101
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Stachler MD, Chen I, Ting AY, Bartlett JS. Site-specific modification of AAV vector particles with biophysical probes and targeting ligands using biotin ligase. Mol Ther 2008; 16:1467-73. [PMID: 18560418 DOI: 10.1038/mt.2008.129] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We have developed a highly specific and robust new method for labeling adeno-associated virus (AAV) vector particles with either biophysical probes or targeting ligands. Our approach uses the Escherichia coli enzyme biotin ligase (BirA), which ligates biotin to a 15-amino-acid biotin acceptor peptide (BAP) in a sequence-specific manner. In this study we demonstrate that by using a ketone isotere of biotin as a cofactor we can ligate this probe to BAP-modified AAV capsids. Because ketones are absent from AAV, BAP-modified AAV particles can be tagged with the ketone probe and then specifically conjugated to hydrazide- or hydroxylamine-functionalized molecules. We demonstrate this two-stage modification methodology in the context of a mammalian cell lysate for the labeling of AAV vector particles with various fluorophores, and for the attachment of a synthetic cyclic arginine-glycine-aspartate (RGD) peptide (c(RGDfC)) to target integrin receptors that are present on neovasculature. Fluorophore labeling allowed the straightforward determination of intracellular particle distribution. Ligand conjugation mediated a significant increase in the transduction of endothelial cells in vitro, and permitted the intravascular targeting of AAV vectors to tumor-associated vasculature in vivo. These results suggest that this approach holds significant promise for future studies aimed at understanding and modifying AAV vector-cellular interactions.
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Affiliation(s)
- Matthew D Stachler
- Gene Therapy Center, The Research Institute at Nationwide Children's Hospital, Nationwide Children's Hospital, Columbus, Ohio, USA
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102
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Next generation of adeno-associated virus 2 vectors: point mutations in tyrosines lead to high-efficiency transduction at lower doses. Proc Natl Acad Sci U S A 2008; 105:7827-32. [PMID: 18511559 DOI: 10.1073/pnas.0802866105] [Citation(s) in RCA: 438] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Recombinant adeno-associated virus 2 (AAV2) vectors are in use in several Phase I/II clinical trials, but relatively large vector doses are needed to achieve therapeutic benefits. Large vector doses also trigger an immune response as a significant fraction of the vectors fails to traffic efficiently to the nucleus and is targeted for degradation by the host cell proteasome machinery. We have reported that epidermal growth factor receptor protein tyrosine kinase (EGFR-PTK) signaling negatively affects transduction by AAV2 vectors by impairing nuclear transport of the vectors. We have also observed that EGFR-PTK can phosphorylate AAV2 capsids at tyrosine residues. Tyrosine-phosphorylated AAV2 vectors enter cells efficiently but fail to transduce effectively, in part because of ubiquitination of AAV capsids followed by proteasome-mediated degradation. We reasoned that mutations of the surface-exposed tyrosine residues might allow the vectors to evade phosphorylation and subsequent ubiquitination and, thus, prevent proteasome-mediated degradation. Here, we document that site-directed mutagenesis of surface-exposed tyrosine residues leads to production of vectors that transduce HeLa cells approximately 10-fold more efficiently in vitro and murine hepatocytes nearly 30-fold more efficiently in vivo at a log lower vector dose. Therapeutic levels of human Factor IX (F.IX) are also produced at an approximately 10-fold reduced vector dose. The increased transduction efficiency of tyrosine-mutant vectors is due to lack of capsid ubiquitination and improved intracellular trafficking to the nucleus. These studies have led to the development of AAV vectors that are capable of high-efficiency transduction at lower doses, which has important implications in their use in human gene therapy.
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103
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Schultz BR, Chamberlain JS. Recombinant adeno-associated virus transduction and integration. Mol Ther 2008; 16:1189-99. [PMID: 18500252 DOI: 10.1038/mt.2008.103] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Recombinant adeno-associated virus (rAAV) holds promise as a gene therapy vector for a multitude of genetic disorders such as hemophilia, cystic fibrosis, and the muscular dystrophies. Given the variety of applications and tissue types toward which these vectors may be targeted, an understanding of rAAV transduction is crucial for the effective application of therapy. rAAV transduction mechanisms have been the subject of much study, resulting in a body of knowledge relating to events from virus-cell attachment through to vector genome conformation in the target cell nucleus. Instead of utilizing one mechanism in each phase of vector transduction, rAAV appears to employ multiple possible pathways toward transgene expression, in part dependent on rAAV serotype, dose, and target cell type. Once inside the nucleus, the rAAV genome exists in a predominantly episomal form; therefore, nondividing cells tend to be most stably transduced. However, rAAV has a low frequency of integration into the host cell genome, often in or near genes, and can be associated with host genome mutations. This review describes the current understanding of the mechanisms and rate-limiting steps involved in rAAV transduction.
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Affiliation(s)
- Brian R Schultz
- Molecular and Cellular Biology, Senator Paul D Wellstone Muscular Dystrophy Cooperative Research Center, University of Washington, Seattle, Washington, USA
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104
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Harbison CE, Chiorini JA, Parrish CR. The parvovirus capsid odyssey: from the cell surface to the nucleus. Trends Microbiol 2008; 16:208-14. [DOI: 10.1016/j.tim.2008.01.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 01/14/2008] [Accepted: 01/25/2008] [Indexed: 12/21/2022]
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105
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Murphy SL, Li H, Zhou S, Schlachterman A, High KA, High K. Prolonged susceptibility to antibody-mediated neutralization for adeno-associated vectors targeted to the liver. Mol Ther 2007; 16:138-45. [PMID: 17955024 DOI: 10.1038/sj.mt.6300334] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Adeno-associated virus (AAV) vectors demonstrate highly efficient gene transfer to hepatocytes in vivo. One of the remaining obstacles to the treatment of hemophilia B patients with AAV vectors is the sensitivity of these vectors to antibody-mediated neutralization following systemic delivery. Testing and implementation of strategies to circumvent pre-existing antibodies requires knowledge of the clearance kinetics of AAV from circulation. In this study, AAV clearance kinetics were established for serotypes 2 and 8 in cell culture and in mice. Administration of pooled neutralizing serum subsequent to administration of the vector was used to define the time period in which the vector is susceptible to antibody-mediated neutralization. These experiments defined the in vivo clearance rates for both AAV2 and AAV8 vectors to be between 2 and 4 hours. In mice, portal vein and tail vein administration of each vector was tested with similar results. Cell culture studies in W162 cells established that cellular attachment and internalization both contribute to the clearance kinetics of AAV vectors. These studies characterize the in vivo clearance rates of AAV vectors for the first time and guide the development of future strategies for the avoidance of antibody-mediated AAV vector neutralization.
