Intrazelluläres Überleben und Expression der Virulenzdeterminanten von Legionella pneumophila

Hacker, Jörg; Ott, Manfred; Ludwig, Birgit; Rdest, Ursula

doi:10.1007/bf01644033

Cited by 11 publications

(8 citation statements)

References 20 publications

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“…LEGIONELLA PilD AND TYPE II PROTEIN SECRETION 2093 been done by a number of investigators, human U937 cells served as the model for L. pneumophila intracellular infection of macrophages (25,31,42,51,58,65). Briefly, wells containing amoebae or U937 cells were infected with comparable numbers of CFU of wild-type and mutant strains, and at various time points the number of bacteria per monolayer was determined by plating (38).…”

Section: Vol 69 2001mentioning

confidence: 99%

Type II Protein Secretion Is a Subset of the PilD-Dependent Processes That Facilitate Intracellular Infection by Legionella pneumophila

2001

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Previously, we had demonstrated that a Legionella pneumophila prepilin peptidase (pilD) mutant does not produce type IV pili and shows reduced secretion of enzymatic activities. Moreover, it displays a distinct colony morphology and a dramatic reduction in intracellular growth within amoebae and macrophages, two phenotypes that are not exhibited by a pilin (pilE L ) mutant. To determine whether these pilD-dependent defects were linked to type II secretion, we have constructed two new mutants of L. pneumophila strain 130b. Mutations were introduced into either lspDE, which encodes the type II outer membrane secretin and ATPase, or lspFGHIJK, which encodes the pseudopilins. Unlike the wild-type and pilE L strains, both lspDE and lspG mutants showed reduced secretion of six pilD-dependent enzymatic activities; i.e., protease, acid phosphatase, p-nitrophenol phosphorylcholine hydrolase, lipase, phospholipase A, and lysophospholipase A. However, they exhibited a colony morphology different from that of the pilD mutant, suggesting that their surfaces are distinct. The pilD, lspDE, and lspG mutants were similarly and greatly impaired for growth within Hartmannella vermiformis, indicating that the intracellular defect of the peptidase mutant in amoebae is explained by the loss of type II secretion. When assessed for infection of U937 macrophages, both lsp mutants exhibited a 10-fold reduction in intracellular multiplication and a diminished cytopathic effect. Interestingly, the pilD mutant was clearly 100-fold more defective than the type II secretion mutants in U937 cells. These results suggest the existence of a novel pilD-dependent mechanism for promoting L. pneumophila intracellular infection of human cells.The gram-negative bacterium Legionella pneumophila is the agent of Legionnaires' disease, a potentially fatal pneumonia (14,66). In nature, the organism replicates within protozoan hosts and biofilms found in aquatic environments (8,16,24). Following inhalation of aerosolized droplets, L. pneumophila invades and multiplies within alveolar macrophages (1,57,60,64,66). Various factors that are associated with L. pneumophila infection of protozoa and macrophages have been reported. These include major outer membrane proteins (29, 37), Mip (18,27), flagella (49), type IV pili (58), a catalaseperoxidase (12), growth phase (17), iron acquisition (63), and the Dot-Icm putative type IV secretion apparatus (52,55,64).Our previous studies have shown that a prepilin peptidase gene, pilD, is essential for Legionella growth in amoebae and human macrophages (38, 39). Moreover, a pilD mutant is dramatically reduced in virulence, following intratracheal inoculation of guinea pigs (38). By virtue of their ability to process pilin and the so-called pseudopilins, prepilin peptidases are implicated both in the formation of type IV pili and in protein secretion (41,45,46,48,59). One set of pseudopilins is involved in the assembly of the pili, and another one is involved in the genesis of a functional type II protein secretion system....

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Section: Vol 69 2001mentioning

confidence: 99%

Type II Protein Secretion Is a Subset of the PilD-Dependent Processes That Facilitate Intracellular Infection by Legionella pneumophila

2001

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“…and other groups (20,22,46). It is immunodominant, displaying homology to the groEL family of heat shock proteins (23).…”

Section: Molecular Cloning Of Other Putative Virulence Factorsmentioning

confidence: 92%

“…The Mip Protein: A Legionella Virulence Factor with an Unusual Enzymarie Activity Several groups have reported about the construction of Legionella genomic libraries from patient isolates (17,20,21). Various L. pneumophila-specific proteins have been cloned in E. coli K-12.…”

mentioning

confidence: 99%

Analysis of Virulence Factors of Legionella pneumophila

Hacker¹,

Ott²,

Wintermeyer³

et al. 1993

Zentralblatt für Bakteriologie

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SummaryLegionella pneumophila, the causative agent of Legionnaires' disease is a facultative intracellular bacterium, which in the course of human infection multiplies in lung macrophages predominantly manifesting as pneumonia. The natural habitat of Legionella is found in sweet water reservoirs and man-made water systems. Virulent L. pneumophila spontaneously convert to an avirulent status at a high frequency. Genetic approaches have led to the identification of various L. pneumophila genes. The mip (macrophage infectivity potentiator) determinant remains at present the sole established virulence factor. The Mip protein exhibits activity of a peptidyl prolyl cis trans isomerase (PPiase), an enzyme which is able to bind the immunosuppressant FK506 and is involved in protein folding. The recently cloned major outer membrane protein (MOMP) could play a role in the uptake of legionellae by macrophages. Cellular models are useful in studying the intracellular replication of legionellae in eukaryotic cells. Human celllines and protozoan models are appropriate for this purpose. By using U 937 macrophage-like cells and Acanthamoeba castellanii as hosts, we could discriminate virulent and avirulent L. pneumophila variants since only the virulent strain was capable of intracellular growth at 37 oc. By using these systems we further demonstrated that a hemolytic factor cloned and characterized in our laboratory, legiolysin (lly), had no influence on the intracellular growth of L. pneumophila.

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“…Polarized epithelial monolayers grown on porous membranes retain brush border structures and have been used to study the penetration and intracellular survival of enteric pathogens such as Salmonella [ 141. In vitro studies with macrophages have been used to determine mechanisms by which infectious agents evade the immune response, e.g., how capsules enable microorganisms to resist phagocytosis [55], and how microorganisms evade phagocytic destruction if they are engulfed [23]. Rapid antigenic variation by viruses, bacteria, and protozoans is another means of evading the host's immune response.…”

Section: Basic Researchmentioning

confidence: 99%

Contributions of cell culture to the investigation and control of infectious diseases

Buehring

1996

Methods Cell Sci

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The investigation and control of infectious diseases has relied heavily on the science of cell culture. The propagation of many infectious agents is dependent on growth in cell culture and some of the most exciting research frontiers in microbiology involve the development of culture systems for fastidious organisms and agents of emerging diseases. Research on the pathogenesis and drug sensitivity of infectious agents has utilized many creative and rewarding in vitro cellular models. The contributions of cell cultures as factories for the manufacture of viral vaccines and as substrates for diagnostic tests have been profound. The review details the strategies and major accomplishments in each of these areas.

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Intrazelluläres Überleben und Expression der Virulenzdeterminanten von Legionella pneumophila

Cited by 11 publications

References 20 publications

Type II Protein Secretion Is a Subset of the PilD-Dependent Processes That Facilitate Intracellular Infection by Legionella pneumophila

Type II Protein Secretion Is a Subset of the PilD-Dependent Processes That Facilitate Intracellular Infection by Legionella pneumophila

Analysis of Virulence Factors of Legionella pneumophila

Contributions of cell culture to the investigation and control of infectious diseases

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