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J. Virol., Apr 1997, 3228-3235, Vol 71, No. 4
EL Oleszak, CD Katsetos, J Kuzmak and A Varadhachary
We investigated the role of inducible nitric oxide synthase (iNOS) in
Theiler's murine encephalomyelitis virus (TMEV) infection of susceptible
(SJL) and resistant (C57BL/6 [B6]) strains of mice. TMEV is an excellent
model of virus-induced demyelinating disease, such as multiple sclerosis
(MS). Previous studies of others have suggested that NO may play a role in
the pathogenesis of demyelinating disease. The presence and level of iNOS
were determined in the brains and spinal cords of SJL and B6 TMEV-infected
mice by the following methods: (i) PCR amplification of iNOS transcripts,
followed by Southern blotting with an iNOS-specific probe, and (ii)
immunohistochemical staining with an anti-iNOS-specific affinity-purified
rabbit antibody. iNOS-specific transcripts were determined in the brains
and spinal cord of both SJL and B6 TMEV-infected mice on days 0 (control),
days 3, 6, and 10 (encephalitic stage of disease), and days 39 to 42, 66,
and 180 (demyelinating phase) postinfection (p.i.). iNOS-specific
transcripts were found in the brains and spinal cords of both SJL and B6
TMEV- infected mice at 6, 10, and 39 (SJL) days p.i., but they were absent
in mock-infected mice and in TMEV-infected SJL and B6 mice at 0, 3, 66, and
180 days p.i. Immunohistochemical staining confirmed the presence of iNOS
protein in both TMEV-infected SJL and B6 mice at days 6 and 10 p.i., but
not at days 0, 3, 66, and 180 days p.i. Weak iNOS staining was also
observed in TMEV-infected SJL mice at 42 days p.i. iNOS- positive staining
was found in reactive astrocytes surrounding areas of necrotizing
inflammation, particularly in the midbrain. Weak iNOS staining was also
observed in cells of the monocyte/macrophage lineage in areas of
parenchymal inflammation and necrosis (mesencephalon) and in leptomeningeal
and white matter perivascular infiltrates of the spinal cord. Rod-shaped
microglia-like cells and foamy macrophages (myelin-laden) were iNOS
negative. These results suggest that NO does not play a direct role in the
late phase of demyelinating disease in TMEV-infected mice.
Copyright © 1997, American Society for Microbiology
Inducible nitric oxide synthase in Theiler's murine encephalomyelitis virus infection
Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19106, USA.
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