L. pneumophila colocalized with host lysosomes prelabeled with rhodamine-dextran. Remarkably, mutations in the six genes that were studied resulted in maximal levels of PLF as quickly as 30 min following infection. These results indicate that several, and possibly all, of the icm and dotA gene products act at an early step during phagosome establishment to determine whether L. pneumophila-containing phagosomes will fuse with lysosomes. Although not ruled out, subsequent activity of these gene products may not be necessary for successful intracellular replication.

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Cytotoxicity of extracellular Legionella pneumophila

Cited by 51 publications

References 17 publications

The mechanism of killing and exiting the protozoan host Acanthamoeba polyphaga by Legionella pneumophila

The mechanism of killing and exiting the protozoan host Acanthamoeba polyphaga by Legionella pneumophila

Multiplication of Legionella pneumophila in HeLa Cells in the Presence of Cytoskeleton and Metabolic Inhibitors

Early Events in Phagosome Establishment Are Required for Intracellular Survival of Legionella pneumophila

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