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Infection and Immunity, November 1998, p. 5067-5072, Vol. 66, No. 11
Department of Medical Microbiology and
Immunology, University of Wisconsin Medical School, Madison,
Wisconsin 53706
Received 7 May 1998/Returned for modification 15 July 1998/Accepted 12 August 1998
Chlamydia pneumoniae infection is associated with
atherosclerotic heart and vessel disease, but a causal relationship
between this pathogen and the disease process has not been established. Recently, it was reported that C. pneumoniae induces human
macrophage foam cell formation, a key event in early atheroma
development, suggesting a role for the organism in atherogenesis. This
study further examines C. pneumoniae-induced foam cell
formation in the murine macrophage cell line RAW-264.7. Infected RAW
cells accumulated cholesteryl esters when cultured in the presence of low-density lipoprotein in a manner similar to that described for human
macrophages. Exposure of C. pneumoniae elementary bodies to
periodate, but not elevated temperatures, inhibited cholesteryl ester
accumulation, suggesting a role for chlamydial lipopolysaccharide (cLPS) in macrophage foam cell formation. Purified cLPS was found to be
sufficient to induce cholesteryl ester accumulation and foam cell
formation. Furthermore, the LPS antagonist lipid X inhibited C. pneumoniae and cLPS-induced lipid uptake. These data indicate that cLPS is a C. pneumoniae component that induces
macrophage foam cell formation and suggest that infected macrophages
chronically exposed to cLPS may accumulate excess cholesterol to
contribute to atheroma development.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
A Chlamydia pneumoniae Component That
Induces Macrophage Foam Cell Formation Is Chlamydial
Lipopolysaccharide
*
Corresponding author. Mailing address: Dept. of Medical
Microbiology & Immunology, University of Wisconsin Medical School, 471 SMI, 1300 University Ave., Madison, WI 53706. Phone: (608) 263-2494. Fax: (608) 262-8418. E-mail: gibyrne{at}facstaff.wisc.edu.
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