Differential Regulation of host cellular gene expression by HIV-1 Viral protein R (Vpr): Implications for host cell function

The HIV/AIDS epidemic is one of the most important public health problems facing this generation. The failure of recent vaccine trials and growing resistance to anti-retroviral drugs underscores the need for novel therapeutic strategies. Design of such therapies will depend on a detailed understanding of the mechanism of action of the HIV-1 gene products. To further that goal, we have undertaken a detailed investigation of the HIV-1 viral protein R (Vpr). We employed cDNA microarray and antibody array analyses using isogenic virus with or without Vpr to determine the effect on host cellular gene expression. Vpr induced differential regulation of 109 cellular genes representing diverse families of signaling molecules. Two gene products, NHE1 and TNF alpha, were further studied for their potential roles in Vpr-mediated apoptosis. NHE1 expression was decreased by 50% at both the protein and mRNA levels in the presence of Vpr. Vpr-mediated NHE1 downregulation correlated with a dose dependent decrease in intracellular pH as well as a decrease in the active form of the pro-survival kinase Akt. The loss of these anti-apoptotic functions of NHE1 is proposed to contribute to the apoptotic role of Vpr. The pro-inflammatory cytokine TNF alpha may also play a part in Vpr-mediated apoptosis. Macrophages infected with vpr-expressing virus secreted 1.1-8.5 fold more soluble TNF alpha in response to LPS stimulation than their counterparts infected with isogenic virus lacking Vpr expression. Fold upregulation of TNF alpha directly correlated with induction of apoptosis in uninfected lymphocytes, implicating TNF alpha regulation by Vpr in bystander cell death. Two polymorphisms in the TNF alpha promoter, positions -238 and -963, were found at a higher prevalence in donors showing the lowest and highest effect of Vpr on the TNF alpha response. These results suggest that host genetic determinants may affect bystander cell death and thus the course of HIV pathogenesis. Together, the results of this study present a molecular basis for changes induced in the host cell by HIV-1 Vpr and elucidate two potential pathways for the design of anti-retroviral therapeutics targeting HIV-1 Vpr

Dendritic Cells Infected with vpr-Positive Human Immunodeficiency Virus Type 1 Induce CD8+ T-Cell Apoptosis via Upregulation of Tumor Necrosis Factor Alpha▿

Human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) plays a crucial role in viral replication and pathogenesis by inducing cell cycle arrest, apoptosis, translocation of preintegration complex, potentiation of glucocorticoid action, impairment of dendritic cell (DC) maturation, and T-cell activation. Recent studies involving the direct effects of Vpr on DCs and T cells indicated that HIV-1 containing Vpr selectively impairs phenotypic maturation, cytokine network, and antigen presentation in DCs and dysregulates costimulatory molecules and cytokine production in T cells. Here, we have further investigated the indirect effect of HIV-1 Vpr+ virus-infected DCs on the bystander CD8+ T-cell population. Our results indicate that HIV-1 Vpr+ virus-infected DCs dysregulate CD8+ T-cell proliferation and induce apoptosis. Vpr-containing virus-infected DC-mediated CD8+ T-cell killing occurred in part through enhanced tumor necrosis factor alpha production by infected DCs and subsequent induction of death receptor signaling and activation of the caspase 8-dependent pathway in CD8+ T cells. Collectively, these results provide evidence that Vpr could be one of the important contributors to the host immune escape by HIV-1 through its ability to dysregulate both directly and indirectly the DC biology and T-cell functions

Human Immunodeficiency Virus Type 1 Vpr Impairs Dendritic Cell Maturation and T-Cell Activation: Implications for Viral Immune Escape

Antigen presentation and T-cell activation are dynamic processes involving signaling molecules present in both APCs and T cells. Effective APC function and T-cell activation can be compromised by viral immune evasion strategies, including those of human immunodeficiency virus type 1 (HIV-1). In this study, we determined the effects of HIV-1 Vpr on one of the initial target of the virus, dendritic cells (DC), by investigating DC maturation, cytokine profiling, and CD8-specific T-cell stimulation function followed by a second signal. Vpr impaired the expression of CD80, CD83, and CD86 at the transcriptional level without altering normal cellular transcription. Cytokine profiling indicated that the presence of Vpr inhibited production of interleukin 12 (IL-12) and upregulated IL-10, whereas IL-6 and IL-1β were unaltered. Furthermore, DC infected with HIV-1 vpr(+) significantly reduced the activation of antigen-specific memory and recall cytotoxic-T-lymphocyte responses. Taken together, these results indicate that HIV-1 Vpr may in part be responsible for HIV-1 immune evasion by inhibiting the maturation of costimulatory molecules and cytokines essential for immune activation