scholarly journals Fusion-Induced Apoptosis Contributes to Thymocyte Depletion by a Pathogenic Human Immunodeficiency Virus Type 1 Envelope in the Human Thymus

2006 ◽  
Vol 80 (22) ◽  
pp. 11019-11030 ◽  
Author(s):  
Eric G. Meissner ◽  
Liguo Zhang ◽  
S. Jiang ◽  
Lishan Su
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Caspase 3 ◽  
Fusion Inhibitors ◽  
Immunodeficiency Virus ◽  
Induced Apoptosis ◽  
Hiv 1 ◽  
Active Caspase

ABSTRACT The mechanisms of CD4+ T-cell depletion during human immunodeficiency virus type 1 (HIV-1) infection remain incompletely characterized. Of particular importance is how CD4+ T cells are depleted within the lymphoid organs, including the lymph nodes and thymus. Herein we characterize the pathogenic mechanisms of an envelope from a rapid progressor (R3A Env) in the NL4-3 backbone (NL4-R3A) which is able to efficiently replicate and deplete CD4+ thymocytes in the human fetal-thymus organ culture (HF-TOC). We demonstrate that uninterrupted replication is required for continual thymocyte depletion. During depletion, NL4-R3A induces an increase in thymocytes which uptake 7AAD, a marker of cell death, and which express active caspase-3, a marker of apoptosis. While 7AAD uptake is observed predominantly in uninfected thymocytes (p24−), active caspase-3 is expressed in both infected (p24+) and uninfected thymocytes (p24−). When added to HF-TOC with ongoing infection, the protease inhibitor saquinavir efficiently suppresses NL4-R3A replication. In contrast, the fusion inhibitors T20 and C34 allow for sustained HIV-1 production. Interestingly, T20 and C34 effectively prevent thymocyte depletion in spite of this sustained replication. Apoptosis of both p24− and p24+ thymocytes appears to be envelope fusion dependent, as T20, but not saquinavir, is capable of reducing thymocyte apoptosis. Together, our data support a model whereby pathogenic envelope-dependent fusion contributes to thymocyte depletion in HIV-1-infected thymus, correlated with induction of apoptosis in both p24+ and p24− thymocytes.

scholarly journals Human Immunodeficiency Virus Type 1 Variants Resistant to First- and Second-Version Fusion Inhibitors and Cytopathic in Ex Vivo Human Lymphoid Tissue

2007 ◽  
Vol 81 (12) ◽  
pp. 6563-6572 ◽  
Author(s):  
Raghavan Chinnadurai ◽  
Devi Rajan ◽  
Jan Münch ◽  
Frank Kirchhoff
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Lymphoid Tissue ◽  
Ex Vivo ◽  
Fusion Inhibitors ◽  
Immunodeficiency Virus ◽  
Human Lymphoid Tissue ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) fusion inhibitors blocking viral entry by binding the gp41 heptad repeat 1 (HR1) region offer great promise for antiretroviral therapy, and the first of these inhibitors, T20 (Fuzeon; enfuvirtide), is successfully used in the clinic. It has been reported previously that changes in the 3-amino-acid GIV motif at positions 36 to 38 of gp41 HR1 mediate resistance to T20 but usually not to second-version fusion inhibitors, such as T1249, which target an overlapping but distinct region in HR1 including a conserved hydrophobic pocket (HP). Based on the common lack of cross-resistance and the difficulty of selecting T1249-resistant HIV-1 variants, it has been suggested that the determinants of resistance to first- and second-version fusion inhibitors may be different. To further assess HIV-1 resistance to fusion inhibitors and to analyze where changes in HR1 are tolerated, we randomized 16 codons in the HR1 region, including those making contact with HR2 codons and/or encoding residues in the GIV motif and the HP. We found that changes only at positions 37I, 38V, and 40Q near the N terminus of HR1 were tolerated. The propagation of randomly gp41-mutated HIV-1 variants in the presence of T1249 allowed the effective selection of highly resistant forms, all containing changes in the IV residues. Overall, the extent of T1249 resistance was inversely correlated to viral fitness and cytopathicity. Notably, one HIV-1 mutant showing ∼10-fold-reduced susceptibility to T1249 inhibition replicated with wild type-like kinetics and caused substantial CD4+-T-cell depletion in ex vivo-infected human lymphoid tissue in the presence and absence of an inhibitor. Taken together, our results show that the GIV motif also plays a key role in resistance to second-version fusion inhibitors and suggest that some resistant HIV-1 variants may be pathogenic in vivo.

