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Infect. Immun., Apr 1996, 1197-1202, Vol 64, No. 4
JN Samsom, JA Langermans, PH Groeneveld and R van Furth
During an infection, inflammatory mediators can induce the production of
nitric oxide, a reactive nitrogen intermediate (RNI) which plays a role in
antimicrobial activity against a wide variety of pathogens. In vitro
experiments have shown that release of RNI by macrophages is mediated by
tumor necrosis factor alpha (TNF). Since TNF is essential for acquired
resistance during a secondary Listeria monocytogenes infection in mice, the
aim of the present study was to determine whether RNI are also involved in
the course of such an infection. Mice which had recovered from a sublethal
primary infection with 0.1 50% lethal dose of (LD50) L. monocytogenes were
infected intravenously with 10LD50 of L. monocytogenes. During a primary
infection, the number of bacteria in the liver and spleen, as well as the
concentration of RNI in plasma, increased. During a secondary infection,
the number of bacteria in the liver and spleen decreased whereas no
significant increase in the concentration of RNI in plasma was observed.
Neutralization of endogenously produced TNF and gamma interferon by
subcutaneous injection of alginate-encapsulated monoclonal antibody-
forming cells during a secondary infection resulted in an increase in the
number of bacteria in the liver and spleen an increase in the concentration
of RNI in plasma. When the production of RNI was inhibited by treatment of
mice with competitive NO-synthase inhibitor N omega-nitro-L-arginine methyl
ester hydrochloride (L-Name) and an iota- arginine-deficient diet during a
secondary infection, the proliferation of L. monocytogenes in the liver and
spleen was not affected whereas the concentration of RNI in plasma of these
mice was significantly reduced. Our findings that inhibition of RNI
formation during a secondary infection does not affect the proliferation of
L. monocytogenes in the liver and spleen and that enhanced elimination of
bacteria from these organs is not accompanied by an increase in the
concentration of RNI in plasma led to the conclusion that resistance
against a secondary infection with L. monocytogenes is not dependent on
RNI.
Copyright © 1996, American Society for Microbiology
Acquired resistance against a secondary infection with Listeria monocytogenes in mice is not dependent on reactive nitrogen intermediates
Department of Infectious Diseases, University Hospital, Leiden, The Netherlands.
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