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Viruses Jan 2023After the onset of the AIDS pandemic, HIV-1 (genus ) became the predominant model for studying retrovirus Env glycoproteins and their role in entry. However, HIV Env is... (Review)
Review
After the onset of the AIDS pandemic, HIV-1 (genus ) became the predominant model for studying retrovirus Env glycoproteins and their role in entry. However, HIV Env is an inadequate model for understanding entry of viruses in the , and genera. For example, oncogenic model system viruses such as Rous sarcoma virus (RSV, ), murine leukemia virus (MLV, ) and human T-cell leukemia viruses (HTLV-I and HTLV-II, ) encode Envs that are structurally and functionally distinct from HIV Env. We refer to these as Gamma-type Envs. Gamma-type Envs are probably the most widespread retroviral Envs in nature. They are found in exogenous and endogenous retroviruses representing a broad spectrum of vertebrate hosts including amphibians, birds, reptiles, mammals and fish. In endogenous form, gamma-type Envs have been evolutionarily coopted numerous times, most notably as placental syncytins (e.g., human SYNC1 and SYNC2). Remarkably, gamma-type Envs are also found outside of the . Gp2 proteins of filoviruses (e.g., Ebolavirus) and snake arenaviruses in the genus are gamma-type Env homologs, products of ancient recombination events involving viruses of different Baltimore classes. Distinctive hallmarks of gamma-type Envs include a labile disulfide bond linking the surface and transmembrane subunits, a multi-stage attachment and fusion mechanism, a highly conserved (but poorly understood) "immunosuppressive domain", and activation by the viral protease during virion maturation. Here, we synthesize work from diverse retrovirus model systems to illustrate these distinctive properties and to highlight avenues for further exploration of gamma-type Env structure and function.
Topics: Female; Pregnancy; Animals; Humans; Mice; Placenta; Gammaretrovirus; Alpharetrovirus; Leukemia Virus, Murine; Ebolavirus; Endogenous Retroviruses; HIV Seropositivity; Glycoproteins; Mammals
PubMed: 36851488
DOI: 10.3390/v15020274 -
Frontiers in Bioscience : a Journal and... May 2008Upon integration into the host chromosome, retroviral gene expression requires transcription by the host RNA polymerase II, and viral messages are subject RNA processing... (Review)
Review
Upon integration into the host chromosome, retroviral gene expression requires transcription by the host RNA polymerase II, and viral messages are subject RNA processing events including 5'-end capping, pre-mRNA splicing, and polyadenylation. At a minimum, RNA splicing is required to generate the env mRNA, but viral replication requires substantial amounts of unspliced RNA to serve as mRNA and for incorporation into progeny virions as genomic RNA. Therefore, splicing has to be controlled to preserve the large unspliced RNA pool. Considering the current view that splicing and polyadenylation are coupled, the question arises as to how genome-length viral RNA is efficiently polyadenylated in the absence of splicing. Polyadenylation of many retroviral mRNAs is inefficient; in avian retroviruses, approximately 15 percent of viral transcripts extend into and are polyadenylated at downstream host genes, which often has profound biological consequences. Retroviruses have served as important models to study RNA processing and this review summarizes a body of work using avian retroviruses that has led to the discovery of novel RNA splicing and polyadenylation control mechanisms.
Topics: Alpharetrovirus; RNA Precursors; RNA Processing, Post-Transcriptional; RNA Splicing; RNA, Messenger; RNA, Viral; Rous sarcoma virus
PubMed: 18508481
DOI: 10.2741/2975 -
British Medical Journal Mar 1964
Review
Topics: Avian Sarcoma Viruses; DNA; DNA, Viral; Neoplasms; Neoplasms, Experimental; Oncogenic Viruses; Polyomavirus; RNA; RNA, Viral; Rous sarcoma virus; Simian virus 40; Vertebrates; Viruses
PubMed: 14096457
DOI: 10.1136/bmj.1.5384.653 -
Viruses Apr 2018The Czech scientist Jan Svoboda was a pioneer of Rous sarcoma virus (RSV). In the 1960s, before the discovery of reverse transcriptase, he demonstrated the long-term...
