scholarly journals Population analysis of Legionella pneumophila reveals a basis for resistance to complement-mediated killing

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bryan A. Wee ◽  
Joana Alves ◽  
Diane S. J. Lindsay ◽  
Ann-Brit Klatt ◽  
Fiona A. Sargison ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Population Analysis ◽  
Single Gene ◽  
Human Neutrophils ◽  
Classical Pathway ◽  
Genetic Traits ◽  
Bacterial Surface ◽  
Genomic Study ◽  
Legionnaires Disease ◽  
Severe Respiratory Infection

AbstractLegionella pneumophila is the most common cause of the severe respiratory infection known as Legionnaires’ disease. However, the microorganism is typically a symbiont of free-living amoeba, and our understanding of the bacterial factors that determine human pathogenicity is limited. Here we carried out a population genomic study of 902 L. pneumophila isolates from human clinical and environmental samples to examine their genetic diversity, global distribution and the basis for human pathogenicity. We find that the capacity for human disease is representative of the breadth of species diversity although some clones are more commonly associated with clinical infections. We identified a single gene (lag-1) to be most strongly associated with clinical isolates. lag-1, which encodes an O-acetyltransferase for lipopolysaccharide modification, has been distributed horizontally across all major phylogenetic clades of L. pneumophila by frequent recent recombination events. The gene confers resistance to complement-mediated killing in human serum by inhibiting deposition of classical pathway molecules on the bacterial surface. Furthermore, acquisition of lag-1 inhibits complement-dependent phagocytosis by human neutrophils, and promoted survival in a mouse model of pulmonary legionellosis. Thus, our results reveal L. pneumophila genetic traits linked to disease and provide a molecular basis for resistance to complement-mediated killing.

scholarly journals Population analysis of Legionella pneumophila reveals the basis of resistance to complement-mediated killing

2020 ◽  
Author(s):  
Bryan A. Wee ◽  
Joana Alves ◽  
Diane S. J. Lindsay ◽  
Ross L. Cameron ◽  
Amy Pickering ◽  
...  
Keyword(s):  
Functional Analysis ◽  
Human Serum ◽  
Legionella Pneumophila ◽  
Human Disease ◽  
Population Analysis ◽  
Single Gene ◽  
Clinical Isolates ◽  
Classical Pathway ◽  
Evolutionary Analysis ◽  
Legionnaires Disease

AbstractLegionella pneumophila is the most common cause of the severe respiratory infection known as Legionnaires’ disease. L. pneumophila is typically a symbiont of free-living amoeba, and our understanding of the bacterial factors that determine human pathogenicity is limited. Here we carried out a population genomic study of 900 L. pneumophila isolates from human clinical and environmental samples to examine their genetic diversity, global distribution and the basis for human pathogenicity. We found that although some clones are more commonly associated with clinical infections, the capacity for human disease is representative of the breadth of species diversity. To investigate the bacterial genetic basis for human disease potential, we carried out a genome-wide association study that identified a single gene (lag-1), to be most strongly associated with clinical isolates. Molecular evolutionary analysis showed that lag-1, which encodes an O-acetyltransferase responsible for lipopolysaccharide modification, has been distributed horizontally across all major phylogenetic clades of L. pneumophila by frequent recent recombination events. Functional analysis revealed a correlation between the presence of a functional lag-1 gene and resistance to killing in human serum and bovine broncho-alveolar lavage. In addition, L. pneumophila strains that express lag-1 escaped complement-mediated phagocytosis by neutrophils. Importantly, we discovered that the expression of lag-1 confers the capacity to evade complement-mediated killing by inhibiting deposition of classical pathway molecules on the bacterial surface. In summary, our combined population and functional analyses identified L. pneumophila genetic traits linked to human disease and revealed the molecular basis for resistance to complement-mediated killing, a previously elusive trait of direct relevance to human disease pathogenicity.SignificanceLegionella pneumophila is an environmental bacterium associated with a severe pneumonia known as Legionnaires’ disease. A small number of L. pneumophila clones are responsible for a large proportion of human infections suggesting they have enhanced pathogenicity. Here, we employed a large-scale population analysis to investigate the evolution of human pathogenicity and identified a single gene (lag-1) that was more frequently found in clinical isolates. Functional analysis revealed that the lag-1-encoded O-acetyltransferase, involved in modification of lipopolysaccharide, conferred resistance to the classical pathway of complement in human serum. These findings solve a long-standing mystery in the field regarding L. pneumophila resistance to serum killing, revealing a novel mechanism by which L. pneumophila may avoid immune defences during infection.

