scholarly journals Human Immunodeficiency Virus Type 1 Particles Pseudotyped with Envelope Proteins That Fuse at Low pH No Longer Require Nef for Optimal Infectivity

2001 ◽  
Vol 75 (8) ◽  
pp. 4014-4018 ◽  
Author(s):  
Nathalie Chazal ◽  
Gregory Singer ◽  
Christopher Aiken ◽  
Marie-Louise Hammarskjöld ◽  
David Rekosh
Keyword(s):  
Human Immunodeficiency Virus ◽  
Ebola Virus ◽  
Leukemia Virus ◽  
Envelope Proteins ◽  
Low Ph ◽  
Viral Envelope ◽  
Vector System ◽  
Virus Particles ◽  
Virus Glycoprotein ◽  
Immunodeficiency Virus

ABSTRACT We have investigated the effects of Nef on infectivity in the context of various viral envelope proteins. These experiments were performed with a minimal vector system where Nef is the only accessory protein present. Our results support the hypothesis that the route of entry influences the ability of Nef to enhance human immunodeficiency virus (HIV) infectivity. We show that HIV particles pseudotyped with Ebola virus glycoprotein or vesicular stomatitis virus glycoprotein (VSV-G), which fuse at low pH, do not require Nef for optimal infectivity. In contrast, Nef significantly enhances the infectivity of virus particles that contain envelope proteins that fuse at neutral pH (CCR5-dependent HIV Env, CXCR4-dependent HIV Env, or amphotropic murine leukemia virus Env). In addition, our results demonstrate that virus particles containing mixed CXCR4-dependent HIV and VSV-G envelope proteins show a conditional requirement for Nef for optimal infectivity, depending on which protein is allowed to facilitate entry.

scholarly journals Differential N-Linked Glycosylation of Human Immunodeficiency Virus and Ebola Virus Envelope Glycoproteins Modulates Interactions with DC-SIGN and DC-SIGNR

2003 ◽  
Vol 77 (2) ◽  
pp. 1337-1346 ◽  
Author(s):  
George Lin ◽  
Graham Simmons ◽  
Stefan Pöhlmann ◽  
Frédéric Baribaud ◽  
Houping Ni ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Ebola Virus ◽  
Leukemia Virus ◽  
Viral Envelope ◽  
Virus Envelope ◽  
Immunodeficiency Virus ◽  
High Mannose ◽  
Virus Interactions ◽  
Do So

ABSTRACT The C-type lectins DC-SIGN and DC-SIGNR [collectively referred to as DC-SIGN(R)] bind and transmit human immunodeficiency virus (HIV) and simian immunodeficiency virus to T cells via the viral envelope glycoprotein (Env). Other viruses containing heavily glycosylated glycoproteins (GPs) fail to interact with DC-SIGN(R), suggesting some degree of specificity in this interaction. We show here that DC-SIGN(R) selectively interact with HIV Env and Ebola virus GPs containing more high-mannose than complex carbohydrate structures. Modulation of N-glycans on Env or GP through production of viruses in different primary cells or in the presence of the mannosidase I inhibitor deoxymannojirimycin dramatically affected DC-SIGN(R) infectivity enhancement. Further, murine leukemia virus, which typically does not interact efficiently with DC-SIGN(R), could do so when produced in the presence of deoxymannojirimycin. We predict that other viruses containing GPs with a large proportion of high-mannose N-glycans will efficiently interact with DC-SIGN(R), whereas those with solely complex N-glycans will not. Thus, the virus-producing cell type is an important factor in dictating both N-glycan status and virus interactions with DC-SIGN(R), which may impact virus tropism and transmissibility in vivo.

scholarly journals Inefficient Human Immunodeficiency Virus Replication in Mobile Lymphocytes

2006 ◽  
Vol 81 (2) ◽  
pp. 1000-1012 ◽  
Author(s):  
Marion Sourisseau ◽  
Nathalie Sol-Foulon ◽  
Françoise Porrot ◽  
Fabien Blanchet ◽  
Olivier Schwartz
Keyword(s):  
Human Immunodeficiency Virus ◽  
Viral Replication ◽  
Leukemia Virus ◽  
Viral Envelope ◽  
Human Immunodeficiency Virus Replication ◽  
Target Cells ◽  
Human T Cell ◽  
Donor Cells ◽  
Immunodeficiency Virus ◽  
Viral Transfer

