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Jalšić L, Lytvyn V, Elahi SM, Hrapovic S, Nassoury N, Chahal PS, Gaillet B, Gilbert R. Inducible HEK293 AAV packaging cell lines expressing Rep proteins. Mol Ther Methods Clin Dev 2023; 30:259-275. [PMID: 37560197 PMCID: PMC10407821 DOI: 10.1016/j.omtm.2023.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 07/11/2023] [Indexed: 08/11/2023]
Abstract
Packaging or producer cell lines for scalable recombinant adeno-associated virus (rAAV) production have been notoriously difficult to create due in part to the cytostatic nature of the Rep proteins required for AAV production. The most difficult challenge being creating AAV packaging cell lines using HEK293 parental cells, currently the best mammalian platform for rAAV production due to the constitutive expression of E1A in HEK293 cells, a key REP transcription activator. Using suspension and serum-free media adapted HEK293SF carrying a gene expression regulation system induced by addition of cumate and coumermycin, we were able to create REP-expressing AAV packaging cells. This was achieved by carefully choosing two of the AAV Rep proteins (Rep 40 and 68), using two inducible promoters with different expression levels and integrating into the cells through lentiviral vector transduction. Three of our best clones produced rAAV titers comparable to titers obtained by standard triple plasmid transfection of their parental cells. These clones were stable for up to 7 weeks under continuous cultures condition. rAAV production from one clone was also validated at scale of 1 L in a wave bioreactor using serum-free suspension culture.
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Affiliation(s)
- Lovro Jalšić
- Département de Génie Chimique, Université Laval, Québec, QC G1V0A6, Canada
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Viktoria Lytvyn
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Seyyed Mehdy Elahi
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Sabahudin Hrapovic
- Advanced Biomaterials and Chemical Synthesis Team, Aquatic and Crop Resource Development Research Centre, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Nasha Nassoury
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Parminder Singh Chahal
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
| | - Bruno Gaillet
- Département de Génie Chimique, Université Laval, Québec, QC G1V0A6, Canada
| | - Rénald Gilbert
- Département de Génie Chimique, Université Laval, Québec, QC G1V0A6, Canada
- Department of Production Platforms and Analytics, Human Health Therapeutics Research Center, National Research Council Canada, Montréal, QC H4P 2R2, Canada
- Department of Bioengineering, McGill University, Montréal, QC H3A 0E9 Canada
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Xiang YS, Hao GG. Biophysical characterization of adeno-associated virus capsid through the viral transduction life cycle. J Genet Eng Biotechnol 2023; 21:62. [PMID: 37195476 DOI: 10.1186/s43141-023-00518-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 05/11/2023] [Indexed: 05/18/2023]
Abstract
Adeno-associated virus (AAV) vectors have emerged as the leading delivery platforms for gene therapy. Throughout the life cycle of the virions, the capsid vector carries out diverse functions, ranging from cell surface receptor engagement, cellular entry, endosomal escape, nuclear import to new particle packaging, and assembly. Each of these steps is mediated by exquisite structure features of the viral capsid and its interaction with viral genome, Rep proteins, and cellular organelle and apparatus. In this brief review, we provide an overview of results from over a decade of extensive biophysical studies of the capsid employing various techniques. The remaining unaddressed questions and perspective are also discussed. The detailed understanding of the structure and function interplay would provide insight to the strategy for improving the efficacy and safety of the viral vectors.
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Affiliation(s)
| | - Gang Gary Hao
- Weston Biomedical Reviews, 65 Autumn Road, Weston, MA, 02493, USA.
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Bastola P, Song L, Gilger BC, Hirsch ML. Adeno-Associated Virus Mediated Gene Therapy for Corneal Diseases. Pharmaceutics 2020; 12:pharmaceutics12080767. [PMID: 32823625 PMCID: PMC7464341 DOI: 10.3390/pharmaceutics12080767] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 12/14/2022] Open
Abstract
According to the World Health Organization, corneal diseases are the fourth leading cause of blindness worldwide accounting for 5.1% of all ocular deficiencies. Current therapies for corneal diseases, which include eye drops, oral medications, corrective surgeries, and corneal transplantation are largely inadequate, have undesirable side effects including blindness, and can require life-long applications. Adeno-associated virus (AAV) mediated gene therapy is an optimistic strategy that involves the delivery of genetic material to target human diseases through gene augmentation, gene deletion, and/or gene editing. With two therapies already approved by the United States Food and Drug Administration and 200 ongoing clinical trials, recombinant AAV (rAAV) has emerged as the in vivo viral vector-of-choice to deliver genetic material to target human diseases. Likewise, the relative ease of applications through targeted delivery and its compartmental nature makes the cornea an enticing tissue for AAV mediated gene therapy applications. This current review seeks to summarize the development of AAV gene therapy, highlight preclinical efficacy studies, and discuss potential applications and challenges of this technology for targeting corneal diseases.
