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Inadvertent Transfer of Murine VL30 Retrotransposons to CAR-T Cells. ADVANCES IN CELL AND GENE THERAPY 2022; 2022. [PMID: 36081760 PMCID: PMC9450689 DOI: 10.1155/2022/6435077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
For more than a decade, genetically engineered autologous T-cells have been successfully employed as immunotherapy drugs for patients with incurable blood cancers. The active components in some of these game-changing medicines are autologous T-cells that express viral vector-delivered chimeric antigen receptors (CARs), which specifically target proteins that are preferentially expressed on cancer cells. Some of these therapeutic CAR expressing T-cells (CAR-Ts) are engineered via transduction with
-retroviral vectors (
-RVVs) produced in a stable producer cell line that was derived from murine PG13 packaging cells (ATCC CRL-10686). Earlier studies reported on the copackaging of murine virus-like 30S RNA (VL30) genomes with
-retroviral vectors generated in murine stable packaging cells. In an earlier study, VL30 mRNA was found to enhance the metastatic potential of human melanoma cells. These findings raise biosafety concerns regarding the possibility that therapeutic CAR-Ts have been inadvertently contaminated with potentially oncogenic VL30 retrotransposons. In this study, we demonstrated the presence of infectious VL30 particles in PG13 cell-conditioned media and observed the ability of these particles to deliver transcriptionally active VL30 genomes to human cells. Notably, VL30 genomes packaged by HIV-1-based vector particles transduced naïve human cells in culture. Furthermore, we detected the transfer and expression of VL30 genomes in clinical-grade CAR-T cells generated by transduction with PG13 cell-derived
-retroviral vectors. Our findings raise biosafety concerns regarding the use of murine packaging cell lines in ongoing clinical applications.
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Telesnitsky A, Wolin SL. The Host RNAs in Retroviral Particles. Viruses 2016; 8:v8080235. [PMID: 27548206 PMCID: PMC4997597 DOI: 10.3390/v8080235] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/15/2016] [Accepted: 08/16/2016] [Indexed: 12/15/2022] Open
Abstract
As they assemble, retroviruses encapsidate both their genomic RNAs and several types of host RNA. Whereas limited amounts of messenger RNA (mRNA) are detectable within virion populations, the predominant classes of encapsidated host RNAs do not encode proteins, but instead include endogenous retroelements and several classes of non-coding RNA (ncRNA), some of which are packaged in significant molar excess to the viral genome. Surprisingly, although the most abundant host RNAs in retroviruses are also abundant in cells, unusual forms of these RNAs are packaged preferentially, suggesting that these RNAs are recruited early in their biogenesis: before associating with their cognate protein partners, and/or from transient or rare RNA populations. These RNAs' packaging determinants differ from the viral genome's, and several of the abundantly packaged host ncRNAs serve cells as the scaffolds of ribonucleoprotein particles. Because virion assembly is equally efficient whether or not genomic RNA is available, yet RNA appears critical to the structural integrity of retroviral particles, it seems possible that the selectively encapsidated host ncRNAs might play roles in assembly. Indeed, some host ncRNAs appear to act during replication, as some transfer RNA (tRNA) species may contribute to nuclear import of human immunodeficiency virus 1 (HIV-1) reverse transcription complexes, and other tRNA interactions with the viral Gag protein aid correct trafficking to plasma membrane assembly sites. However, despite high conservation of packaging for certain host RNAs, replication roles for most of these selectively encapsidated RNAs-if any-have remained elusive.
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Affiliation(s)
- Alice Telesnitsky
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Sandra L Wolin
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06536, USA.
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Diehl WE, Patel N, Halm K, Johnson WE. Tracking interspecies transmission and long-term evolution of an ancient retrovirus using the genomes of modern mammals. eLife 2016; 5:e12704. [PMID: 26952212 PMCID: PMC4798954 DOI: 10.7554/elife.12704] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 01/26/2016] [Indexed: 12/03/2022] Open
Abstract
Mammalian genomes typically contain hundreds of thousands of endogenous retroviruses (ERVs), derived from ancient retroviral infections. Using this molecular 'fossil' record, we reconstructed the natural history of a specific retrovirus lineage (ERV-Fc) that disseminated widely between ~33 and ~15 million years ago, corresponding to the Oligocene and early Miocene epochs. Intercontinental viral spread, numerous instances of interspecies transmission and emergence in hosts representing at least 11 mammalian orders, and a significant role for recombination in diversification of this viral lineage were also revealed. By reconstructing the canonical retroviral genes, we identified patterns of adaptation consistent with selection to maintain essential viral protein functions. Our results demonstrate the unique potential of the ERV fossil record for studying the processes of viral spread and emergence as they play out across macro-evolutionary timescales, such that looking back in time may prove insightful for predicting the long-term consequences of newly emerging viral infections. DOI:http://dx.doi.org/10.7554/eLife.12704.001 Viruses have been with us for billions of years, and exist everywhere in nature that life is found. Viruses therefore have had a significant impact on the evolution of all organisms, from bacteria to humans. Unfortunately, viruses do not leave fossils, and so we know very little about how viruses originate and evolve over time. Fortunately, over the course of millions of years, genetic sequences from the viruses accumulate in the DNA genomes of living organisms (including humans). These sequences can serve as molecular “fossils” for exploring the natural history of viruses and their hosts. Diehl et al. have now searched the genomes of 50 modern mammals for “fossil” viral remnants of an ancient group of viruses known as ERV-Fc. This revealed that ERV-Fc viruses infected the ancestors of at least 28 of these mammal species between 15 million and 30 million years ago. The viruses affected a diverse range of hosts, including carnivores, rodents and primates. The distribution of ERV-Fc among different mammals indicates that the viruses spread to every continent except Antarctica and Australia, and that they jumped between species more than 20 times. Diehl et al. also pinpointed patterns of evolutionary change in the genes of the ERV-Fc viruses that reflect how the viruses adapted to different host mammals. As part of this process, the viruses often exchanged genes with each other and with other types of viruses. Such genetic recombination is likely to have played a significant role in the evolutionary success of the ERV-Fc viruses. Mammalian genomes contain hundreds of thousands of ancient viral fossils similar to ERV-Fc. Future work could study these to improve our understanding of when and why new viruses emerge and how long-term contact with viruses affects the evolution of their host organisms. DOI:http://dx.doi.org/10.7554/eLife.12704.002
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Affiliation(s)
- William E Diehl
- Biology Department, Boston College, Chestnut Hill, United States
| | - Nirali Patel
- Biology Department, Boston College, Chestnut Hill, United States
| | - Kate Halm
- Biology Department, Boston College, Chestnut Hill, United States
| | - Welkin E Johnson
- Biology Department, Boston College, Chestnut Hill, United States
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Affiliation(s)
- A Dusty Miller
- Fred Hutchinson Cancer Research Center , Seattle, WA 98109
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Abstract
PURPOSE OF REVIEW This review will explore two new aspects of the involvement of viruses in multiple sclerosis pathogenesis. The first aspect is the complex interactions between viruses. The second aspect is the proposal of a mechanism by which autoreactive T cells are able to escape thymic selection and potentially recognize self and a pathogen. RECENT FINDINGS With regard to viruses, recent work has demonstrated that one virus may enhance the replication of another virus, potentially leading to an increase in inflammation and disease progression. Also, interactions between human endogenous retroviruses, which likely do not replicate, and certain herpes viruses, may also play a role in disease pathogenesis. Mechanistically, T cells expressing dual T-cell receptors would be able to recognize self and a foreign antigen specifically. Therefore, human endogenous retroviruses potentially play a role in multiple sclerosis pathogenesis, and both interactions between multiple viruses and autoreactive CD8(+) T cells with dual T-cell receptors may play a role in the pathogenesis of the disease. SUMMARY The complex interactions between multiple viral infections, either within the central nervous system or in the periphery, and the host immune response to viral infection may be such that a variety of viral specificities result in the activation of T cells that recognize self and induce multiple sclerosis. Therefore, it is unlikely that any one microbe will be determined to be the causative agent of multiple sclerosis as reflected by the number of potential triggering mechanisms of the disease.
