Human immunodeficiency virus type 1 (HIV-1) Vpr-regulated cell death: insights into mechanism

Many viruses have evolved genes encoding proteins that regulate cell death by apoptosis. The human immunodeficiency virus type 1 (HIV-1) Nef protein alters T-cell development and signaling and is required for optimal viral replication and pathogenicity in vivo. To analyze the interference of Nef with cell survival, we used both regulated and constitutively expressed nef alleles in stably transfected T-cell lines. Nef-expressing cells were sensitized to cell death by apoptosis, which was specifically exacerbated by an anti-CD95 IgM monoclonal antibody (MoAb). Flow cytometric analysis showed that the surface expression of both CD95 and CD95 ligand (CD95L) was upregulated by endogenous Nef expression. Nef-mediated apoptosis was almost completely suppressed by the addition in culture of an anti-CD95 Fab′ IgG MoAb, which specifically blocks CD95/CD95L interactions. Lastly, mutation of a proline motif in the core region of the nef gene, which disrupts its ability to interact with cellular kinases and reduces HIV-1 replication in vitro, completely abrogated the Nef-mediated induction of apoptosis as well as its ability to upregulate surface CD95 and CD95L. These findings may provide molecular insight into the role of endogenous Nef in the T-cell depletion observed in vivo, particularly HIV-specific cytotoxic CD8+ T cells.

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Human Immunodeficiency Virus Type 1 Nef Protein Sensitizes CD4+ T Lymphoid Cells to Apoptosis via Functional Upregulation of the CD95/CD95 Ligand Pathway

Blood ◽

10.1182/blood.v93.3.1000 ◽

1999 ◽

Vol 93 (3) ◽

pp. 1000-1010 ◽

Cited By ~ 84

Author(s):

Giorgio Zauli ◽

Davide Gibellini ◽

Paola Secchiero ◽

Hélène Dutartre ◽

Daniel Olive ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Cell Death ◽

T Cell ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Cd95 Ligand ◽

Immunodeficiency Virus ◽

Hiv 1

Abstract Many viruses have evolved genes encoding proteins that regulate cell death by apoptosis. The human immunodeficiency virus type 1 (HIV-1) Nef protein alters T-cell development and signaling and is required for optimal viral replication and pathogenicity in vivo. To analyze the interference of Nef with cell survival, we used both regulated and constitutively expressed nef alleles in stably transfected T-cell lines. Nef-expressing cells were sensitized to cell death by apoptosis, which was specifically exacerbated by an anti-CD95 IgM monoclonal antibody (MoAb). Flow cytometric analysis showed that the surface expression of both CD95 and CD95 ligand (CD95L) was upregulated by endogenous Nef expression. Nef-mediated apoptosis was almost completely suppressed by the addition in culture of an anti-CD95 Fab′ IgG MoAb, which specifically blocks CD95/CD95L interactions. Lastly, mutation of a proline motif in the core region of the nef gene, which disrupts its ability to interact with cellular kinases and reduces HIV-1 replication in vitro, completely abrogated the Nef-mediated induction of apoptosis as well as its ability to upregulate surface CD95 and CD95L. These findings may provide molecular insight into the role of endogenous Nef in the T-cell depletion observed in vivo, particularly HIV-specific cytotoxic CD8+ T cells.

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Preferential Cytolysis of Peripheral Memory CD4+ T Cells by In Vitro X4-Tropic Human Immunodeficiency Virus Type 1 Infection before the Completion of Reverse Transcription

Journal of Virology ◽

10.1128/jvi.00773-08 ◽

2008 ◽

Vol 82 (18) ◽

pp. 9154-9163 ◽

Cited By ~ 11

Author(s):

Yan Zhou ◽

Lin Shen ◽

Hung-Chih Yang ◽

Robert F. Siliciano

Keyword(s):

Human Immunodeficiency Virus ◽

T Cells ◽

Cell Death ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Reverse Transcription ◽

