Restoration of Wild-Type Infectivity to Human Immunodeficiency Virus Type 1 Strains Lacking nef by Intravirion Reverse Transcription

Department of Microbiology/Biochemistry/Immunology, Morehouse School of Medicine, Atlanta, Georgia 30310, USA.
Journal of Virology (Impact Factor: 4.44). 01/2002; 75(24):12081-7. DOI: 10.1128/JVI.75.24.12081-12087.2001
Source: PubMed


Human immunodeficiency virus type 1 (HIV-1) Nef protein exerts several effects, both on infected cells and as a virion protein,
which work together to enhance viral replication. One of these activities is the ability to enhance infectivity and the formation
of proviral DNA. The mechanism of this enhancement remains incompletely understood. We show that virions with nef deleted can be restored to wild-type infectivity by stimulating intravirion reverse transcription. Particle composition and
measures of reverse transcriptase activity remain the same for Nef+ and Nef− virions both before and after natural endogenous reverse transcription (NERT) treatment. The effect of NERT treatment on
virions pseudotyped with murine leukemia virus envelope protein was similar to that on particles pseudotyped with HIV-1 envelope
protein. However, virions pseudotyped with vesicular stomatitis virus G envelope protein showed no influence of Nef on NERT
enhancement of infectivity. These observations suggest that Nef may function at a level prior to reverse transcription. Since
NERT treatment results in partial disassembly of the viral core, we speculate that Nef may function at the level of core particle

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Available from: Mahfuz Bano Khan
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    • "The Guatelli lab was the first to report that HIV-1 lacking the ability to express Nef has lower infectivity compared with the Nef-positive counterpart (Chowers et al., 1994). This observation has then been confirmed by several labs using a variety of experimental systems differing for producer cell type, target cells and viral molecular clones (Aiken and Trono, 1995; Goldsmith et al., 1995; Miller et al., 1995; Tokunaga et al., 1998; Khan et al., 2001; Tobiume et al., 2001; Papkalla et al., 2002). Altogether, the magnitude by which Nef alters HIV-1 infectivity is highly variable, ranging from 3 to 40. "
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    • "The concentration of p24 in the filtered medium was determined by ELISA (Immunodiagnostics, Inc.) and equivalent amounts of p24 were used to infect MAGI cells [39]. Efficiency of infectivity at 48 hrs was measured as described [66]. As a control to verify that equivalent amounts of Env was expressed in each transfection, virus preps were run on SDS-PAGE followed by Western blot analysis using anti-HIV envelope antibodies (Immunodiagnostics, Inc.). "
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    • "The HIV-1 nef gene encodes a small myristoylated protein expressed early in the HIV-1 life cycle [1]–[3]. Nef, one of several accessory factors unique to primate lentiviruses, is not required for HIV-1 replication in vitro [4] but is essential for high-titer virus replication [5]–[9] and AIDS pathogenesis in vivo [10]–[13]. Nef has no known enzymatic activity, and appears to exert its effects by interacting with a diverse group of host cell proteins involved in cellular activation, immune recognition and survival [14], [15]. Many protein-protein interaction motifs have been mapped to the Nef structure, which account for its diverse functions including down-regulation of CD4 and MHC-1 molecules and activation of cellular signaling pathways [9], [16]–[37]. "
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