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Affiliation(s)
- Samuel L Murphy
- Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
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106
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Cearley CN, Wolfe JH. A single injection of an adeno-associated virus vector into nuclei with divergent connections results in widespread vector distribution in the brain and global correction of a neurogenetic disease. J Neurosci 2007; 27:9928-40. [PMID: 17855607 PMCID: PMC6672652 DOI: 10.1523/jneurosci.2185-07.2007] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Neurogenetic disorders typically affect cells throughout the brain. Adeno-associated virus (AAV) vector-mediated transfer of a normal cDNA can correct the metabolic defects at the site of injection, but treatment of the entire brain requires widespread delivery of the normal gene and/or protein. Current methods require multiple injections for widespread distribution. However, some AAV vectors can be transported along neuronal pathways associated with the injected region. Thus, targeting widely dispersed systems in the CNS might be a pathway for gene dispersal from a limited number of sites. We tested this hypothesis in the ventral tegmental area (VTA), a region with numerous efferent and afferent projections. A single 1 mul injection resulted in transport of the vector genome to projection sites in distal parts of the brain. When compared with injections into the striatum, the VTA injection resulted in higher enzyme levels in more regions of the brain. The AAV-9 serotype vector was the most widely disseminated, but AAV-Rh.10 and AAV-1 were also transported after VTA injection. The effect on global lesions of a neurogenetic disease was tested in the mouse model of MPS VII (mucopolysaccharidosis VII), a lysosomal storage disorder. Widespread distribution of the vector genome after AAV-9 VTA injection resulted in even further distribution of the enzyme product, by secretion and uptake by surrounding cells, and complete correction of the storage lesions throughout the entire brain. This unprecedented level of correction from a single injection into the developed brain provides a potential strategy to correct a large volume of brain while minimizing the number of injections.
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Affiliation(s)
- Cassia N. Cearley
- Walter Flato Goodman Center for Comparative Medical Genetics, School of Veterinary Medicine, University of Pennsylvania, and Division of Neurology, Stokes Research Institute, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
| | - John H. Wolfe
- Walter Flato Goodman Center for Comparative Medical Genetics, School of Veterinary Medicine, University of Pennsylvania, and Division of Neurology, Stokes Research Institute, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
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107
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Abstract
To overcome barriers to diffusion, many viruses utilize the microtubule-associated molecular motor cytoplasmic dynein 1 to drive transport towards the nucleus of a target cell. Cytoplasmic dynein 1 generates movement towards the minus end of microtubules located at the microtubule organizing centre (MTOC), a structure that is typically in close proximity to the nucleus. Physiological cargoes for cytoplasmic dynein include membranous organelles, protein complexes and aggregates of misfolded protein. In this review, we discuss the study of microtubule-based translocation of viruses and raise questions about the mechanisms for association with and then dissociation from cytoplasmic dynein with a goal of understanding whether viruses are seen by the intracellular trafficking machinery as functional protein complexes or misfolded protein aggregates.
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Affiliation(s)
- Philip L Leopold
- Department of Genetic Medicine, Weill Medical College of Cornell University, New York, NY, USA.
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108
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Xu H, Yao L, Lu S, Qi Y. Host filamentous actin is associated with Heliothis armigera single nucleopolyhedrosis virus (HaSNPV) nucleocapsid transport to the host nucleus. Curr Microbiol 2007; 54:199-206. [PMID: 17294324 DOI: 10.1007/s00284-006-8261-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2006] [Accepted: 08/28/2006] [Indexed: 01/16/2023]
Abstract
VP39 is the major capsid protein of Heliothis armigera nucleopolyhedrovirus (HaSNPV), and it might have induced the aggregation of host cellular actin in vitro in our previous study. We demonstrated here that VP39 could interact with host actin in vivo in Helicoverpazea (Hz-AM1 cells) through coimmunoprecipitation assay. With confocal immunofluorescence microscopy, it was confirmed further that the released HaSNPV nucleocapsids/VP39s in the host cytoplasm (0.5 hours after infection) colocalized where the actin aggregated and that the nucleocapsids/VP39s were transported from the host cytoplasm to the nucleus (2 hours after infection). Because cytochalasin D (CD) was used to prevent host global actin from forming filamentous structures, the infection efficiency of the recombinant virus HaSNPV/gfpdeltap74, with the gfp gene inserted into HaSNPV p74 gene loci, was decreased to 7.34%, whereas it was 34.7% in normal host cells and 55.7% in the cells whose microtubules had been destroyed by colchicin. Ultramicroscopy assay revealed that HaSNPV nucleocapsids could enter the cytoplasm of CD-treated cells but could not be transported to the nucleus, which resulted in the lower infection efficiency of HaSNPV/gfpdeltap74 in CD-treated cells. However, transportation of the nucleocapsids was not inhibited in colchicin-treated cells, demonstrating that the transportation of HaSNPV nucleocapsid from the cytoplasm to the nucleus was associated with actin filaments but not with microtubules, a conclusion that is also strongly supported by evidence from the RNAi interference of host actin during HaSNPV infection.
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Affiliation(s)
- H Xu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PRC
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109
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Grieger JC, Snowdy S, Samulski RJ. Separate basic region motifs within the adeno-associated virus capsid proteins are essential for infectivity and assembly. J Virol 2007; 80:5199-210. [PMID: 16699000 PMCID: PMC1472161 DOI: 10.1128/jvi.02723-05] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Adeno-associated virus (AAV) is gaining momentum as a gene therapy vector for human applications. However, there remain impediments to the development of this virus as a vector. One of these is the incomplete understanding of the biology of the virus, including nuclear targeting of the incoming virion during initial infection, as well as assembly of progeny virions from structural components in the nucleus. Toward this end, we have identified four basic regions (BR) on the AAV2 capsid that represent possible nuclear localization sequence (NLS) motifs. Mutagenesis of BR1 ((120)QAKKRVL(126)) and BR2 ((140)PGKKRPV(146)) had minor effects on viral infectivity ( approximately 4- and approximately 10-fold, respectively), whereas BR3 ((166)PARKRLN(172)) and BR4 ((307)RPKRLN(312)) were found to be essential for infectivity and virion assembly, respectively. Mutagenesis of BR3, which is located in Vp1 and Vp2 capsid proteins, does not interfere with viral production or trafficking of intact AAV capsids to the nuclear periphery but does inhibit transfer of encapsidated DNA into the nucleus. Substitution of the canine parvovirus NLS rescued the BR3 mutant to wild-type (wt) levels, supporting the role of an AAV NLS motif. In addition, rAAV2 containing a mutant form of BR3 in Vp1 and a wt BR3 in Vp2 was found to be infectious, suggesting that the function of BR3 is redundant between Vp1 and Vp2 and that Vp2 may play a role in infectivity. Mutagenesis of BR4 was found to inhibit virion assembly in the nucleus of transfected cells. This affect was not completely due to the inefficient nuclear import of capsid subunits based on Western blot analysis. In fact, aberrant capsid foci were observed in the cytoplasm of transfected cells, compared to the wild type, suggesting a defect in early viral assembly or trafficking. Using three-dimensional structural analysis, the lysine- and arginine-to-asparagine change disrupts hydrogen bonding between these basic residues and adjacent beta strand glutamine residues that may prevent assembly of intact virions. Taken together, these data support that the BR4 domain is essential for virion assembly. Each BR was also found to be conserved in serotypes 1 to 11, suggesting that these regions are significant and function similarly in each serotype. This study establishes the importance of two BR motifs on the AAV2 capsid that are essential for infectivity and virion assembly.
