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Journal of Virology, March 2001, p. 2288-2300, Vol. 75, No. 5
Department of Molecular Biology and
Biochemistry, University of California at Irvine, Irvine, California
92697,1 and Fred Hutchinson Cancer
Research Center, Seattle, Washington 981092
Received 24 August 2000/Accepted 7 December 2000
Cell tropism of human and simian immunodeficiency viruses (HIV and
SIV, respectively) is governed in part by interactions between the
viral envelope protein and the cellular receptors. However, there is
evidence that envelope-host cell interactions also affect postentry
steps in viral replication. We used a helper-free replication-defective
SIV macaque (SIVmac)-based retroviral vector carrying the
enhanced jellyfish green fluorescent protein inserted into the
nef region (V1EGFP) to examine SIV tropism in a single cycle of infection. Vector stocks containing envelope proteins from
three different SIVmac clones, namely, SIVmac239 (T-lymphocyte tropic
[T-tropic]), SIVmac316 (macrophage tropic [M-tropic]), and
SIVmac1A11 (dualtropic), were tested. SIVmac239 replicates efficiently in many human T-cell lines, but it does not efficiently infect primary rhesus macrophages. Conversely, SIVmac316 efficiently infects primary macrophages, but it does not replicate in Molt4-Clone8 (M4C8) T cells. SIVmac1A11 replicates efficiently in both cell types.
When primary macrophages were infected with V1EGFP pseudotyped by
SIVmac316 or SIVmac1A11 envelopes, the infection was substantially (ca.
200- to 300-fold) more efficient than for the SIVmac239 pseudotype. Thus, in primary macrophages, a major component of M versus T tropism
involves relatively early events in the infection cycle. Quantitative
PCR studies indicated that synthesis and transport of vector DNA into
the nucleus were similar for macrophages infected with the clone 239 and 316 pseudotypes, suggesting that the restriction for SIVmac239
infection is after reverse transcription and nuclear import of viral
DNA. When the same vector pseudotypes were used to infect M4C8 cells,
they all showed approximately equivalent infectivities, even though
replication-competent SIVmac316 does not continue to replicate in these
cells. Therefore, in M4C8 cells, restriction involves a late step in
the infection cycle (after proviral integration and expression). Thus,
depending on the cell type infected, envelope-dependent cell
interactions that govern SIV M and T tropism may involve different
steps in infection.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.5.2288-2300.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Use of Helper-Free Replication-Defective Simian Immunodeficiency
Virus-Based Vectors To Study Macrophage and T Tropism: Evidence for
Distinct Levels of Restriction in Primary Macrophages and a
T-Cell Line
*
Corresponding author. Mailing address: Department of
Molecular Biology and Biochemistry, University of California, Irvine, 3221 Biological Sciences II, Irvine, CA 92697-3905. Phone: (949) 824-5554. Fax: (949) 824-4023. E-mail:
hyfan{at}uci.edu.
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