scholarly journals Nef Can Enhance the Infectivity of Receptor-Pseudotyped Human Immunodeficiency Virus Type 1 Particles

2008 ◽  
Vol 82 (21) ◽  
pp. 10811-10819 ◽  
Author(s):  
Massimo Pizzato ◽  
Elena Popova ◽  
Heinrich G. Göttlinger
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Viral Infectivity ◽  
Endosomal Acidification ◽  
Immunodeficiency Virus ◽  
Ph Dependent ◽  
Env Protein ◽  
Hiv 1

ABSTRACT Nef is an accessory protein of human immunodeficiency virus type 1 (HIV-1) that enhances the infectivity of progeny virions when expressed in virus-producing cells. The requirement for Nef for optimal infectivity is, at least in part, determined by the envelope (Env) glycoprotein, because it can be eliminated by pseudotyping HIV-1 particles with pH-dependent Env proteins. To investigate the role of Env in the function of Nef, we have examined the effect of Nef on the infectivity of Env-deficient HIV-1 particles pseudotyped with viral receptors for cells expressing cognate Env proteins. We found that Nef significantly enhances the infectivity of CD4-chemokine receptor pseudotypes for cells expressing HIV-1 Env. Nef also increased the infectivity of HIV-1 particles pseudotyped with Tva, the receptor for subgroup A Rous sarcoma virus (RSV-A), even though Nef had no effect if the pH-dependent Env protein of RSV-A was used for pseudotyping. However, Nef does not always enhance viral infectivity if the normal orientation of the Env-receptor interaction is reversed, because the entry of Env-deficient HIV-1 into cells expressing the vesicular stomatitis virus G protein was unaffected by Nef. Together, our results demonstrate that the presence of a viral Env protein during virus production is not required for the ability of Nef to increase viral infectivity. Furthermore, since the infectivity of Tva pseudotypes was blocked by inhibitors of endosomal acidification, we conclude that low-pH-dependent entry does not always bypass the requirement for Nef.

scholarly journals Baseline Resistance of Primary Human Immunodeficiency Virus Type 1 Strains to the CXCR4 Inhibitor AMD3100

2008 ◽  
Vol 82 (23) ◽  
pp. 11695-11704 ◽  
Author(s):  
Jessamina E. Harrison ◽  
Jonathan B. Lynch ◽  
Luz-Jeannette Sierra ◽  
Leslie A. Blackburn ◽  
Neelanjana Ray ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Antiviral Agents ◽  
Viral Envelope ◽  
Cxcr4 Antagonist ◽  
Immunodeficiency Virus ◽  
Env Protein ◽  
Hiv 1

ABSTRACT We screened a panel of R5X4 and X4 human immunodeficiency virus type 1 (HIV-1) strains for their sensitivities to AMD3100, a small-molecule CXCR4 antagonist that blocks HIV-1 infection via this coreceptor. While no longer under clinical development, AMD3100 is a useful tool with which to probe interactions between the viral envelope (Env) protein and CXCR4 and to identify pathways by which HIV-1 may become resistant to this class of antiviral agents. While infection by most virus strains was completely blocked by AMD3100, we identified several R5X4 and X4 isolates that exhibited plateau effects: as the AMD3100 concentration was increased, virus infection and membrane fusion diminished to variable degrees. Once saturating concentrations of AMD3100 were achieved, further inhibition was not observed, indicating a noncompetitive mode of viral resistance to the drug. The magnitude of the plateau varied depending on the virus isolate, as well as the cell type used, with considerable variation observed when primary human T cells from different human donors were used. Structure-function studies indicated that the V1/V2 region of the R5X4 HIV-1 isolate DH12 was necessary for AMD3100 resistance and could confer this property on two heterologous Env proteins. We conclude that some R5X4 and X4 HIV-1 isolates can utilize the AMD3100-bound conformation of CXCR4, with the efficiency being influenced by both viral and host factors. Baseline resistance to this CXCR4 antagonist could influence the clinical use of such compounds.

scholarly journals Inhibitory role of CXCR4 glycan in CD4-independent X4-tropic human immunodeficiency virus type 1 infection and its abrogation in CD4-dependent infection

