scholarly journals Vpu Is the Main Determinant for Tetraspanin Downregulation in HIV-1-Infected Cells

2015 ◽  
Vol 89 (6) ◽  
pp. 3247-3255 ◽  
Author(s):  
Marie Lambelé ◽  
Herwig Koppensteiner ◽  
Menelaos Symeonides ◽  
Nathan H. Roy ◽  
Jany Chan ◽  
...  
Keyword(s):  
Host Cell ◽  
Virus Propagation ◽  
Main Determinant ◽  
Additional Group ◽  
Viral Particles ◽  
Viral Determinant ◽  
Immune Attack ◽  
Host Cell Factors ◽  
Infected Cells ◽  
Hiv 1

ABSTRACTTetraspanins constitute a family of cellular proteins that organize various membrane-based processes. Several members of this family, including CD81, are actively recruited by HIV-1 Gag to viral assembly and release sites. Despite their enrichment at viral exit sites, the overall levels of tetraspanins are decreased in HIV-1-infected cells. Here, we identify Vpu as the main viral determinant for tetraspanin downregulation. We also show that reduction of CD81 levels by Vpu is not a by-product of CD4 or BST-2/tetherin elimination from the surfaces of infected cells and likely occurs through an interaction between Vpu and CD81. Finally, we document that Vpu-mediated downregulation of CD81 from the surfaces of infected T cells can contribute to preserving the infectiousness of viral particles, thus revealing a novel Vpu function that promotes virus propagation by modulating the host cell environment.IMPORTANCEThe HIV-1 accessory protein Vpu has previously been shown to downregulate various host cell factors, thus helping the virus to overcome restriction barriers, evade immune attack, and maintain the infectivity of viral particles. Our study identifies tetraspanins as an additional group of host factors whose expression at the surfaces of infected cells is lowered by Vpu. While the downregulation of these integral membrane proteins, including CD81 and CD82, likely affects more than one function of HIV-1-infected cells, we document that Vpu-mediated lowering of CD81 levels in viral particles can be critical to maintaining their infectiousness.

scholarly journals Novel compound inhibitors of HIV-1NL4-3 Vpu

2021 ◽  
Author(s):  
Carolyn A Robinson ◽  
Terri D Lyddon ◽  
Hwi Min Gil ◽  
David T. Evans ◽  
Yury V Kuzmichev ◽  
...  
Keyword(s):  
Host Cell ◽  
Particle Production ◽  
Viral Glycoprotein ◽  
New Class ◽  
Host Cell Proteins ◽  
Viral Particles ◽  
Dependent Cell ◽  
A Cell ◽  
Hiv 1

HIV-1 Vpu targets the host cell proteins CD4 and BST-2/Tetherin for degradation, ultimately resulting in enhanced virus spread and host immune evasion. The discovery and characterization of small molecules that antagonize Vpu would further elucidate the contribution of Vpu to pathogenesis and lay the foundation for the study of a new class of novel HIV-1 therapeutics. To identify novel compounds that block Vpu activity, we developed a cell-based 'gain of function' assay that produces a positive signal in response to Vpu inhibition. To develop this assay, we took advantage of the viral glycoprotein, GaLV Env. In the presence of Vpu, GaLV Env is not incorporated into viral particles, resulting in non-infectious virions. Vpu inhibition restores infectious particle production. Using this assay, a high throughput screen of >650,000 compounds was performed to identify inhibitors that block the biological activity of Vpu. From this screen, we identified several positive hits but focused on two compounds from one structural family, SRI-41897 and SRI-42371. It was conceivable that the compounds inhibited the formation of infectious virions by targeting host cell proteins instead of Vpu directly, so we developed independent counter-screens for off target interactions of the compounds and found no off target interactions. Additionally, these compounds block Vpu-mediated modulation of CD4, BST-2/Tetherin and antibody dependent cell-mediated toxicity (ADCC). Unfortunately, both SRI-41897 and SRI-42371 were shown to be specific to the N-terminal region of NL4-3 Vpu and did not function against other, more clinically relevant, strains of Vpu.

