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Platinum_GP Retroviral Packaging Cell Line, Pantropic

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[#RV-103] Platinum_GP Retroviral Packaging Cell Line, Pantropic


RV-103 | Platinum_GP Retroviral Packaging Cell Line, Pantropic, 1 vial
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(1) Screening Clinical Cell Products for Replication Competent Retrovirus: The National Gene Vector Biorepository Experience.[TOP]

Pubmed ID :30211249
Publication Date : //
Replication-competent retrovirus (RCR) is a safety concern for individuals treated with retroviral gene therapy. RCR detection assays are used to detect RCR in manufactured vector, transduced cell products infused into research subjects, and in the research subjects after treatment. In this study, we reviewed 286 control (n = 4) and transduced cell products (n = 282) screened for RCR in the National Gene Vector Biorepository. The transduced cell samples were submitted from 14 clinical trials. All vector products were previously shown to be negative for RCR prior to use in cell transduction. After transduction, all 282 transduced cell products were negative for RCR. In addition, 241 of the clinical trial participants were also screened for RCR by analyzing peripheral blood at least 1 month after infusion, all of which were also negative for evidence of RCR infection. The majority of vector products used in the clinical trials were generated in the PG13 packaging cell line. The findings suggest that screening of the retroviral vector product generated in PG13 cell line may be sufficient and that further screening of transduced cells does not provide added value.

Authors : Cornetta Kenneth, Duffy Lisa, Feldman Steven A, Mackall Crystal L, Davila Marco L, Curran Kevin J, Junghans Richard P, Tang Jean Yuh, Kochenderfer James N, O'Cearbhaill Roisin, Archer Gary, Kiem Hans-Peter, Shah Nirali N, Delbrook Cindy, Kaplan Rosie, Brentjens Renier J, Rivière Isabelle, Sadelain Michel, Rosenberg Steven A,

(2) Lentiviral Vector-Mediated SHC3 Silencing Exacerbates Oxidative Stress Injury in Nigral Dopamine Neurons by Regulating the PI3K-AKT-FoxO Signaling Pathway in Rats with Parkinson's Disease.[TOP]

Pubmed ID :30184529
Publication Date : //
Parkinson's disease (PD) is a prevalent disease that leads to motor and cognitive disabilities, and oxidative stress (OS) injury was found to be related to the etiology of PD. Increasing evidence has shown that SHC3 is aberrantly expressed in neurons. The current study examines the involvement of SHC3 silencing in OS injury in the nigral dopamine neurons in rats with PD via the PI3K-AKT-FoxO signaling pathway.

Authors : Gong Jian, Zhang Lei, Zhang Qian, Li Xiang, Xia Xiang-Jun, Liu Yin-Yuan, Yang Qin-Shang,

(3) Lentivector Producer Cell Lines with Stably Expressed Vesiculovirus Envelopes.[TOP]

Pubmed ID :30182034
Publication Date : //
Retroviral and lentiviral vectors often use the envelope G protein from the vesicular stomatitis virus Indiana strain (VSVind.G). However, lentivector producer cell lines that stably express VSVind.G have not been reported, presumably because of its cytotoxicity, preventing simple scale-up of vector production. Interestingly, we showed that VSVind.G and other vesiculovirus G from the VSV New Jersey strain (VSVnj), Cocal virus (COCV), and Piry virus (PIRYV) could be constitutively expressed and supported lentivector production for up to 10 weeks. All G-enveloped particles were robust, allowing concentration and freeze-thawing. COCV.G and PIRYV.G were resistant to complement inactivation, and, using chimeras between VSVind.G and COCV.G, the determinant for complement inactivation of VSVind.G was mapped to amino acid residues 136-370. Clonal packaging cell lines using COCV.G could be generated; however, during attempts to establish LV producer cells, vector superinfection was observed following the introduction of a lentivector genome. This could be prevented by culturing the cells with the antiviral drug nevirapine. As an alternative countermeasure, we demonstrated that functional lentivectors could be reconstituted by admixing supernatant from stable cells producing unenveloped virus with supernatant containing envelopes harvested from cells stably expressing VSVind.G, COCV.G, or PIRYV.G.

Authors : Tijani Maha, Munis Altar M, Perry Christopher, Sanber Khaled, Ferraresso Marta, Mukhopadhyay Tarit, Themis Michael, Nisoli Ilaria, Mattiuzzo Giada, Collins Mary K, Takeuchi Yasuhiro,

(4) A High-throughput Cre-Lox Activated Viral Membrane Fusion Assay to Identify Inhibitors of HIV-1 Viral Membrane Fusion.[TOP]

Pubmed ID :30176017
Publication Date : //
This assay is designed to specifically report on HIV-1 fusion via the expression of green fluorescent protein (GFP) detectable by flow cytometry or fluorescence microscopy. An HIV-1 reporter virus (HIV-1 Gag-iCre) is generated by inserting Cre recombinase into the HIV-1 genome between the matrix and the capsid proteins of the Gag polyprotein. This results in a packaging of Cre recombinase into virus particles, which is then released into a target cell line stably expressing a Cre recombinase-activated red fluorescent protein (RFP) to GFP switch cassette. In the basal state, this cassette expresses RFP only. Following the delivery of Cre recombinase into the target cell, the RFP, flanked by loxP sites, excises, resulting in GFP expression. This assay can be used to test any inhibitors of viral entry (specifically at the fusion step) in cell-free and cell-to-cell infection systems and has been used to identify a class of purinergic receptor antagonists as novel inhibitors of HIV-1 viral membrane fusion.