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Affiliation(s)
- Joshua C Grieger
- Curriculum in Genetics and Molecular Biology, Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7352, USA
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110
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Sipo I, Fechner H, Pinkert S, Suckau L, Wang X, Weger S, Poller W. Differential internalization and nuclear uncoating of self-complementary adeno-associated virus pseudotype vectors as determinants of cardiac cell transduction. Gene Ther 2007; 14:1319-29. [PMID: 17611587 DOI: 10.1038/sj.gt.3302987] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Recently it was shown that several new pseudotyped adeno-associated virus (AAV) vectors support cardioselective expression of transgenes. The molecular mechanisms underlying this propensity for cardiac cell transduction are not well understood. We comparatively analyzed AAV vector attachment, internalization, intracellular trafficking, and nuclear uncoating of recombinant self-complementary (sc) AAV2.2 versus pseudotyped scAAV2.6 vectors expressing green fluorescence protein (GFP) in cells of cardiac origin. In cardiac-derived HL-1 cells and primary neonatal rat cardiomyocytes (PNCMs), expression of GFP increased rapidly after incubation with scAAV2.6-GFP, but remained low after scAAV2.2-GFP. Internalization of scAAV2.6-GFP was more efficient than that of scAAV2.2-GFP. Nuclear translocation was similarly efficient for both, but differential nuclear uncoating rates emerged as a key additional determinant of transduction: 30% of all scAAV2.6-GFP genomes translocated to the nucleus became uncoated within 48 h, but only 16% of scAAV2.2-GFP genomes. In contrast to this situation in cells of cardiac origin, scAAV2.2-GFP displayed more efficient internalization and similar (tumor cell line HeLa) or higher (human microvascular endothelial cell (HMEC)) uncoating rates than scAAV.2.6-GFP in non-cardiac cell types. In summary, both internalization and nuclear uncoating are key determinants of cardiac transduction by scAAV2.6 vectors. Any in vitro screening for the AAV pseudotype most suitable for cardiac gene therapy - which is desirable since it may allow significant reductions in vector load in upcoming clinical trials--needs to quantitate both key steps in transduction.
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Affiliation(s)
- I Sipo
- Department of Cardiology & Pneumology, Institute of Infectious Diseases, Campus Benjamin Franklin, Charité - Universitätsmedizin Berlin, Berlin, Germany
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111
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Akache B, Grimm D, Shen X, Fuess S, Yant SR, Glazer DS, Park J, Kay MA. A two-hybrid screen identifies cathepsins B and L as uncoating factors for adeno-associated virus 2 and 8. Mol Ther 2007; 15:330-9. [PMID: 17235311 PMCID: PMC7106033 DOI: 10.1038/sj.mt.6300053] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Vectors based on different serotypes of adeno-associated virus hold great promise for human gene therapy, based on their unique tissue tropisms and distinct immunological profiles. A particularly interesting candidate is AAV8, which can efficiently and rapidly transduce a wide range of tissues in vivo. To further unravel the mechanisms behind AAV8 transduction, we used yeast two-hybrid analyses to screen a mouse liver complementary DNA library for cellular proteins capable of interacting with the viral capsid proteins. In total, we recovered approximately 700 clones, comprising over 300 independent genes. Sequence analyses revealed multiple hits for over 100 genes, including two encoding the endosomal cysteine proteases cathepsins B and L. Notably, these two proteases also physically interacted with the corresponding portion of the AAV2 capsid in yeast, but not with AAV5. We demonstrate that cathepsins B and L are essential for efficient AAV2- and AAV8-mediated transduction of mammalian cells, and document the ability of purified cathepsin B and L proteins to bind and cleave intact AAV2 and AAV8 particles in vitro. These data suggest that cathepsin-mediated cleavage could prime AAV capsids for subsequent nuclear uncoating, and indicate that analysis of additional genes recovered in our screen may help to further elucidate the mechanisms behind transduction by AAV8 and related serotypes.
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Affiliation(s)
- Bassel Akache
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Dirk Grimm
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Xuan Shen
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Sally Fuess
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Stephen R Yant
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Dariya S Glazer
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Julie Park
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Mark A Kay
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
- Department of Pediatrics, Stanford University, 300 Pasteur Drive, Room G305, Stanford, California 94305-5208, USA
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112
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Hirosue S, Senn K, Clément N, Nonnenmacher M, Gigout L, Linden RM, Weber T. Effect of inhibition of dynein function and microtubule-altering drugs on AAV2 transduction. Virology 2007; 367:10-8. [PMID: 17588632 PMCID: PMC2099573 DOI: 10.1016/j.virol.2007.05.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 02/12/2007] [Accepted: 05/02/2007] [Indexed: 11/28/2022]
Abstract
Over the past decade, adeno-associated (AAV) virus has emerged as an important vector for gene therapy. As a result, understanding its basic biology, including intracellular trafficking, has become increasingly important. Here, we describe the effect of inhibiting dynein function or altering the state of microtubule polymerization on rAAV2 transduction. Overexpression of dynamitin, resulting in a functional inhibition of the minus-end-directed microtubule motor protein dynein, did not inhibit transduction. Equally, treatment of cells with nocodazole, or concentrations of vinblastine that result in the disruption of microtubules, had no significant effect on transduction. In contrast, high concentrations of Taxol and vinblastine, resulting in microtubule stabilization and the formation of tubulin paracrystals respectively, reduced rAAV2 transduction in a vector-dose-dependent manner. These results demonstrate that AAV2 can infect HeLa cells independently of dynein function or an intact microtubule network.
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Affiliation(s)
- Sachiko Hirosue
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
| | - Karin Senn
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
| | - Nathalie Clément
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
| | - Mathieu Nonnenmacher
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
| | - Laure Gigout
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
| | - R. Michael Linden
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
- Department of Microbiology, Mount Sinai School of Medicine, New York, NY 10029
| | - Thomas Weber
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029
- Department of Molecular, Cell and Developmental Biology, Mount Sinai School of Medicine, New York, NY 10029
- Correspondence should be addressed to T.W. 1 Gustave L. Levy Place, Box 1496, New York, New York 10029-6514, Tel. 1-212-659-8293; Fax. 1-212-849-2437; E-mail:
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113
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Abstract
Cell adhesion, migration and the maintenance of cell polarity are all processes that depend on the correct targeting of integrins and the dynamic remodelling of integrin-containing adhesion sites. The importance of the endo/exocytic cycle of integrins as a key regulator of these functions is increasingly recognized. Several recent publications have provided mechanistic insight into how integrin traffic is regulated in cells. Increasing evidence suggests that small GTPases such as Arf6 and members of the Rab family control integrin internalization and recycling back to the plasma membrane along microtubules. The fine tuning of these trafficking events seems to be mediated by specific guanine-nucleotide-exchange factors (GEFs) and GTPase-activating proteins (GAPs). In addition, several kinases regulate integrin traffic. The identification of their substrates has demonstrated how these kinases regulate integrin traffic by controlling small GTPases or stabilizing cytoskeletal tracks that are crucial for efficient traffic of integrins to the plasma membrane.