The Czech scientist Jan Svoboda was a pioneer of Rous sarcoma virus (RSV). In the 1960s, before the discovery of reverse transcriptase, he demonstrated the long-term persistence of the viral genome in non-productive mammalian cells, and he supported the DNA provirus hypothesis of Howard Temin. He showed how the virus can be rescued in the infectious form and elucidated the replication-competent nature of the Prague strain of RSV later used for the identification of the oncogene. His studies straddled molecular oncology and virology, and he remained an active contributor to the field until his death last year. Throughout the 50 years that I was privileged to know Svoboda as my mentor and friend, I admired his depth of scientific inquiry and his steadfast integrity in the face of political oppression.
Topics: Animals; History, 20th Century; History, 21st Century; Host-Pathogen Interactions; Humans; Rous sarcoma virus; Sarcoma, Avian; Virus Replication
PubMed: 29670049
DOI: 10.3390/v10040203 -
3'UTR of ALV-J can affect viral replication through promoting transcription and mRNA nuclear export.Journal of Virology Nov 20233'UTRs can affect gene transcription and post-transcriptional regulation in multiple ways, further influencing the function of proteins in a unique manner. Recently,...
3'UTRs can affect gene transcription and post-transcriptional regulation in multiple ways, further influencing the function of proteins in a unique manner. Recently, ALV-J has been mutating and evolving rapidly, especially the 3'UTR of viral genome. Meanwhile, clinical symptoms caused by ALV-J have changed significantly. In this study, we found that the ALV-J strains containing △-r-TM-type 3'UTR are the most abundant. By constructing ALV-J infectious clones and subgenomic vectors containing different 3'UTRs, we prove that 3'UTRs directly affect viral tissue preference and can promote virus replication as an enhancer. ALV-J strain containing 3'UTR of △-r-TM proliferated fastest in primary cells. All five forms of 3'UTRs can assist intron-containing viral mRNA nuclear export, with similar efficiency. ALV-J mRNA half-life is not influenced by different 3'UTRs. Our results dissect the roles of 3'UTR on regulating viral replication and pathogenicity, providing novel insights into potential anti-viral strategies.
Topics: 3' Untranslated Regions; Active Transport, Cell Nucleus; Gene Expression; Gene Expression Regulation; Virus Replication; Avian Leukosis Virus
PubMed: 37902396
DOI: 10.1128/jvi.01152-23 -
Viruses Dec 2014Gene therapy using integrating retroviral vectors has proven its effectiveness in several clinical trials for the treatment of inherited diseases and cancer. However,... (Review)
Review
Gene therapy using integrating retroviral vectors has proven its effectiveness in several clinical trials for the treatment of inherited diseases and cancer. However, vector-mediated adverse events related to insertional mutagenesis were also observed, emphasizing the need for safer therapeutic vectors. Paradoxically, alpharetroviruses, originally discovered as cancer-causing agents, have a more random and potentially safer integration pattern compared to gammaretro- and lentiviruses. In this review, we provide a short overview of the history of alpharetroviruses and explain how they can be converted into state-of-the-art gene delivery tools with improved safety features. We discuss development of alpharetroviral vectors in compliance with regulatory requirements for clinical translation, and provide an outlook on possible future gene therapy applications. Taken together, this review is a broad overview of alpharetroviral vectors spanning the bridge from their parental virus discovery to their potential applicability in clinical settings.
Topics: Alpharetrovirus; Animals; Genetic Therapy; Genetic Vectors; Humans; Neoplasms; Virus Integration
PubMed: 25490763
DOI: 10.3390/v6124811 -
Molecular and Cellular Endocrinology Jan 2011Aggresome formation, a cellular response to misfolded protein aggregates, is linked to cancer and neurodegenerative disorders. Previously we showed that Gag-v-ErbA...
Aggresome formation, a cellular response to misfolded protein aggregates, is linked to cancer and neurodegenerative disorders. Previously we showed that Gag-v-ErbA (v-ErbA), a retroviral variant of the thyroid hormone receptor (TRα1), accumulates in and sequesters TRα1 into cytoplasmic foci. Here, we show that foci represent v-ErbA targeting to aggresomes. v-ErbA colocalizes with aggresomal markers, proteasomes, hsp70, HDAC6, and mitochondria. Foci have hallmark characteristics of aggresomes: formation is microtubule-dependent, accelerated by proteasome inhibitors, and they disrupt intermediate filaments. Proteasome-mediated degradation is critical for clearance of v-ErbA and T(3)-dependent TRα1 clearance. Our studies highlight v-ErbA's complex mode of action: the oncoprotein is highly mobile and trafficks between the nucleus, cytoplasm, and aggresome, carrying out distinct activities within each compartment. Dynamic trafficking to aggresomes contributes to the dominant negative activity of v-ErbA and may be enhanced by the viral Gag sequence. These studies provide insight into novel modes of oncogenesis across multiple cellular compartments.