scholarly journals Determination of Number of Infected Cells and Concentration of Viral Particles in Plasma during HIV-1 Infections Using Shehu Transformation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
M. Higazy ◽  
Sudhanshu Aggarwal ◽  
Y. S. Hamed
Keyword(s):  
Initial Conditions ◽  
Integral Transformation ◽  
Mathematical Representation ◽  
Infection Model ◽  
Viral Particles ◽  
Infected Cells ◽  
Linear Differential ◽  
The Mathematical Model ◽  
Ordinary Linear Differential Equations ◽  
Hiv 1

In this paper, the authors determine the number of infected cells and concentration of infected (viral) particles in plasma during HIV-1 (human immunodeficiency virus type one) infections using Shehu transformation. For this, the authors first defined some useful properties of Shehu transformation with proof and then applied Shehu transformation on the mathematical representation of the HIV-1 infection model. The mathematical model of HIV-1 infections contains a system of two simultaneous ordinary linear differential equations with initial conditions. Results depict that Shehu transformation is very effective integral transformation for determining the number of infected cells and concentration of viral particles in plasma during HIV-1 infections.

scholarly journals The host-cell restriction factor SERINC5 restricts HIV-1 infectivity without altering the lipid composition and organization of viral particles

2017 ◽  
Vol 292 (33) ◽  
pp. 13702-13713 ◽  
Author(s):  
Birthe Trautz ◽  
Hannah Wiedemann ◽  
Christian Lüchtenborg ◽  
Virginia Pierini ◽  
Jan Kranich ◽  
...  
Keyword(s):  
Host Cell ◽  
Lipid Composition ◽  
Restriction Factor ◽  
Viral Particles ◽  
Hiv 1

scholarly journals Flow Cytometry Analysis of HIV-1 Env Conformations at the Surface of Infected Cells and Virions: Role of Nef, CD4, and SERINC5

2019 ◽  
Vol 94 (6) ◽  
Author(s):  
Isabelle Staropoli ◽  
Jérémy Dufloo ◽  
Anaïs Ducher ◽  
Pierre-Henri Commere ◽  
Anna Sartori-Rupp ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Cellular Proteins ◽  
Viral Infectivity ◽  
Viral Particles ◽  
Immunodeficiency Virus ◽  
Infected Cells ◽  
Env Protein ◽  
The Impact ◽  
Hiv 1

ABSTRACT The HIV-1 Env protein is exposed at the surface of virions and infected cells. Env fluctuates between different closed and open structural states and these conformations influence both viral infectivity and sensitivity to antibody binding and neutralization. We established a flow virometry assay to visualize Env proteins at the surface of human immunodeficiency virus type 1 (HIV-1) virions. The assay is performed on ultracentrifuged fluorescent viral particles that are stained with a panel of broadly neutralizing antibodies (bNAbs) and nonneutralizing antibodies (nnAbs) that probe different epitopes of Env. We used this assay to compare Env at the surface of producer cells and viral particles and to analyze the effect of Nef, CD4, and SERINC5 on Env accessibility to antibodies. We studied the laboratory-adapted strain NL4-3 and two transmitted/founder viruses, THRO and CH058. We confirm that antibody accessibility varies between viral strains and show that Nef, CD4, and SERINC5 additively impact Env conformations. We further demonstrate that the Env accessibility profile on virions is globally similar to that observed on HIV-1-infected cells, with some noticeable differences. For instance, nnAbs bind to virions more efficiently than to producer cells, likely reflecting changes in Env conformational states on mature viral particles. This test complements other techniques and provides a convenient and simple tool for quantifying and probing the structure of Env at the virion surface and to analyze the impact of viral and cellular proteins on these parameters. IMPORTANCE HIV-1 Env conformation is one of the key parameters determining viral infectivity. The flow virometry-based assay developed in this study allows for the characterization of proteins incorporated in HIV-1 particles. We studied the conformation of HIV-1 Env and the impact that the viral protein Nef and the cellular proteins CD4 and SERINC5 have on Env accessibility to antibodies. Our assay permitted us to highlight some noticeable differences in the conformation of Env between producer cells and viral particles. It contributes to a better understanding of the actual composition of HIV-1 particles.

scholarly journals TRIM34 acts with TRIM5 to restrict HIV and SIV capsids

2019 ◽  
Author(s):  
Molly Ohainle ◽  
Kyusik Kim ◽  
Sevnur Keceli ◽  
Abby Felton ◽  
Ed Campbell ◽  
...  
Keyword(s):  
Host Cell ◽  
Critical Role ◽  
Restriction Factor ◽  
Target Cells ◽  
Restriction Factors ◽  
Host Proteins ◽  
Hiv Replication ◽  
Cytoplasmic Bodies ◽  
Host Cell Factors ◽  
Hiv 1

