Journal of Virology, March 2001, p. 2848-2856, Vol. 75, No. 6
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.6.2848-2856.2001
Laboratory of Persistent Viral Diseases,
Rocky Mountain Laboratories, National Institute of Allergy and
Infectious Diseases, National Institutes of Health, Hamilton, Montana
59840,1 and Department of Molecular
Biology, University of Wyoming
Laramie, Laramie, Wyoming
820712
Received 25 August 2000/Accepted 20 December 2000
Infection of the central nervous system (CNS) by several
viruses can lead to upregulation of proinflammatory cytokines and chemokines. In immunocompetent adults, these molecules induce prominent
inflammatory infiltrates. However, with immunosuppressive retroviruses,
such as human immunodeficiency virus (HIV), little CNS
inflammation is observed yet proinflammatory cytokines and chemokines
are still upregulated in some patients and may mediate pathogenesis.
The present study examined expression of cytokines and chemokines in
brain tissue of neonatal mice infected with virulent (Fr98) and
avirulent (Fr54) polytropic murine retroviruses. While both viruses
infect microglia and endothelia primarily in the white matter areas of
the CNS, only Fr98 induces clinical CNS disease. The pathology
consists of gliosis with minimal morphological changes and no
inflammation, similar to HIV. In the present experiments, mice infected
with Fr98 had increased cerebellar mRNA levels of proinflammatory
cytokines tumor necrosis factor alpha (TNF-
), TNF-
, and
interleukin-1
and chemokines macrophage inflammatory protein-1
(MIP-1
), MIP-1
, monocyte chemoattractant protein 1 (MCP-1),
gamma-interferon-inducible protein 10 (IP-10), and RANTES compared
to mice infected with Fr54 or mock-infected controls. The increased
expression of these genes occurred prior to the development of clinical
symptoms, suggesting that these cytokines and chemokines might be
involved in induction of neuropathogenesis. Two separate regions of the
Fr98 envelope gene are associated with neurovirulence. CNS disease
associated with the N-terminal portion of the Fr98 env
gene was preceded by upregulation of cytokines and chemokines. In
contrast, disease associated with the central region of the Fr98
env gene showed no upregulation of cytokines or chemokines
and thus did not require increased expression of these genes for
disease induction.
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