scholarly journals Surface-Associated Heat Shock Proteins ofLegionella pneumophilaandHelicobacter pylori:Roles in Pathogenesis and Immunity

1999 ◽  
Vol 7 (1-2) ◽  
pp. 58-63 ◽  
Author(s):  
P. S. Hoffman ◽  
R. A. Garduno
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Legionella Pneumophila ◽  
Cell Model ◽  
Bacterial Surface ◽  
Acid Shock ◽  
Mucosal Infection ◽  
Microbial Infections ◽  
Legionnaires Disease ◽  
Shock Proteins

Bacterial heat shock proteins (Hsps) are abundantly produced during the course of most microbial infections and are often targeted by the mammalian immune response. While Hsps have been well characterized for their roles in protein folding and secretion activities, little attention has been given to their participation in pathogenesis. In the case ofLegionella pneumophila, an aquatic intracellular parasite of protozoa and cause of Legionnaires' disease, Hsp60 is uniquely located in the periplasm and on the bacterial surface. Surface-associated Hsp60 promotes attachment and invasion in a HeLa cell model and may alter an early step associated with the fusion of phagosomes with lysosomes. Avirulent strains ofL. pneumophilacontaining defined mutations in severaldot/icmgenes are defective in localizing Hsp60 onto their surface and are reduced approximately 1000-fold in their invasiveness towards HeLa cells. For the ulcer-causing bacteriumHelicobacter pylori, surfaceassociated Hsp60 and Hsp70 mediate attachment to gastric epithelial cells. The increased expression of these Hsps following acid shock correlates with both increased association with and inflammation of the gastric mucosa. A role for Hsps in colonization, mucosal infection and in promoting inflammation is discussed. Infect. Dis. Obstet. Gynecol. 7:58–63, 1999.

scholarly journals NAD(H)-mediated tetramerization controls the activity of Legionella pneumophila phospholipase PlaB

2020 ◽  
Author(s):  
Maurice Diwo ◽  
Wiebke Michel ◽  
Philipp Aurass ◽  
Katja Kuhle-Keindorf ◽  
Jan Pippel ◽  
...  
Keyword(s):  
Virulence Factor ◽  
Legionella Pneumophila ◽  
Enzyme Activation ◽  
Enzyme Inactivation ◽  
Activation Mechanism ◽  
Tissue Destruction ◽  
Bacterial Surface ◽  
Lung Colonization ◽  
Legionnaires Disease ◽  
Tetrameric Form

AbstractThe virulence factor and phospholipase PlaB promotes lung colonization, tissue destruction, and intracellular replication of Legionella pneumophila, the causative agent of Legionnaires’ disease. It is exposed at the bacterial surface and shows an extraordinary activation mechanism by tetramer deoligomerization. To unravel the molecular basis for enzyme activation and localization, we determined the crystal structure of PlaB in its tetrameric form. We found that the tetramer is a dimer of identical dimers, and a monomer consists of an N-terminal phospholipase α/β-hydrolase domain augmented by two non-canonical two-stranded β-sheets, β6/β7 and β9/β10. The C- terminal domain reveals a novel fold displaying a bilobed β-sandwich with a hook structure that is required for dimer formation and complementation of the phospholipase domain in the neighboring monomer. Unexpectedly, we observed eight NAD(H) molecules at the dimer/dimer interface, suggesting that these molecules stabilize the tetramer and hence lead to enzyme inactivation. Indeed, addition of NAD(H) increased the fraction of the tetrameric form and concomitantly reduced activity. β9/β10 mutants revealed a decrease in the tetrameric fraction, altered activity profiles, and mislocalization. Protein variants lacking the hook or strands β6/β7 were unaffected in terms of localization but lost their activity, and lid mutants changed substrate specificity. Together, these data reveal structural elements and an unprecedented NAD(H)- mediated tetramerization mechanism required for spatial and enzymatic control of a phospholipase virulence factor. The regulatory process identified is ideally suited to fine tune PlaB in a way that protects L. pneumophila from self-inflicted lysis while ensuring its activity at the pathogen–host interface.

