Abstract

Shigellae are the etiological agents of bacillary dysentery, a severe form of diarrhea that is often fatal in infants. Shigellosis is an acute inflammatory disease. Here we propose to investigate the role of apoptosis in the initiation of inflammation. We have demonstrated that Shigella induces apoptosis in macrophages in vitro and in vivo. Shigella first invades cells and then escapes from the phagocytic vacuole into the cytoplasm. In the cytoplasm, Shigella secretes the plasmid-encoded virulence factor Invasion Plasmid Antigen (Ipa) B which is necessary to induce cell death. IpaB binds to caspase (Casp)-1, a host cysteine protease that is required for Shigella induced apoptosis. Apoptosis mediated by Casp-1 appears to be pro- inflammatory in Shigella infections, since Casp-1 proteolytically activates the cytokines pro-Interleukin (IL)-1beta and pro-IL-18. Macrophages infected with Shigella release mature IL-1beta and IL-18. Furthermore, casp-1 knock-out mice do not mount an acute inflammation in response to Shigella infection. In vivo, some apoptotic cells are localized to regions of the lymphoid follicle where Shigella is not detectable. This difference in distribution suggested that Shigella possesses a second cytotoxic molecule, not IpaB, that can diffuse within infected tissue. We identified the novel diffusible cytotoxic activity in Shigella culture supernatants as Bacterial Lipoproteins (BLP). We also demonstrated that BLP activates both apoptosis and the host cell transcription factor Nuclear Factor - kappa B (NF-kappaB) through the Toll Like Receptor (TLR)2. In this application we propose to further understand the significance of apoptosis in Shigella infections. More specifically we will determine: (1) the role of Casp-1 activated cytokines in acute inflammation and whether apoptosis is required for the release of mature IL-1beta and IL-18 and (2) the signal transduction pathway activated by TLR2 after treatment with BLP and the role of BLP and TLR2 in vivo.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI037720-06
Application #
6373465
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Project Start
1996-03-01
Project End
2005-05-31
Budget Start
2001-06-01
Budget End
2002-05-31
Support Year
6
Fiscal Year
2001
Total Cost
$323,445
Indirect Cost

  Institution

Name
New York University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
City
New York
State
NY
Country
United States
Zip Code
10016

  Publications

Brinkmann, Volker; Reichard, Ulrike; Goosmann, Christian et al. (2004) Neutrophil extracellular traps kill bacteria. Science 303:1532-5
Aliprantis, A O; Weiss, D S; Radolf, J D et al. (2001) Release of Toll-like receptor-2-activating bacterial lipoproteins in Shigella flexneri culture supernatants. Infect Immun 69:6248-55
Aliprantis, A O; Weiss, D S; Zychlinsky, A (2001) Toll-like receptor-2 transduces signals for NF-kappa B activation, apoptosis and reactive oxygen species production. J Endotoxin Res 7:287-91
Sansonetti, P J; Phalipon, A; Arondel, J et al. (2000) Caspase-1 activation of IL-1beta and IL-18 are essential for Shigella flexneri-induced inflammation. Immunity 12:581-90
Aliprantis, A O; Yang, R B; Weiss, D S et al. (2000) The apoptotic signaling pathway activated by Toll-like receptor-2. EMBO J 19:3325-36
Navarre, W W; Zychlinsky, A (2000) Pathogen-induced apoptosis of macrophages: a common end for different pathogenic strategies. Cell Microbiol 2:265-73
Moss, J E; Fisher, P E; Vick, B et al. (2000) The regulatory protein PhoP controls susceptibility to the host inflammatory response in Shigella flexneri. Cell Microbiol 2:443-52
Moss, J E; Cardozo, T J; Zychlinsky, A et al. (1999) The selC-associated SHI-2 pathogenicity island of Shigella flexneri. Mol Microbiol 33:74-83
Weinrauch, Y; Zychlinsky, A (1999) The induction of apoptosis by bacterial pathogens. Annu Rev Microbiol 53:155-87
Aliprantis, A O; Yang, R B; Mark, M R et al. (1999) Cell activation and apoptosis by bacterial lipoproteins through toll-like receptor-2. Science 285:736-9

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