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114
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Ren C, White AF, Ponnazhagan S. Notch1 augments intracellular trafficking of adeno-associated virus type 2. J Virol 2006; 81:2069-73. [PMID: 17151095 PMCID: PMC1797595 DOI: 10.1128/jvi.01811-06] [Citation(s) in RCA: 10] [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
We report here the significance of the Notch1 receptor in intracellular trafficking of recombinant adeno-associated virus type 2 (rAAV2). RNA profiling of human prostate cancer cell lines with various degrees of AAV transduction indicated a correlation of the amount of Notch1 with rAAV transgene expression. A definitive role of Notch1 in enhancing AAV transduction was confirmed by developing clonal derivatives of DU145 cells overexpressing either full-length or intracellular Notch1. To discern stages of AAV2 transduction influenced by Notch1, competitive binding with soluble heparin and Notch1 antibody, intracellular trafficking using Cy3-labeled rAAV2, and blocking assays for proteasome and dynamin pathways were performed. Results indicated that in the absence or low-level expression of Notch1, only binding of virus was found on the cell surface and internalization was impaired. However, increased Notch1 expression in these cells allowed efficient perinuclear accumulation of labeled capsids. Nuclear transport of the vector was evident by transgene expression and real-time PCR analyses. Dynamin levels were not found to be different among these cell lines, but blocking dynamin function abrogated AAV2 transduction in DU145 clones overexpressing full-length Notch1 but not in clones overexpressing intracellular Notch1. These studies provide evidence for the role of activated Notch1 in intracellular trafficking of AAV2, which may have implications in the optimal use of AAV2 in human gene therapy.
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Affiliation(s)
- Changchun Ren
- Department of Pathology, LHRB 513, 701, 19th Street South, University of Alabama at Birmingham, Birmingham, AL 35294-0007, USA
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115
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Asokan A, Hamra JB, Govindasamy L, Agbandje-McKenna M, Samulski RJ. Adeno-associated virus type 2 contains an integrin alpha5beta1 binding domain essential for viral cell entry. J Virol 2006; 80:8961-9. [PMID: 16940508 PMCID: PMC1563945 DOI: 10.1128/jvi.00843-06] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrins have been implicated as coreceptors in the infectious pathways of several nonenveloped viruses. For example, adenoviruses are known to interact with alphaV integrins by virtue of a high-affinity arginine-glycine-aspartate (RGD) domain present in the penton bases of the capsids. In the case of adeno-associated virus type 2 (AAV2), which lacks this RGD motif, integrin alphaVbeta5 has been identified as a coreceptor for cellular entry. However, the molecular determinants of AAV2 capsid-integrin interactions and the potential exploitation of alternative integrins as coreceptors by AAV2 have not been established thus far. In this report, we demonstrate that integrin alpha5beta1 serves as an alternative coreceptor for AAV2 infection in human embryonic kidney 293 cells. Such interactions appear to be mediated by a highly conserved domain that contains an asparagine-glycine-arginine (NGR) motif known to bind alpha5beta1 integrin with moderate affinity. The mutation of this domain reduces transduction efficiency by an order of magnitude relative to that of wild-type AAV2 vectors in vitro and in vivo. Further characterization of mutant and wild-type AAV2 capsids through transduction assays in cell lines lacking specific integrins, cell adhesion studies, and cell surface/solid-phase binding assays confirmed the role of the NGR domain in promoting AAV2-integrin interactions. Molecular modeling studies suggest that NGR residues form a surface loop close to the threefold axis of symmetry adjacent to residues previously implicated in binding heparan sulfate, the primary receptor for AAV2. The aforementioned results suggest that the internalization of AAV2 in 293 cells might follow a "click-to-fit" mechanism that involves the cooperative binding of heparan sulfate and alpha5beta1 integrin by the AAV2 capsids.
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Affiliation(s)
- Aravind Asokan
- Gene Therapy Center, 7113 Thurston Building, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7352, USA
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116
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Traister RS, Fabre S, Wang Z, Xiao X, Hirsch R. Inflammatory cytokine regulation of transgene expression in human fibroblast-like synoviocytes infected with adeno-associated virus. ACTA ACUST UNITED AC 2006; 54:2119-26. [PMID: 16802345 DOI: 10.1002/art.21940] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE An ideal gene transfer vector for chronic inflammatory diseases such as rheumatoid arthritis (RA) would provide local transgene expression only when the disease is active. To determine whether adeno-associated virus (AAV) possesses this ability, the effects of inflammatory cytokines on transgene expression were evaluated in human RA fibroblast-like synoviocytes (FLS). METHODS Human FLS were infected with AAV in the presence or absence of inflammatory cytokines or synovial fluid obtained from patients with RA. Transgene expression was monitored by either enzyme-linked immunosorbent assay or flow cytometry. Transgene messenger RNA (mRNA) was measured by real-time quantitative reverse transcription-polymerase chain reaction. RESULTS Inflammatory cytokines increased transgene expression in FLS by up to 60-fold. Synovial fluid from patients with RA, but not from patients without arthritis, was also able to increase expression in synoviocytes. Protein expression correlated with transgene mRNA levels. The enhanced expression required the continued presence of cytokines because, upon removal, transgene expression returned to baseline levels. Expression could be repeatedly reinduced by reexposure to cytokines. The effect was not promoter specific and was demonstrated to be phosphatidylinositol 3-kinase-dependent. CONCLUSION These results suggest that expression of a therapeutic transgene can be controlled by the presence of inflammation following AAV gene transfer, making it an attractive vector for chronic inflammatory diseases such as RA.
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Sonntag F, Bleker S, Leuchs B, Fischer R, Kleinschmidt JA. Adeno-associated virus type 2 capsids with externalized VP1/VP2 trafficking domains are generated prior to passage through the cytoplasm and are maintained until uncoating occurs in the nucleus. J Virol 2006; 80:11040-54. [PMID: 16956943 PMCID: PMC1642181 DOI: 10.1128/jvi.01056-06] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Common features of parvovirus capsids are open pores at the fivefold symmetry axes that traverse the virion shell. Upon limited heat treatment in vitro, the pores can function as portals to externalize VP1/VP2 protein N-terminal sequences which harbor infection-relevant functional domains, such as a phospholipase A(2) catalytic domain. Here we show that adeno-associated virus type 2 (AAV2) also exposes its VP1/VP2 N termini in vivo during infection, presumably in the endosomal compartment. This conformational change is influenced by treatment with lysosomotropic reagents. While incubation of cells with bafilomycin A1 reduced exposure of VP1/VP2 N termini, incubation with chloroquine stimulated externalization transiently. N-terminally located basic amino acid clusters with nuclear localization activity also become exposed in this process and are accessible on the virus capsid when it enters the cytoplasm. This is an obligatory step in AAV2 infection. However, a direct role of these sequences in nuclear translocation of viral capsids could not be determined by microinjection of wild-type or mutant viruses. This suggests that further modifications of the capsid have to take place in a precytoplasmic entry step that prepares the virus for nuclear entry. Microinjection of several capsid-specific antibodies into the cell nucleus blocked AAV2 infection completely, supporting the conclusion that AAV2 capsids bring the infectious genome into the nucleus.