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SENP3-mediated deSUMOylation of dynamin-related protein 1 promotes cell death following ischaemia. EMBO J 2013; 32:1514-28. [PMID: 23524851 PMCID: PMC3671254 DOI: 10.1038/emboj.2013.65] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 02/27/2013] [Indexed: 01/10/2023] Open
Abstract
Global increases in small ubiquitin-like modifier (SUMO)-2/3 conjugation are a neuroprotective response to severe stress but the mechanisms and specific target proteins that determine cell survival have not been identified. Here, we demonstrate that the SUMO-2/3-specific protease SENP3 is degraded during oxygen/glucose deprivation (OGD), an in vitro model of ischaemia, via a pathway involving the unfolded protein response (UPR) kinase PERK and the lysosomal enzyme cathepsin B. A key target for SENP3-mediated deSUMOylation is the GTPase Drp1, which plays a major role in regulating mitochondrial fission. We show that depletion of SENP3 prolongs Drp1 SUMOylation, which suppresses Drp1-mediated cytochrome c release and caspase-mediated cell death. SENP3 levels recover following reoxygenation after OGD allowing deSUMOylation of Drp1, which facilitates Drp1 localization at mitochondria and promotes fragmentation and cytochrome c release. RNAi knockdown of SENP3 protects cells from reoxygenation-induced cell death via a mechanism that requires Drp1 SUMOylation. Thus, we identify a novel adaptive pathway to extreme cell stress in which dynamic changes in SENP3 stability and regulation of Drp1 SUMOylation are crucial determinants of cell fate.
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Jover B, Girardot D, de Courtois Roy de Vacquières F, Casellas D, Molès JP. Wnt-4 potently inhibits capillary outgrowth from rat aorta in 3D culture. Fundam Clin Pharmacol 2012; 27:465-70. [PMID: 22607657 DOI: 10.1111/j.1472-8206.2012.01044.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 03/08/2012] [Accepted: 03/27/2012] [Indexed: 12/01/2022]
Abstract
Regulation of angiogenesis involves tight cell-to-cell and cell-to-extracellular-matrix interactions. Various reports demonstrate that the Wnt signaling pathways participate in this regulation. Using a three-dimensional aortic ring culture combined with an ex vivo retroviral infection approach, we evaluated the effects of two Wnt growth factors, Wnt-1 and Wnt-4, on the formation and growth of new capillaries. Our results show that Wnt-1 had no effect, whereas Wnt-4 was a potent inhibitor of capillary outgrowth in vitro.
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Affiliation(s)
- Bernard Jover
- Groupe Rein & Hypertension, Institut Universitaire de Recherche Clinique, CNRS FRE3400, 641 Ave Doyen Giraud, 34093, Montpellier Cedex 5, France.
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Antony JM, Deslauriers AM, Bhat RK, Ellestad KK, Power C. Human endogenous retroviruses and multiple sclerosis: innocent bystanders or disease determinants? Biochim Biophys Acta Mol Basis Dis 2010; 1812:162-76. [PMID: 20696240 PMCID: PMC7172332 DOI: 10.1016/j.bbadis.2010.07.016] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 07/14/2010] [Accepted: 07/26/2010] [Indexed: 12/21/2022]
Abstract
Human endogenous retroviruses (HERVs) constitute 5–8% of human genomic DNA and are replication incompetent despite expression of individual HERV genes from different chromosomal loci depending on the specific tissue. Several HERV genes have been detected as transcripts and proteins in the central nervous system, frequently in the context of neuroinflammation. The HERV-W family has received substantial attention in large part because of associations with diverse syndromes including multiple sclerosis (MS) and several psychiatric disorders. A HERV-W-related retroelement, multiple sclerosis retrovirus (MSRV), has been reported in MS patients to be both a biomarker as well as an effector of aberrant immune responses. HERV-H and HERV-K have also been implicated in MS and other neurological diseases but await delineation of their contributions to disease. The HERV-W envelope-encoded glycosylated protein, syncytin-1, is encoded by chromosome 7q21 and exhibits increased glial expression within MS lesions. Overexpression of syncytin-1 in glia induces endoplasmic reticulum stress leading to neuroinflammation and the induction of free radicals, which damage proximate cells. Syncytin-1's receptor, ASCT1 is a neutral amino acid transporter expressed on glia and is suppressed in white matter of MS patients. Of interest, antioxidants ameliorate syncytin-1's neuropathogenic effects raising the possibility of using these agents as therapeutics for neuroinflammatory diseases. Given the multiple insertion sites of HERV genes as complete and incomplete open reading frames, together with their differing capacity to be expressed and the complexities of individual HERVs as both disease markers and bioactive effectors, HERV biology is a compelling area for understanding neuropathogenic mechanisms and developing new therapeutic strategies.
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Identification of gammaretroviruses constitutively released from cell lines used for human immunodeficiency virus research. J Virol 2008; 82:12585-8. [PMID: 18842727 DOI: 10.1128/jvi.01726-08] [Citation(s) in RCA: 219] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Three human cell lines used in human immunodeficiency virus research were found to be contaminated with previously undetected retroviruses. On the bases of partial nucleotide sequence, capsid protein antigenicity, vector mobilization, and receptor usage studies, these contaminants were shown to be replication competent and to belong to the Gammaretrovirus genus. While the TZM-bl cells harbor ecotropic murine leukemia virus (MLV), Jurkat J6 cells were found to release xenotropic MLV and the A3.01/F7 cells to produce gibbon ape leukemia virus. These findings highlight the importance of routine testing of cell lines for retrovirus contamination to prevent potential experimental artifacts and allow correct biohazard assessment.
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10
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Dalba C, Bellier B, Kasahara N, Klatzmann D. Replication-competent Vectors and Empty Virus-like Particles: New Retroviral Vector Designs for Cancer Gene Therapy or Vaccines. Mol Ther 2007; 15:457-66. [PMID: 17245356 DOI: 10.1038/sj.mt.6300054] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Replication-defective vectors based on murine oncoretroviruses were the first gene transfer vectors to be used in successful gene therapies. Despite this achievement, they have two major drawbacks: insufficient efficacy for in vivo gene transfer and insertional mutagenesis. Attempts to overcome these problems have led to two retroviral vector designs of principally opposite character: replication-competent vectors transducing largely intact genomes and genome-free vectors. Replication-competent retroviral vectors have achieved dramatically improved efficacy for in vivo cancer gene therapy and genome-free retroviral vectors expressing different kinds of antigens have proven excellent as immunogens. Current developments aim to improve the safety of the replication-competent vectors and to augment the production efficiency of the genome-free vectors by expression from heterologous viral or non-viral vectors. Together with the continuous advances of classical defective retroviral vectors for ex vivo gene therapy, these developments illustrate that, due to their tremendous design versatility, retroviral vectors remain important vectors for gene therapy applications.
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Affiliation(s)
- Charlotte Dalba
- Biologie et Thérapeutique des Pathologies Immunitaires, CNRS, Université Pierre et Marie Curie-Paris, UMR 7087, Paris, France.
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11
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Abstract
When endogenous retroviruses (ERV) were discovered in the late 1960s, the Mendelian inheritance of retroviral genomes by their hosts was an entirely new concept. Indeed Howard M Temin's DNA provirus hypothesis enunciated in 1964 was not generally accepted, and reverse transcriptase was yet to be discovered. Nonetheless, the evidence that we accrued in the pre-molecular era has stood the test of time, and our hypothesis on ERV, which one reviewer described as 'impossible', proved to be correct. Here I recount some of the key observations in birds and mammals that led to the discovery of ERV, and comment on their evolution, cross-species dispersion, and what remains to be elucidated.
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Affiliation(s)
- Robin A Weiss
- Division of Infection & Immunity, University College London, 46 Cleveland Street, London W1T 4JF, UK.
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Zeilfelder U, Frank O, Sparacio S, Schön U, Bosch V, Seifarth W, Leib-Mösch C. The potential of retroviral vectors to cotransfer human endogenous retroviruses (HERVs) from human packaging cell lines. Gene 2006; 390:175-9. [PMID: 17045761 DOI: 10.1016/j.gene.2006.08.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Revised: 08/10/2006] [Accepted: 08/10/2006] [Indexed: 10/24/2022]
Abstract
Using a versatile and highly sensitive retroviral microarray, we have investigated particle preparations from three different human packaging cell lines harboring retroviral vector systems based on human immunodeficiency virus (HIV) and murine leukemia virus (MLV). 293Rev/Gag/Pol(i) cells inducibly express high titers of HIV-derived particles for packaging of HIV vectors. The Phoenix-GP and the Anjou 65 cell lines constitutively express MLV vector particles. We compared the transcription profiles of human endogenous retroviruses (HERVs) in all cell lines with the HERV sequences present in the particles. In addition, the influence of the transfected vector plasmid on the copackaging of HERVs was investigated. All particle preparations showed a defined pattern of endogenous retroviral sequences that differed from the cellular HERV expression pattern. HERV transcripts were observed in the particle preparations independent of whether a vector construct was coexpressed or not. Furthermore, our results suggest that particle preparations are frequently contaminated by cellular vesicles (exosomes) containing cellular RNAs including HERV transcripts.
