Legionnaires’ Disease

Cianciotto, Nicholas P.; Hilbi, Hubert; Buchrieser, Carmen

doi:10.1007/978-3-642-30144-5_94

Cited by 16 publications

(14 citation statements)

References 991 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…egionella pneumophila is widespread in natural and man-made water systems and is best known as the etiologic agent of Legionnaires' disease (1)(2)(3). Recently, the incidence of pneumonias caused by Gram-negative L. pneumophila has roughly tripled in the United States and elsewhere (4)(5)(6).…”

mentioning

confidence: 99%

Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms

White

Cianciotto

2016

Infect Immun

Self Cite

View full text Add to dashboard Cite

Previously, we documented that type II secretion (T2S) promotes intracellular infection of macrophages by Legionella pneumophila. In the present study, we identified infection events that are modulated by T2S by comparing the behaviors of wild-type and T2S mutant bacteria in murine bone marrow-derived macrophages and human U937 cells. Although the two strains behaved similarly for entry into the host cells and evasion of lysosomal fusion, the mutant was impaired in the ability to initiate replication between 4 and 8 h postentry and to grow to large numbers in the Legionella-containing vacuole (LCV), as evident at 12 h. At 4 h postinoculation, mutant LCVs had a significantly reduced association with Rab1B, a host GTPase that facilitates the tethering of endoplasmic reticulum (ER)-derived vesicles to LCVs. The mutant did not lose expression or translocation of six type IV secretion effectors (e.g., SidM) that are well known for mediating Rab1B association with the LCV, indicating that T2S promotes the interaction between the LCV and Rab1B via a novel mechanism. Interestingly, the mutant's growth defect was exacerbated in macrophages that had been depleted of Rab1B by short hairpin RNA (shRNA) treatment, indicating that T2S also potentiates events beyond Rab1B association. In support of this, a sidM lspF double mutant had an intracellular growth defect that was more dramatic than that of the lspF mutant (and a sidM mutant) and showed a growth difference of as much as a 400-fold compared to the wild type. Together, these data reveal a new role for T2S in intracellular infection that involves both Rab1B-dependent and Rab1B-independent processes. L egionella pneumophila is widespread in natural and man-made water systems and is best known as the etiologic agent of Legionnaires' disease (1-3). Recently, the incidence of pneumonias caused by Gram-negative L. pneumophila has roughly tripled in the United States and elsewhere (4-6). In water, L. pneumophila grows primarily as an intracellular parasite of amoebae (7-11). Human infection occurs mainly by the inhalation of contaminated water droplets originating from a wide range of aerosolgenerating devices (12,13). Yet the first case of person-to-person spread was reported in 2016 (14). In the lungs, L. pneumophila invades and grows in the resident macrophage population and ultimately triggers severe inflammation (3). In both amoebae and macrophages, the bacterium evades the host's degradative lysosomal pathway and replicates to large numbers within a membrane-bound vacuole, the Legionella-containing vacuole (LCV) (15, 16). The Dot/Icm type IV secretion (T4S) system of L. pneumophila plays a major role in pathogenesis (17-19). Indeed, the Dot/Icm apparatus translocates myriad proteins across the LCV membrane and into the host cell cytoplasm, and then the delivered effectors proceed to modulate a wide variety of host processes. One of the earliest and most notable events that has been ascribed to the Dot/Icm system is the recruitment of host GTPases and endoplasmic reticulu...

show abstract

mentioning

confidence: 99%

Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms

White

Cianciotto

2016

Infect Immun

Self Cite

View full text Add to dashboard Cite

show abstract

“…egionella pneumophila is a Gram-negative, aquatic bacterium and the agent of a Legionnaires' disease pneumonia (1). The number of reported cases of Legionnaires' disease in the United States has more than tripled since 2001, with similar trends occurring in Canada and Europe (2).…”

mentioning

confidence: 99%

Nuclease Activity of Legionella pneumophila Cas2 Promotes Intracellular Infection of Amoebal Host Cells

et al. 2015

Self Cite

View full text Add to dashboard Cite

Legionella pneumophila, the primary agent of Legionnaires' disease, flourishes in both natural and man-made environments by growing in a wide variety of aquatic amoebae. Recently, we determined that the Cas2 protein of L. pneumophila promotes intracellular infection of Acanthamoeba castellanii and Hartmannella vermiformis, the two amoebae most commonly linked to cases of disease. The Cas2 family of proteins is best known for its role in the bacterial and archeal clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein (Cas) system that constitutes a form of adaptive immunity against phage and plasmid. However, the infection event mediated by L. pneumophila Cas2 appeared to be distinct from this function, because cas2 mutants exhibited infectivity defects in the absence of added phage or plasmid and since mutants lacking the CRISPR array or any one of the other cas genes were not impaired in infection ability. We now report that the Cas2 protein of L. pneumophila has both RNase and DNase activities, with the RNase activity being more pronounced. By characterizing a catalytically deficient version of Cas2, we determined that nuclease activity is critical for promoting infection of amoebae. Also, introduction of Cas2, but not its catalytic mutant form, into a strain of L. pneumophila that naturally lacks a CRISPR-Cas locus caused that strain to be 40-to 80-fold more infective for amoebae, unequivocally demonstrating that Cas2 facilitates the infection process independently of any other component encoded within the CRISPR-Cas locus. Finally, a cas2 mutant was impaired for infection of Willaertia magna but not Naegleria lovaniensis, suggesting that Cas2 promotes infection of most but not all amoebal hosts. L egionella pneumophila is a Gram-negative, aquatic bacterium and the agent of a Legionnaires' disease pneumonia (1). The number of reported cases of Legionnaires' disease in the United States has more than tripled since 2001, with similar trends occurring in Canada and Europe (2). Humans acquire L. pneumophila mainly by inhaling contaminated water droplets from aerosolgenerating devices (3). In the lung, the bacterium infects resident macrophages (4). Amoebae are the major replicative niche for L. pneumophila in natural and man-made water systems (5-7). Indeed, L. pneumophila infects Ն20 species of amoebae encompassing the genera Acanthamoeba, Echinamoeba, Hartmannella, Naegleria, Vahlkampfia, and Willaertia (8). L. pneumophila bacteria in amoebae remain viable for long periods of time and are resistant to biocides (9, 10), and internalization by amoebae resuscitates viable-but-not-culturable legionellae (11,12). Also, amoebae may be part of the inoculum that initiates lung infection (3,13,14). Recently, we found that the Cas2 protein of L. pneumophila promotes infection of Acanthamoeba castellanii and Hartmannella vermiformis; i.e., although cas2 mutants grow normally in broth and macrophages, they exhibit a 1,000-fold reduced recovery from A. castellanii and a 20-fold defect i...