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Affiliation(s)
- Florian Sonntag
- German Cancer Research Center, Infection and Cancer, Im Neuenheimer Feld 242, D-69120 Heidelberg, Germany
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118
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Kelkar S, De BP, Gao G, Wilson JM, Crystal RG, Leopold PL. A common mechanism for cytoplasmic dynein-dependent microtubule binding shared among adeno-associated virus and adenovirus serotypes. J Virol 2006; 80:7781-5. [PMID: 16840360 PMCID: PMC1563724 DOI: 10.1128/jvi.00481-06] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
During infection, adenovirus-associated virus (AAV) undergoes microtubule-dependent retrograde transport as part of a program of vectorial transport of viral genome to the nucleus. A microtubule binding assay was used to evaluate the hypothesis that cytoplasmic dynein mediates AAV interaction with microtubules. Binding of AAV serotype 2 (AAV2) was enhanced in a nucleotide-dependent manner by the presence of total cellular microtubule-associated proteins (MAPs) but not cytoplasmic dynein-depleted MAPs. Excess AAV2 capsid protein prevented microtubule binding by AAV serotypes 2, 5, and rh.10, as well as adenovirus serotype 5, indicating that similar binding sites are used by these viruses.
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Affiliation(s)
- Samir Kelkar
- Department of Genetic Medicine, Weill Medical College of Cornell University, 515 E. 71st Street, S-1000, New York, NY 10021, USA.
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Hingtgen SD, Tian X, Yang J, Dunlay SM, Peek AS, Wu Y, Sharma RV, Engelhardt JF, Davisson RL. Nox2-containing NADPH oxidase and Akt activation play a key role in angiotensin II-induced cardiomyocyte hypertrophy. Physiol Genomics 2006; 26:180-91. [PMID: 16670255 DOI: 10.1152/physiolgenomics.00029.2005] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Angiotensin II (ANG II) has profound effects on the development and progression of pathological cardiac hypertrophy; however, the intracellular signaling mechanisms are not fully understood. In this study, we used genetic tools to test the hypothesis that increased formation of superoxide (O2−·) radicals from a Rac1-regulated Nox2-containing NADPH oxidase is a key upstream mediator of ANG II-induced activation of serine-threonine kinase Akt, and that this signaling cascade plays a crucial role in ANG II-dependent cardiomyocyte hypertrophy. ANG II caused a significant time-dependent increase in Rac1 activation and O2−· production in primary neonatal rat cardiomyocytes, and these responses were abolished by adenoviral (Ad)-mediated expression of a dominant-negative Rac1 (AdN17Rac1) or cytoplasmic Cu/ZnSOD (AdCu/ZnSOD). Moreover, both AdN17Rac1 and AdCu/ZnSOD significantly attenuated ANG II-stimulated increases in cardiomyocyte size. Quantitative real-time PCR analysis demonstrated that Nox2 is the homolog expressed at highest levels in primary neonatal cardiomyocytes, and small interference RNA (siRNA) directed against it selectively decreased Nox2 expression by >95% and abolished both ANG II-induced O2−· generation and cardiomyocyte hypertrophy. Finally, ANG II caused a time-dependent increase in Akt activity via activation of AT1 receptors, and this response was abolished by Ad-mediated expression of cytosolic human O2−· dismutase (AdCu/ZnSOD). Furthermore, pretreatment of cardiomyocytes with dominant-negative Akt (AdDNAkt) abolished ANG II-induced cellular hypertrophy. These findings suggest that O2−· generated by a Nox2-containing NADPH oxidase is a central mediator of ANG II-induced Akt activation and cardiomyocyte hypertrophy, and that dysregulation of this signaling cascade may play an important role in cardiac hypertrophy.
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Affiliation(s)
- Shawn D Hingtgen
- Department of Anatomy and Cell Biology, The Free Radical and Radiation Biology Program, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa 52242, USA
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Sarkar R, Mucci M, Addya S, Tetreault R, Bellinger DA, Nichols TC, Kazazian HH. Long-term efficacy of adeno-associated virus serotypes 8 and 9 in hemophilia a dogs and mice. Hum Gene Ther 2006; 17:427-39. [PMID: 16610930 DOI: 10.1089/hum.2006.17.427] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We reported total correction of blood coagulation plasma factor VIII (FVIII) activity, using adeno-associated virus serotype 8 (AAV8) vectors for liver-specific gene transfer in hemophilia A mice. We now show, irrespective of immunosuppression or route of administration, total long-term correction of hemophilia A mice with pseudotyped AAV8 and AAV9 vectors. We delivered two FVIII vectors, one expressing canine heavy chain and the other expressing canine light chain. Interestingly, when these vectors were given by hepatic portal vein to hemophilia A dogs, only modest FVIII levels were seen despite the species-specific transgene. No dogs treated developed FVIII inhibitors. However, of three dogs treated with AAV8 vector, the single male, given 1.25 x 10(13) genome copies per vector per kilogram (GC/vector/kg), maintained a level of >4.5% for more than 2 years. In contrast, the two female dogs expressed only 2% FVIII activity despite receiving higher doses of 1.52 x 10(13) and 3 x 10(13) GC/vector/kg, respectively. On the other hand, a male dog treated with AAV9 vector at a low dose (6 x 10(12) GC/vector/kg) maintained FVIII levels of 2-2.5% of normal without bleeding for 200 days (observation ongoing). Although hemophilia A mice were not predictive of vector efficacy in dogs, the two treated male dogs became symptom-free for long periods. Even so, translation of these robust vectors either in appropriate large animals or human beings remains challenging.
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Affiliation(s)
- Rita Sarkar
- Department of Genetics, University of Pennsylvania, Philadelphia, PA 19104-6145, USA
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Zhao W, Zhong L, Wu J, Chen L, Qing K, Weigel-Kelley KA, Larsen SH, Shou W, Warrington KH, Srivastava A. Role of cellular FKBP52 protein in intracellular trafficking of recombinant adeno-associated virus 2 vectors. Virology 2006; 353:283-93. [PMID: 16828834 PMCID: PMC2598389 DOI: 10.1016/j.virol.2006.04.042] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 04/12/2006] [Accepted: 04/26/2006] [Indexed: 01/21/2023]
Abstract
We have reported that tyrosine-phosphorylated forms of a cellular protein, FKBP52, inhibit the second-strand DNA synthesis of adeno-associated virus 2 (AAV), leading to inefficient transgene expression from recombinant AAV vectors. To further explore the role of FKBP52 in AAV-mediated transduction, we established murine embryo fibroblasts (MEFs) cultures from FKBP52 wild-type (WT), heterozygous (HE), and knockout (KO) mice. Conventional AAV vectors failed to transduce WT MEFs efficiently, and the transduction efficiency was not significantly increased in HE or KO MEFs. AAV vectors failed to traffic efficiently to the nucleus in these cells. Treatment with hydroxyurea (HU) increased the transduction efficiency of conventional AAV vectors by approximately 25-fold in WT MEFs, but only by approximately 4-fold in KO MEFs. The use of self-complementary AAV (scAAV) vectors, which bypass the requirement of viral second-strand DNA synthesis, revealed that HU treatment increased the transduction efficiency approximately 23-fold in WT MEFs, but only approximately 4-fold in KO MEFs, indicating that the lack of HU treatment-mediated increase in KO MEFs was not due to failure of AAV to undergo viral second-strand DNA synthesis. Following HU treatment, approximately 59% of AAV genomes were present in the nuclear fraction from WT MEFs, but only approximately 28% in KO MEFs, indicating that the pathway by which HU treatment mediates nuclear transport of AAV was impaired in KO MEFs. When KO MEFs were stably transfected with an FKBP52 expression plasmid, HU treatment-mediated increase in the transduction efficiency was restored in these cells, which correlated directly with improved intracellular trafficking. Intact AAV particles were also shown to interact with FKBP52 as well as with dynein, a known cellular protein involved in AAV trafficking. These studies suggest that FKBP52, being a cellular chaperone protein, facilitates intracellular trafficking of AAV, which has implications in the optimal use of recombinant AAV vectors in human gene therapy.
