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Infection and Immunity, August 2001, p. 4823-4830, Vol. 69, No. 8
INSERM U431, Microbiologie et Pathologie
Cellulaire Infectieuse, Université de Montpellier-II, 34095 Montpellier Cedex 05,1 and Laboratoire
de Pathologie Infectieuse et Immunologie, I.N.R.A., 37380 Nouzilly,2 France
Received 28 February 2001/Returned for modification 12 April
2001/Accepted 24 May 2001
Brucella spp. can establish themselves and cause
disease in humans and animals. The mechanisms by which
Brucella spp. evade the antibacterial defenses of their
host, however, remain largely unknown. We have previously reported that
live brucellae failed to induce tumor necrosis factor alpha (TNF-
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.8.4823-4830.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Major Outer Membrane Protein Omp25 of Brucella suis Is
Involved in Inhibition of Tumor Necrosis Factor Alpha
Production during Infection of Human Macrophages
)
production upon human macrophage infection. This inhibition is
associated with a nonidentified protein that is released into culture
medium. Outer membrane proteins (OMPs) of gram-negative bacteria have been shown to modulate macrophage functions, including cytokine production. Thus, we have analyzed the effects of two major OMPs (Omp25
and Omp31) of Brucella suis 1330 (wild-type [WT] B. suis) on TNF-
production. For this purpose, omp25
and omp31 null mutants of B. suis
(
omp25 B. suis and
omp31 B. suis,
respectively) were constructed and analyzed for the ability to activate
human macrophages to secrete TNF-
. We showed that, in contrast to WT
B. suis or
omp31 B. suis,
omp25 B. suis induced TNF-
production when phagocytosed by human
macrophages. The complementation of
omp25 B. suis with WT omp25 (
omp25-omp25 B. suis mutant)
significantly reversed this effect:
omp25-omp25 B. suis-infected macrophages secreted significantly less TNF-
than did macrophages infected with the
omp25 B. suis
mutant. Furthermore, pretreatment of WT B. suis with an
anti-Omp25 monoclonal antibody directed against an epitope exposed at
the surface of the bacteria resulted in substancial TNF-
production
during macrophage infection. These observations demonstrated that Omp25
of B. suis is involved in the negative regulation of
TNF-
production upon infection of human macrophages.
*
Corresponding author. Mailing address: INSERM U431, IFR
Eugène Bataillon, Université de Montpellier-II, 34095 Montpellier Cedex 05, France. Phone: (33) 467 14 32 09. Fax: (33) 467 14 33 38. E-mail: liautard{at}crit.univ-montp2.fr.
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