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Journal of Virology, August 1999, p. 6453-6459, Vol. 73, No. 8
Laboratory of
Immunology1 and Laboratory of
Virology,2 Istituto Superiore di Sanità,
Rome, Italy
Received 22 February 1999/Accepted 9 May 1999
In a previous study, we had found that the extent of T-cell
dysfunctions induced by a T-tropic strain of human immunodeficiency virus type 1 (HIV-1) in SCID mice reconstituted with human peripheral blood lymphocytes (hu-PBLs) (hu-PBL-SCID mice) was related to the in
vivo state of activation of the human lymphocytes. In this article, we
compared the effect of infection of hu-PBL-SCID mice with either
T-tropic (X4) or M-tropic (R5) strains of HIV-1 by performing virus
inoculation at either 2 h or 2 weeks after the hu-PBL transfer,
when the human T cells exhibited a marked activation state or a
predominant memory phenotype, respectively. A comparable level of
infection was found when hu-PBL-SCID mice were challenged with either
the SF162 R5 or the IIIB X4 strain of HIV at 2 h
postreconstitution, while at 2 weeks, the R5 virus infection resulted
in a higher level of HIV replication than the X4 virus. The R5 strain
induced a marked human CD4+ T-cell depletion along with a
drop in levels of human immunoglobulin M in serum and release of
soluble factors at both infection times, while the X4 virus induced
severe immune dysfunctions only at 2 h. Of interest, injection of
hu-PBLs into SCID mice resulted in a marked up-regulation of CCR5 on
human CD4+ T cells. The percentage of CXCR4+
cells did not change after transplantation, even though a significant decrease in antigen expression was observed. Comparative experiments with two molecular clones of HIV-1 (X4 SF2 and R5 SF162) and two envelope recombinant viruses generated from these viruses showed that
R5 viruses (SF162 and the chimeric env-SF162-SF2) caused an extensive
depletion of human CD4+ T cells in SCID mice at both 2 h and 2 weeks after reconstitution, while the X4 viruses (SF2 and the
chimeric env-SF2-SF162) induced CD4 T-cell depletion only when
infection was performed at the 2-h reconstitution time. These results
emphasize the importance of the state of activation/differentiation of
human CD4+ T cells and gp120-coreceptor interactions at the
time of primary infection in determining HIV-1 pathogenicity in the
hu-PBL-SCID mouse model.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Human Immunodeficiency Virus Type 1 Strains R5 and X4 Induce
Different Pathogenic Effects in hu-PBL-SCID Mice, Depending on the
State of Activation/Differentiation of Human Target Cells at the
Time of Primary Infection
*
Corresponding author. Mailing address: Laboratory of
Virology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. Phone: 3906.49903290. Fax: 3906.49387184. E-mail: belard{at}virus1.net.iss.it.
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