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Affiliation(s)
- Weihong Zhao
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
- The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210029 P.R. China
| | - Li Zhong
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Jianqing Wu
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
- The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210029 P.R. China
| | - Linyuan Chen
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Keyun Qing
- Eli Lilly & Company, Indianapolis, IN 46285, USA
| | - Kirsten A. Weigel-Kelley
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Steven H. Larsen
- Department of Microbiology & Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Weinian Shou
- Herman B Wells Center for Pediatric Research and Department of Molecular Biology & Biochemistry, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Kenneth H. Warrington
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Arun Srivastava
- The Division of Cellular and Molecular Therapy, Departments of Pediatrics, Molecular Genetics & Microbiology, Powell Gene Therapy Center University of Florida College of Medicine, Gainesville, FL 32610, USA
- Corresponding author: Dr. Arun Srivastava, Division of Cellular & Molecular Therapy, Department of Pediatrics, University of Florida College of Medicine, 13706 Innovation Drive, Room 201, Progress Park, Alachua, FL 32615, USA; Fax: 386-462-4099, E-mail address:
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Wu Z, Asokan A, Samulski RJ. Adeno-associated virus serotypes: vector toolkit for human gene therapy. Mol Ther 2006; 14:316-27. [PMID: 16824801 DOI: 10.1016/j.ymthe.2006.05.009] [Citation(s) in RCA: 599] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 05/17/2006] [Accepted: 05/17/2006] [Indexed: 01/11/2023] Open
Abstract
Recombinant adeno-associated viral (AAV) vectors have rapidly advanced to the forefront of gene therapy in the past decade. The exponential progress of AAV-based vectors has been made possible by the isolation of several naturally occurring AAV serotypes and over 100 AAV variants from different animal species. These isolates are ideally suited to development into human gene therapy vectors due to their diverse tissue tropisms and potential to evade preexisting neutralizing antibodies against the common human AAV serotype 2. Despite their prolific application in several animal models of disease, the mechanisms underlying selective tropisms of AAV serotypes remain largely unknown. Efforts to understand cell surface receptor usage and intracellular trafficking pathways exploited by AAV continue to provide significant insight into the biology of AAV vectors. Such unique traits are thought to arise from differences in surface topology of the capsids of AAV serotypes and variants. In addition to the aforementioned naturally evolved AAV isolates, several strategies to engineer hybrid AAV serotype vectors have been formulated in recent years. The generation of mosaic or chimeric vectors through the transcapsidation or marker-rescue/domain-swapping approach, respectively, is notable in this regard. More recently, combinatorial strategies for engineering AAV vectors using error-prone PCR, DNA shuffling, and other molecular cloning techniques have been established. The latter library-based approaches can serve as powerful tools in the generation of low-immunogenic and cell/tissue type-specific AAV vectors for gene delivery. This review is focused on recent developments in the isolation of novel AAV serotypes and isolates, their production and purification, diverse tissue tropisms, mechanisms of cellular entry/trafficking, and capsid structure. Strategies for engineering hybrid AAV vectors derived from AAV serotypes and potential implications of the rapidly expanding AAV vector toolkit are discussed.
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Affiliation(s)
- Zhijian Wu
- Gene Therapy Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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123
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Li C, Bowles DE, van Dyke T, Samulski RJ. Adeno-associated virus vectors: potential applications for cancer gene therapy. Cancer Gene Ther 2006; 12:913-25. [PMID: 15962012 PMCID: PMC1361306 DOI: 10.1038/sj.cgt.7700876] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Augmenting cancer treatment by protein and gene delivery continues to gain momentum based on success in animal models. The primary hurdle of fully exploiting the arsenal of molecular targets and therapeutic transgenes continues to be efficient delivery. Vectors based on adeno-associated virus (AAV) are of particular interest as they are capable of inducing transgene expression in a broad range of tissues for a relatively long time without stimulation of a cell-mediated immune response. Perhaps the most important attribute of AAV vectors is their safety profile in phase I clinical trials ranging from CF to Parkinson's disease. The utility of AAV vectors as a gene delivery agent in cancer therapy is showing promise in preclinical studies. In this review, we will focus on the basic biology of AAV as well as recent progress in the use of this vector in cancer gene therapy.
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Affiliation(s)
- Chengwen Li
- Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Dawn E Bowles
- Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Terry van Dyke
- Department of Biochemistry and Biophysics, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA; and
| | - Richard Jude Samulski
- Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Pharmacology, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Address correspondence and reprint requests to: Professor Richard Jude Samulski/Terry van Dyke, Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, CB#7352, Chapel Hill, NC27599, USA. E-mails: or
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Arechavaleta-Velasco F, Ma Y, Zhang J, McGrath CM, Parry S. Adeno-associated virus-2 (AAV-2) causes trophoblast dysfunction, and placental AAV-2 infection is associated with preeclampsia. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 168:1951-9. [PMID: 16723710 PMCID: PMC1606626 DOI: 10.2353/ajpath.2006.050781] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/13/2006] [Indexed: 02/01/2023]
Abstract
Shallow invasion by extravillous trophoblast cells into the uterine wall reduces placental perfusion and causes placental dysfunction, but the one or more causes of shallow placental invasion are unknown. We hypothesized that infection with adeno-associated virus-2 (AAV-2) inhibits trophoblast invasion and is associated with preeclampsia, which is a common obstetric complication resulting from placental dysfunction. We determined that transformed extravillous trophoblast (HTR-8/SVneo) cells were susceptible to AAV-2 infection in the presence or absence of adenovirus, which provides helper function for AAV-2 replication, and that AAV-2 infection reduced invasion of HTR-8/SVneo cells through an extracellular matrix before cytopathic effects were detected. In a case-control study, AAV-2 DNA was found more frequently in trophoblast cells from cases of severe preeclampsia (22/40) than from normal term deliveries (5/27, P = 0.002). These results indicate that AAV-2 infection is a previously unidentified cause of placental dysfunction. Additional studies to determine the susceptibility of extravillous trophoblast to other viruses, and the mechanisms by which viral infection impairs placental function, are warranted.