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Affiliation(s)
- Udo Zeilfelder
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, 68305 Mannheim, Germany
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Silva FH, Nardi NB. From leading role to the backstage: Mesenchymal stem cells as packaging cell lines for in situ production of viral vectors. Med Hypotheses 2006; 67:922-5. [PMID: 16737782 DOI: 10.1016/j.mehy.2006.01.065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Accepted: 01/27/2006] [Indexed: 11/19/2022]
Abstract
Gene therapy is based on the genetic manipulation of target cells. The genetic information required to genetically engineer these cells can be delivered through non-viral or viral vectors that present different biologic properties. The production of viral vectors for gene therapy depends on the nature of the cells transfected with plasmids containing the genetic information for recombinant viral assemblage. These so-called packaging cell lines (PCL) can be injected into the target organ, for the in situ transduction of target cells. There have been recent reports about the capacity of mesenchymal stem cells (MSCs) to target tumor cells. Different research groups, including our own, have isolated these MSCs, but they have not yet been studied as potential PCL to produce viral vectors. We propose here that a MSC packaging cell line could be employed for in situ gene therapy of solid tumors. The tropism of MSCs for tumor cells may render this PCL more efficient in that microenvironment, producing viral vectors for longer periods of time, shifting MSCs from target cell to the backstage level of viral gene therapy.
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Affiliation(s)
- F H Silva
- Genetics Department, Universidade Federal do Rio Grande do Sul, Av Bento Gonçalves 9500, 91501-970 Porto Alegre, RS, Brazil
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Yi JM, Kim HM, Kim HS. Human endogenous retrovirus HERV-H family in human tissues and cancer cells: expression, identification, and phylogeny. Cancer Lett 2006; 231:228-39. [PMID: 16399224 DOI: 10.1016/j.canlet.2005.02.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Revised: 01/31/2005] [Accepted: 02/04/2005] [Indexed: 10/25/2022]
Abstract
HERV-H family is the most abundant HERV families in the human genome with more than 1000 copies including full-length, truncated form, and solitary LTRs. We investigated envelope (env) gene fragments of HERV-H family in various human tissues and cancer cells. The env fragments were detected in mRNA of several human tissues (placenta, skeletal muscle, spleen, and thymus) and cancer cells (RT4, BT-474, HCT-116, TE-1, UO-31, Jurkat, HepG2, A549, MCF7, OVCAR-3, MIA-PaCa-2, PC3, LOX-IMVI, AZ521, 2F7, U-937, and C-33A) by RT-PCR approach. The RT-PCR products were cloned and sequenced. New 12 clones from human tissues and 48 clones from cancer cells of env gene sequences belonging to the HERV-H family showed 84.3-98.1% sequence similarity to that of HERV-H (AF108843). Deduced amino acid sequences of 60 clones from human tissues and cancer cell lines showed multiple frameshifts and termination codons caused by deletion/insertion or point mutation with the exception of eight clones as following: HHE9-1, HHE9-5 (skeletal muscle), HHE10-5 (spleen), CHE10-9 (MCF7), CHE12-4, CHE12-5 (MIA-PaCa-2), and CHE18-1, CHE18-3 (C-33A) to that of HERV-H (AF108843). A phylogenetic tree of the HERV-H family was constructed to understand their relationship, indicating that they were divided into three groups, one major (group I) and two minor (group II and III), through sequence divergence. The HERV-H families in group I has been proliferated on human genome during hominoid evolution. These active HERV-H elements are worthy of further investigations as potential pathogenic effects to various human diseases including cancers.
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Affiliation(s)
- Joo-Mi Yi
- Division of Biological Sciences, College of Natural Sciences, Pusan National University, Pusan 609-735, South Korea
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Amit M, Winkler ME, Menke S, Brüning E, Büscher K, Denner J, Haverich A, Itskovitz-Eldor J, Martin U. No evidence for infection of human embryonic stem cells by feeder cell-derived murine leukemia viruses. Stem Cells 2005; 23:761-71. [PMID: 15917472 DOI: 10.1634/stemcells.2004-0046] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Until recently, culture and expansion of nondifferentiated human embryonic stem cells (hESCs) depended on coculture with murine embryonic fibroblasts. Because mice are known to harbor a variety of pathogens, such culture conditions implicate the risk of xenozoonoses. Among these pathogens, endogenous retroviruses, including murine leukemia viruses (MuLVs), are of special importance. It is well known that some strains cause pathogenic (e.g., leukemic) effects and that xenotropic, polytropic, and amphotropic MuLVs are able to infect human cells. In view of potential clinical applications of hESC lines, it is therefore imperative to investigate potential infection of hESCs by mouse feeder cell-derived viruses. As a first step towards a comprehensive infection risk assessment, we have analyzed embryonic fibroblasts derived from different mouse strains for expression and release of xenotropic, polytropic, and amphotropic MuLVs. Moreover, several hESC lines have been investigated for expression of specific receptors for xenotropic/polytropic MuLVs, as well as for MuLV infection and expression. Evidence for expression of humantropic MuLVs was found in cultures of mouse embryonic fibroblasts (MEFs). Moreover, expression of specific receptors for xenotropic/ polytropic MuLV on human HEK293 and hESC lines and infection after coculture with an MuLV-producing mink cell line could be demonstrated. In contrast, no evidence of MuLV transmission from MEFs to human HEK293 cells or to the hESC lines I-3, I-6, I-8, and H-9 has been obtained. Our results suggest that recently established hESC lines are free of MuLV infections despite long-term close contact with MEFs.
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Affiliation(s)
- Michal Amit
- Department of Obstetrics and Gynecology, Rambam Medical Center, Faculty of Medicine, The Technion, Haifa, Israel
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Martina Y, Kurian S, Cherqui S, Evanoff G, Wilson C, Salomon DR. Pseudotyping of porcine endogenous retrovirus by xenotropic murine leukemia virus in a pig islet xenotransplantation model. Am J Transplant 2005; 5:1837-47. [PMID: 15996230 DOI: 10.1111/j.1600-6143.2005.00978.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The potential of porcine endogenous retrovirus (PERV) as a human pathogen, particularly as a public health risk, is a major concern for xenotransplantation. In vitroPERV transmission to human cells is well established. Evidence from human/pig hematopoietic chimeras in immunodeficient mice suggests PERV transmission from pig to human cells in vivo. However, recently Yang et al. demonstrated in such a model that PERV-C, a nonhuman-tropic class, could be transmitted via pseudotyping by xenotropic murine leukemia virus (X-MLV). We developed a mouse pig islet xenotransplant model, where pig and human cells are located in physically separate compartments, to directly assess PERV transmission from a functional pig xenograft. X-MLV efficiently pseudotypes all three classes of PERV, including PERV-A and -B that are known to productively infect human cell lines and PERV-C that is normally not infectious for human cells. Pseudotyping also extends PERV's natural tropism to nonpermissive, nonhuman primate cells. X-MLV is activated locally by the surgical procedure involved in the tissue transplants. Thus, the presence and activation of endogenous X-MLV in immunodeficient mice limits the clinical significance of previous reports of in vivo PERV transmission from pig tissues to human cells.
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Affiliation(s)
- Yuri Martina
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, USA
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17
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Christensen T. Association of human endogenous retroviruses with multiple sclerosis and possible interactions with herpes viruses. Rev Med Virol 2005; 15:179-211. [PMID: 15782388 DOI: 10.1002/rmv.465] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The hypothesis that human endogenous retroviruses (HERVs) play a role in autoimmune diseases is subject to increasing attention. HERVs represent both putative susceptibility genes and putative pathogenic viruses in the immune-mediated neurological disease multiple sclerosis (MS). Gammaretroviral HERV sequences are found in reverse transcriptase-positive virions produced by cultured mononuclear cells from MS patients, and they have been isolated from MS samples of plasma, serum and CSF, and characterised to some extent at the nucleotide, protein/enzyme, virion and immunogenic level. Two types of sequences, HERV-H and HERV-W, have been reported. No known HERV-H or HERV-W copy contains complete ORFs in all prerequisite genes, although several copies have coding potential, and several such sequences are specifically activated in MS, apparently resulting in the production of complete, competent virions. Increased antibody reactivity to specific Gammaretroviral HERV epitopes is found in MS serum and CSF, and cell-mediated immune responses have also been reported. Further, HERV-encoded proteins can have neuropathogenic effects. The activating factor(s) in the process resulting in protein or virion production may be members of the Herpesviridae. Several herpes viruses, such as HSV-1, VZV, EBV and HHV-6, have been associated with MS pathogenesis, and retroviruses and herpes viruses have complex interactions. The current understanding of HERVs, and specifically the investigations of HERV activation and expression in MS are the major subjects of this review, which also proposes to synergise the herpes and HERV findings, and presents several possible pathogenic mechanisms for HERVs in MS.