ABSTRACT Cell-to-cell viral transfer facilitates the spread of lymphotropic retroviruses such as human immunodeficiency virus (HIV) and human T-cell leukemia virus (HTLV), likely through the formation of “virological synapses” between donor and target cells. Regarding HIV replication, the importance of cell contacts has been demonstrated, but this phenomenon remains only partly characterized. In order to alter cell-to-cell HIV transmission, we have maintained cultures under continuous gentle shaking and followed viral replication in this experimental system. In lymphoid cell lines, as well as in primary lymphocytes, viral replication was dramatically reduced in shaken cultures. To document this phenomenon, we have developed an assay to assess the relative contributions of free and cell-associated virions in HIV propagation. Acutely infected donor cells were mixed with carboxyfluorescein diacetate succinimidyl ester-labeled lymphocytes as targets, and viral production was followed by measuring HIV Gag expression at different time points by flow cytometry. We report that cellular contacts drastically enhance productive viral transfer compared to what is seen with infection with free virus. Productive cell-to-cell viral transmission required fusogenic viral envelope glycoproteins on donor cells and adequate receptors on targets. Only a few syncytia were observed in this coculture system. Virus release from donor cells was unaffected when cultures were gently shaken, whereas virus transfer to recipient cells was severely impaired. Altogether, these results indicate that cell-to-cell transfer is the predominant mode of HIV spread and help to explain why this virus replicates so efficiently in lymphoid organs.

scholarly journals Inhibition of Endosomal/Lysosomal Degradation Increases the Infectivity of Human Immunodeficiency Virus

2002 ◽  
Vol 76 (22) ◽  
pp. 11440-11446 ◽  
Author(s):  
Brenda L. Fredericksen ◽  
Bangdong L. Wei ◽  
Jian Yao ◽  
Tianci Luo ◽  
J. Victor Garcia
Keyword(s):  
Human Immunodeficiency Virus ◽  
Host Cell ◽  
Leukemia Virus ◽  
Fold Increase ◽  
Viral Envelope ◽  
Endocytic Pathway ◽  
Target Cells ◽  
Concanamycin A ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Productive entry of human immunodeficiency virus type 1 (HIV-1) into a host cell is believed to proceed via fusion of the viral envelope with the host cell's plasma membrane. Interestingly, the majority of HIV-1 particles that bind to the cell surface are taken up by the host cell via endocytosis; however, this mode of internalization generally does not result in infection. Presumably, virus particles remain trapped in the endocytic pathway and are eventually degraded. Here, we demonstrate that treatment of cells with various pharmacological agents known to elevate the pH of endosomes and lysosomes allows HIV-1 to efficiently enter and infect the host cell. Pretreatment of cells with bafilomycin A1 results in up to a 50-fold increase in the infectivity of HIV-1SF2. Similarly, pretreatment of target cells with amantadine, concanamycin A, concanamycin B, chloroquine, and ammonium chloride resulted in increases in HIV-1 infectivity ranging between 2- and 15-fold. Analysis of receptor and coreceptor expression, HIV-long terminal repeat (LTR) transactivation, and transduction with amphotropic-pseudotyped murine leukemia virus (MLV)-based vectors suggests that the increase in infectivity is not artifactual. The increased infectivity under these conditions appears to be due to the ability of HIV-1 and MLV particles to enter via the endocytic pathway when spared from degradation in the late endosomes and lysosomes. These results could have significant implications for the administration of current and future lysosmotropic agents to patients with HIV disease.

scholarly journals The Proteolytic Cleavage of Human Immunodeficiency Virus Type 1 Nef Does Not Correlate with Its Ability To Stimulate Virion Infectivity

1998 ◽  
Vol 72 (4) ◽  
pp. 3178-3184 ◽  
Author(s):  
Yen-Liang Chen ◽  
Didier Trono ◽  
Diana Camaur
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Leukemia Virus ◽  
Proteolytic Processing ◽  
Virus Particles ◽  
Immunodeficiency Virus ◽  
Specific Proteins ◽  
Hiv 1