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Affiliation(s)
- Prabhakar Bastola
- Ophthalmology, University of North Carolina, Chapel Hill, NC 27599, USA; (P.B.); (L.S.); (B.C.G.)
- Gene Therapy Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Liujiang Song
- Ophthalmology, University of North Carolina, Chapel Hill, NC 27599, USA; (P.B.); (L.S.); (B.C.G.)
- Gene Therapy Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Brian C. Gilger
- Ophthalmology, University of North Carolina, Chapel Hill, NC 27599, USA; (P.B.); (L.S.); (B.C.G.)
- Clinical Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Matthew L. Hirsch
- Ophthalmology, University of North Carolina, Chapel Hill, NC 27599, USA; (P.B.); (L.S.); (B.C.G.)
- Gene Therapy Center, University of North Carolina, Chapel Hill, NC 27599, USA
- Correspondence: ; Tel.: +1-919-966-0696
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Maurer AC, Weitzman MD. Adeno-Associated Virus Genome Interactions Important for Vector Production and Transduction. Hum Gene Ther 2020; 31:499-511. [PMID: 32303138 PMCID: PMC7232694 DOI: 10.1089/hum.2020.069] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Accepted: 04/16/2020] [Indexed: 12/12/2022] Open
Abstract
Recombinant adeno-associated virus has emerged as one of the most promising gene therapy delivery vectors. Development of these vectors took advantage of key features of the wild-type adeno-associated virus (AAV), enabled by basic studies of the underlying biology and requirements for transcription, replication, and packaging of the viral genome. Each step in generating and utilizing viral vectors involves numerous molecular interactions that together determine the efficiency of vector production and gene delivery. Once delivered into the cell, interactions with host proteins will determine the fate of the viral genome, and these will impact the intended goal of gene delivery. Here, we provide an overview of known interactions of the AAV genome with viral and cellular proteins involved in its amplification, packaging, and expression. Further appreciation of how the AAV genome interacts with host factors will enhance how this simple virus can be harnessed for an array of vector purposes that benefit human health.
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Affiliation(s)
- Anna C. Maurer
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Matthew D. Weitzman
- Division of Protective Immunity, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Division of Cancer Pathobiology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
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5
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Govindasamy L, DiMattia MA, Gurda BL, Halder S, McKenna R, Chiorini JA, Muzyczka N, Zolotukhin S, Agbandje-McKenna M. Structural insights into adeno-associated virus serotype 5. J Virol 2013; 87:11187-99. [PMID: 23926356 PMCID: PMC3807309 DOI: 10.1128/jvi.00867-13] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Accepted: 08/01/2013] [Indexed: 11/20/2022] Open
Abstract
The adeno-associated viruses (AAVs) display differential cell binding, transduction, and antigenic characteristics specified by their capsid viral protein (VP) composition. Toward structure-function annotation, the crystal structure of AAV5, one of the most sequence diverse AAV serotypes, was determined to 3.45-Å resolution. The AAV5 VP and capsid conserve topological features previously described for other AAVs but uniquely differ in the surface-exposed HI loop between βH and βI of the core β-barrel motif and have pronounced conformational differences in two of the AAV surface variable regions (VRs), VR-IV and VR-VII. The HI loop is structurally conserved in other AAVs despite amino acid differences but is smaller in AAV5 due to an amino acid deletion. This HI loop is adjacent to VR-VII, which is largest in AAV5. The VR-IV, which forms the larger outermost finger-like loop contributing to the protrusions surrounding the icosahedral 3-fold axes of the AAVs, is shorter in AAV5, creating a smoother capsid surface topology. The HI loop plays a role in AAV capsid assembly and genome packaging, and VR-IV and VR-VII are associated with transduction and antigenic differences, respectively, between the AAVs. A comparison of interior capsid surface charge and volume of AAV5 to AAV2 and AAV4 showed a higher propensity of acidic residues but similar volumes, consistent with comparable DNA packaging capacities. This structure provided a three-dimensional (3D) template for functional annotation of the AAV5 capsid with respect to regions that confer assembly efficiency, dictate cellular transduction phenotypes, and control antigenicity.