2007 ◽  
Vol 88 (11) ◽  
pp. 3139-3144 ◽  
Author(s):  
Yoshinao Kubo ◽  
Masaru Yokoyama ◽  
Hiroaki Yoshii ◽  
Chiho Mitani ◽  
Chika Tominaga ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Virus Infection ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Viral Envelope ◽  
Extracellular Region ◽  
Immunodeficiency Virus ◽  
Env Protein ◽  
Hiv 1

CXCR4 functions as an infection receptor of X4 human immunodeficiency virus type 1 (HIV-1) . CXCR4 is glycosylated at the N-terminal extracellular region, which is important for viral envelope (Env) protein binding. We compared the effects of CXCR4 glycan on the CD4-dependent and –independent infections in human cells by X4 viruses. We found that transduction mediated by Env proteins of CD4-independent HIV-1 strains increased up to 5.5-fold in cells expressing unglycosylated CXCR4, suggesting that the CXCR4 glycan inhibits CD4-independent X4 virus infection. Co-expression of CD4 on the target cell surface or pre-incubation of virus particles with soluble CD4 abrogates the glycan-mediated inhibition of X4 virus infection, suggesting that interaction of Env protein with CD4 counteracts the inhibition. These findings indicate that it will be advantageous for X4 HIV-1 to remain CD4-dependent. A structural model that explains the glycan-mediated inhibition is discussed.

scholarly journals Inhibition of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{tRNA}_{3}^{\mathrm{Lys}}\) \end{document}-Primed Reverse Transcription by Human APOBEC3G during Human Immunodeficiency Virus Type 1 Replication

2006 ◽  
Vol 80 (23) ◽  
pp. 11710-11722 ◽  
Author(s):  
Fei Guo ◽  
Shan Cen ◽  
Meijuan Niu ◽  
Jenan Saadatmand ◽  
Lawrence Kleiman
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Reverse Transcription ◽  
Viral Infectivity ◽  
Viral Dna ◽  
Immunodeficiency Virus ◽  
Dna Production ◽  
Hiv 1

ABSTRACT Cells are categorized as being permissive or nonpermissive according to their ability to produce infectious human immunodeficiency virus type 1 (HIV-1) lacking the viral protein Vif. Nonpermissive cells express the human cytidine deaminase APOBEC3G (hA3G), and Vif has been shown to bind to APOBEC3G and facilitate its degradation. Vif-negative HIV-1 virions produced in nonpermissive cells incorporate hA3G and have a severely reduced ability to produce viral DNA in newly infected cells. While it has been proposed that the reduction in DNA production is due to hA3G-facilitated deamination of cytidine, followed by DNA degradation, we provide evidence here that a decrease in the synthesis of the DNA by reverse transcriptase may account for a significant part of this reduction. During the infection of cells with Vif-negative HIV-1 produced from 293T cells transiently expressing hA3G, much of the inhibition of early (≥50% reduction) and late (≥95% reduction) viral DNA production, and of viral infectivity (≥95% reduction), can occur independently of DNA deamination. The inhibition of the production of early minus-sense strong stop DNA is also correlated with a similar inability of tRNA3 Lys to prime reverse transcription. A similar reduction in tRNA3 Lys priming and viral infectivity is also seen in the naturally nonpermissive cell H9, albeit at significantly lower levels of hA3G expression.

Mechanism of translation of monocistronic and multicistronic human immunodeficiency virus type 1 mRNAs

1992 ◽  
Vol 12 (1) ◽  
pp. 207-219 ◽  
Author(s):  
S Schwartz ◽  
B K Felber ◽  
G N Pavlakis
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Cdna Clones ◽  
Leaky Scanning ◽  
Reading Frame ◽  
Immunodeficiency Virus ◽  
Env Protein ◽  
Hiv 1

We have used a panel of cDNA clones expressing wild-type and mutant human immunodeficiency virus type 1 (HIV-1) mRNAs to study translation of these mRNAs in eucaryotic cells. The tat open reading frame (ORF) has a strong signal for translation initiation, while rev and vpu ORFs have weaker signals. The expression of downstream ORFs is inhibited in mRNAs that contain the tat ORF as the first ORF. In contrast, downstream ORFs are expressed efficiently from mRNAs that have rev or vpu as the first ORF. All env mRNAs contain the upstream vpu ORF. Expression of HIV-1 Env protein requires a weak vpu AUG, which allows leaky scanning to occur, thereby allowing ribosomes access to the downstream env ORF. We concluded that HIV-1 mRNAs are translated by the scanning mechanism and that expression of more than one protein from each mRNA was caused by leaky scanning at the first AUG of the mRNA.