Authors : Esposito Anthony M, Soare Alexandra Y, Patel Foramben, Satija Namita, Chen Benjamin K, Swartz Talia H,

(5) The chromatin binding domain, including the QPQRYG motif, of feline foamy virus Gag is required for viral DNA integration and nuclear accumulation of Gag and the viral genome.[TOP]

Pubmed ID :30145377
Publication Date : //
The retroviral Gag protein, the major component of released particles, plays different roles in particle assembly, maturation or infection of new host cells. Here, we characterize the Gag chromatin binding site including the highly conserved QPQRYG motif of feline foamy virus, a member of the Spumaretrovirinae. Mutagenesis of critical residues in the chromatin binding site/QPQRYG motif almost completely abrogates viral DNA integration and reduces nuclear accumulation of Gag and viral DNA. Genome packaging, reverse transcription, particle release and uptake into new target cells are not affected. The integrity of the QPQRYG motif appears to be important for processes after cytosolic entry, likely influencing incoming virus capsids or disassembly intermediates but not Gag synthesized de novo in progeny virus-producing cells. According to our data, chromatin binding is a shared feature among foamy viruses but further work is needed to understand the mechanisms involved.

Authors : Wei Guochao, Kehl Timo, Bao Qiuying, Benner Axel, Lei Janet, Löchelt Martin,

(6) Biochemical and Functional Characterization of Mouse Mammary Tumor Virus Full-Length Pr77 Expressed in Prokaryotic and Eukaryotic Cells.[TOP]

Pubmed ID :29912170
Publication Date : //
The mouse mammary tumor virus (MMTV) Pr77 polypeptide is an essential retroviral structural protein without which infectious viral particles cannot be formed. This process requires specific recognition and packaging of dimerized genomic RNA (gRNA) by Gag during virus assembly. Most of the previous work on retroviral assembly has used either the nucleocapsid portion of Gag, or other truncated Gag derivatives—not the natural substrate for virus assembly. In order to understand the molecular mechanism of MMTV gRNA packaging process, we expressed and purified full-length recombinant Pr77-His₆-tag fusion protein from soluble fractions of bacterial cultures. We show that the purified Pr77-His₆-tag protein retained the ability to assemble virus-like particles (VLPs) in vitro with morphologically similar immature intracellular particles. The recombinant proteins (with and without His₆-tag) could both be expressed in prokaryotic and eukaryotic cells and had the ability to form VLPs in vivo. Most importantly, the recombinant Pr77-His₆-tag fusion proteins capable of making VLPs in eukaryotic cells were competent for packaging sub-genomic MMTV RNAs. The successful expression and purification of a biologically active, full-length MMTV Pr77 should lay down the foundation towards performing RNA⁻protein interaction(s), especially for structure-function studies and towards understanding molecular intricacies during MMTV gRNA packaging and assembly processes.

Authors : Chameettachal Akhil, Pillai Vineeta Narayana, Ali Lizna Mohamed, Pitchai Fathima Nuzra Nagoor, Ardah Mustafa Taleb, Mustafa Farah, Marquet Roland, Rizvi Tahir Aziz,

(7) HIV-1 adaptation studies reveal a novel Env-mediated homeostasis mechanism for evading lethal hypermutation by APOBEC3G.[TOP]

Pubmed ID :29677220
Publication Date : //
HIV-1 replication normally requires Vif-mediated neutralization of APOBEC3 antiviral enzymes. Viruses lacking Vif succumb to deamination-dependent and -independent restriction processes. Here, HIV-1 adaptation studies were leveraged to ask whether viruses with an irreparable vif deletion could develop resistance to restrictive levels of APOBEC3G. Several resistant viruses were recovered with multiple amino acid substitutions in Env, and these changes alone are sufficient to protect Vif-null viruses from APOBEC3G-dependent restriction in T cell lines. Env adaptations cause decreased fusogenicity, which results in higher levels of Gag-Pol packaging. Increased concentrations of packaged Pol in turn enable faster virus DNA replication and protection from APOBEC3G-mediated hypermutation of viral replication intermediates. Taken together, these studies reveal that a moderate decrease in one essential viral activity, namely Env-mediated fusogenicity, enables the virus to change other activities, here, Gag-Pol packaging during particle production, and thereby escape restriction by the antiviral factor APOBEC3G. We propose a new paradigm in which alterations in viral homeostasis, through compensatory small changes, constitute a general mechanism used by HIV-1 and other viral pathogens to escape innate antiviral responses and other inhibitions including antiviral drugs.