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Affiliation(s)
- Lakshmanan Govindasamy
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Michael A. DiMattia
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Brittney L. Gurda
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Sujata Halder
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Robert McKenna
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - John A. Chiorini
- MPTB, NIDCR, National Institutes of Health, Bethesda, Maryland, USA
| | - Nicholas Muzyczka
- Department of Molecular Genetics and Microbiology and Powell Gene Therapy Center, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Sergei Zolotukhin
- Department of Pediatrics, Division of Cell and Molecular Therapy, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, Center for Structural Biology, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
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6
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Abstract
The Adeno-associated viruses (AAVs) are not associated with any diseases, and their ability to package non-genomic DNA and to transduce different cell/tissue populations has generated significant interest in understanding their basic biology in efforts to improve their utilization for corrective gene delivery. This includes their capsid structure, cellular tropism and interactions for entry, uncoating, replication, DNA packaging, capsid assembly, and antibody neutralization. The human and nonhuman primate AAVs are clustered into serologically distinct genetic clade and serotype groups, which have distinct cellular/tissue tropisms and transduction efficiencies. These properties are highly dependent upon the AAV capsid amino acid sequence, their capsid structure, and their interactions with host cell factors, including cell surface receptors, co-receptors, signaling molecules, proteins involved in host DNA replication, and host-derived antibodies. This chapter reviews the current structural information on AAV capsids and the capsid viral protein regions playing a role in the cellular interactions conferring an infective phenotype, which are then used to annotate the functional regions of the capsid. Based on the current data, the indication is that the AAVs, like other members of the Parvoviridae and other ssDNA viruses that form a T = 1 capsid, have evolved a multifunctional capsid with conserved core regions as is required for efficient capsid trafficking, capsid assembly, and genome packaging. Disparate surface loop structures confer differential receptor recognition and are involved in antibody recognition. The role of structural regions in capsid uncoating remains to be elucidated.
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Affiliation(s)
- Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA.
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7
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Bleker S, Pawlita M, Kleinschmidt JA. Impact of capsid conformation and Rep-capsid interactions on adeno-associated virus type 2 genome packaging. J Virol 2006; 80:810-20. [PMID: 16378983 PMCID: PMC1346863 DOI: 10.1128/jvi.80.2.810-820.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Single-stranded genomes of adeno-associated virus (AAV) are packaged into preformed capsids. It has been proposed that packaging is initiated by interaction of genome-bound Rep proteins to the capsid, thereby targeting the genome to the portal of encapsidation. Here we describe a panel of mutants with amino acid exchanges in the pores at the fivefold axes of symmetry on AAV2 capsids with reduced packaging and reduced Rep-capsid interaction. Mutation of two threonines at the rim of the fivefold pore nearly completely abolished Rep-capsid interaction and packaging. This suggests a Rep-binding site at the highly conserved amino acids at or close to the pores formed by the capsid protein pentamers. A different mutant (P. Wu, W. Xiao, T. Conlon, J. Hughes, M. Agbandje-McKenna, T. Ferkol, T. Flotte, and N. Muzyczka, J. Virol. 74:8635-8647, 2000) with an amino acid exchange at the interface of capsid protein pentamers led to a complete block of DNA encapsidation. Analysis of the capsid conformation of this mutant revealed that the pores at the fivefold axes were occupied by VP1/VP2 N termini, thereby preventing DNA introduction into the capsid. Nevertheless, the corresponding capsids had more Rep proteins bound than wild-type AAV, showing that correct Rep interaction with the capsid depends on a defined capsid conformation. Both mutant types together support the conclusion that the pores at the fivefold symmetry axes are involved in genome packaging and that capsid conformation-dependent Rep-capsid interactions play an essential role in the packaging process.
