Francisella tularensis LVS evades killing by human neutrophils via inhibition of the respiratory burst and phagosome escape. 2006

Ramona L McCaffrey, and Lee-Ann H Allen
University of Iowa, 2501 Crosspark Rd., MTF-D154, Coralville, IA 52241, USA.

Francisella tularensis is a Gram-negative bacterium and the causative agent of tularemia. Recent data indicate that F. tularensis replicates inside macrophages, but its fate in other cell types, including human neutrophils, is unclear. We now show that F. tularensis live vaccine strain (LVS), opsonized with normal human serum, was rapidly ingested by neutrophils but was not eliminated. Moreover, evasion of intracellular killing can be explained, in part, by disruption of the respiratory burst. As judged by luminol-enhanced chemiluminescence and nitroblue tetrazolium staining, neutrophils infected with live F. tularensis did not generate reactive oxygen species. Confocal microscopy demonstrated that NADPH oxidase assembly was disrupted, and LVS phagosomes did not acquire gp91/p22(phox) or p47/p67(phox). At the same time, F. tularensis also impaired neutrophil activation by heterologous stimuli such as phorbol esters and opsonized zymosan particles. Later in infection, LVS escaped the phagosome, and live organisms persisted in the neutrophil cytosol for at least 12 h. To our knowledge, our data are the first demonstration of a facultative intracellular pathogen, which disrupts the oxidative burst and escapes the phagosome to evade elimination inside neutrophils, and as such, our data define a novel mechanism of virulence.

UI MeSH Term Description Entries
D008264 Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.) Bone Marrow-Derived Macrophages,Monocyte-Derived Macrophages,Macrophage,Macrophages, Monocyte-Derived,Bone Marrow Derived Macrophages,Bone Marrow-Derived Macrophage,Macrophage, Bone Marrow-Derived,Macrophage, Monocyte-Derived,Macrophages, Bone Marrow-Derived,Macrophages, Monocyte Derived,Monocyte Derived Macrophages,Monocyte-Derived Macrophage
D009504 Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. LE Cells,Leukocytes, Polymorphonuclear,Polymorphonuclear Leukocytes,Polymorphonuclear Neutrophils,Neutrophil Band Cells,Band Cell, Neutrophil,Cell, LE,LE Cell,Leukocyte, Polymorphonuclear,Neutrophil,Neutrophil Band Cell,Neutrophil, Polymorphonuclear,Polymorphonuclear Leukocyte,Polymorphonuclear Neutrophil
D010588 Phagosomes Membrane-bound cytoplasmic vesicles formed by invagination of phagocytized material. They fuse with lysosomes to form phagolysosomes in which the hydrolytic enzymes of the lysosome digest the phagocytized material. Phagolysosomes,Phagolysosome,Phagosome
D005604 Francisella tularensis The etiologic agent of TULAREMIA in man and other warm-blooded animals. Bacterium tularense,Brucella tularensis,Francisella tularense,Pasteurella tularensis
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001428 Bacterial Vaccines Suspensions of attenuated or killed bacteria administered for the prevention or treatment of infectious bacterial disease. Bacterial Vaccine,Bacterin,Vaccine, Bacterial,Vaccines, Bacterial
D014406 Tularemia A plague-like disease of rodents, transmissible to man. It is caused by FRANCISELLA TULARENSIS and is characterized by fever, chills, headache, backache, and weakness. Francisella tularensis Infection,Francisella tularensis Infections,Infection, Francisella tularensis,Tularemias
D014613 Vaccines, Attenuated Live vaccines prepared from microorganisms which have undergone physical adaptation (e.g., by radiation or temperature conditioning) or serial passage in laboratory animal hosts or infected tissue/cell cultures, in order to produce avirulent mutant strains capable of inducing protective immunity. Attenuated Vaccine,Vaccines, Live, Attenuated,Attenuated Vaccines,Vaccine, Attenuated
D016897 Respiratory Burst A large increase in oxygen uptake by neutrophils and most types of tissue macrophages through activation of an NADPH-cytochrome b-dependent oxidase that reduces oxygen to a superoxide. Individuals with an inherited defect in which the oxidase that reduces oxygen to superoxide is decreased or absent (GRANULOMATOUS DISEASE, CHRONIC) often die as a result of recurrent bacterial infections. Oxidative Burst,Burst, Oxidative,Burst, Respiratory,Bursts, Oxidative,Bursts, Respiratory,Oxidative Bursts,Respiratory Bursts
D018375 Neutrophil Activation The process in which the neutrophil is stimulated by diverse substances, resulting in degranulation and/or generation of reactive oxygen products, and culminating in the destruction of invading pathogens. The stimulatory substances, including opsonized particles, immune complexes, and chemotactic factors, bind to specific cell-surface receptors on the neutrophil. Activation, Neutrophil,Activations, Neutrophil,Neutrophil Activations

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