Authors : Ikeda Terumasa, Symeonides Menelaos, Albin John S, Li Ming, Thali Markus, Harris Reuben S,

(8) Does BCA3 Play a Role in the HIV-1 Replication Cycle?[TOP]

Pubmed ID :29677171
Publication Date : //
The cellular role of breast carcinoma-associated protein (BCA3), also known as A-kinase-interacting protein 1 (AKIP-1), is not fully understood. Recently, we reported that full-length, but not C-terminally truncated, BCA3 is incorporated into virions of Mason-Pfizer monkey virus, and that BCA3 enhances HIV-1 protease-induced apoptosis. In the present study, we report that BCA3 is associated with purified and subtilisin-treated HIV particles. Using a combination of immune-based methods and confocal microscopy, we show that the C-terminus of BCA3 is required for packaging into HIV-1 particles. However, we were unable to identify an HIV-1 binding domain for BCA3, and we did not observe any effect of incorporated BCA3 on HIV-1 infectivity. Interestingly, the BCA3 C-terminus was previously identified as a binding site for the catalytic subunit of protein kinase A (PKAc), a cellular protein that is specifically packaged into HIV-1 particles. Based on our analysis of PKAc⁻BCA3 interactions, we suggest that BCA3 incorporation into HIV-1 particles is mediated by its ability to interact with PKAc.

Authors : Rumlová Michaela, Křížová Ivana, Zelenka Jaroslav, Weber Jan, Ruml Tomáš,

(9) Identifying the assembly intermediate in which Gag first associates with unspliced HIV-1 RNA suggests a novel model for HIV-1 RNA packaging.[TOP]

Pubmed ID :29664940
Publication Date : //
During immature capsid assembly, HIV-1 genome packaging is initiated when Gag first associates with unspliced HIV-1 RNA by a poorly understood process. Previously, we defined a pathway of sequential intracellular HIV-1 capsid assembly intermediates; here we sought to identify the intermediate in which HIV-1 Gag first associates with unspliced HIV-1 RNA. In provirus-expressing cells, unspliced HIV-1 RNA was not found in the soluble fraction of the cytosol, but instead was largely in complexes ≥30S. We did not detect unspliced HIV-1 RNA associated with Gag in the first assembly intermediate, which consists of soluble Gag. Instead, the earliest assembly intermediate in which we detected Gag associated with unspliced HIV-1 RNA was the second assembly intermediate (~80S intermediate), which is derived from a host RNA granule containing two cellular facilitators of assembly, ABCE1 and the RNA granule protein DDX6. At steady-state, this RNA-granule-derived ~80S complex was the smallest assembly intermediate that contained Gag associated with unspliced viral RNA, regardless of whether lysates contained intact or disrupted ribosomes, or expressed WT or assembly-defective Gag. A similar complex was identified in HIV-1-infected T cells. RNA-granule-derived assembly intermediates were detected in situ as sites of Gag colocalization with ABCE1 and DDX6; moreover these granules were far more numerous and smaller than well-studied RNA granules termed P bodies. Finally, we identified two steps that lead to association of assembling Gag with unspliced HIV-1 RNA. Independent of viral-RNA-binding, Gag associates with a broad class of RNA granules that largely lacks unspliced viral RNA (step 1). If a viral-RNA-binding domain is present, Gag further localizes to a subset of these granules that contains unspliced viral RNA (step 2). Thus, our data raise the possibility that HIV-1 packaging is initiated not by soluble Gag, but by Gag targeted to a subset of host RNA granules containing unspliced HIV-1 RNA.

Authors : Barajas Brook C, Tanaka Motoko, Robinson Bridget A, Phuong Daryl J, Chutiraka Kasana, Reed Jonathan C, Lingappa Jaisri R,

(10) Retroviral RNA Dimerization: From Structure to Functions.[TOP]

Pubmed ID :29623074
Publication Date : //
The genome of the retroviruses is a dimer composed by two homologous copies of genomic RNA (gRNA) molecules of positive polarity. The dimerization process allows two gRNA molecules to be non-covalently linked together through intermolecular base-pairing. This step is critical for the viral life cycle and is highly conserved among retroviruses with the exception of spumaretroviruses. Furthermore, packaging of two gRNA copies into viral particles presents an important evolutionary advantage for immune system evasion and drug resistance. Recent studies reported RNA switches models regulating not only gRNA dimerization, but also translation and packaging, and a spatio-temporal characterization of viral gRNA dimerization within cells are now at hand. This review summarizes our current understanding on the structural features of the dimerization signals for a variety of retroviruses (HIVs, MLV, RSV, BLV, MMTV, MPMV…), the mechanisms of RNA dimer formation and functional implications in the retroviral cycle.

Authors : Dubois Noé, Marquet Roland, Paillart Jean-Christophe, Bernacchi Serena,