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Affiliation(s)
- Svenja Bleker
- German Cancer Research Centre, Infection and Cancer Research Program, Division of Tumor Virology, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany
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8
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Casper JM, Timpe JM, Dignam JD, Trempe JP. Identification of an adeno-associated virus Rep protein binding site in the adenovirus E2a promoter. J Virol 2005; 79:28-38. [PMID: 15596798 PMCID: PMC538739 DOI: 10.1128/jvi.79.1.28-38.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated virus (AAV) and other parvoviruses inhibit proliferation of nonpermissive cells. The mechanism of this inhibition is not thoroughly understood. To learn how AAV interacts with host cells, we investigated AAV's interaction with adenovirus (Ad), AAV's most efficient helper virus. Coinfection with Ad and AAV results in an AAV-mediated inhibition of Ad5 gene expression and replication. The AAV replication proteins (Rep) activate and repress gene expression from AAV and heterologous transcription promoters. To investigate the role of Rep proteins in the suppression of Ad propagation, we performed chromatin immunoprecipitation analyses that demonstrated in vivo AAV Rep protein interaction with the Ad E2a gene promoter. In vitro binding of purified AAV Rep68 protein to the Ad E2a promoter was characterized by electrophoretic mobility shift assays (Kd= 200 +/- 25 nM). A 38 bp, Rep68-protected region (5'-TAAGAGTCAGCGCGCAGTATTTACTGAAGAGAGCCT-3') was identified by DNase I footprint analysis. The 38-bp protected region contains the weak E2a TATA box, sequence elements that resemble the Rep binding sites identified by random sequence oligonucleotide selection, and the transcription start site. These results suggest that Rep binding to the E2a promoter contributes to the inhibition of E2a gene expression from the Ad E2a promoter and may affect Ad replication.
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Affiliation(s)
- John M Casper
- Department of Biochemistry and Cancer Biology, Medical College of Ohio, Toledo, Ohio 43614-5804, USA
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9
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Steigerwald R, Rabe C, Schmitz V, Schmidt-Wolf IG, Alt M, Caselmann WH. Requirements for adeno-associated virus-derived non-viral vectors to achieve stable and site-specific integration of plasmid DNA in liver carcinoma cells. Digestion 2004; 68:13-23. [PMID: 12949435 DOI: 10.1159/000073221] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Accepted: 05/22/2003] [Indexed: 02/04/2023]
Abstract
BACKGROUND AND AIMS Adeno-associated virus (AAV) is the only known virus capable of site-specific genomic integration in human cells. Thus, AAV-based vectors may be an attractive option to achieve prolonged transgene expression in human cells. We therefore studied the minimal elements of gene therapy vectors necessary for stable integration and tested the effectiveness of this approach in hepatoma cells. METHODS Plasmids were constructed that contained a GFPneo fusion transgene with or without the AAV-inverted terminal repeats (ITRs). In addition, Rep protein was either encoded in CIS or supplied in TRANS by co-transfections. Stable clones were analyzed by Southern blotting for site-specific integration. RESULTS The ITRs alone conferred neither stable nor site-specific transgene integration. Expression of Rep protein in CIS or TRANS resulted in an increased frequency of integration regardless of the presence of ITRs. It was shown that in the absence of the ITRs, other Rep-binding site (RBS) like sequences such as the ColE1 sequence present in plasmid backbones can function as RBS. Site-specific integration was achieved in up to 26% of clones derived from hepatoma cells. CONCLUSION Both expression of Rep proteins and inclusion of a RBS are necessary for enhanced and stable integration of AAV-based non-viral vectors. A novel two-plasmid system capable of achieving stable and site-specific gene transfer in hepatoma cells is introduced.
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Affiliation(s)
- Robin Steigerwald
- Department of Virus Research, Max Plank Institute for Biochemistry, Martinsried, Germany
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10
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Narasimhan D, Collaco R, Kalman-Maltese V, Trempe JP. Hyper-phosphorylation of the adeno-associated virus Rep78 protein inhibits terminal repeat binding and helicase activity. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1576:298-305. [PMID: 12084576 DOI: 10.1016/s0167-4781(02)00394-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The replication (Rep) proteins of adeno-associated virus (AAV) play prominent roles in regulation of viral DNA replication, RNA transcription, assembly of an infectious virion and establishment of the provirus. We have previously demonstrated that all four Rep proteins are phosphorylated on serine residues [Virology 23 (1997) 332-336]. Reversible phosphorylation may provide a mechanism for regulating Rep protein function. To test this hypothesis, we used the phosphatase inhibitor okadaic acid (OA) to obtain hyper-phosphorylated Rep proteins. OA treatment of AAV- and adenovirus (Ad)-infected cells and baculovirus-infected insect cells at a concentration of 100 nM resulted in a significant increase in Rep protein phosphorylation. This concentration suggests that protein phosphatase 2A (PP2A) is one of the enzymes involved in regulation of Rep phosphorylation. The increased phosphorylation occurred primarily on serine residues with a detectable amount of phosphate on threonine. Hyper-phosphorylation of Rep78 resulted in reduced binding to the AAV origin of DNA replication. Hyper-phosphorylated Rep78 also had diminished helicase activity. These results suggest that regulated phosphorylation of Rep78 plays a role in controlling Rep functions in the virus replication cycle.