Topics: Alpharetrovirus; Biological Transport; Biomarkers; Dyneins; Erythroblasts; Gene Products, gag; HSP70 Heat-Shock Proteins; HeLa Cells; Histone Deacetylase 6; Histone Deacetylases; Humans; Inclusion Bodies; Intermediate Filaments; Microtubules; Mitochondria; Oncogene Proteins v-erbA; Proteasome Endopeptidase Complex; Recombinant Fusion Proteins; Vimentin
PubMed: 21075170
DOI: 10.1016/j.mce.2010.10.012 -
Journal of Virology Dec 2007The mammalian APOBEC3 family of cytidine deaminases includes members that can act as potent inhibitors of retroviral infectivity and retrotransposon mobility. Here, we...
The mammalian APOBEC3 family of cytidine deaminases includes members that can act as potent inhibitors of retroviral infectivity and retrotransposon mobility. Here, we have examined whether the alpharetrovirus Rous sarcoma virus (RSV) is susceptible to inhibition by a range of human APOBEC3 proteins. We report that RSV is highly susceptible to inhibition by human APOBEC3G, APOBEC3F, and APOBEC3B and moderately susceptible to inhibition by human APOBEC3C and APOBEC3A. For all five proteins, inhibition of RSV infectivity was associated with selective virion incorporation and with C-to-T editing of the proviral DNA minus strand. In the case of APOBEC3G, editing appeared to be critical for effective inhibition. These data represent the first report of inhibition of retroviral infectivity and induction of proviral DNA editing by human APOBEC3A and reveal that alpharetroviruses, which do not normally encounter APOBEC3 proteins in their avian hosts, are susceptible to inhibition by all human APOBEC3 proteins tested. These data further suggest that the resistance of mammalian retroviruses to inhibition by the APOBEC3 proteins expressed in their normal host species is likely to have evolved subsequent to the appearance of this family of mammalian antiretroviral proteins some 35 million years ago; i.e., the base state of a naïve retrovirus is susceptibility to inhibition.
Topics: APOBEC Deaminases; APOBEC-3G Deaminase; Animals; Cell Line; Cytidine Deaminase; Cytosine Deaminase; Humans; Minor Histocompatibility Antigens; Proviruses; Quail; RNA Editing; Rous sarcoma virus; Transfection; Virion; Virus Assembly; Virus Replication
PubMed: 17913830
DOI: 10.1128/JVI.01646-07 -
Human Gene Therapy Methods Jun 2019In cellular immunotherapies, natural killer (NK) cells often demonstrate potent antitumor effects in high-risk cancer patients. But Good Manufacturing Practice...
Development of Automated Separation, Expansion, and Quality Control Protocols for Clinical-Scale Manufacturing of Primary Human NK Cells and Alpharetroviral Chimeric Antigen Receptor Engineering.
