title: Human immunodeficiency virus type 2 vpx protein augments viral infectivity.
abstract: The genomes of HIV and SIV are complex and contain several accessory genes which modulate viral replication and pathogenicity. One of these genes, vpx, is unique to the HIV-2/SIV group of viruses and encodes a virion-associated protein of unknown function. To examine the function of vpx, we constructed a vpx-deficient HIV-2 proviral clone and characterized its in vitro biological properties. Following transfection into immortalized T-cell lines, vpx-mutant HIV-2 was fully replication competent and exhibited growth kinetics and cytopathic properties equivalent to wild-type HIV-2. In addition, vpx-deficient virions were indistinguishable from wild-type HIV-2 in ultrastructure, composition of major structural proteins, and reverse transcriptase activity. In PHA-stimulated normal peripheral blood mononuclear cells (PBMCs), however, vpx-deficient virus replicated at substantially lower titers and required a 100- to 1000-fold higher inoculum to establish a productive infection. This defect was localized to early events in the viral life cycle since vpx-deficient virus exhibited a 5- to 10-fold reduction in initial (single cycle) viral DNA synthesis following acute infection of primary PBMCs. Paradoxically, in long-term (9-23 months) cultures of immortalized T-cells (SupT1) continuous high level replication of vpx-deficient, but not wild-type, virus was observed, indicating less efficient viral spread and cell killing and a more attenuated phenotype of vpx-deficient HIV-2. Taken together, these results demonstrate that vpx is required for the production of fully infectious and cytopathic HIV-2 virions and that it functions early in the viral life cycle by facilitating viral entry and/or reverse transcription. The pronounced replicative defect of vpx-deficient HIV-2 in primary PBMCs but not in short-term cultures of immortalized T-cell lines emphasizes the need to characterize the properties of nonessential HIV accessory gene products in natural target cells.
authors.affiliation: Department of Medicine, University of Alabama, Birmingham 35294.
authors.forename: J C
authors.initials: JC
authors.lastname: Kappes
authors.forename: J A
authors.initials: JA
authors.lastname: Conway
authors.forename: S W
authors.initials: SW
authors.lastname: Lee
authors.forename: G M
authors.initials: GM
authors.lastname: Shaw
authors.forename: B H
authors.initials: BH
authors.lastname: Hahn
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D002460:Cell Line; D002472:Cell Transformation, Viral; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification; D005814:Genes, Viral; D016325:HIV Long Terminal Repeat; D015498:HIV-2 / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction / Q000379:methods; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism; D015183:Restriction Mapping; D012191:Retroviridae Proteins / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D015345:Oligonucleotide Probes; D012191:Retroviridae Proteins; C074286:VPX protein, Human immunodeficiency virus 2; D054334:Viral Regulatory and Accessory Proteins; D012194:RNA-Directed DNA Polymerase