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Affiliation(s)
- Diwahar Narasimhan
- Department of Biochemistry and Molecular Biology, Medical College of Ohio, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA
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11
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Affiliation(s)
- E Sadowy
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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12
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Jing XJ, Kalman-Maltese V, Cao X, Yang Q, Trempe JP. Inhibition of adenovirus cytotoxicity, replication, and E2a gene expression by adeno-associated virus. Virology 2001; 291:140-51. [PMID: 11878883 DOI: 10.1006/viro.2001.1192] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adeno-associated virus (AAV) and the other parvoviruses have long been known to inhibit proliferation of nonpermissive cells. The mechanism of this inhibition is not thoroughly understood. To learn how AAV interacts with host cells, we have begun an investigation into AAV's relationship with adenovirus (Ad), AAV's most efficient helper virus. AAV, but not UV-inactivated AAV, delayed Ad-induced cytotoxicity and inhibited Ad E2a gene expression. AAV, but not UV-inactivated AAV or a recombinant AAV vector, inhibited Ad DNA replication. To determine whether AAV or its replication (Rep) proteins alter Ad early gene expression, we measured steady state E2a mRNA levels in AAV and Ad coinfected cultures and in a cell line (Neo6) that inducibly expresses the Rep proteins. AAV, but not UV-AAV, and Rep expression resulted in diminution of E2a protein and mRNA levels. To determine whether the AAV Rep proteins directly affect the individual Ad early promoters, we constructed luciferase reporter plasmids containing each of the five early promoters. Cotransfection of Ad-luciferase and an AAV rep gene-expressing plasmid in HeLa cells demonstrated that Rep78 repressed the E1a, E2a, and E4 promoters but trans-activated the E1b and E3 promoters. In the presence of a cotransfected E1a-expressing plasmid, Rep78 repressed expression from all five promoters. These results indicate that Rep may have different effects on the Ad early promoters dependent upon the presence of the E1a trans-activating protein.
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Affiliation(s)
- X J Jing
- Department of Biochemistry and Molecular Biology, Medical College of Ohio, 3035 Arlington Avenue, Toledo, Ohio 43614-5804, USA
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13
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Cathomen T, Collete D, Weitzman MD. A chimeric protein containing the N terminus of the adeno-associated virus Rep protein recognizes its target site in an in vivo assay. J Virol 2000; 74:2372-82. [PMID: 10666268 PMCID: PMC111719 DOI: 10.1128/jvi.74.5.2372-2382.2000] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rep78 and Rep68 proteins of adeno-associated virus (AAV) type 2 are involved in DNA replication, regulation of gene expression, and targeting site-specific integration. They bind to a specific Rep recognition sequence (RRS) found in both the viral inverted terminal repeats and the AAVS1 integration locus on human chromosome 19. Previous in vitro studies implied that an N-terminal segment of Rep is involved in DNA recognition, while additional domains might stabilize binding and mediate multimerization. In order to define the minimal requirements for Rep to recognize its target site in the human genome, we developed one-hybrid assays in which DNA-protein interactions are detected in vivo. Chimeric proteins consisting of the N terminus of Rep fused to different oligomerization motifs and a transcriptional activation domain were analyzed for oligomerization, DNA binding, and activation of reporter gene expression. Expression of reporter genes was driven from RRS motifs cloned upstream of minimal promoters and examined in mammalian cells from transfected plasmids and in Saccharomyces cerevisiae from a reporter cassette integrated into the yeast genome. Our results show for the first time that chimeric proteins containing the amino-terminal 244 residues of Rep are able to target the RRS in vitro and in vivo when incorporated into artificial multimers. These studies suggest that chimeric proteins may be used to harness the unique targeting feature of AAV for gene therapy applications.
