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Infection and Immunity, January 2000, p. 160-164, Vol. 68, No. 1
Unité des Rickettsies, Université
de la Méditerranée, CNRS UPRESA 6020, Faculté de
Médecine, 13385 Marseille Cedex 05, France
Received 22 July 1999/Returned for modification 1 September
1999/Accepted 5 October 1999
Endocarditis is the most frequent form of chronic Q fever, an
infectious disease caused by Coxiella burnetii. As this
obligate intracellular bacterium inhabits monocytes and macrophages, we wondered if pathogenesis of Q fever endocarditis is related to defective intracellular killing of C. burnetii by
monocytes. Monocytes from healthy controls eliminated virulent C. burnetii within 3 days. In contrast, monocytes from patients
with ongoing Q fever endocarditis were unable to eliminate
bacteria even after 6 days. In patients who were cured of endocarditis,
the monocyte infection was close to that of control monocytes. This
killing deficiency was not the consequence of generalized functional
impairment, since patient monocytes eliminated avirulent C. burnetii as did control cells. The addition of supernatants of
C. burnetii-stimulated monocytes from patients with ongoing
endocarditis to control monocytes enabled them to support C. burnetii survival, suggesting that some soluble factor is
responsible for bacterial survival. This factor was related to tumor
necrosis factor (TNF): expression of TNF mRNA and TNF release were
increased in response to C. burnetii in patients with
ongoing endocarditis compared to cured patients and healthy controls.
In addition, neutralizing anti-TNF antibodies decreased C. burnetii internalization, an early step of bacterial killing, in
monocytes from patients with ongoing endocarditis but did not affect
delayed steps of intracellular killing. We suggest that Q
fever-associated activation of monocytes allows the survival of
C. burnetii by modulating early phases of microbial killing.
0019-9567/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Coxiella burnetii Survives in Monocytes from Patients
with Q Fever Endocarditis: Involvement of Tumor Necrosis
Factor
*
Corresponding author. Mailing address: Unité des
Rickettsies, CNRS UPRESA 6020, Faculté de Médecine, 27 Bd
J. Moulin, 13385 Marseille Cedex 05, France. Phone: (33) 4 91 32 43 75. Fax: (33) 4 91 38 77 72. E-mail:
Jean-Louis.Mege{at}medecine.univ-mrs.fr.
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