Host Cells ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT CD4+ T-cell depletion is the hallmark of AIDS pathogenesis. Multiple mechanisms may contribute to the death of productively infected CD4+ T cells and innocent-bystander cells. In this study, we characterize a novel mechanism in which human immunodeficiency virus type 1 (HIV-1) infection preferentially depletes peripheral memory CD4+ T cells before the completion of reverse transcription. Using a recombinant HIV-1 carrying the green fluorescent protein reporter gene, we demonstrate that memory CD4+ T cells were susceptible to infection-induced cell death at a low multiplicity of infection. Infected memory CD4+ T cells underwent rapid necrotic cell death. Killing of host cells was dependent on X4 envelope-mediated viral fusion, but not on virion-associated Vpr or Nef. In contrast to peripheral resting CD4+ T cells, CD4+ T cells stimulated by mitogen or certain cytokines were resistant to HIV-1-induced early cell death. These results demonstrate that early steps in HIV-1 infection have a detrimental effect on certain subsets of CD4+ T cells. The early cell death may serve as a selective disadvantage for X4-tropic HIV-1 in acute infection but may play a role in accelerated disease progression, which is associated with the emergence of X4-tropic HIV-1 in the late stage of AIDS.

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Delayed Human Immunodeficiency Virus Type 1-Induced Apoptosis in Cells Expressing Truncated Forms of CD4

Journal of Virology ◽

10.1128/jvi.72.3.1754-1761.1998 ◽

1998 ◽

Vol 72 (3) ◽

pp. 1754-1761 ◽

Cited By ~ 9

Author(s):

Claire Guillerm ◽

Nolwenn Coudronnière ◽

Véronique Robert-Hebmann ◽

Christian Devaux

Keyword(s):

Human Immunodeficiency Virus ◽

Cell Death ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Antigen Expression ◽

Immunodeficiency Virus ◽

Virus Exposure ◽

Induced Apoptosis ◽

Hiv 1

ABSTRACT It has been reported previously that cells expressing a truncated form of CD4 which lacks the cytoplasmic tail of the molecule (truncation at position 402) were not sensitive to human immunodeficiency virus type 1 (HIV-1)-induced apoptosis in an acute-phase model of infection (J. Corbeil, M. Tremblay, and D. D. Richman, J. Exp. Med. 183:39–48, 1996). The role played by the cytoplasmic domain of CD4 in HIV-1-induced apoptosis was reexamined here with clones of A2.01 cells expressing different forms of CD4 and the DNA intercalant YOPRO-1 assay. Six days after virus exposure, we found evidence of apoptosis in A2.01 cells expressing the wild-type CD4 (A2.01/CD4), whereas enhanced apoptosis remained absent in cultures of A2.01/CD4.401 and A2.01/CD4.403 cells (A2.01 cells which express CD4.401 and CD4.403 molecules with truncations at positions 401 and 403, respectively). However, cell death by apoptosis measured with YOPRO-1 was found in cultures of A2.01/CD4.401 and A2.01/CD4.403 cells 15 days after virus exposure. This result was confirmed with a terminal dUTP nick end-labeling assay and propidium iodide staining. The long lag time postinfection required for apoptosis to be observed in cultures of infected cells expressing truncated forms of CD4 was due to the delayed viral replication in these cells, as shown by monitoring of the viral reverse transcriptase activity and HIV-1 p24 gag antigen expression. These results emphasize the relationship between virus replication and cell death by apoptosis.

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Human Immunodeficiency Virus Type 1 Inhibits DNA Damage-Triggered Apoptosis by a Nef-Independent Mechanism

Journal of Virology ◽

10.1128/jvi.79.9.5489-5498.2005 ◽

2005 ◽

Vol 79 (9) ◽

pp. 5489-5498 ◽

Cited By ~ 50

Author(s):

Michael Schindler ◽

Jan Münch ◽

Frank Kirchhoff

Keyword(s):

Human Immunodeficiency Virus ◽

Dna Damage ◽

Cell Death ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Serum Starvation ◽

Immunodeficiency Virus ◽

Independent Mechanism ◽

Hiv 1

ABSTRACT It is controversial whether the accessory human immunodeficiency virus type 1 (HIV-1) Nef protein inhibits or enhances apoptosis. To address this issue, we investigated the effect of Nef on programmed cell death with vectors or proviral HIV-1 constructs coexpressing Nef and green fluorescent protein from single bicistronic RNAs. This approach allows us to readily identify transfected or infected cells and to correlate cell death directly with Nef expression levels. We demonstrate that Nef does not significantly affect apoptosis in transfected or HIV-1-infected Jurkat T cells or primary human peripheral blood mononuclear cells. Unexpectedly, however, both nef + and nef-defective HIV-1 infection blocked apoptosis in cells treated with UV light or etoposide but not cell death induced by CD95 antibody, TRAIL, Ly294002, or serum starvation. Our results show that HIV-1 infection inhibits DNA damage-induced but not death receptor-dependent cell death by a Nef-independent mechanism.

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