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Affiliation(s)
- T Cathomen
- Laboratory of Genetics, The Salk Institute for Biological Studies, San Diego, California 92186, USA
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14
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Dubielzig R, King JA, Weger S, Kern A, Kleinschmidt JA. Adeno-associated virus type 2 protein interactions: formation of pre-encapsidation complexes. J Virol 1999; 73:8989-98. [PMID: 10516005 PMCID: PMC112931 DOI: 10.1128/jvi.73.11.8989-8998.1999] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nonstructural adeno-associated virus type 2 Rep proteins are known to control viral replication and thus provide the single-stranded DNA genomes required for packaging into preformed capsids. In addition, complexes between Rep proteins and capsids have previously been observed in the course of productive infections. Such complexes have been interpreted as genome-linked Rep molecules associated with the capsid upon successful DNA encapsidation. Here we demonstrate via coimmunoprecipitation, cosedimentation, and yeast two-hybrid analyses that the Rep-VP association also occurs in the absence of packageable genomes, suggesting that such complexes could be involved in the preparation of empty capsids for subsequent encapsidation steps. The Rep domain responsible for the observed Rep-VP interactions is situated within amino acids 322 to 482. In the presence of all Rep proteins, Rep52 and, to a lesser extent, Rep78 are most abundantly recovered with capsids, whereas Rep68 and Rep40 vary in association depending on their expression levels. Rep78 and Rep52 are bound to capsids to roughly the same extent as the minor capsid protein VP2. Complexes of Rep78 and Rep52 with capsids differ in their respective detergent stabilities, indicating that they result from different types of interactions. Rep-VP interaction studies suggest that Rep proteins become stably associated with the capsid during the assembly process. Rep-capsid complexes can reach even higher complexity through additional Rep-Rep interactions, which are particularly detergent labile. Coimmunoprecipitation and yeast two-hybrid data demonstrate the interaction of Rep78 with Rep68, of Rep68 with Rep52, and weak interactions of Rep40 with Rep52 and Rep78. We propose that the large complexes arising from these interactions represent intermediates in the DNA packaging pathway.
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Affiliation(s)
- R Dubielzig
- Deutsches Krebsforschungszentrum, Forschungsschwerpunkt Angewandte Tumorvirologie, D-69120 Heidelberg, Germany
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15
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Lamartina S, Roscilli G, Rinaudo D, Delmastro P, Toniatti C. Lipofection of purified adeno-associated virus Rep68 protein: toward a chromosome-targeting nonviral particle. J Virol 1998; 72:7653-8. [PMID: 9696870 PMCID: PMC110032 DOI: 10.1128/jvi.72.9.7653-7658.1998] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated virus (AAV) integrates very efficiently into a specific site (AAVS1) of human chromosome 19. Two elements of the AAV genome are sufficient: the inverted terminal repeats (ITRs) and the Rep78 or Rep68 protein. The incorporation of the AAV integration machinery in nonviral delivery systems is of great interest for gene therapy. We demonstrate that purified recombinant Rep68 protein is functionally active when directly delivered into human cells by using the polycationic liposome Lipofectamine, promoting the rescue-replication of a codelivered ITR-flanked cassette in adenovirus-infected cells and its site-specific integration in noninfected cells. The sequencing of cloned virus-host DNA junctions confirmed that lipofected Rep68 protein triggers site-specific integration at the same sites in chromosome 19 already characterized in cells latently infected with AAV.
