Human immunodeficiency virus type 2 vpx protein augments viral infectivity

Academic Article


  • 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 itsin 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. © 1991 Academic Press, Inc.
  • Published In

  • Virology  Journal
  • Digital Object Identifier (doi)

    Author List

  • Kappes JC; Conway JA; Lee SW; Shaw GM; Hahn BH
  • Start Page

  • 197
  • End Page

  • 209
  • Volume

  • 184
  • Issue

  • 1