AbstractThe HIV-1 capsid protein makes up the core of the virion and plays a critical role in early steps of HIV replication. Due to its exposure in the cytoplasm after entry, HIV capsid is a target for host cell factors that act directly to block infection such as TRIM5 and MxB. Several host proteins also play a role in facilitating infection, including in the protection of HIV-1 capsid from recognition by host cell restriction factors. Through an unbiased screening approach, called HIV-CRISPR, we show that the Cyclophilin A-binding deficient P90A HIV-1 capsid mutant becomes highly-sensitized to TRIM5alpha restriction in IFN-treated cells. Further, the CPSF6-binding deficient, N74D HIV-1 capsid mutant is sensitive to restriction mediated by human TRIM34, a close paralog of the well-characterized HIV restriction factor TRIM5. This restriction occurs at the step of reverse transcription, is independent of interferon stimulation and limits HIV-1 infection in key target cells of HIV infection including CD4+ T cells and monocyte-derived dendritic cells. TRIM34 restriction requires TRIM5alpha as knockout or knockdown of TRIM5alpha results in a loss of antiviral activity. TRIM34 can also restrict some SIV capsids. Through immunofluorescence studies, we show that TRIM34 and TRIM5alpha colocalize to cytoplasmic bodies and are more frequently observed to be associated with infecting N74D capsids than with WT capsids. Our results identify TRIM34 as an HIV-1 CA-targeting restriction factor and highlight the potential role for heteromultimeric TRIM interactions in contributing restriction of HIV-1 infection in human cells.

scholarly journals An ultrasensitive planar array p24 Gag ELISA to detect individual HIV-1 viral particles and infected cells

2021 ◽  
Author(s):  
Alberto Bosque ◽  
Callie Levinger ◽  
J Natalie Howard ◽  
Pingtao Tang ◽  
Amit Joshi
Keyword(s):  
Biological Fluids ◽  
Low Frequency ◽  
Viral Reservoirs ◽  
Hiv Persistence ◽  
Viral Particles ◽  
Planar Array ◽  
Infected Cells ◽  
Major Loss ◽  
Hiv 1

Abstract Human Immunodeficiency virus-1 (HIV-1) persistence in the presence of antiretroviral therapy (ART) has halted the development of curative strategies. Measuring HIV persistence is complex due to the low frequency of cells containing virus in vivo. Most of the commercially available assays to date measure nucleic acid. These assays have the advantage of being highly sensitive and allow for the analysis of sequence diversity, intactness of the HIV genome or evaluation of diverse RNA species. However, these assays are limited in evaluating translational competent viral reservoirs. In here, we developed an ultrasensitive p24 ELISA that uses the SimoaTM planar array technology that can detect as low as a single HIV-1 particle and a single HIV-1 infected cell. Furthermore, the assay is optimized to measure very low levels of p24 in different biological fluids without a major loss of sensitivity or reproducibility. Our results demonstrate that the ‘homebrew' planar p24 ELISA immunoassay is a broadly applicable new tool to evaluate HIV persistence in diverse biological fluids.

scholarly journals Host cell factors stimulate HIV-1 transcription by antagonizing substrate-binding function of Siah1 ubiquitin ligase to stabilize transcription elongation factor ELL2

2020 ◽  
Author(s):  
Jun Wu ◽  
Yuhua Xue ◽  
Xiang Gao ◽  
Qiang Zhou
Keyword(s):  
Host Cell ◽  
Stress Responses ◽  
Substrate Binding ◽  
Elongation Factor ◽  
Transcriptional Elongation ◽  
Elongation Complex ◽  
Binding Function ◽  
Cellular Stress Responses ◽  
Host Cell Factors ◽  
Hiv 1

