This thesis examines directly the function of the vpr regulatory gene of HIV-1. Previous work by others, using vpr deletion mutants, suggested that vpr is an enhancer of virus replication, particularly in monocyte/macrophages. The nature of this activity was not known. This project began with the serendipitous observation that transfection of HIV-1 genomic DNA into a muscle cell tumor line induced cell differentiation. The first study in this thesis examines this phenomenon and determines that the vpr gene of HIV-1 is the responsible agent. Vpr was observed to inhibit proliferation and induce gross changes in a variety of tumor lines, indicating that vpr targets a fundamental and common cell regulatory pathway, and suggesting that vpr functions in a manner analogous to a tumor suppressor gene. The remaining studies examine the role of vpr in HIV-1 infection in several novel aspects. Several lines of evidence indicate that vpr is active as a soluble, cell free molecule, and that this form of vpr in the bodily fluid of HIV infected individuals may increase HIV replication and contribute to development of disease. Recombinant vpr-containing baculovirus supernatant was found to induce cell differentiation and to inhibit the proliferation of several transformed cell types. Extracellular vpr was found to greatly enhance wild type HIV replication at a pre-translation stage. It was determined that vpr enhances virus replication through its interaction with the cell, inducing the population of cells to be more permissive to productive infection and HIV replication. Vpr protein that was purified from the serum of HIV+ AIDS patients enhanced virus replication, but was capable of enhancing replication of only the macrophage tropic strain of HIV-1 and only in monocytic cell lines. Finally, recombinant vpr and serum vpr restored virus expression from latently infected cell lines and the PBMC of HIV+ individuals. These studies provide novel evidence for the role of vpr in the virus life cycle, and indicate that HIV can, as many other viruses do, modify the intracellular environment and affect cell permissiveness to infection and virus replication.
Thesis (Ph.D. in Immunolgy) -- Graduate School of Arts and Sciences, University of Pennsylvania, 1994. Source: Dissertation Abstracts International, Volume: 55-05, Section: B, page: 1742. Supervisor: David B. Weiner.