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Affiliation(s)
- Tove Christensen
- Institute of Medical Microbiology and Immunology, Bartholin Building, University of Aarhus, DK-8000 Aarhus C, Denmark.
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18
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Li Z, Schwieger M, Lange C, Kraunus J, Sun H, van den Akker E, Modlich U, Serinsöz E, Will E, von Laer D, Stocking C, Fehse B, Schiedlmeier B, Baum C. Predictable and efficient retroviral gene transfer into murine bone marrow repopulating cells using a defined vector dose. Exp Hematol 2004; 31:1206-14. [PMID: 14662326 DOI: 10.1016/j.exphem.2003.08.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Current protocols of retroviral gene transfer into murine hematopoietic stem cells (HSC) result in variable gene transfer efficiency and involve various procedures that are not clinically applicable. We developed and evaluated a reliable transduction protocol that is more related to clinical methods. MATERIALS AND METHODS HSC were enriched from steady-state bone marrow by magnetic cell sorting (lineage depletion) and cultured in defined serum-free medium containing an improved growth factor cocktail (Flt3-ligand, stem cell factor, interleukin-3, interleukin-11). Cell-free ecotropic retroviral vector particles, generated by transient transfection of human 293T-based packaging cells, were preloaded at defined titers on CH296-coated tissue culture plates, thus largely avoiding serum contamination. These conditions were evaluated in 17 experiments involving 29 transduction cultures and 185 recipient mice. RESULTS After two rounds of infection, the gene marking rates in cultured mononuclear cells and stem/progenitor cells (Lin(-)c-Kit(+)) were 15 to 85% (53.7%+/-21.7%, n=23) and 30 to 95% (69.8%+/-20.4%, n=17), respectively. Even after one round of infection, gene transfer was efficient (31.2%+/-15.1%, n=12). Using identical conditions, gene transfer rates were highly reproducible. Average transgene expression in reconstituted animals correlated well with pretransplant data. Using a moderate multiplicity of infection, the majority of transduced cells carried less than three transgene copies. In addition, coinfection was possible to establish two different vectors in single cells. CONCLUSION The protocol described here achieves efficient retroviral transduction of murine bone marrow repopulating cells with a defined gene dosage, largely avoiding procedures that decrease stem cell output and repopulating capacity. This protocol may help to improve the predictive value of preclinical efficiency/toxicity studies for gene therapeutic interventions and basic research.
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Affiliation(s)
- Zhixiong Li
- Experimental Cell Therapy, Department of Hematology and Oncology, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
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19
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Seifarth W, Spiess B, Zeilfelder U, Speth C, Hehlmann R, Leib-Mösch C. Assessment of retroviral activity using a universal retrovirus chip. J Virol Methods 2003; 112:79-91. [PMID: 12951215 DOI: 10.1016/s0166-0934(03)00194-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A DNA chip-based assay is described for parallel detection and identification of a wide variety of human and mammalian exogenous and endogenous retroviruses. The assay combines multiplex polymerase chain reaction (PCR) using fluorochrome-modified primer mixtures and chip hybridization. The microarray is composed of retrovirus-specific synthetic oligonucleotides as capture probes deposited on glass slides. The retrovirus chip can be used to assess the occurrence of reverse transcriptase (RT)-related transcripts in biological samples of human and mammalian origin. For example, distinct expression profiles of human endogenous retroviruses (HERV) were established reproducibly in human white blood cells, mammary gland and other human tissues. In particles released by human cells, packaging of specific HERV transcripts could be observed. Monitoring of human exogenous retroviruses (HIV, HTLV) and detection of putative cross-species transmissions (MLV, PERV) in human samples was efficient and reliable. The DNA chip should be an excellent tool for the detection of most relevant retroviruses and offers insights into differential retroviral activities and replication strategies. Furthermore, it could improve significantly the safety of gene therapy, tissue engineering, xenotransplantation and production of therapeutic polypeptides in cell culture.
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Affiliation(s)
- Wolfgang Seifarth
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, D-68305, Mannheim, Germany.
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20
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Suling K, Quinn G, Wood J, Patience C. Packaging of human endogenous retrovirus sequences is undetectable in porcine endogenous retrovirus particles produced from human cells. Virology 2003; 312:330-6. [PMID: 12919738 DOI: 10.1016/s0042-6822(03)00380-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The chronic shortage of human donor organs and tissues for allotransplantation could be relieved if clinical xenotransplantation were to become a viable clinical therapy. Balanced against the benefits of xenotransplantation are the possible consequences of zoonotic infections, and in particular, infection by porcine endogenous retrovirus (PERV). An often-proclaimed risk of PERV infection is the possible recombination of PERV with human endogenous retroviruses (HERV). To address this issue, we examined the potential for HERV sequences to be cross-packaged into PERV particles produced from infected human 293 cells. Although HERV-K, W, E, R, and ERV-9 RNA transcripts are expressed in 293 cells, we did not detect cross-packaging of any of these HERV groups. Quantitative analysis indicated that less than approximately 1 in 10(4)-10(7) PERV particles might contain HERV sequences. In comparison, we found that murine leukemia virus (MLV)-based vector transcripts were cross-packaged at a rate of approximately one copy in 10(4) PERV particles. Our results indicate that the potential for recombination of PERV and HERV sequences is low and that novel viruses generated by this mechanism are unlikely to represent a significant risk for xenotransplantation.
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Affiliation(s)
- Kristen Suling
- Immerge BioTherapeutics Inc., 300 Technology Square, Cambridge, MA 02129, USA
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21
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Abstract
The safety of retroviral-based systems and the possible transmission of replication-competent virus to patients is a major concern associated with using retroviral vectors for gene therapy. While much effort has been put into the design of safe retroviral production methods and effective in vitro monitoring assays, there is little data evaluating the risks resulting from retroviral vector instability at post-transduction stages especially following in vivo gene delivery. Here, we briefly describe and discuss our observations in an in vivo experimental model based on the inoculation of retroviral vector-transduced tumor cells in sheep. Our data indicates that the in vivo generation of mosaic viruses is a dynamic process and that virus variants, generated by retroviral vector-mediated recombination, may be stored and persist in infected individuals prior to selection at the level of replication. Recombination may not only restore essential viral functions or provide selective advantages in a changing environment but also reestablish or enhance the pathogenic potential of the particular virus undergoing recombination. These observations in sheep break new ground in our understanding of how retroviral vectors may have an impact on the course of a preestablished disease or reactivate dormant or endogenous viruses. The in vivo aspects of vector stability raise important biosafety issues for the future development of safe retroviral vector-based gene therapy.
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Affiliation(s)
- Anne Van den Broeke
- Laboratory of Experimental Hematology, Bordet Institute, 1000 Brussels, Belgium
| | - Arsène Burny
- Laboratory of Experimental Hematology, Bordet Institute, 1000 Brussels, Belgium
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22
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Baum C, Düllmann J, Li Z, Fehse B, Meyer J, Williams DA, von Kalle C. Side effects of retroviral gene transfer into hematopoietic stem cells. Blood 2003; 101:2099-114. [PMID: 12511419 DOI: 10.1182/blood-2002-07-2314] [Citation(s) in RCA: 311] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recent conceptual and technical improvements have resulted in clinically meaningful levels of gene transfer into repopulating hematopoietic stem cells. At the same time, evidence is accumulating that gene therapy may induce several kinds of unexpected side effects, based on preclinical and clinical data. To assess the therapeutic potential of genetic interventions in hematopoietic cells, it will be important to derive a classification of side effects, to obtain insights into their underlying mechanisms, and to use rigorous statistical approaches in comparing data. We here review side effects related to target cell manipulation; vector production; transgene insertion and expression; selection procedures for transgenic cells; and immune surveillance. We also address some inherent differences between hematopoiesis in the most commonly used animal model, the laboratory mouse, and in humans. It is our intention to emphasize the need for a critical and hypothesis-driven analysis of "transgene toxicology," in order to improve safety, efficiency, and prognosis for the yet small but expanding group of patients that could benefit from gene therapy.
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Affiliation(s)
- Christopher Baum
- Department of Hematology and Oncology, Hannover Medical School, Hannover, Germany.