scholarly journals Structure and functional analysis of theLegionellachitinase ChiA reveals a novel mechanism of metal-dependent mucin degradation

2019 ◽  
Author(s):  
Katherine H. Richardson ◽  
Lubov S. Grigoryeva ◽  
Paula Corsini ◽  
Richard C. White ◽  
Rosie Shaw ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Vaccine Development ◽  
Dual Function ◽  
Peptidase Activity ◽  
Chain Polymer ◽  
Bacterial Surface ◽  
Carbon And Nitrogen ◽  
Promising Target ◽  
Legionnaires Disease ◽  
Insight Into

AbstractChitinases are important enzymes that contribute to the generation of carbon and nitrogen from chitin, a long chain polymer of N-acetylglucosamine that is abundant in insects, fungi, invertebrates and fish. Although mammals do not produce chitin, chitinases have been identified in bacteria that are key virulence factors in severe respiratory, gastrointestinal and urinary diseases. However, it is unclear how these enzymes are able to carry out this dual function.Legionella pneumophilais the causative agent of Legionnaires’ disease, an often-fatal pneumonia and its chitinase ChiA is essential for the survival ofL. pneumophilain the lung. Here we report the first atomic resolution insight into the pathogenic mechanism of a bacterial chitinase. We derive an experimental model of intact ChiA and show how its N-terminal region targets ChiA to the bacterial surface after its secretion. We provide the first evidence thatL. pneumophilacan bind mucins on its surface but this is not dependent onchiA. This demonstrates that additional peripheral mucin binding proteins are also expressed inL. pneumophila. Finally, we show that the ChiA C-terminal chitinase domain has novel metal-dependent peptidase activity against mammalian mucins. These findings suggest that ChiA facilitates bacterial penetration of the alveolar mucosa and ChiA may be a promising target for vaccine development.

Heated birthing pools as a source of Legionnaires' disease

2015 ◽  
Vol 144 (4) ◽  
pp. 796-802 ◽  
Author(s):  
S. L. COLLINS ◽  
B. AFSHAR ◽  
J. T. WALKER ◽  
H. AIRD ◽  
F. NAIK ◽  
...  
Keyword(s):  
Public Health ◽  
Legionella Pneumophila ◽  
Opportunistic Infections ◽  
Quantitative Polymerase Chain Reaction ◽  
Opportunistic Pathogens ◽  
Health Authorities ◽  
Safety Alert ◽  
Public Health Authorities ◽  
Legionnaires Disease ◽  
Severe Respiratory Infection

SUMMARYIn June 2014 Public Health England confirmed a case of Legionnaires' disease (LD) in a neonate following birth at home in a hired birthing pool incorporating a heater and a recirculation pump which had been filled in advance of labour. The case triggered a public health investigation and a microbiological survey of an additional ten heated birthing pools hired or recently hired to the general public across England. The birthing pool used by the parent of the confirmed case was identified as the source of the neonate's infection following detection of Legionella pneumophila ST48 in both patient and environmental samples. Legionella species were detected by quantitative polymerase chain reaction but not culture in a further three pools together with other opportunistic pathogens identified by culture and matrix-assisted laser desorption ionization–time of flight (MALDI–ToF) mass spectrometry. A Patient Safety Alert from NHS England and Public Health England was issued stating that heated birthing pools filled in advance of labour should not be used for home births. This recommendation remains in place. This investigation in conjunction with other recent reports has highlighted a lack of awareness regarding the microbiological safety of heated birthing pools and their potential to be a source of LD and other opportunistic infections. Furthermore, the investigation raised important considerations with regards to microbiological sampling and testing in such incidents. Public health authorities and clinicians should consider LD in the differential diagnosis of severe respiratory infection in neonates within 14 days of a water birth.