Abstract The Siah1 and Siah2 ubiquitin ligases are implicated in diverse biological processes ranging from cellular stress responses, signaling to transcriptional regulation. A key substrate of Siah1 is ELL2, which undergoes proteolysis upon polyubiquitination. ELL2 stimulates transcriptional elongation and is a subunit of the Super Elongation Complex (SEC) essential for HIV-1 transactivation. Previously, multiple transcriptional and post-translational mechanisms are reported to control Siah's expression and activity. Here we show that the activity of Siah1/2 can also be suppressed by host cell factor 1 (HCF1), and the hitherto poorly characterized HCF2, which themselves are not degraded but can bind and block the substrate-binding domain (SBD) of Siah1/2 to prevent their autoubiquitination and trans-ubiquitination of downstream targets including ELL2. This effect stabilizes ELL2 and enhances the ELL2-SEC formation for robust HIV-1 transactivation. Thus, our study not only identifies HCF1/2 as novel activators of HIV-1 transcription through inhibiting Siah1 to stabilize ELL2, but also reveals the SBD of Siah1/2 as a previously unrecognized new target for HCF1/2 to exert this inhibition.

Comparative study of ultrastructure of HIV and SIV

1990 ◽  
Vol 48 (3) ◽  
pp. 342-343
Author(s):  
Takashi Nakano ◽  
Shunro Imura ◽  
Masuyo Nakai
Keyword(s):  
Osmium Tetroxide ◽  
Staining Method ◽  
Culture Fluid ◽  
Ultrastructural Feature ◽  
Uranyl Acetate ◽  
Negative Staining ◽  
Thin Sections ◽  
Viral Particles ◽  
Infected Cells ◽  
Hiv 1

The ultrastructural feature of AIDS viruses (HIV and SIV) was observed by ultrathin-sectioning and negative staining method, and the surface structures of these viruses were compared.HIV-1 group including, HTLV-III and LAV-1 were used. And in HIV-2 group, LAV-2, which was isolated from a Senegalese AIDS patient, and GH-1, which was isolated from a Ghanan AIDS patient, were used. SIV group was used AGM-1, which was isolated from an African green monkey. The virions were used which was produced from Molt-4 cells after the infection of each viruses of these strains. The infected cells and viral particles, which were collected by centrifugation were fixed with 2% glutaraldehyde (GA), washed with PBS, and postfixed with 1% osmium tetroxide. The specimens were dehydrated in graded ethanol, and embedded in Epon 812. The thin sections were stained with uranyl acetate and lead citrate. On the other hand, for negative staining, 25% GA was added to the supernatant culture fluid and finally concentrated on 2% GA. Then virions were collected by ultracentrifugation.

Host cell factors and HIV-1 integration

2007 ◽  
Vol 1 (4) ◽  
pp. 415-426 ◽  
Author(s):  
Alan Engelman
Keyword(s):  
Host Cell ◽  
Host Cell Factors ◽  
Hiv 1

scholarly journals Temporal Gene Regulation During HIV-1 Infection of Human CD4+ T Cells

2001 ◽  
Vol 11 (7) ◽  
pp. 1198-1204
Author(s):  
Jacques Corbeil ◽  
Dennis Sheeter ◽  
Davide Genini ◽  
Steffney Rought ◽  
Lorenzo Leoni ◽  
...  
Keyword(s):  
T Cell ◽  
Host Cell ◽  
Genotoxic Stress ◽  
Repair Gene ◽  
Dna Repair Gene ◽  
Its Gene ◽  
Gene Transcripts ◽  
Infected Cells ◽  
Induced Apoptosis ◽  
Hiv 1

CD4+ T-cell depletion is a characteristic of human immunodeficiency virus type 1 (HIV-1) infection. In this study, modulation of mRNA expression of 6800 genes was monitored simultaneously at eight time points in a CD4+ T-cell line (CEM-GFP) during HIV infection. The responses to infection included: (1) >30% decrease at 72 h after infection in overall host-cell production of monitored mRNA synthesis, with the replacement of host-cell mRNA by viral mRNA, (2) suppression of the expression of selected mitochondrial and DNA repair gene transcripts, (3) increased expression of the proapoptotic gene and its gene p53-induced product Bax, and (4) activation of caspases 2, 3, and 9. The intense HIV-1 transcription resulted in the repression of much cellular RNA expression and was associated with the induction of apoptosis of infected cells but not bystander cells. This choreographed host gene response indicated that the subversion of the cell transcriptional machinery for the purpose of HIV-1 replication is akin to genotoxic stress and represents a major factor leading to HIV-induced apoptosis.

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