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23
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Abstract
In contrast to other retroviruses, lentiviruses have the unique property of infecting non-proliferating cells. Thus vectors derived from lentiviruses are promising tools for in vivo gene delivery applications. Vectors derived from human primate and non-primate lentiviruses have recently been described and, unlike retroviral vectors derived from murine leukemia viruses, lead to stable integration of the transgene into quiescent cells in various organs. Despite all the safety safeguards that have been progressively introduced in lentiviral vectors, the clinical acceptance of vectors derived from pathogenic lentiviruses is subject to debate. It is therefore essential to design vectors derived from a wide range of lentivirus types and to comparatively examine their properties in terms of transduction efficiency and bio-safety. Here, we review the properties of lentiviral vectors derived from simian immunodeficiency virus (SIV).
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Affiliation(s)
- Didier Nègre
- Laboratoire de vectorologie rétrovirale et thérapie génique. INSERM U412, IFR 74, Ecole normale supérieure de Lyon, 46, allée d'Italie, France
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24
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Sena-Esteves M, Hampl JA, Camp SM, Breakefield XO. Generation of stable retrovirus packaging cell lines after transduction with herpes simplex virus hybrid amplicon vectors. J Gene Med 2002; 4:229-39. [PMID: 12112640 DOI: 10.1002/jgm.276] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND A number of properties have relegated the use of Moloney murine leukemia virus (Mo-MLV)-based retrovirus vectors primarily to ex vivo protocols. Direct implantation of retrovirus producer cells can bypass some of the limitations, and in situ vector production may result in a large number of gene transfer events. However, the fibroblast nature of most retrovirus packaging cells does not provide for an effective distribution of vector producing foci in vivo, especially in the brain. Effective development of new retrovirus producer cells with enhanced biologic properties may require the testing of a large number of different cell types, and a quick and efficient method to generate them is needed. METHODS Moloney murine leukemia virus (Mo-MLV) gag-pol and env genes and retrovirus vector sequences carrying lacZ were cloned into different minimal HSV/AAV hybrid amplicons. Helper virus-free amplicon vectors were used to co-infect glioma cells in culture. Titers and stability of retrovirus vector production were assessed. RESULTS Simultaneous infection of two glioma lines, Gli-36 (human) and J3T (dog), with both types of amplicon vectors, generated stable packaging populations that produced retrovirus titers of 0.5-1.2 x 10(5) and 3.1-7.1 x 10(3) tu/ml, respectively. Alternatively, when cells were first infected with retrovirus vectors followed by infection with HyRMOVAmpho amplicon vector, stable retrovirus packaging populations were obtained from Gli-36 and J3T cells producing retrovirus titers comparable to those obtained with a traditional retrovirus packaging cell line, Psi CRIPlacZ. CONCLUSIONS This amplicon vector system should facilitate generation of new types of retrovirus producer cells. Conversion of cells with migratory or tumor/tissue homing properties could result in expansion of the spatial distribution or targeting capacity, respectively, of gene delivery by retrovirus vectors in vivo.
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Affiliation(s)
- Miguel Sena-Esteves
- Molecular Neurogenetics Unit and Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
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25
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Pambalk K, Hohenadl C, Salmons B, Günzburg WH, Renner M. Specific packaging of spliced retroviral vector transcripts lacking the Psi-region. Biochem Biophys Res Commun 2002; 293:239-46. [PMID: 12054590 DOI: 10.1016/s0006-291x(02)00207-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The effect of a cryptic splice acceptor (cSA) site located at the end of the extended packaging signal in murine leukemia virus (MLV)-based vectors was investigated. Although this cSA is also present in wild type MLV, it was found to result in a smaller transcript in which the packaging signal (Psi) had been removed by splicing only in MLV-derived vectors. Splicing occurs both in packaging cells producing the MLV-vectors as well as in the infected target cells. Transcripts lacking the Psi-sequence (Psi(-)) are packaged relatively efficiently into virus particles, even in the presence of wild type Psi(+)-vector transcripts. The Psi(-)-viral RNA is reverse transcribed in vector transduced cells as is any other retroviral genome. The titer obtained from the Psi(-)-vector was only 1000-fold reduced in comparison to the same Psi(+)-vector. These results suggest that Psi(-)-transcripts may be packaged more frequently than previously supposed and that splicing patterns should be carefully analysed on an individual basis for retroviral vectors used in gene therapy.
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Affiliation(s)
- Konstanze Pambalk
- Institute of Virology, University of Veterinary Medicine, Veterinaerplatz 1, A-1210 Vienna, Austria
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26
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Nègre D, Duisit G, Mangeot PE, Moullier P, Darlix JL, Cosset FL. Lentiviral vectors derived from simian immunodeficiency virus. Curr Top Microbiol Immunol 2002; 261:53-74. [PMID: 11892253 DOI: 10.1007/978-3-642-56114-6_3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Affiliation(s)
- D Nègre
- Laboratoire de Vectorologie Rétrovirale et Thérapie Génique, INSERM U412, Ecole Normale Supérieure de Lyon, IFR 74, 46 Allée d'Italie, 69364 Lyon, France
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27
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Rohll JB, Mitrophanous KA, Martin-Rendon E, Ellard FM, Radcliffe PA, Mazarakis ND, Kingsman SM. Design, production, safety, evaluation, and clinical applications of nonprimate lentiviral vectors. Methods Enzymol 2002; 346:466-500. [PMID: 11883086 DOI: 10.1016/s0076-6879(02)46072-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- Jonathan B Rohll
- Department of Biochemistry, Oxford BioMedica (UK) Limited, Oxford OX4 4GA, United Kingdom
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28
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Abstract
Advances in transplantation immunology have enhanced the possibility of xenotransplantation as a therapeutic option for end-stage organ failure. The potential spread of animal-derived pathogens to the recipient and to the general population, termed "xenosis," is a potential complication of interspecies transplantation. Recognition of such novel infections may be complicated by infections due to altered microbiologic behavior and clinical symptomatology of these organisms, particularly in the immunocompromised xenograft recipient. Particular concern exists over the activation of latent viruses, including retroviruses, from xenograft tissues. Based on experience with human allogeneic transplantation, those pathogens considered most likely to cause human disease can be excluded prospectively from herds of animals developed for organ donation. Research is needed into the activation and behavior of retroviruses and other potential pathogens in xenotransplantation. Xenotransplantation may also provide unique opportunities not only for the care of patients with organ failure, but in the therapy of individuals with chronic infections to which the xenograft may be resistant. Clinical protocols must be developed so as to enhance the safety of the recipient and of the community-at-large.
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Affiliation(s)
- J A Fishman
- Infectious Disease and Transplantation Units, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
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29
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Pizzato M, Merten OW, Blair ED, Takeuchi Y. Development of a suspension packaging cell line for production of high titre, serum-resistant murine leukemia virus vectors. Gene Ther 2001; 8:737-45. [PMID: 11420637 DOI: 10.1038/sj.gt.3301457] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2000] [Accepted: 02/26/2001] [Indexed: 12/20/2022]
Abstract
To date, only adherent cell lines have been used for the generation of packaging cells for the production of type C retrovirus vectors. The large-scale production of high titre retrovirus vectors could benefit from the development of packaging cells growing in suspension. Here, we describe the ability of two different lymphoid cell lines, one B- and one T-lymphoblastoid cell line (Namalwa and CEM, respectively), to produce MLV-based vectors. Upon transfection with a third generation packaging construct, the virus particle production by Namalwa cells was characterised by low RT-activity, and by CEM cells as high RT activity as previously established adherent packaging cells. An amphotropic packaging cell line (CEMFLYA) was therefore established from CEM cells. Upon introduction of a lacZ vector genome, the novel packaging cell line produced vector particles routinely in the region of 10(7) infectious units/ml. The vectors were helper-free and highly stable in fresh human serum. The potential for scaled up vector production was demonstrated by continuous culture of the new packaging cells for 14 days in a 250 ml spinner flask. These suspension packaging cells should be applicable to large bioreactor systems to bulk produce high titre, complement-resistant retrovirus vectors for gene therapy.