scholarly journals Efficacy of SCH27899 in an Animal Model of Legionnaires' Disease Using Immunocompromised A/J Mice

2000 ◽  
Vol 44 (5) ◽  
pp. 1333-1336 ◽  
Author(s):  
Joan K. Brieland ◽  
David Loebenberg ◽  
Fred Menzel ◽  
Roberta S. Hare
Keyword(s):  
Animal Model ◽  
Murine Model ◽  
Legionella Pneumophila ◽  
Immunocompromised Host ◽  
Lung Infection ◽  
Cortisone Acetate ◽  
Contrast Administration ◽  
Once Daily ◽  
Legionnaires Disease ◽  
Lung Infections

ABSTRACT The efficacy of SCH27899, a new everninomicin antibiotic, against replicative Legionella pneumophila lung infections in an immunocompromised host was evaluated using a murine model of Legionnaires' disease. A/J mice were immunocompromised with cortisone acetate and inoculated intratracheally with L. pneumophilaserogroup 1 (105 CFU per mouse). At 24 h postinoculation, mice were administered either SCH27899 (6 to 60 mg/kg [MPK] intravenously) or a placebo once daily for 5 days, and mortality and intrapulmonary growth of L. pneumophila were assessed. In the absence of SCH27899, there was 100% mortality inL. pneumophila-infected mice, with exponential intrapulmonary growth of the bacteria. In contrast, administration of SCH27899 at a dose of ≥30 MPK resulted in ≥90% survival of infected mice, which was associated with inhibition of intrapulmonary growth ofL. pneumophila. In subsequent studies, the efficacy of SCH27899 was compared to ofloxacin (OFX) and azithromycin (AZI). Administration of SCH27899, OFX, or AZI at a dose of ≥30 MPK once daily for 5 days resulted in ≥85% survival of infected mice and inhibition of intrapulmonary growth of the bacteria. However, L. pneumophila CFU were recovered in lung homogenates following cessation of therapy with all three antibiotics. These studies demonstrate that SCH27899 effectively prevents fatal replicativeL. pneumophila lung infection in immunocompromised A/J mice by inhibition of intrapulmonary growth of the bacteria. However, in this murine model of pulmonary legionellosis, SCH27899, like OFX and AZI, was bacteriostatic.

Subtyping ofLegionella pneumophilaisolates by arbitrarily primed polymerase chain reaction

1995 ◽  
Vol 41 (9) ◽  
pp. 846-848 ◽  
Author(s):  
E. Ledesma ◽  
J. Llorca ◽  
M. A. Dasí ◽  
M. L. Camaró ◽  
E. Carbonell ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Legionella Pneumophila ◽  
Water Sources ◽  
Chain Reaction ◽  
Single Room ◽  
Legionnaires Disease ◽  
Polymerase Chain ◽  
Resort Hotel ◽  
Different Water Sources

Arbitrarily primed polymerase chain reaction (AP-PCR) was used to differentiate strains of Legionella pneumophila isolated from different water sources in a resort hotel in Benidorm, Alicante, Spain, where an outbreak of Legionnaires' disease occurred among a group of tourists between 65 and 80 years of age. All isolates were L. pneumophila serogroup 1, subtype Pontiac (Knoxville 1). Five different patterns (P1 to P5) were obtained by AP-PCR. The number of bands per pattern varied between 4 and 11. Patterns P1 and P2 represented 60 and 20% of L. pneumophila isolates, respectively. Since different subpopulations of L. pneumophila coexisted (up to three different AP-PCR patterns were identified in a single room), it was not possible to link an individual L. pneumophila strain to the occurrence of this outbreak.Key words: Legionella pneumophila, AP-PCR, subtyping, outbreak.

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 Salmonella typhimurium attachment to human intestinal epithelial monolayers: transcellular signalling to subepithelial neutrophils.