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Affiliation(s)
- S Lamartina
- Department of Genetics, Istituto di Ricerche di Biologia Molecolare, I.R.B.M.-Piero Angeletti, 00040 Pomezia, Rome, Italy
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16
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Salvetti A, Orève S, Chadeuf G, Favre D, Cherel Y, Champion-Arnaud P, David-Ameline J, Moullier P. Factors influencing recombinant adeno-associated virus production. Hum Gene Ther 1998; 9:695-706. [PMID: 9551617 DOI: 10.1089/hum.1998.9.5-695] [Citation(s) in RCA: 205] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Recombinant adeno-associated virus (rAAV) is produced by transfecting cells with two constructs: the rAAV vector plasmid and the rep-cap plasmid. After subsequent adenoviral infection, needed for rAAV replication and assembly, the virus is purified from total cell lysates through CsCl gradients. Because this is a long and complex procedure, the precise titration of rAAV stocks, as well as the measure of the level of contamination with adenovirus and rep-positive AAV, are essential to evaluate the transduction efficiency of these vectors in vitro and in vivo. Our vector core is in charge of producing rAAV for outside investigators as part of a national network promoted by the Association Française contre les Myopathies/Généthon. We report here the characterization of 18 large-scale rAAV stocks produced during the past year. Three major improvements were introduced and combined in the rAAV production procedure: (i) the titration and characterization of rAAV stocks using a stable rep-cap HeLa cell line in a modified Replication Center Assay (RCA); (ii) the use of different rep-cap constructs to provide AAV regulatory and structural proteins; (iii) the use of an adenoviral plasmid to provide helper functions needed for rAAV replication and assembly. Our results indicate that: (i) rAAV yields ranged between 10(11) to 5 x 10(12) total particles; (ii) the physical particle to infectious particle (measured by RCA) ratios were consistently below 50 when using a rep-cap plasmid harboring an ITR-deleted AAV genome; the physical particle to transducing particle ratios ranged between 400 and 600; (iii) the use of an adenoviral plasmid instead of an infectious virion did not affect the particles or the infectious particles yields nor the above ratio. Most of large-scale rAAV stocks (7/9) produced using this plasmid were free of detectable infectious adenovirus as determined by RCA; (iv) all the rAAV stocks were contaminated with rep-positive AAV as detected by RCA. In summary, this study describes a general method to titrate rAAV, independently of the transgene and its expression, and to measure the level of contamination with adenovirus and rep-positive AAV. Furthermore, we report a new production procedure using adenoviral plasmids instead of virions and resulting in rAAV stocks with undetectable adenovirus contamination.
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Affiliation(s)
- A Salvetti
- Laboratoire de Thérapie Génique, CHU Hotel-DIEU, Nantes, France
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17
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Kube DM, Ponnazhagan S, Srivastava A. Encapsidation of adeno-associated virus type 2 Rep proteins in wild-type and recombinant progeny virions: Rep-mediated growth inhibition of primary human cells. J Virol 1997; 71:7361-71. [PMID: 9311814 PMCID: PMC192081 DOI: 10.1128/jvi.71.10.7361-7371.1997] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The adeno-associated virus type 2 (AAV) arrests the growth of primary human fibroblasts in vitro at high particle-to-cell ratios. To test the role of AAV gene expression in the observed growth inhibition, primary human cells were infected, under identical conditions, with wild-type (wt) AAV or with recombinant AAV that lacked all viral promoters and coding sequences. Significant, dose-dependent growth inhibition of primary human cells was observed with both wt and recombinant AAV at particle-to-cell ratios equal to or exceeding 10(4). In contrast, neither virus affected the growth of immortalized human cells even at a 10-fold-higher particle-to-cell ratio. AAV-induced growth arrest could be overcome by reculturing cells after treatment with trypsin. Even after reculturing, cells still harbored the proviral AAV genome. Thus, neither integration nor expression of the AAV genome appears to be required for the virus-induced growth-inhibitory effect on primary human cells. The growth-inhibitory effect of AAV was hypothesized to be mediated by virion-associated AAV Rep proteins, since these proteins have been reported to inhibit cellular DNA synthesis. Rep proteins tightly associated with wt as well as recombinant AAV could be detected on Western blots. Coinfection by adenovirus was necessary and sufficient for ample replication of recombinant AAV genomes lacking the rep gene. Although wt AAV-like particles arose during production of the recombinant AAV stocks, their low-titer levels were insufficient to cause the observed growth inhibition. AAV rep gene expression from these contaminating particles was not required for replication of the recombinant AAV genomes, which could be detected even in the absence of de novo Rep protein synthesis. Exposure of recombinant AAV to anti-AAV Rep protein antibodies did not abrogate viral infectivity. These results suggest that biologically active Rep proteins are encapsidated in mature progeny AAV particles. AAV Rep protein-mediated growth inhibition of primary human cells has implications in the use of AAV-based vectors in human gene therapy.
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Affiliation(s)
- D M Kube
- Department of Microbiology and Immunology, Walther Oncology Center, Indiana University School of Medicine, and Walther Cancer Institute, Indianapolis 46202, USA
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