scholarly journals N-Substituted Pyrrole Derivatives as Novel Human Immunodeficiency Virus Type 1 Entry Inhibitors That Interfere with the gp41 Six-Helix Bundle Formation and Block Virus Fusion

2004 ◽  
Vol 48 (11) ◽  
pp. 4349-4359 ◽  
Author(s):  
Shibo Jiang ◽  
Hong Lu ◽  
Shuwen Liu ◽  
Qian Zhao ◽  
Yuxian He ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Small Molecule ◽  
Cooh Group ◽  
Hydrophobic Pocket ◽  
Fusion Inhibitors ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT A recently approved peptidic human immunodeficiency virus type 1 (HIV-1) fusion inhibitor, T-20 (Fuzeon; Trimeris Inc.), has shown significant promise in clinical application for treating HIV-1-infected individuals who have failed to respond to the currently available antiretroviral drugs. However, T-20 must be injected twice daily and is too expensive. Therefore, it is essential to develop orally available small molecule HIV-1 fusion inhibitors. By screening a chemical library consisting of “drug-like” compounds, we identified two N-substituted pyrroles, designated NB-2 and NB-64, that inhibited HIV-1 replication at a low micromolar range. The absence of the COOH group in NB-2 and NB-64 resulted in a loss of anti-HIV-1 activity, suggesting that this acid group plays an important role in mediating the antiviral activity. NB-2 and NB-64 inhibited HIV-1 fusion and entry by interfering with the gp41 six-helix bundle formation and disrupting the α-helical conformation. They blocked a d-peptide binding to the hydrophobic pocket on surface of the gp41 internal trimeric coiled-coil domain. Computer-aided molecular docking analysis has shown that they fit inside the hydrophobic pocket and that their COOH group interacts with a positively charged residue (K574) around the pocket to form a salt bridge. These results suggest that NB-2 and NB-64 may bind to the gp41 hydrophobic pocket through hydrophobic and ionic interactions and block the formation of the fusion-active gp41 core, thereby inhibiting HIV-1-mediated membrane fusion and virus entry. Therefore, NB-2 and NB-64 can be used as lead compounds toward designing and developing more potent small molecule HIV-1 fusion inhibitors targeting gp41.

scholarly journals Identification of a Critical Motif for the Human Immunodeficiency Virus Type 1 (HIV-1) gp41 Core Structure: Implications for Designing Novel Anti-HIV Fusion Inhibitors