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Affiliation(s)
- M Pizzato
- Wohl Virion Centre, Windeyer Institute of Medical Sciences, University College London, UK
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30
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Patience C, Switzer WM, Takeuchi Y, Griffiths DJ, Goward ME, Heneine W, Stoye JP, Weiss RA. Multiple groups of novel retroviral genomes in pigs and related species. J Virol 2001; 75:2771-5. [PMID: 11222700 PMCID: PMC115901 DOI: 10.1128/jvi.75.6.2771-2775.2001] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In view of the concern over potential infection hazards in the use of porcine tissues and organs for xenotransplantation to humans, we investigated the diversity of porcine endogenous retrovirus (PERV) genomes in the DNA of domestic pigs and related species. In addition to the three known envelope subgroups of infectious gamma retroviruses (PERV-A, -B, and -C), classed together here as PERV group gamma 1, four novel groups of gamma retrovirus (gamma 2 to gamma 5) and four novel groups of beta retrovirus (beta 1 to beta 4) genomes were detected in pig DNA using generic and specific PCR primers. PCR quantification indicated that the retroviral genome copy number in the Landrace x Duroc F(1) hybrid pig ranged from 2 (beta 2 and gamma 5) to approximately 50 (gamma 1). The gamma 1, gamma 2, and beta 4 genomes were transcribed into RNA in adult kidney tissue. Apart from gamma 1, the retroviral genomes are not known to be infectious, and sequencing of a small number of amplified genome fragments revealed stop codons in putative open reading frames in several cases. Analysis of DNA from wild boar and other species of Old World pigs (Suidae) and New World peccaries (Tayassuidae) showed that one retrovirus group, beta 2, was common to all species tested, while the others were present among all Old World species but absent from New World species. The PERV-C subgroup of gamma1 genomes segregated among domestic pigs and were absent from two African species (red river hog and warthog). Thus domestic swine and their phylogenetic relatives harbor multiple groups of hitherto undescribed PERV genomes.
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Affiliation(s)
- C Patience
- Institute of Cancer Research, University College London, London, United Kingdom
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31
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32
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Abstract
The shortage of cadaveric human organs for transplantation may, be alleviated by the use of xenografts as a therapeutic option for end-stage organ failure. Successful attempts have been made to prevent rejection of xenograft tissues in humans. The potential spread of animal-derived pathogens to the xenograft recipient is a complication of xenotransplantation, which must be addressed. This can be complicated further by, the presence of new pathogens, new clinical syndromes, and altered behaviour of these organisms in the immunocompromised recipient. There is concern over the possible activation of latent viruses, including retroviruses, from xenograft tissues. This paper discusses the possible dangers of transmission of animal viruses to humans via xenotransplantation.
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Affiliation(s)
- D K Langat
- Institute of Primate Research, National Museums of Kenya, Karen, Nairobi
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33
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Palmarini M, Hallwirth C, York D, Murgia C, de Oliveira T, Spencer T, Fan H. Molecular cloning and functional analysis of three type D endogenous retroviruses of sheep reveal a different cell tropism from that of the highly related exogenous jaagsiekte sheep retrovirus. J Virol 2000; 74:8065-76. [PMID: 10933716 PMCID: PMC112339 DOI: 10.1128/jvi.74.17.8065-8076.2000] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrated into the sheep genome are 15 to 20 copies of type D endogenous loci that are highly related to two exogenous oncogenic viruses, jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV). The exogenous viruses cause infectious neoplasms of the respiratory tract in small ruminants. In this study, we molecularly cloned three intact type D endogenous retroviruses of sheep (enJS56A1, enJS5F16, and enJS59A1; collectively called enJRSVs) and analyzed their genomic structures, their phylogenies with respect to their exogenous counterparts, their capacity to form viral particles, and the expression specificities of their long terminal repeats (LTRs). In addition, the pattern of expression of enJSRVs in vivo was studied by in situ hybridization. All of the three enJSRV proviruses had open reading frames for at least one of the structural genes. In particular, enJS56A1 had open reading frames for all structural genes, but it could not assemble viral particles when highly expressed in human 293T cells. We localized the defect for viral assembly in the first two-thirds of the gag gene by making a series of chimeras between enJS56A1 and the exogenous infectious molecular clone JSRV(21). Phylogenetic analysis distinguished five ovine type D retroviruses: enJSRV groups A and B, ENTV, and two exogenous JSRV groups (African versus United Kingdom/North America isolates). Transient transfection assays indicated that the LTRs of the three enJSRVs were not preferentially active in differentiated lung epithelial cells. This suggests that the pulmonary tropic JSRV developed from a type D retrovirus that did not have lung specificity. Consistent with this, in situ hybridization of a panel of normal ovine tissues revealed high expression of enJSRV mRNA in the luminal epithelium and glandular epithelium of the uterus; lower expression was localized in the lamina propria of the gut and in the bronchiolar epithelium of the lungs.
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Affiliation(s)
- M Palmarini
- Cancer Research Institute and Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California 92697, USA
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34
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Takeuchi Y, Pizzato M. Retrovirus vectors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 465:23-35. [PMID: 10810612 DOI: 10.1007/0-306-46817-4_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Y Takeuchi
- Chester Beatty Laboratories, Institute of Cancer Research, London, England
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35
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Seifarth W, Krause U, Hohenadl C, Baust C, Hehlmann R, Leib-Mösch C. Rapid identification of all known retroviral reverse transcriptase sequences with a novel versatile detection assay. AIDS Res Hum Retroviruses 2000; 16:721-9. [PMID: 10826479 DOI: 10.1089/088922200308729] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have developed a highly sensitive, universal assay that allows detection as well as identification of all known retroviral reverse transcriptase (RT)-related nucleic acids in a biological sample by a single two-step experiment. The assay combines polymerase chain reaction (PCR) and reverse dot-blot hybridization (RDBH), using an array of immobilized synthetic retrovirus-specific oligonucleotides and two sets of mixed oligo primers (MOPs). These primers were derived from highly conserved motifs found in all known reverse transcriptase genes. The PCR/RDBH assay was used for qualitative analyses of human endogenous retrovirus (HERV) transcription in peripheral blood mononuclear cells (PBMCs) and in particles released by the human mammary carcinoma-derived cell line T47D. Sensitivity was further demonstrated by detection of down to 10 copies of pig endogenous retrovirus (PERV) DNA in human cDNA samples. Therefore, this assay is particularly useful for the identification of retroviral sequences in xenografts as well as in recipients of xenografted tissues and organs. Moreover, it is a valuable tool to detect retroviral transcripts and particles in cell cultures used for production of therapeutic polypeptides. The assay is further suitable for monitoring vector preparation used in human gene therapy to exclude transfer of copackaged endogenous retroviruses into target cells.
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Affiliation(s)
- W Seifarth
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany.
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36
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37
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Abstract
Retroviral vectors have become a standard tool for gene transfer technology. Compared with other gene transfer systems, retroviral vectors have several advantages, including their ability to transduce a variety of cell types, to integrate efficiently into the genomic DNA of the recipient cells and to express the transduced gene at high levels. The relatively well understood biology of retroviruses has made possible the development of packaging cell lines which provide in trans all the viral proteins required for viral particle formation. The design of different types of packaging cells has evolved to reduce the possibility of helper virus production. The host range of retroviruses has been expanded by pseudotyping the vectors with heterologous viral glycoproteins and receptor-specific ligands. The development of lentivirus vectors has allowed efficient gene transfer to quiescent cells. This review describes different strategies adopted for developing vectors to be used in gene therapy applications.
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Affiliation(s)
- G Palù
- Department of Histology, Microbiology and Medical Biotechnologies, University of Padova, Italy
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38
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Günzburg WH, Salmons B. Xenotransplantation: is the risk of viral infection as great as we thought? MOLECULAR MEDICINE TODAY 2000; 6:199-208. [PMID: 10782067 DOI: 10.1016/s1357-4310(00)01708-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Two major hurdles remain before xenotransplantation can enter the clinic. The first is the more technical issue of being able to overcome the human immune response that leads to rejection of transplanted organs/cells from other species. The second, reviewed here, concerns the potential risk of inadvertent transfer of animal viruses present in the xenotransplant that are able to infect the human recipient. The threat from viruses is a particularly contentious topic because it poses a risk not only to those individuals who receive xenotransplants, but also to healthy individuals who come into contact, either directly or indirectly, with the xenotransplant recipient. In this review, we describe some of the virus types, in addition to the much discussed porcine endogenous retroviruses that might cross the species barrier, and assess the risk of such viruses causing disease in human hosts.
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Affiliation(s)
- W H Günzburg
- Institute of Virology, University of Veterinary Sciences, Veterinärplatz 1, A-1210 Vienna, Austria.
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39
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Abstract
Retroviral vectors derived from murine retroviruses are being used in several clinical gene therapy trials. Recently, progress has been made in the development of vectors based on the lentivirus genus of retroviruses, which ironically includes a major human pathogen, human immunodeficiency virus (HIV). As these vector systems for clinical gene transfer are developed, it is important to understand the rationale behind their design and development. This article reviews the fundamental features of retrovirus replication and of the elements necessary for development of a retroviral vector system, and it discusses why vector systems based on HIV or other lentiviruses have the potential to become important tools in clinical gene therapy.
