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Journal of Virology, September 2001, p. 8498-8506, Vol. 75, No. 18
The Lineberger Comprehensive Cancer Center,
Department of Microbiology and Immunology, School of Medicine,
University of North Carolina, Chapel Hill, North Carolina
27599-72951; Institute of Human
Virology, University of Maryland at Baltimore, Baltimore, Maryland
212012; and Department of Medicine,
University of Pennsylvania School of Medicine, Philadelphia,
Pennsylvania 19104-60613
Received 30 March 2001/Accepted 14 June 2001
Analysis of viral replication and pathogenicity after in vivo
selection of human immunodeficiency virus type 1 (HIV-1) attenuated in
vitro will help to define the functions involved in replication and
pathogenesis in vivo. Using the SCID-hu Thy/Liv mouse and human fetal
thymus organ culture as in vivo models, we previously defined HIV-1
env determinants (HXB2/LW) which were reverted for replication in vivo (L. Su et al., Virology 227:46-52,
1997). In this study, we examined the replication of four highly
related HIV-1 clones directly derived from Lai/IIIB or after selection in vivo to investigate the envelope gp120 determinants associated with
replication in macrophages and in the thymus models in vivo. The LW/C
clone derived from the IIIB-infected laboratory worker and HXB2/LW both
efficiently infected monocyte-derived macrophages (MDM) and the human
thymus. Although the laboratory worker (LW) isolates showed altered
tropism from IIIB, they still predominantly used CXCR4 as coreceptors
for infecting peripheral blood mononuclear cells, macrophages, and the
thymus. Interestingly, a single amino acid mutation in the V3 loop
associated with resistance to neutralizing antibodies was also
essential for the replication activity of the LW virus in the thymus
models but not for its activity in infecting MDM. The LW virions were
equally sensitive to a CXCR4 antagonist. We further demonstrated that
the LW HIV-1 isolate selected in vivo produced more infectious viral
particles that contained higher levels of the Env protein gp120. Thus,
selection of the laboratory-attenuated Lai/IIIB isolate in vivo leads
to altered tropism but not coreceptor usage of the virus. The acquired replication activity in vivo is correlated with an early A-to-T mutation in the V3 loop and increased virion association of HIV-1 Env
gp120, but it is genetically separable from the acquired replication activity in macrophages.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.18.8498-8506.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Human Immunodeficiency Virus Type 1 IIIB Selected
for Replication In Vivo Exhibits Increased Envelope Glycoproteins in
Virions without Alteration in Coreceptor Usage: Separation of In Vivo
Replication from Macrophage Tropism

*
Corresponding author. Mailing address: Lineberger
Comprehensive Cancer Center, School of Medicine, University of North
Carolina, Chapel Hill, NC 27599-7295. Phone: (919) 966-6654. Fax: (919) 966-8212. E-mail: lsu{at}med.unc.edu.
Dedicated to the memory of Eric D. Miller.
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