1993 ◽  
Vol 123 (4) ◽  
pp. 895-907 ◽  
Author(s):  
B A McCormick ◽  
S P Colgan ◽  
C Delp-Archer ◽  
S I Miller ◽  
J L Madara
Keyword(s):  
Epithelial Cells ◽  
Salmonella Typhimurium ◽  
Apical Membrane ◽  
Coli Strain ◽  
Formyl Peptide Receptor ◽  
Human Neutrophils ◽  
Classical Pathway ◽  
Intestinal Epithelial ◽  
Formyl Peptide

In human intestinal disease induced by Salmonella typhimurium, transepithelial migration of neutrophils (PMN) rapidly follows attachment of the bacteria to the epithelial apical membrane. In this report, we model those interactions in vitro, using polarized monolayers of the human intestinal epithelial cell, T84, isolated human PMN, and S. typhimurium. We show that Salmonella attachment to T84 cell apical membranes did not alter monolayer integrity as assessed by transepithelial resistance and measurements of ion transport. However, when human neutrophils were subsequently placed on the basolateral surface of monolayers apically colonized by Salmonella, physiologically directed transepithelial PMN migration ensued. In contrast, attachment of a non-pathogenic Escherichia coli strain to the apical membrane of epithelial cells at comparable densities failed to stimulate a directed PMN transepithelial migration. Use of the n-formyl-peptide receptor antagonist N-t-BOC-1-methionyl-1-leucyl-1- phenylalanine (tBOC-MLP) indicated that the Salmonella-induced PMN transepithelial migration response was not attributable to the classical pathway by which bacteria induce directed migration of PMN. Moreover, the PMN transmigration response required Salmonella adhesion to the epithelial apical membrane and subsequent reciprocal protein synthesis in both bacteria and epithelial cells. Among the events stimulated by this interaction was the epithelial synthesis and polarized release of the potent PMN chemotactic peptide interleukin-8 (IL-8). However, IL-8 neutralization, transfer, and induction experiments indicated that this cytokine was not responsible for the elicited PMN transmigration. These data indicate that a novel transcellular pathway exists in which subepithelial PMN respond to lumenal pathogens across a functionally intact epithelium. Based on the known unique characteristics of the intestinal mucosa, we speculate that IL-8 may act in concert with an as yet unidentified transcellular chemotactic factor(s) (TCF) which directs PMN migration across the intestinal epithelium.

How the parasitic bacterium Legionella pneumophila modifies its phagosome and transforms it into rough ER: implications for conversion of plasma membrane to the ER membrane

2001 ◽  
Vol 114 (24) ◽  
pp. 4637-4650 ◽  
Author(s):  
Lewis G. Tilney ◽  
Omar S. Harb ◽  
Patricia S. Connelly ◽  
Camenzind G. Robinson ◽  
Craig R. Roy
Keyword(s):  
Legionella Pneumophila ◽  
Mitochondrial Membranes ◽  
Macrophage Infection ◽  
Thin Sections ◽  
Stage Process ◽  
Legionnaires Disease ◽  
Rough Er ◽  
Membrane Changes ◽  
Phagosomal Membrane

Within five minutes of macrophage infection by Legionella pneumophila, the bacterium responsible for Legionnaires’ disease, elements of the rough endoplasmic reticulum (RER) and mitochondria attach to the surface of the bacteria-enclosed phagosome. Connecting these abutting membranes are tiny hairs, which are frequently periodic like the rungs of a ladder. These connections are stable and of high affinity - phagosomes from infected macrophages remain connected to the ER and mitochondria (as they were in situ) even after infected macrophages are homogenized. Thin sections through the plasma and phagosomal membranes show that the phagosomal membrane is thicker (72±2 Å) than the ER and mitochondrial membranes (60±2 Å), presumably owing to the lack of cholesterol, sphingolipids and glycolipids in the ER. Interestingly, within 15 minutes of infection, the phagosomal membrane changes thickness to resemble that of the attached ER vesicles. Only later (e.g. after six hours) does the ER-phagosome association become less frequent. Instead ribosomes stud the former phagosomal membrane and L. pneumophila reside directly in the rough ER. Examination of phagosomes of various L. pneumophila mutants suggests that this membrane conversion is a four-stage process used by L. pneumophila to establish itself in the RER and to survive intracellularly. But what is particularly interesting is that L. pneumophila is exploiting a poorly characterized naturally occuring cellular process.

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