title: Effect of Bacillus anthracis lethal toxin on human peripheral blood mononuclear cells.
abstract: Lethal toxin (LeTx) plays a central role in anthrax pathogenesis, however a cytotoxicity of LeTx has been difficult to demonstrate in vitro. No cytolytic effect has been reported for human cells, in contrast to murine cell lines, indicating that cell lysis can not be considered as a marker of LeTx activity. We have recently shown that murine macrophage-like RAW 264.7 cells treated with LeTx or infected with anthrax spores underwent changes typical of apoptotic death. Here we demonstrate that cells from human peripheral blood display a proapoptotic behavior similar to murine cells. TUNEL assay detected a nucleosomal degradation typical of apoptosis in peripheral blood mononuclear cells (PBMC) treated with LeTx. Membrane staining with apoptotic dyes was detected in macrophages derived from monocytes in presence of LeTx. The toxin inhibited production of proinflammatory cytokines in PBMC stimulated with a preparation of Bacillus anthracis cell wall. Infection of PBMC with anthrax spores led to the appearance of a large population of cells stained positively for apoptosis, with a reduced capacity to eliminate spores and vegetative bacteria. The aminopeptidase inhibitor, bestatin, capable of protecting cells from LeTx, restored a bactericidal activity of infected cells. These findings may be explained by LeTx expression within phagocytes and support an important role of LeTx as an early intracellular virulence factor contributing to bacterial dissemination and disease progression.
authors.affiliation: Advanced Biosystems, Inc., 10900 University Blvd., MSN 1A8, Manassas, VA 20110, USA. seruei.popov@hadron.com
authors.forename: Serguei G
authors.initials: SG
authors.lastname: Popov
authors.forename: Rafael
authors.initials: R
authors.lastname: Villasmil
authors.forename: Jessica
authors.initials: J
authors.lastname: Bernardi
authors.forename: Edith
authors.initials: E
authors.lastname: Grene
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cardwell
authors.forename: Taissia
authors.initials: T
authors.lastname: Popova
authors.forename: Aiguo
authors.initials: A
authors.lastname: Wu
authors.forename: Darya
authors.initials: D
authors.lastname: Alibek
authors.forename: Charles
authors.initials: C
authors.lastname: Bailey
authors.forename: Ken
authors.initials: K
authors.lastname: Alibek
mesh_terms: D000881:Anthrax / Q000097:blood / Q000276:immunology / Q000382:microbiology; D000942:Antigens, Bacterial; D017209:Apoptosis / Q000187:drug effects; D001408:Bacillus anthracis; D001427:Bacterial Toxins / Q000494:pharmacology* / Q000633:toxicity*; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000382:microbiology* / Q000473:pathology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D013171:Spores, Bacterial; D019311:Staurosporine
chemical_list: D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D016207:Cytokines; D007155:Immunologic Factors; C030325:anthrax toxin; D007930:Leucine; D019311:Staurosporine; C012211:ubenimex