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Affiliation(s)
- Fabian Arechavaleta-Velasco
- Center for Research on Reproduction and Women's Health, University of Pennsylvania School of Medicine, 421 Curie Blvd., Philadelphia, PA 19104-6160, USA
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Krishna D, Le Doux JM. Murine leukemia virus particles activate Rac1 in HeLa cells. Biochem Biophys Res Commun 2006; 345:1184-93. [PMID: 16716260 DOI: 10.1016/j.bbrc.2006.05.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Accepted: 05/05/2006] [Indexed: 12/19/2022]
Abstract
A number of viruses, when they bind to cells, activate intracellular signals that facilitate post-binding steps of infection. To determine if retroviruses activate intracellular signaling, we transduced HeLa cells with amphotropic retroviruses produced by TelCeB6 cells and examined cell lysates for activated Rac1. We found that retroviruses activate Rac1. Rac1 activation was blocked when cells were depleted of cholesterol, cultured in suspension, or incubated with an anti-beta(1) integrin antibody, and when viruses were treated with heparinase III. Retrovirus activation of Rac1 did not require the amphotropic envelope protein. Gene transfer was reduced 2.4-fold when viruses were treated with heparinase III, but did not change when cells were transduced in the presence of function-blocking anti-beta(1) integrin antibodies. The implications of these findings with respect to retrovirus-cell interactions are discussed.
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Affiliation(s)
- Delfi Krishna
- The School of Chemical and Biomolecular Engineering, Atlanta, GA 30332-0535, USA
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126
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Hadaczek P, Kohutnicka M, Krauze MT, Bringas J, Pivirotto P, Cunningham J, Bankiewicz K. Convection-enhanced delivery of adeno-associated virus type 2 (AAV2) into the striatum and transport of AAV2 within monkey brain. Hum Gene Ther 2006; 17:291-302. [PMID: 16544978 DOI: 10.1089/hum.2006.17.291] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Adeno-associated virus type 2 (AAV2)-based vectors are promising transgene carriers for experimental gene therapy treatments of brain diseases. However, detailed evaluation of transgene distribution, trafficking, and transport within the brain is of the utmost importance before applying any type of gene therapy in humans. We examined the distribution of AAV2-thymidine kinase (AAV2-TK) and AAV2-aromatic L-amino acid decarboxylase (AAV2-AADC) in monkey brain after convection-enhanced delivery (CED). The AADC group consisted of two 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys that received unilateral infusions of AAV2-AADC into six sites in the right hemisphere. The TK group consisted of three monkeys that received bilateral CED infusion of AAV2-TK into the putamen; one side in all three monkeys was coinfused with heparin. Six weeks after AAV delivery, the brains were collected and processed for immunohistochemical staining. Volumetric measurement of TK distribution showed that at least 75% of the putamen could be covered by a single infusion of the vector; however, no effects of heparin coadministration were found, most likely because of the already robust gene transfer achieved by CED. Interestingly, TK- and AADCimmunoreactive cells were also present outside the striatum, in the globus pallidus, subthalamic nucleus, thalamus, and substantia nigra. CED proved to be an efficient method for delivery of the AAV2 vector. Detection of the transgenes in brain structures distant from the site of injection emphasizes the potential for gene transport, and the advantages and disadvantages of CED for gene therapy deserve further study.
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Affiliation(s)
- Piotr Hadaczek
- Laboratory of Molecular Therapeutics, Neurological Surgery, University of California, San Francisco, San Francisco, CA 94103, USA
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Sarkar R, Mucci M, Addya S, Tetreault R, Bellinger DA, Nichols TC, Kazazian HH. Long-Term Efficacy of Adeno-associated Virus Serotypes 8 and 9 in Hemophilia A Dogs and Mice. Hum Gene Ther 2006. [DOI: 10.1089/hum.2006.17.ft-186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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128
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Mani B, Baltzer C, Valle N, Almendral JM, Kempf C, Ros C. Low pH-dependent endosomal processing of the incoming parvovirus minute virus of mice virion leads to externalization of the VP1 N-terminal sequence (N-VP1), N-VP2 cleavage, and uncoating of the full-length genome. J Virol 2006; 80:1015-24. [PMID: 16379002 PMCID: PMC1346861 DOI: 10.1128/jvi.80.2.1015-1024.2006] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Minute virus of mice (MVM) enters the host cell via receptor-mediated endocytosis. Although endosomal processing is required, its role remains uncertain. In particular, the effect of low endosomal pH on capsid configuration and nuclear delivery of the viral genome is unclear. We have followed the progression and structural transitions of DNA full-virus capsids (FC) and empty capsids (EC) containing the VP1 and VP2 structural proteins and of VP2-only virus-like particles (VLP) during the endosomal trafficking. Three capsid rearrangements were detected in FC: externalization of the VP1 N-terminal sequence (N-VP1), cleavage of the exposed VP2 N-terminal sequence (N-VP2), and uncoating of the full-length genome. All three capsid modifications occurred simultaneously, starting as early as 30 min after internalization, and all of them were blocked by raising the endosomal pH. In particles lacking viral single-stranded DNA (EC and VLP), the N-VP2 was not exposed and thus it was not cleaved. However, the EC did externalize N-VP1 with kinetics similar to those of FC. The bulk of all the incoming particles (FC, EC, and VLP) accumulated in lysosomes without signs of lysosomal membrane destabilization. Inside lysosomes, capsid degradation was not detected, although the uncoated DNA of FC was slowly degraded. Interestingly, at any time postinfection, the amount of structural proteins of the incoming virions accumulating in the nuclear fraction was negligible. These results indicate that during the early endosomal trafficking, the MVM particles are structurally modified by low-pH-dependent mechanisms. Regardless of the structural transitions and protein composition, the majority of the entering viral particles and genomes end in lysosomes, limiting the efficiency of MVM nuclear translocation.
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Affiliation(s)
- Bernhard Mani
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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Ding W, Zhang LN, Yeaman C, Engelhardt JF. rAAV2 traffics through both the late and the recycling endosomes in a dose-dependent fashion. Mol Ther 2006; 13:671-82. [PMID: 16442847 PMCID: PMC1712670 DOI: 10.1016/j.ymthe.2005.12.002] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 12/08/2005] [Accepted: 12/08/2005] [Indexed: 01/01/2023] Open
Abstract
Inefficient trafficking of recombinant adeno-associated virus type-2 (rAAV2) to the nucleus is a major barrier for transduction. Using imaging and subcellular fractionation techniques, we evaluated the extent of rAAV2 movement through the late (Rab7) and recycling (Rab11) endosomes. Following rAAV2 infection of HeLa cells, immunoisolation of HA-Rab7- or HA-Rab11-tagged endosomes and intracellular colocalization of Cy3-labeled rAAV2 with EGFP-Rab7 or EGFP-Rab11 markers demonstrated dose-dependent trafficking of rAAV2 through the recycling and late endosomal compartments. At low multiplicities of infection (m.o.i. 100 genomes/cell), rAAV2 predominantly trafficked to the Rab7 compartment. In contrast, rAAV2 predominantly trafficked to the recycling endosome at 100-fold higher m.o.i. siRNA studies inhibiting either Rab7 or Rab11 demonstrated that reducing Rab11 protein levels more significantly inhibited rAAV2 transduction on a per genome basis compared to inhibition of Rab7. Dose-response curves, comparing the m.o.i. of AV2Luc infection to relative transduction, also supported the hypothesis that viral movement through the Rab11 compartment at high m.o.i. is more competent for transgene expression ( approximately 100-fold) than virus that moves through the Rab7 compartment at low m.o.i. These findings suggest that strategies to shunt viral movement from the late to the recycling endosome may be effective at increasing viral transduction for gene therapy.