In cellular immunotherapies, natural killer (NK) cells often demonstrate potent antitumor effects in high-risk cancer patients. But Good Manufacturing Practice (GMP)-compliant manufacturing of clinical-grade NK cells in high numbers for patient treatment is still a challenge. Therefore, new protocols for isolation and expansion of NK cells are required. In order to attack resistant tumor entities, NK cell killing can be improved by genetic engineering using alpharetroviral vectors that encode for chimeric antigen receptors (CARs). The aim of this work was to demonstrate GMP-grade manufacturing of NK cells using the CliniMACS Prodigy device (Prodigy) with implemented applicable quality controls. Additionally, the study aimed to define the best time point to transduce expanding NK cells with alpharetroviral CAR vectors. Manufacturing and clinical-scale expansion of primary human NK cells were performed with the Prodigy starting with 8-15.0 × 10 leukocytes (including 1.1-2.3 × 10 NK cells) collected by small-scale lymphapheresis ( = 3). Positive fraction after immunoselection, in-process controls (IPCs), and end product were quantified by flow cytometric no-wash, single-platform assessment, and gating strategy using positive (CD56/CD16/CD45), negative (CD14/CD19/CD3), and dead cell (7-aminoactinomycine [7-AAD]) discriminators. The three runs on the fully integrated manufacturing platform included immunomagnetic separation (CD3 depletion/CD56 enrichment) followed by NK cell expansion over 14 days. This process led to high NK cell purities (median 99.1%) and adequate NK cell viabilities (median 86.9%) and achieved a median CD3+ cell depletion of log -3.6 after CD3 depletion and log -3.7 after immunomagnetic CD3 depletion and consecutive CD56 selection. Subsequent cultivation of separated NK cells in the CentriCult chamber of Prodigy resulted in approximately 4.2-8.5-fold NK cell expansion rates by adding of NK MACS basal medium containing NK MACS supplement, interleukin (IL)-2/IL-15 and initial IL-21. NK cells expanded for 14 days revealed higher expression of natural cytotoxicity receptors (NKp30, NKp44, NKp46, and NKG2D) and degranulation/apoptotic markers and stronger cytolytic properties against K562 compared to non-activated NK cells before automated cultivation. Moreover, expanded NK cells had robust growth and killing activities even after cryopreservation. As a crucial result, it was possible to determine the appropriate time period for optimal CAR transduction of cultivated NK cells between days 8 and 14, with the highest anti-CD123 CAR expression levels on day 14. The anti-CD123 CAR NK cells showed retargeted killing and degranulation properties against CD123-expressing KG1a target cells, while basal cytotoxicity of non-transduced NK cells was determined using the CD123-negative cell line K562. Time-lapse imaging to monitor redirected effector-to-target contacts between anti-CD123 CAR NK and KG1a showed long-term effector-target interaction. In conclusion, the integration of the clinical-scale expansion procedure in the automated and closed Prodigy system, including IPC samples and quality controls and optimal time frames for NK cell transduction with CAR vectors, was established on 48-well plates and resulted in a standardized GMP-compliant overall process.
Topics: Alpharetrovirus; Cell Engineering; Cell Line; Cell Survival; Cytokines; Genetic Vectors; Humans; Killer Cells, Natural; Quality Control; Receptors, Chimeric Antigen; Transduction, Genetic
PubMed: 30997855
DOI: 10.1089/hgtb.2019.039 -
Journal of Virology Feb 2013Integrated retroviral DNA is subject to epigenetic transcriptional silencing at different frequencies. This process is mediated by repressive DNA methylation and histone...
Integrated retroviral DNA is subject to epigenetic transcriptional silencing at different frequencies. This process is mediated by repressive DNA methylation and histone modifications on viral chromatin. However, the detailed mechanisms by which retroviral silencing is initiated and maintained are not well understood. Using a model system in which avian sarcoma virus (ASV) DNA is epigenetically repressed in mammalian cells, we previously found that a cellular scaffolding protein, Daxx, acts as an antiretroviral factor that promotes epigenetic repression through recruitment of histone deacetylases (HDACs). Here we show that human Daxx protein levels are increased in response to retroviral infection and that Daxx acts at the time of infection to initiate epigenetic repression. Consistent with a rapid and active antiviral epigenetic response, we found that repressive histone marks and long terminal repeat (LTR) DNA methylation could be detected within 12 h to 3 days postinfection, respectively. Daxx was also found to be required for long-term ASV silencing maintenance and full viral DNA methylation, and it was physically associated with both viral DNA and DNA methyltransferases (DNMTs). These findings support a model in which incoming retroviral protein-DNA complexes are detected by Daxx, and the integrated provirus is rapidly chromatinized and repressed by DNA methylation and histone modification as part of an antiviral response. These results uncover a possible direct and active antiviral mechanism by which DNMTs can be recruited to retroviral DNA.
Topics: Adaptor Proteins, Signal Transducing; Animals; Avian Sarcoma Viruses; Cell Line; Co-Repressor Proteins; DNA Methylation; Epigenetic Repression; Gene Expression Regulation, Viral; Gene Silencing; Host-Pathogen Interactions; Humans; Molecular Chaperones; Nuclear Proteins
PubMed: 23221555
DOI: 10.1128/JVI.02026-12