show abstract

“…he Gram-negative bacterium Legionella pneumophila is both an inhabitant of natural and man-made water systems and the primary etiologic agent of Legionnaires' disease, an increasingly common and serious form of pneumonia (1)(2)(3). In its aquatic habitats, L. pneumophila survives in biofilms and as an intracellular parasite of amoebae, and in the lung, it grows primarily in macrophages (4)(5)(6)(7).…”

mentioning

confidence: 99%

The Legionella pneumophila Siderophore Legiobactin Is a Polycarboxylate That Is Identical in Structure to Rhizoferrin

Burnside

Shafaie

et al. 2015

Infect Immun

Self Cite

View full text Add to dashboard Cite

bLegionella pneumophila, the agent of Legionnaires' disease, secretes a siderophore (legiobactin) that promotes bacterial infection of the lung. In past work, we determined that cytoplasmic LbtA (from Legiobactin gene A) promotes synthesis of legiobactin, inner membrane LbtB aids in export of the siderophore, and outer membrane LbtU and inner membrane LbtC help mediate ferrilegiobactin uptake and assimilation. However, the past studies examined legiobactin contained within bacterial culture supernatants. By utilizing high-pressure liquid chromatography that incorporates hydrophilic interaction-based chemistry, we have now purified legiobactin from supernatants of virulent strain 130b that is suitable for detailed chemical analysis. High-resolution mass spectrometry (MS) revealed that the molecular mass of (protonated) legiobactin is 437.140 Da. On the basis of the results obtained from both MS analysis and various forms of nuclear magnetic resonance, we found that legiobactin is composed of two citric acid residues linked by a putrescine bridge and thus is identical in structure to rhizoferrin, a polycarboxylate-type siderophore made by many fungi and several unrelated bacteria. Both purified legiobactin and rhizoferrin obtained from the fungus Cunninghamella elegans were able to promote Fe 3؉ uptake by wild-type L. pneumophila as well as enhance growth of iron-starved bacteria. These results did not occur with 130b mutants lacking lbtU or lbtC, indicating that both endogenously made legiobactin and exogenously derived rhizoferrin are assimilated by L. pneumophila in an LbtU-and LbtC-dependent manner.T he Gram-negative bacterium Legionella pneumophila is both an inhabitant of natural and man-made water systems and the primary etiologic agent of Legionnaires' disease, an increasingly common and serious form of pneumonia (1-3). In its aquatic habitats, L. pneumophila survives in biofilms and as an intracellular parasite of amoebae, and in the lung, it grows primarily in macrophages (4-7). Iron has long been recognized as a major aspect of L. pneumophila replication, intracellular infection, and virulence (8, 9). For ferrous iron assimilation, L. pneumophila utilizes a secreted pyomelanin that has ferric reductase activity and the inner membrane Fe 2ϩ transporter FeoB (10, 11). For ferric iron uptake, the bacterium uses the siderophore legiobactin (12, 13). Both of these iron acquisition pathways are required for infection of the lungs by L. pneumophila (10,14).The investigation of legiobactin has followed a rather circuitous path. Indeed, it was originally thought that L. pneumophila does not produce siderophores; this conclusion was based on negative data obtained from both the Arnow and Csáky assays, which detect catecholate and hydroxymate structures, respectively, and the Chrome Azurol S (CAS) assay, which detects iron chelators independently of their structure (15-17). However, in 2000, we demonstrated that L. pneumophila strains can secrete a siderophore activity that is detected by the CAS assay when the ba...

show abstract

Legionnaires’ Disease

Cited by 16 publications

References 991 publications

Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms

Type II Secretion Is Necessary for Optimal Association of the Legionella-Containing Vacuole with Macrophage Rab1B but Enhances Intracellular Replication Mainly by Rab1B-Independent Mechanisms

Nuclease Activity of Legionella pneumophila Cas2 Promotes Intracellular Infection of Amoebal Host Cells

The Legionella pneumophila Siderophore Legiobactin Is a Polycarboxylate That Is Identical in Structure to Rhizoferrin

Contact Info

Product

Resources

About