scholarly journals High-Titer Human Immunodeficiency Virus Type 1-Based Vector Systems for Gene Delivery into Nondividing Cells

1998 ◽  
Vol 72 (11) ◽  
pp. 8873-8883 ◽  
Author(s):  
Hideki Mochizuki ◽  
Joan P. Schwartz ◽  
Koichi Tanaka ◽  
Roscoe O. Brady ◽  
Jakob Reiser
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
High Titer ◽  
Vector System ◽  
Coding Region ◽  
Immunodeficiency Virus ◽  
Env Protein ◽  
Hiv 1

ABSTRACT Previously we designed novel pseudotyped high-titer replication defective human immunodeficiency virus type 1 (HIV-1) vectors to deliver genes into nondividing cells (J. Reiser, G. Harmison, S. Kluepfel-Stahl, R. O. Brady, S. Karlsson, and M. Schubert, Proc. Natl. Acad. Sci. USA 93:15266–15271, 1996). Since then we have made several improvements with respect to the safety, flexibility, and efficiency of the vector system. A three-plasmid expression system is used to generate pseudotyped HIV-1 particles by transient transfection of human embryonic kidney 293T cells with a defective packaging construct, a plasmid coding for a heterologous envelope (Env) protein, and a vector construct harboring a reporter gene such as neo, ShlacZ (encoding a phleomycin resistance/β-galactosidase fusion protein), HSA (encoding mouse heat-stable antigen), or EGFP (encoding enhanced green fluorescent protein). The packaging constructs lack functional Vif, Vpr, and Vpu proteins and/or a large portion of the Env coding region as well as the 5′ and 3′ long terminal repeats, the Nef function, and the presumed packaging signal. Using G418 selection, we routinely obtained vector particles pseudotyped with the vesicular stomatitis virus G glycoprotein (VSV-G) with titers of up to 8 × 107 CFU/μg of p24, provided that a functional Tat coding region was present in the vector. Vector constructs lacking a functional Tat protein yielded titers of around 4 × 106 to 8 × 106 CFU/μg of p24. Packaging constructs with a mutation within the integrase (IN) core domain profoundly affected colony formation and expression of the reporter genes, indicating that a functional IN protein is required for efficient transduction. We explored the abilities of other Env proteins to allow formation of pseudotyped HIV-1 particles. The rabies virus and Mokola virus G proteins yielded high-titer infectious pseudotypes, while the human foamy virus Env protein did not. Using the improved vector system, we successfully transduced contact-inhibited primary human skin fibroblasts and postmitotic rat cerebellar neurons and cardiac myocytes, a process not affected by the lack of the accessory proteins.

scholarly journals Tumultuous Relationship between the Human Immunodeficiency Virus Type 1 Viral Infectivity Factor (Vif) and the Human APOBEC-3G and APOBEC-3F Restriction Factors

2009 ◽  
Vol 73 (2) ◽  
pp. 211-232 ◽  
Author(s):  
Simon Henriet ◽  
Gaëlle Mercenne ◽  
Serena Bernacchi ◽  
Jean-Christophe Paillart ◽  
Roland Marquet
Keyword(s):  
Human Immunodeficiency Virus ◽  
Antiviral Activity ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Reverse Transcription ◽  
Viral Infectivity ◽  
Immunodeficiency Virus ◽  
Viral Infectivity Factor ◽  
Hiv 1

