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Journal of Virology, February 2000, p. 1648-1657, Vol. 74, No. 4
Department of Virology and
Immunology,1 Department of Laboratory
Animal Medicine,3 and Southwest Regional
Primate Research Center,2 Southwest Foundation
for Biomedical Research, San Antonio, Texas 78245
Received 5 August 1999/Accepted 10 November 1999
We studied the innate and adaptive immune system of rhesus macaques
infected with the virulent simian immunodeficiency virus isolate
SIVmac251 by evaluating natural killer (NK) cell activity, cytokine
levels in plasma, humoral and virological parameters, and changes in
the activation markers CD25 (interleukin 2R [IL-2R]
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Cytokine Expression, Natural Killer Cell Activation, and
Phenotypic Changes in Lymphoid Cells from Rhesus Macaques during Acute
Infection with Pathogenic Simian Immunodeficiency Virus
chain), CD69
(early activation marker), and CD154 (CD40 ligand) in lymphoid cells.
We found that infection with SIVmac251 induced the sequential
production of interferon-
/
(IFN-
/
), IL-18, and IL-12.
IFN-
, IL-4, and granulocyte-macrophage colony-stimulating factor
were undetected in plasma by the assays used. NK cell activity peaked
at 1 to 2 weeks postinfection and paralleled changes in viral loads.
Maximum expression of CD69 on CD3
CD16+
lymphocytes correlated with NK cytotoxicity during this period. CD25
expression, which is associated with proliferation, was static or
slightly down-regulated in CD4+ T cells from both
peripheral blood (PB) and lymph nodes (LN). CD69, which is normally
present in LN CD4+ T cells and absent in peripheral blood
leukocyte (PBL) CD4+ T cells, was down-regulated in LN
CD4+ T cells and up-regulated in PBL CD4+ T
cells immediately after infection. CD8+ T cells increased
CD69 but not CD25 expression, indicating the activation of this
cellular subset in PB and LN. Finally, CD154 was transiently
up-regulated in PBL CD4+ T cells but not in LN
CD4+ T cells. Levels of antibodies to SIV Gag and Env did
not correlate with the level of activation of CD154, a critical
costimulatory molecule for T-cell-dependent immunity. In summary, we
present the first documented evidence that the innate immune system of rhesus macaques recognizes SIV infection by sequential production of
proinflammatory cytokines and transient activation of NK cytotoxic activity. Additionally, pathogenic SIV induces drastic changes in the
level of activation markers on T cells from different anatomic compartments. These changes involve activation in the absence of
proliferation, indicating that activation-induced cell death may cause
some of the reported increase in lymphocyte turnover during SIV infection.
*
Corresponding author. Mailing address: Southwest
Foundation for Biomedical Research, P.O. Box 760549, San Antonio, TX
78245-0549. Phone: (210) 258-9603. Fax: (210) 670-3310. E-mail:
Lgiavedo{at}icarus.sfbr.org.
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