Dual regulation of silent and productive infection in monocytes by distinct human immunodeficiency virus type 1 determinants

Abstract

The regulation of human immunodeficiency virus type 1 infection and replication in primary monocytes was investigated by mutagenesis of recombinant proviral clones containing an env determinant required for the infectivity of monocytes. Virus replication was assayed by determination of reverse transcriptase activity in culture fluids and by recovery of virus from monocytes following cocultivation with uninfected peripheral blood mononuclear cells. Three virus replication phenotypes were observed in monocytes: productive infection, silent infection, and no infection. Incorporation of the monocytetropic env determinant in a full-length clone incapable of infection or replication in primary monocytes (no infection) conferred the capacity for highly efficient virus replication in monocytes (productive infection). Clones with the env determinant but lacking either functional vpr or vpu genes generated lower replication levels in monocytes. Mutation of both vpr and vpu, however, resulted in nearly complete attenuation of virus replication in monocytes, despite subsequent virus recovery from infected monocytes by cocultivation with uninfected peripheral blood mononuclear cells (silent infection). These findings indicate a central role for the "accessory" genes vpu and vpr in productive human immunodeficiency virus type 1 replication in monocytes and indicate that vpu and vpr may be capable of functional complementation.

Micronuclei formation and aneuploidy induced byVpr, an accessory gene of human immunodeficiency virus type 1

“…vpr is an accessory gene of human immunodeficiency virus type 1 (HIV-1) 2 encoding a virionassociated nuclear protein of about 15 kDa in size (1)(2)(3). It is a conserved gene present in HIV-2 as well as in the simian immunodeficiency virus (4, 5), crucial for productive infection to macrophages (6,7). Recently, several groups have reported that the Vpr of HIV-1 induces cell cycle abnormality (see review, ref 8), causing cell accumulation at G2/M phase and increased ploidy.…”

Augmentation of virus secretion by the human immunodeficiency virus type 1 Vpu protein is cell type independent and occurs in cultured human primary macrophages and lymphocytes

“…HIV-1 infection of monocytes/macrophages has been demonstrated for several organs, such as the brain, spinal cord, lungs, lymph nodes, and skin (3,6,18,20,33,56,60). The susceptibility of monocyte-derived macrophages (MDM) to HIV infection has been documented both in vivo and in vitro (4,18,19,21,30,43,58,59). The observation that cytopathic changes in MDM are less severe than in PBMC or CD4 ϩ T-cell lines after infection with HIV-1 has led to the hypothesis that monocytes/macro-phages may be an important reservoir for continuous virus replication even in the presence of an effective host immune response (13, 18-21, 33, 41, 43).…”

“…It has been reported by several authors that Vpu augments the release of progeny virions from various established human cell lines (23,26,32,48,(52)(53)(54)68). However, there are conflicting reports regarding the activity of Vpu in primary cells (2,4,30,59): while Westervelt et al (59) found only a moderate support of Vpu on virus replication in MDM, which was functionally complemented by Vpr, an up to 1,000-fold Vpu-mediated enhancement of virus replication was reported by Balliet et al (4). In contrast, no Vpu effect was detected for monocytetropic viruses in PBMC by Balliet et al (4) or Kawamura et al (30).…”

“…These findings could indicate a cell type-dependent function of Vpu. However, conclusions regarding the function of Vpu in primary cell systems, either macrophages or PBMC, are hampered because they rely exclusively on the analysis of extracellular virus, by either reverse transcriptase (RT) or p24 antigen capture assays (2,4,30,59), and do not provide a comparison with the corresponding intracellular levels of viral proteins. The goal of our present study was therefore to analyze the function of Vpu in primary cells by a variety of biological and biochemical means, including Western blot (immunoblot) analyses, steady-state metabolic labeling, and pulsechase analyses.…”

“…The goal of our present study was therefore to analyze the function of Vpu in primary cells by a variety of biological and biochemical means, including Western blot (immunoblot) analyses, steady-state metabolic labeling, and pulsechase analyses. For construction of chimeric monocyte-tropic viruses, we made use of the fact that T-cell-tropic isolates can be made competent for replication in macrophages by introduction of a portion of the env gene, including the V3 loop from primary monocyte-tropic isolates (16,17,42,49,59). This feature allowed us to analyze the activity of the well-characterized vpu gene from the T-cell-tropic isolate NL4-3 (1) in cultured PBMC and MDM and to compare its activity with the function of a vpu gene derived from the primary monocytetropic isolate AD8 ϩ (55).…”