2008 ◽  
Vol 82 (13) ◽  
pp. 6349-6358 ◽  
Author(s):  
Yuxian He ◽  
Jianwei Cheng ◽  
Jingjing Li ◽  
Zhi Qi ◽  
Hong Lu ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Core Structure ◽  
Heptad Repeat ◽  
Fusion Inhibitors ◽  
Immunodeficiency Virus ◽  
Anti Hiv ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) entry into the host cell involves a cascade of events and currently represents one of most attractive targets in the search for new antiviral drugs. The fusion-active gp41 core structure is a stable six-helix bundle (6-HB) folded by its trimeric N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR). Peptides derived from the CHR region of HIV-1 gp41 are potent fusion inhibitors that target the NHR to block viral and cellular membrane fusion in a dominant negative fashion. However, all CHR peptides reported to date are derived primarily from residues 628 to 673 of gp41; little attention has been paid to the upstream sequence of the pocket binding domain (PBD) in the CHR. Here, we have identified a motif (621QIWNNMT627) located at the upstream region of the gp41 CHR, immediately adjacent to the PBD (628WMEWEREI635). Biophysical characterization demonstrated that this motif is critical for the stabilization of the gp41 6-HB core. The peptide CP621-652, containing the 621QIWNNMT627 motif, was able to interact with T21, a counterpart peptide derived from the NHR, to form a typical 6-HB structure with a high thermostability (thermal unfolding transition [T m ] value of 82°C). In contrast, the 6-HB formed by the peptides N36 and C34, which has been considered to be a core structure of the fusion-active gp41, had a T m of 64°C. Different from T-20 (brand name Fuseon), which is the first and only HIV-1 fusion inhibitor approved for clinical use, CP621-652 could efficiently block 6-HB formation in a dose-dependent manner. Significantly, CP621-652 had potent inhibitory activity against HIV-1-mediated cell-cell fusion and infection, especially against T-20- and C34-resistant virus. Therefore, our works provide important information for understanding the core structure of the fusion-active gp41 and for designing novel anti-HIV peptides.

scholarly journals Human Immunodeficiency Virus Type 1 Vpr Induces Apoptosis through Caspase Activation

2000 ◽  
Vol 74 (7) ◽  
pp. 3105-3111 ◽  
Author(s):  
Sheila A. Stewart ◽  
Betty Poon ◽  
Joo Y. Song ◽  
Irvin S. Y. Chen
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Ectopic Expression ◽  
Caspase Activity ◽  
Immunodeficiency Virus ◽  
Induced Apoptosis ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Vpr is a 96-amino-acid protein that is found associated with the HIV-1 virion. Vpr induces cell cycle arrest at the G2/M phase of the cell cycle, and this arrest is followed by apoptosis. We examined the mechanism of Vpr-induced apoptosis and found that HIV-1 Vpr-induced apoptosis requires the activation of a number of cellular cysteinyl aspartate-specific proteases (caspases). We demonstrate that ectopic expression of anti-apoptotic viral proteins, which inhibit caspase activity, and addition of synthetic peptides, which represent caspase cleavage sites, can inhibit Vpr-induced apoptosis. Finally, inhibition of caspase activity and subsequent inhibition of apoptosis results in increased viral expression, suggesting that therapeutic strategies aimed at reducing Vpr-induced apoptosis in vivo require careful consideration.

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

1998 ◽  
Vol 72 (3) ◽  
pp. 1754-1761 ◽  
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.

scholarly journals Inhibition of Human Immunodeficiency Virus Type 1 Integration by Diketo Derivatives

2002 ◽  
Vol 46 (10) ◽  
pp. 3292-3297 ◽  
Author(s):  
Wim Pluymers ◽  
Godwin Pais ◽  
Bénédicte Van Maele ◽  
Christophe Pannecouque ◽  
Valery Fikkert ◽  
...  
Keyword(s):  
Cell Culture ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Effective Concentration ◽  
Fusion Inhibitors ◽  
Immunodeficiency Virus ◽  
Hiv Integration ◽  
Hiv 1

ABSTRACT A series of diketo derivatives was found to inhibit human immunodeficiency virus type 1 (HIV-1) integrase activity. Only L-708,906 inhibited the replication of HIV-1(IIIB) (50% effective concentration, 12 μM), HIV-1 clinical strains, HIV-1 strains resistant to reverse transcriptase or fusion inhibitors, HIV-2 (ROD strain) and simian immunodeficiency virus (MAC251). The combinations of L-708,906 with zidovudine, nevirapine, or nelfinavir proved to be subsynergistic. In cell culture, addition of L-708,906 could be postponed for 7 h after infection, a moment coinciding with HIV integration. Inhibition of integration in cell culture was confirmed by quantitative Alu-PCR.

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