ABSTRACT The Nef protein of human immunodeficiency virus type 1 (HIV-1) promotes virion infectivity through mechanisms that are yet ill defined. Some Nef is incorporated into particles, where it is cleaved by the viral protease between amino acids 57 and 58. The functional significance of this event, which liberates the C-terminal core domain of the protein from its membrane-associated N terminus, is unknown. To address this question, we examined the modalities of Nef virion association and processing. We found that although significant levels of Nef were detected in HIV-1 virions partly in a cleaved form, cell-specific variations existed in the efficiency of Nef proteolytic processing. The virion association of Nef was strongly enhanced by myristoylation but did not require other HIV-1-specific proteins, since Nef was efficiently incorporated into and cleaved inside murine leukemia virus particles. Substituting alanine for tryptophan57 decreased the efficiency of Nef processing, while mutating leucine58 had little effect. In contrast, replacing both of these residues simultaneously almost completely prevented this process. However, when the resulting mutants were compared with a wild-type control in viral infectivity assays, no correlation was found between the levels of cleavage and the ability to stimulate virion infectivity. Furthermore, simian immunodeficiency virus Nef, which lacks the sequence recognized by the protease and as a consequence is not cleaved despite its incorporation into virions, could stimulate the infectivity of a nef-defective HIV-1 variant as efficiently as HIV-1 Nef. On these bases, we conclude that the proteolytic processing of Nef is not required for the ability of this protein to enhance virion infectivity.

scholarly journals Evidence for a Stable Interaction of gp41 with Pr55Gag in Immature Human Immunodeficiency Virus Type 1 Particles

2000 ◽  
Vol 74 (20) ◽  
pp. 9381-9387 ◽  
Author(s):  
Donald J. Wyma ◽  
Alexander Kotov ◽  
Christopher Aiken
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Cytoplasmic Tail ◽  
Envelope Proteins ◽  
Viral Envelope ◽  
Major Fraction ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Assembly of infectious human immunodeficiency virus type 1 (HIV-1) virions requires incorporation of the viral envelope glycoproteins gp41 and gp120. Several lines of evidence have suggested that the cytoplasmic tail of the transmembrane glycoprotein, gp41, associates with Pr55Gag in infected cells to facilitate the incorporation of HIV-1 envelope proteins into budding virions. However, direct evidence for an interaction between gp41 and Pr55Gagin HIV-1 particles has not been reported. To determine whether gp41 is associated with Pr55Gag in HIV-1 particles, viral cores were isolated from immature HIV-1 virions by sedimentation through detergent. The cores contained a major fraction of the gp41 that was present on untreated virions. Association of gp41 with cores required the presence of the gp41 cytoplasmic tail. In HIV-1 particles containing a functional protease, a mutation that prevents cleavage of Pr55Gag at the matrix-capsid junction was sufficient for the detergent-resistant association of gp41 with the isolated cores. In addition to gp41, a major fraction of virion-associated gp120 was also detected on immature HIV-1 cores. Isolation of cores under conditions known to disrupt lipid rafts resulted in the removal of a raft-associated protein incorporated into virions but not the HIV-1 envelope proteins. These results provide biochemical evidence for a stable interaction between Pr55Gag and the cytoplasmic tail of gp41 in immature HIV-1 particles. Moreover, findings in this study suggest that the interaction of Pr55Gag with gp41 may regulate the function of the envelope proteins during HIV-1 maturation.

Biological and Surface Properties of C-Type Virus Particles Produced by Novikoff Ascites Hepatoma Cells

1977 ◽  
Vol 35 ◽  
pp. 388-389
Author(s):  
D.C. Hixson ◽  
J.C. Chan ◽  
J.M. Bowen ◽  
E.F. Walborg
Keyword(s):  
Surface Properties ◽  
Ricinus Communis ◽  
Rat Kidney ◽  
Leukemia Virus ◽  
Viral Envelope ◽  
Virus Particles ◽  
Chemically Induced ◽  
Sarcoma Virus ◽  
Hepatocarcinoma Cells ◽  
Type C

Several years ago Karasaki (1) reported the production of type C virus particles by Novikoff ascites hepatocarcinoma cells. More recently, Weinstein (2) has reported the presence of type C virus particles in cell cultures derived from transplantable and primary hepatocellular carcinomas. To date, the biological function of these virus and their significance in chemically induced hepatocarcinogenesis are unknown. The present studies were initiated to determine a possible role for type C virus particles in chemically induced hepatocarcinogenesis. This communication describes results of studies on the biological and surface properties of type C virus associated with Novikoff hepatocarcinoma cells.Ecotropic and xenotropic murine leukemia virus (MuLV) activity in ascitic fluid of Novikoff tumor-bearing rats was assayed in murine sarcoma virus transformed S+L- mouse cells and S+L- mink cells, respectively. The presence of sarcoma virus activity was assayed in non-virus-producing normal rat kidney (NRK) cells. Ferritin conjugates of concanavalin A (Fer-Con wheat germ agglutinin (Fer-WGA), and Ricinus communis agglutinins I and II (Fer-RCAI and Fer-RCAII) were used to probe the structure and topography of saccharide determinants present on the viral envelope.