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40
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Abstract
Abstract
Retroviral vectors derived from murine retroviruses are being used in several clinical gene therapy trials. Recently, progress has been made in the development of vectors based on the lentivirus genus of retroviruses, which ironically includes a major human pathogen, human immunodeficiency virus (HIV). As these vector systems for clinical gene transfer are developed, it is important to understand the rationale behind their design and development. This article reviews the fundamental features of retrovirus replication and of the elements necessary for development of a retroviral vector system, and it discusses why vector systems based on HIV or other lentiviruses have the potential to become important tools in clinical gene therapy.
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41
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Blond JL, Lavillette D, Cheynet V, Bouton O, Oriol G, Chapel-Fernandes S, Mandrand B, Mallet F, Cosset FL. An envelope glycoprotein of the human endogenous retrovirus HERV-W is expressed in the human placenta and fuses cells expressing the type D mammalian retrovirus receptor. J Virol 2000; 74:3321-9. [PMID: 10708449 PMCID: PMC111833 DOI: 10.1128/jvi.74.7.3321-3329.2000] [Citation(s) in RCA: 483] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A new human endogenous retrovirus (HERV) family, termed HERV-W, was recently described (J.-L. Blond, F. Besème, L. Duret, O. Bouton, F. Bedin, H. Perron, B. Mandrand, and F. Mallet, J. Virol. 73:1175-1185, 1999). HERV-W mRNAs were found to be specifically expressed in placenta cells, and an env cDNA containing a complete open reading frame was recovered. In cell-cell fusion assays, we demonstrate here that the product of the HERV-W env gene is a highly fusogenic membrane glycoprotein. Transfection of an HERV-W Env expression vector in a panel of cell lines derived from different species resulted in formation of syncytia in primate and pig cells upon interaction with the type D mammalian retrovirus receptor. Moreover, envelope glycoproteins encoded by HERV-W were specifically detected in placenta cells, suggesting that they may play a physiological role during pregnancy and placenta formation.
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Affiliation(s)
- J L Blond
- Unité Mixte 103 CNRS-bioMérieux, INSERM U412, Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
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42
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Seppen J, Barry S, Lam GM, Ramesh N, Osborne WR. Retroviral preparations derived from PA317 packaging cells contain inhibitors that copurify with viral particles and are devoid of viral vector RNA. Hum Gene Ther 2000; 11:771-5. [PMID: 10757356 DOI: 10.1089/10430340050015662] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Obtaining high expression levels of a therapeutic gene in target cells could be achieved by integrating multiple copies of a recombinant retrovirus. However, we observed that cells retrovirally infected at high multiplicities of infection (MOIs) carried only single or double integrated proviral copies, suggesting that maximum retroviral transduction was achieved at relatively low MOIs. The same results were obtained when purified virus, free of most medium components, was used. Retroviral infection was shown to be inhibited by supernatants of other viral producer cell lines, and this inhibition could be removed by a centrifugation step that also removed more than 90% of infectious virus. Quantitative-competitive PCR of retroviral preparations showed that the amount of retroviral vector RNA present was similar to the amount expected on the basis of virus titers. Our data suggest that retroviral preparations derived from PA317 packaging cells contain inhibitors that copurify with retroviruses and do not contain viral vector RNA. We postulate that these inhibitor particles cannot achieve a productive infection but interfere with transduction of the target cells by infectious virions. This study might define an important criterion for the selection of more effective packaging cell lines.
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Affiliation(s)
- J Seppen
- Department of Pediatrics, University of Washington School of Medicine, Seattle 98195, USA
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43
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Mikkelsen JG, Pedersen FS. Genetic reassortment and patch repair by recombination in retroviruses. J Biomed Sci 2000; 7:77-99. [PMID: 10754383 DOI: 10.1007/bf02256615] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Retroviral particles contain a diploid RNA genome which serves as template for the synthesis of double-stranded DNA in a complex process guided by virus-encoded reverse transcriptase. The dimeric nature of the genome allows the proceeding polymerase to switch templates during copying of the copackaged RNA molecules, leading to the generation of recombinant proviruses that harbor genetic information derived from both parental RNAs. Template switching abilities of reverse transcriptase facilitate the development of mosaic retroviruses with altered functional properties and thereby contribute to the restoration and evolution of retroviruses facing altering selective forces of their environment. This review focuses on the genetic patchwork of retroviruses and how mixing of sequence patches by recombination may lead to repair in terms of re-established replication and facilitate increased viral fitness, enhanced pathogenic potential, and altered virus tropisms. Endogenous retroelements represent an affluent source of functional viral sequences which may hitchhike with virions and serve as sequence donors in patch repair. We describe here the involvement of endogenous viruses in genetic reassortment and patch repair and review important examples derived from cell culture and animal studies. Moreover, we discuss how the patch repair phenomenon may challenge both safe usage of retrovirus-based gene vehicles in human gene therapy and the use of animal organs as xenografts in humans. Finally, the ongoing mixing of distinct human immunodeficiency virus strains and its implications for antiviral treatment is discussed.
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MESH Headings
- Animals
- DNA, Viral/biosynthesis
- DNA, Viral/genetics
- Endogenous Retroviruses/genetics
- Evolution, Molecular
- Genetic Therapy/adverse effects
- Genetic Variation
- Humans
- Mice
- Models, Genetic
- Mosaicism/genetics
- Proviruses/genetics
- RNA/genetics
- RNA, Double-Stranded/biosynthesis
- RNA, Double-Stranded/genetics
- RNA, Viral/genetics
- RNA-Directed DNA Polymerase/physiology
- Recombination, Genetic
- Retroviridae/genetics
- Retroviridae Infections/genetics
- Retroviridae Infections/transmission
- Retroviridae Infections/virology
- Risk
- Safety
- Templates, Genetic
- Transplantation, Heterologous/adverse effects
- Virion/metabolism
- Virus Replication/genetics
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Affiliation(s)
- J G Mikkelsen
- Department of Molecular and Structural Biology, University of Aarhus, Denmark
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44
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Sena-Esteves M, Saeki Y, Camp SM, Chiocca EA, Breakefield XO. Single-step conversion of cells to retrovirus vector producers with herpes simplex virus-Epstein-Barr virus hybrid amplicons. J Virol 1999; 73:10426-39. [PMID: 10559361 PMCID: PMC113098 DOI: 10.1128/jvi.73.12.10426-10439.1999] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/1999] [Accepted: 08/25/1999] [Indexed: 11/20/2022] Open
Abstract
We report here on the development and characterization of a novel herpes simplex virus type 1 (HSV-1) amplicon-based vector system which takes advantage of the host range and retention properties of HSV-Epstein-Barr virus (EBV) hybrid amplicons to efficiently convert cells to retrovirus vector producer cells after single-step transduction. The retrovirus genes gag-pol and env (GPE) and retroviral vector sequences were modified to minimize sequence overlap and cloned into an HSV-EBV hybrid amplicon. Retrovirus expression cassettes were used to generate the HSV-EBV-retrovirus hybrid vectors, HERE and HERA, which code for the ecotropic and the amphotropic envelopes, respectively. Retrovirus vector sequences encoding lacZ were cloned downstream from the GPE expression unit. Transfection of 293T/17 cells with amplicon plasmids yielded retrovirus titers between 10(6) and 10(7) transducing units/ml, while infection of the same cells with amplicon vectors generated maximum titers 1 order of magnitude lower. Retrovirus titers were dependent on the extent of transduction by amplicon vectors for the same cell line, but different cell lines displayed varying capacities to produce retrovirus vectors even at the same transduction efficiencies. Infection of human and dog primary gliomas with this system resulted in the production of retrovirus vectors for more than 1 week and the long-term retention and increase in transgene activity over time in these cell populations. Although the efficiency of this system still has to be determined in vivo, many applications are foreseeable for this approach to gene delivery.
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Affiliation(s)
- M Sena-Esteves
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA
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45
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Mikkelsen JG, Lund AH, Duch M, Pedersen FS. Forced recombination of psi-modified murine leukaemia virus-based vectors with murine leukaemia-like and VL30 murine endogenous retroviruses. J Gen Virol 1999; 80 ( Pt 11):2957-2967. [PMID: 10580058 DOI: 10.1099/0022-1317-80-11-2957] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Co-encapsidation of retroviral RNAs into virus particles allows for the generation of recombinant proviruses through events of template switching during reverse transcription. By use of a forced recombination system based on recombinational rescue of replication- defective primer binding site-impaired Akv-MLV-derived vectors, we here examine putative genetic interactions between vector RNAs and copackaged endogenous retroviral RNAs of the murine leukaemia virus (MLV) and VL30 retroelement families. We show (i) that MLV recombination is not blocked by nonhomology within the 5' untranslated region harbouring the supposed RNA dimer-forming cis -elements and (ii) that copackaged retroviral RNAs can recombine despite pronounced sequence dissimilarity at the cross-over site(s) and within parts of the genome involved in RNA dimerization, encapsidation and strand transferring during reverse transcription. We note that recombination-based rescue of primer binding site knock-out retroviral vectors may constitute a sensitive assay to register putative genetic interactions involving endogenous retroviral RNAs present in cells of various species.