SUMMARY The viral infectivity factor (Vif) is dispensable for human immunodeficiency virus type 1 (HIV-1) replication in so-called permissive cells but is required for replication in nonpermissive cell lines and for pathogenesis. Virions produced in the absence of Vif have an aberrant morphology and an unstable core and are unable to complete reverse transcription. Recent studies demonstrated that human APOBEC-3G (hA3G) and APOBEC-3F (hA3F), which are selectively expressed in nonpermissive cells, possess strong anti-HIV-1 activity and are sufficient to confer a nonpermissive phenotype. Vif induces the degradation of hA3G and hA3F, suggesting that its main function is to counteract these cellular factors. Most studies focused on the hypermutation induced by the cytidine deaminase activity of hA3G and hA3F and on their Vif-induced degradation by the proteasome. However, recent studies suggested that several mechanisms are involved both in the antiviral activity of hA3G and hA3F and in the way Vif counteracts these antiviral factors. Attempts to reconcile the studies involving Vif in virus assembly and stability with these recent findings suggest that hA3G and hA3F partially exert their antiviral activity independently of their catalytic activity by destabilizing the viral core and the reverse transcription complex, possibly by interfering with the assembly and/or maturation of the viral particles. Vif could then counteract hA3G and hA3F by excluding them from the viral assembly intermediates through competition for the viral genomic RNA, by regulating the proteolytic processing of Pr55Gag, by enhancing the efficiency of the reverse transcription process, and by inhibiting the enzymatic activities of hA3G and hA3F.

scholarly journals Role of Invariant Thr80 in Human Immunodeficiency Virus Type 1 Protease Structure, Function, and Viral Infectivity

2006 ◽  
Vol 80 (14) ◽  
pp. 6906-6916 ◽  
Author(s):  
Jennifer E. Foulkes ◽  
Moses Prabu-Jeyabalan ◽  
Deyna Cooper ◽  
Gavin J. Henderson ◽  
Janera Harris ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Dynamics Simulation ◽  
Viral Infectivity ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Sequence variability associated with human immunodeficiency virus type 1 (HIV-1) is useful for inferring structural and/or functional constraints at specific residues within the viral protease. Positions that are invariant even in the presence of drug selection define critically important residues for protease function. While the importance of conserved active-site residues is easily understood, the role of other invariant residues is not. This work focuses on invariant Thr80 at the apex of the P1 loop of HIV-1, HIV-2, and simian immunodeficiency virus protease. In a previous study, we postulated, on the basis of a molecular dynamics simulation of the unliganded protease, that Thr80 may play a role in the mobility of the flaps of protease. In the present study, both experimental and computational methods were used to study the role of Thr80 in HIV protease. Three protease variants (T80V, T80N, and T80S) were examined for changes in structure, dynamics, enzymatic activity, affinity for protease inhibitors, and viral infectivity. While all three variants were structurally similar to the wild type, only T80S was functionally similar. Both T80V and T80N had decreased the affinity for saquinavir. T80V significantly decreased the ability of the enzyme to cleave a peptide substrate but maintained infectivity, while T80N abolished both activity and viral infectivity. Additionally, T80N decreased the conformational flexibility of the flap region, as observed by simulations of molecular dynamics. Taken together, these data indicate that HIV-1 protease functions best when residue 80 is a small polar residue and that mutations to other amino acids significantly impair enzyme function, possibly by affecting the flexibility of the flap domain.

scholarly journals The CC-Chemokine RANTES Increases the Attachment of Human Immunodeficiency Virus Type 1 to Target Cells via Glycosaminoglycans and Also Activates a Signal Transduction Pathway That Enhances Viral Infectivity

1999 ◽  
Vol 73 (8) ◽  
pp. 6370-6379 ◽  
Author(s):  
Alexandra Trkola ◽  
Cynthia Gordon ◽  
Jamie Matthews ◽  
Elizabeth Maxwell ◽  
Tom Ketas ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Single Amino Acid ◽  
Viral Infectivity ◽  
Enveloped Viruses ◽  
Cc Chemokine ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT We have studied the mechanisms by which the CC-chemokine RANTES can enhance the infectivities of human immunodeficiency virus type 1 (HIV-1) and other enveloped viruses, when present at concentrations in excess of 500 ng/ml in vitro. Understanding the underlying mechanisms might throw light on fundamental processes of viral infection, in particular for HIV-1. Our principal findings are twofold: firstly, that oligomers of RANTES can cross-link enveloped viruses, including HIV-1, to cells via glycosaminoglycans (GAGs) present on the membranes of both virions and cells; secondly, that oligomers of RANTES interact with cell-surface GAGs to transduce a herbimycin A-sensitive signal which, over a period of several hours, renders the cells more permissive to infection by several viruses, including HIV-1. The enhancement mechanisms require that RANTES oligomerize either in solution or following binding to GAGs, since no viral infectivity enhancement is observed with a mutant form of the RANTES molecule that contains a single-amino-acid change (glutamic acid to serine at position 66) which abrogates oligomerization.

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