scholarly journals Gag Regulates Association of Human Immunodeficiency Virus Type 1 Envelope with Detergent-Resistant Membranes

2006 ◽  
Vol 80 (11) ◽  
pp. 5292-5300 ◽  
Author(s):  
Jayanta Bhattacharya ◽  
Alexander Repik ◽  
Paul R. Clapham
Keyword(s):  
Human Immunodeficiency Virus ◽  
Lipid Rafts ◽  
Human Immunodeficiency Virus Type ◽  
Cytoplasmic Domain ◽  
Virus Particles ◽  
Immunodeficiency Virus ◽  
Detergent Resistant Membranes ◽  
Envelope Incorporation ◽  
Hiv 1

ABSTRACT Assembly of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein on budding virus particles is important for efficient infection of target cells. In infected cells, lipid rafts have been proposed to form platforms for virus assembly and budding. Gag precursors partly associate with detergent-resistant membranes (DRMs) that are believed to represent lipid rafts. The cytoplasmic domain of the envelope gp41 usually carries palmitate groups that were also reported to confer DRM association. Gag precursors confer budding and carry envelope glycoproteins onto virions via specific Gag-envelope interactions. Thus, specific mutations in both the matrix domain of the Gag precursor and gp41 cytoplasmic domain abrogate envelope incorporation onto virions. Here, we show that HIV-1 envelope association with DRMs is directly influenced by its interaction with Gag. Thus, in the absence of Gag, envelope fails to associate with DRMs. A mutation in the p17 matrix (L30E) domain in Gag (Gag L30E) that abrogates envelope incorporation onto virions also eliminated envelope association with DRMs in 293T cells and in the T-cell line, MOLT 4. These observations are consistent with a requirement for an Env-Gag interaction for raft association and subsequent assembly onto virions. In addition to this observation, we found that mutations in the gp41 cytoplasmic domain that abrogated envelope incorporation onto virions and impaired infectivity of cell-free virus also eliminated envelope association with DRMs. On the basis of these observations, we propose that Gag-envelope interaction is essential for efficient envelope association with DRMs, which in turn is essential for envelope budding and assembly onto virus particles.

scholarly journals Single-Molecule Analysis of Human Immunodeficiency Virus Type 1 gp120-Receptor Interactions in Living Cells

2005 ◽  
Vol 79 (23) ◽  
pp. 14748-14755 ◽  
Author(s):  
Melissa I. Chang ◽  
Porntula Panorchan ◽  
Terrence M. Dobrowsky ◽  
Yiider Tseng ◽  
Denis Wirtz
Keyword(s):  
Human Immunodeficiency Virus ◽  
Host Cell ◽  
Single Molecule ◽  
Quantitative Description ◽  
Living Cells ◽  
Viral Envelope ◽  
Binding Interactions ◽  
Immunodeficiency Virus ◽  
Single Molecule Analysis

ABSTRACT A quantitative description of the binding interactions between human immunodeficiency virus (HIV) type 1 envelope glycoproteins and their host cell surface receptors remains incomplete. Here, we introduce a single-molecule analysis that directly probes the binding interactions between an individual viral subunit gp120 and a single receptor CD4 and/or chemokine coreceptor CCR5 in living cells. This analysis differentiates single-molecule binding from multimolecule avidity and shows that, while the presence of CD4 is required for gp120 binding to CCR5, the force required to rupture a single gp120-coreceptor bond is significantly higher and its lifetime is much longer than those of a single gp120-receptor bond. The lifetimes of these bonds are themselves shorter than those of the P-selectin/PSGL-1 bond involved in leukocyte attachment to the endothelium bonds during an inflammation response. These results suggest an amended model of HIV entry in which, immediately after the association of gp120 to its receptor, gp120 seeks its coreceptor to rapidly form a new bond. This “bond transfer” occurs only if CCR5 is in close proximity to CD4 and CD4 is still attached to gp120. The analysis presented here may serve as a general framework to study mechanisms of receptor-mediated interactions between viral envelope proteins and host cell receptors at the single-molecule level in living cells.

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