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Affiliation(s)
- Jacob Giehm Mikkelsen
- Department of Molecular and Structural Biology1 and Department of Medical Microbiology and Immunology,2 University of Aarhus, C. F. Moellers Allé, Bldg 130, DK-8000 Aarhus, Denmark
| | - Anders H Lund
- Department of Molecular and Structural Biology1 and Department of Medical Microbiology and Immunology,2 University of Aarhus, C. F. Moellers Allé, Bldg 130, DK-8000 Aarhus, Denmark
| | - Mogens Duch
- Department of Molecular and Structural Biology1 and Department of Medical Microbiology and Immunology,2 University of Aarhus, C. F. Moellers Allé, Bldg 130, DK-8000 Aarhus, Denmark
| | - Finn Skou Pedersen
- Department of Molecular and Structural Biology1 and Department of Medical Microbiology and Immunology,2 University of Aarhus, C. F. Moellers Allé, Bldg 130, DK-8000 Aarhus, Denmark
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46
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López-Lastra M, Ulrici S, Gabus C, Darlix JL. Identification of an internal ribosome entry segment in the 5' region of the mouse VL30 retrotransposon and its use in the development of retroviral vectors. J Virol 1999; 73:8393-402. [PMID: 10482590 PMCID: PMC112857 DOI: 10.1128/jvi.73.10.8393-8402.1999] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mouse virus-like 30S RNAs (VL30m) constitute a family of retrotransposons, present at 100 to 200 copies, dispersed in the mouse genome. They display little sequence homology to Moloney murine leukemia virus (MoMLV), do not encode virus-like proteins, and have not been implicated in retroviral carcinogenesis. However, VL30 RNAs are efficiently packaged into MLV particles that are propagated in cell culture. In this study, we addressed whether the 5' region of VL30m could replace the 5' leader of MoMLV functionally in a recombinant vector construct. Our data confirm that the putative packaging sequence of VL30 is located within the 5' region (nucleotides 362 to 1149 with respect to the cap structure) and that it can replace the packaging sequence of MoMLV. We also show that VL30m contains an internal ribosome entry segment (IRES) in the 5' region, as do MoMLV, Friend murine leukemia virus, Harvey murine sarcoma virus, and avian reticuloendotheliosis virus type A. Our data show that both the packaging and IRES functions of the 5' region of VL30m RNA can be efficiently used to develop retrotransposon-based vectors.
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Affiliation(s)
- M López-Lastra
- Labo Rétro, Unité de Virologie Humaine-U412, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
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47
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Abstract
Endogenous retroviruses are descendants of viruses that became cellular genes by integration into their host's genome. They still contribute to pathogenicity as a partner in recombination events, by de novo insertion after mobilization followed by activation of downstream proto-oncogenes, or by gene disruption. Re-expression of viral proteins accompanied by loss of immune tolerance could induce immune disturbances.
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Affiliation(s)
- R Löwer
- Paul Ehrlich Institut, Paul Ehrlich Str. 51-59, D-63225 Langen, Germany.
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48
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Gerin PA, Gilligan MG, Searle PF, Al-Rubeai M. Improved titers of retroviral vectors from the human FLYRD18 packaging cell line in serum- and protein-free medium. Hum Gene Ther 1999; 10:1965-74. [PMID: 10466630 DOI: 10.1089/10430349950017329] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The influence of serum on the production of retroviral vectors by the HT1080 human fibrosarcoma-derived packaging cell line FLYRD18 was investigated. A fourfold increase in virus titer was observed under serum-free conditions, as compared with medium supplemented with 10% fetal calf serum. A similar improvement was also seen for bulk transduction efficiency. Serum had a negative and dose-dependent effect on titer without affecting cell growth, virus stability, or infectivity. In contrast to virus from NIH 3T3-derived packaging cells [Hanenberg, H., et al. (1996). Nature Med. 2, 876-882], the FLYRD18-derived virus did not adhere to fibronectin or serum proteins adsorbed at the surface of culture flasks. Electron microscopy supports the conclusion that the effect of serum is at the level of virus production by the cells. Addition of soybean trypsin inhibitor had an inhibitory effect on virus production, while pretreatment of serum with trypsin was found to enhance the retroviral titer. These results suggest that protease inhibitors present in serum may be responsible for the inhibition of virus production. The exact mechanism remains, however, to be determined. As compared with medium supplemented with 10% serum, the combination of increased virus titer and absence of exogenous protein under serum-free conditions resulted in a 300-fold increase in the virus:total protein ratio in the supernatants harvested from the FLYRD18 packaging line. This improvement enhances prospects for further concentration and purification of the virus.
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Affiliation(s)
- P A Gerin
- School of Chemical Engineering, University of Birmingham, Edgbaston, England
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49
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Lindeskog M, Mager DL, Blomberg J. Isolation of a human endogenous retroviral HERV-H element with an open env reading frame. Virology 1999; 258:441-50. [PMID: 10366582 DOI: 10.1006/viro.1999.9750] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
About 100 elements of the human endogenous retroviral HERV-H family have full-length env genes potentially coding for Env proteins with sequences highly similar to the immunosuppressive peptide CKS-17 from the MLV transmembrane protein p15E. However, previously sequenced HERV-H env genes have contained stop codons or framehifts. To isolate elements with open env reading frames, we first tried to assess the diversity of HERV-H env genes by comparing PCR-generated env sequences from genomic DNA with published HERV-H sequences. A region at the beginning of env displayed a similarity of 84-98% among 15 different elements. We then used a probe from one of the PCR-generated clones, 98% similar to the consensus sequence in this region, to screen a human genomic lambda library. Three HERV-H elements displaying ca. 98% identity in the env gene were isolated and were shown to have integrated relatively recently, after the divergence of the orangutan and the african great ape lineages. One of these elements, HERV-H19, had a 1752-bp open env reading frame, producing a 77-kDa Env protein in in vitro translation reactions. This is the first demonstration of a coding competent member of the HERV-H family. These findings raise the possibility that HERV-H Env proteins may play a biological role in human cells.
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Affiliation(s)
- M Lindeskog
- Section of Virology, Lund University, Sölvegatan 23, Lund, S-22362, Sweden.
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50
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Tailor CS, Nouri A, Zhao Y, Takeuchi Y, Kabat D. A sodium-dependent neutral-amino-acid transporter mediates infections of feline and baboon endogenous retroviruses and simian type D retroviruses. J Virol 1999; 73:4470-4. [PMID: 10196349 PMCID: PMC104338 DOI: 10.1128/jvi.73.5.4470-4474.1999] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The type D simian retroviruses cause immunosuppression in macaques and have been reported as a presumptive opportunistic infection in a patient with AIDS. Previous evidence based on viral interference has strongly suggested that the type D simian viruses share a common but unknown cell surface receptor with three type C viruses: feline endogenous virus (RD114), baboon endogenous virus, and avian reticuloendotheliosis virus. Furthermore, the receptor gene for these viruses has been mapped to human chromosome 19q13.1-13.2. We now report the isolation and characterization of a cell surface receptor for this group of retroviruses by using a human T-lymphocyte cDNA library in a retroviral vector. Swiss mouse fibroblasts (NIH 3T3), which are naturally resistant to RD114, were transduced with the retroviral library and then challenged with an RD114-pseudotyped virus containing a dominant selectable gene for puromycin resistance. Puromycin selection yielded 12 cellular clones that were highly susceptible to a beta-galactosidase-encoding lacZ(RD114) pseudotype virus. Using PCR primers specific for vector sequences, we amplified a common 2.9-kb product from 10 positive clones. Expression of the 2.9-kb cDNA in Chinese hamster ovary cells conferred susceptibility to RD114, baboon endogenous virus, and the type D simian retroviruses. The 2.9-kb cDNA predicted a protein of 541 amino acids that had 98% identity with the previously cloned human Na+-dependent neutral-amino-acid transporter Bo. Accordingly, expression of the RD114 receptor in NIH 3T3 cells resulted in enhanced cellular uptake of L-[3H]alanine and L-[3H]glutamine. RNA blot (Northern) analysis suggested that the RD114 receptor is widely expressed in human tissues and cell lines, including hematopoietic cells. The human Bo transporter gene has been previously mapped to 19q13.3, which is closely linked to the gene locus of the RD114 receptor.
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Affiliation(s)
- C S Tailor
- Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, Oregon 97201-3098, USA.
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