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Journal of Virology, March 2001, p. 2107-2118, Vol. 75, No. 5
Department of Molecular Microbiology and
Immunology, St. Louis University Health Sciences Center, St. Louis,
Missouri 63104
Received 6 September 2000/Accepted 29 November 2000
Viral encephalitis caused by neuroadapted yellow fever 17D virus
(PYF) was studied in parental and gamma interferon (IFN-
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.5.2107-2118.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Yellow Fever Virus Encephalitis: Properties of the
Brain-Associated T-Cell Response during Virus Clearance in Normal
and Gamma Interferon-Deficient Mice and Requirement for
CD4+ Lymphocytes
and
)-deficient (IFN-
knockout [GKO]) C57BL/6 mice. The T-cell responses which enter the brain during acute fatal encephalitis of nonimmunized mice,
as well as nonfatal encephalitis of immunized mice, were characterized
for relative proportions of CD4+ and CD8+
cells, their proliferative responses, and antigen-specific expression of cytokines during stimulation in vitro. Unimmunized mice accumulated only low levels of T cells within the brain during fatal disease, whereas the brains of immunized mice contained higher levels of both
T-cell subsets in response to challenge, with CD8+ cells
increased relative to the CD4+ subset. The presence of T
cells correlated with the time at which virus was cleared from the
central nervous system in both parental and GKO mice. Lymphocytes
isolated from the brains of challenged immunized mice failed to
proliferate in vitro in response to T-cell mitogens or viral antigens;
however, IFN-
, interleukin 4 (IL-4), and, to a lesser extent, IL-2
were detectable after stimulation. The levels of IFN-
, but not IL-2
or IL-4, were augmented in response to viral antigen, and this
specificity was detectable in the CD4+ compartment. When
tested for the ability to survive both immunization and challenge with
PYF virus, GKO and CD8 knockout mice did not differ from parental mice
(80 to 85% survival), although GKO mice exhibited a defect in virus
clearance. In contrast, CD4 knockout and Igh-6 mice were unable to
resist challenge. The data implicate antibody in conjunction with
CD4+ lymphocytes bearing a Th1 phenotype as the critical
factors involved in virus clearance in this model.
*
Corresponding author. Mailing address: Department of
Molecular Microbiology and Immunology, St. Louis University Health
Sciences Center, 1402 S. Grand Blvd., St. Louis, MO 63104. Phone: (314) 577-8447. Fax: (314) 773-3403. E-mail: chambetj{at}slu.edu.
Present address: Dept. of Pathology, Hahnemann Hospital,
Philadelphia, PA.
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