Modulation of the severe CD4+ T-cell loss caused by a pathogenic simian–human immunodeficiency virus by replacement of the subtype B vpu with the vpu from a subtype C HIV-1 clinical isolate

Abstract

Previously, we showed that the Vpu protein from subtype C human immunodeficiency virus type 1 (HIV-1) was efficiently targeted to the cell surface, suggesting that this protein has biological properties that differ from the well-studied subtype B Vpu protein. In this study, we have further analyzed the biological properties of the subtype C Vpu protein. Flow cytometric analysis revealed that the subtype B Vpu (strain HXB2) was more efficient at down-regulating CD4 surface expression than the Vpu proteins from four subtype C clinical isolates. We constructed a simian-human immunodeficiency virus virus, designated as SHIV(SCVpu), in which the subtype B vpu gene from the pathogenic SHIV(KU-1bMC33) was substituted with the vpu from a clinical isolate of subtype C HIV-1 (strain C.96.BW16B01). Cell culture studies revealed that SHIV(SCVpu) replicated with slightly reduced kinetics when compared with the parental SHIV(KU-1bMC33) and that the viral Env and Gag precursor proteins were synthesized and processed similarly compared to the parental SHIV(KU-1bMC33). To determine if substitution of the subtype C Vpu protein affected the pathogenesis of the virus, three pig-tailed macaques were inoculated with SHIV(SCVpu) and circulating CD4+ T-cell levels and viral loads were monitored for up to 44 weeks. Our results show that SHIV(SCVpu) caused a more gradual decline in the rate of CD4+ T cells in pig-tailed macaques compared to those inoculated with parental subtype B SHIV(KU-1bMC33). These results show for the first time that different Vpu proteins of HIV-1 can influence the rate at which CD4+ T-cell loss occurs in the SHIV/pig-tailed macaque model.

Inhibition of Human Immunodeficiency Virus Type 1 Assembly and Release by the Cholesterol-Binding Compound Amphotericin B Methyl Ester: Evidence for Vpu Dependence

“…We are currently investigating the cell surface localization and lipid raft association of CD317/BST-2/tetherin and the colocalization of this host factor and HIV-1 Gag in the presence of AME when Vpu is coexpressed. Given that Vpu plays an important role in lentiviral pathogenesis in vivo (10), this accessory protein may represent a viable target for the development of antiretroviral agents.…”

Inhibition of β-TrcP–dependent ubiquitination of p53 by HIV-1 Vpu promotes p53–mediated apoptosis in human T cells

“…[1][2][3] Studies in a macaque model have shown that Vpu from subtype B plays a crucial role in massive loss of circulating CD4 ϩ T lymphocytes, 4-6 which can be modulated by replacing it with Vpu from subtype C. 7 The exact mechanism(s) underlying how Vpu makes HIV-1 more pathogenic is only partially understood. 8,9 Vpu is involved in ubiquitination and degradation of antiretroviral restriction factor BM stromal cell Ag 2 (BST-2; also known as tetherin) and surface receptor CD4 through their recruitment to SCF ␤-TrcP (Skp1/Cul1/F-box) ubiquitin ligase (SCF) complex.…”

Simian–Human immunodeficiency viruses expressing chimeric subtype B/C Vpu proteins demonstrate the importance of the amino terminal and transmembrane domains in the rate of CD4+ T cell loss in macaques

“…Previously, we showed that the subtype B (HXB2) Vpu was more efficient at down-modulating cell surface CD4 than several subtype C Vpu proteins (Hill et al, 2008). Therefore, we analyzed the ability of Vpu BC and Vpu CB to down-modulate surface CD4 expression.…”

“…The results of these studies suggest that different HIV-1 Vpu proteins may exhibit distinct anti-BST-2 activity. Additionally, studies from our laboratory have shown that a subtype B Vpu (US.HXB2) and subtype C Vpu (C.96BW16B01) exhibit distinct structural and biological properties that could potentially affect overall HIV-1 pathogenesis (Hill et al, 2008; Pacyniak et al, 2005; Singh et al, 2003). Taken together, these results strongly emphasize a necessity for deviation from the longstanding practice of generalizing HIV-1 Vpu properties based on an accumulation of results using laboratory isolates.…”

“…Previously, we showed that a SHIV expressing a subtype C Vpu replicated less efficiently in T cell cultures and caused a slower rate of CD4 + T cell loss following inoculation into macaques suggesting that the origin of the Vpu could influence the rate of CD4 + T cell loss in vivo (Hill et al, 2008). In the present study, we hypothesized that certain Vpu domains were responsible for the decreased rate of CD4 + T cell loss in macaques.…”