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Affiliation(s)
- Wei Ding
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA
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Hadaczek P, Kohutnicka M, Krauze MT, Bringas J, Pivirotto P, Cunningham J, Bankiewicz K. Convection-Enhanced Delivery of Adeno-Associated Virus Type 2 (AAV2) into the Striatum and Transport of AAV2 Within Monkey Brain. Hum Gene Ther 2006. [DOI: 10.1089/hum.2006.17.ft-174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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131
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Abstract
Upon infection, virions or subviral nucleoprotein complexes are transported from the cell surface to the site of viral transcription and replication. During viral egress, particles containing viral proteins and nucleic acids again move from the site of their synthesis to that of virus assembly and further to the plasma membrane. Because free diffusion of molecules larger than 500 kDa is restricted in the cytoplasm, viruses as well as cellular organelles employ active, energy-consuming enzymes for directed transport. This is particularly evident in the case of neurotropic viruses that travel long distances in the axon during retrograde or anterograde transport. Viruses use two strategies for intracellular transport: Viral components either hijack the cytoplasmic membrane traffic or they interact directly with the cytoskeletal transport machinery. In this review we describe how viruses--particularly members of the Herpesviridae, Adenoviridae, Parvoviridae, Poxviridae, and Baculoviridae--make use of the microtubule and the actin cytoskeleton. Analysing the underlying principles of viral cytosolic transport will be helpful in the design of viral vectors to be used in research as well as human gene therapy, and in the identification of new antiviral target molecules.
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Affiliation(s)
- K Döhner
- Department of Virology, Hannover Medical School, Carl-Neuberg-Str 1, 30625 Hannover, Germany
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132
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Ros C, Baltzer C, Mani B, Kempf C. Parvovirus uncoating in vitro reveals a mechanism of DNA release without capsid disassembly and striking differences in encapsidated DNA stability. Virology 2005; 345:137-47. [PMID: 16242744 DOI: 10.1016/j.virol.2005.09.030] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 08/09/2005] [Accepted: 09/08/2005] [Indexed: 11/28/2022]
Abstract
The uncoating mechanism of parvoviruses is unknown. Their capsid robustness and increasing experimental data would suggest an uncoating mechanism without capsid disassembly. We have developed an in vitro system to detect and quantify viral DNA externalization and applied the assay on two parvoviruses with important differences in capsid structure, human B19 and minute virus of mice (MVM). Upon briefly treating the capsids to increasing temperatures, the viral genome became accessible in its full-length in a growing proportion of virions. Capsid disassembly started at temperatures above 60 degrees C for B19 and 70 degrees C for MVM. For both viruses, the externalization followed an all-or-nothing mechanism, without transitions exposing only a particular genomic region. However, the heat-induced DNA accessibility was remarkably more pronounced in B19 than in MVM. This difference was also evident under conditions mimicking endosomal acidification (pH 6.5 to 5), which triggered the externalization of B19-DNA but not of MVM-DNA. The externalized ssDNA was a suitable template for the full second-strand synthesis. Immunoprecipitation with antibodies against conformational epitopes and quantitative PCR revealed that the DNA externalized by heat was mostly dissociated from its capsid, however, the low pH-induced DNA externalization of B19 was predominantly capsid-associated. These results provide new insights into parvovirus uncoating suggesting a mechanism by which the full-length viral genome is released without capsid disassembly. The remarkable instability of the encapsidated B19 DNA, which is easily released from its capsid, would also explain the faster heat inactivation of B19 when compared to other parvoviruses.
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Affiliation(s)
- Carlos Ros
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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133
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Abstract
Adeno-associated virus (AAV) has attracted considerable interest as a gene therapy vector over the past decade. In all, 85% of the current 2052 PubMed references on AAV (as of December 2004) have been published in the last 10 years. As researchers have moved forward with using this vector system for gene delivery, an increased appreciation for the complexities of AAV biology has emerged. The biology of recombinant AAV (rAAV) transduction has demonstrated considerable diversity in different cell types and target tissues. This review will summarize the current understanding of events that control rAAV transduction following receptor binding and leading to nuclear uptake. These stages are broadly classified as intracellular trafficking and have been found to be a major rate-limiting step in rAAV transduction for many cell types. Advances in understanding this area of rAAV biology will help to improve the efficacy of this vector system for the treatment of inherited and acquired diseases.
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Affiliation(s)
- W Ding
- Department of Anatomy and Cell Biology, University of Iowa School of Medicine, Iowa City, 52242, USA
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134
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Sin M, Walker PD, Bouhamdan M, Quinn JP, Bannon MJ. Preferential expression of an AAV-2 construct in NOS-positive interneurons following intrastriatal injection. ACTA ACUST UNITED AC 2005; 141:74-82. [PMID: 16153741 DOI: 10.1016/j.molbrainres.2005.08.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 08/02/2005] [Accepted: 08/03/2005] [Indexed: 11/26/2022]
Abstract
Most CNS studies using recombinant adeno-associated virus type 2 (rAAV-2) vectors have focused on gene delivery for the purpose of gene therapy. In the present study, we examined the feasibility of using rAAV-2 vectors to study the regulation of preprotachykinin-A (PPT-A) promoter activity in striatal medium spiny projection neurons. An rAAV-2 vector incorporating a PPT promoter fragment (shown previously to confer some cell-specificity of expression in vitro) coupled to a green fluorescent protein (GFP) reporter gene was stereotaxically injected into the rat striatum. Since medium spiny projection neurons represent the predominant neuronal type (90-95%) in the striatum, we predicted that the vast majority of GFP-expressing cells would be of this phenotype. Surprisingly, the transgene was actually expressed in a similar number of medium spiny projection neurons and interneurons, while glial expression of GFP was not observed. A preponderance of GFP-expressing interneurons was immunoreactive for the marker neuronal nitric oxide synthase (nNOS). Our results suggest that viral vector-related events that occur during transduction are the determining factor in the pattern of transgene expression observed, while the influence of the transgene promoter appears to be secondary, at least under the conditions employed.
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Affiliation(s)
- Mihaela Sin
- Cellular and Clinical Neurobiology Program, Department of Psychiatry and Behavioral Neurosciences, Wayne State University, School of Medicine, Detroit, MI 48201, USA
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135
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Newcomb DC, Sajjan U, Nanua S, Jia Y, Goldsmith AM, Bentley JK, Hershenson MB. Phosphatidylinositol 3-kinase is required for rhinovirus-induced airway epithelial cell interleukin-8 expression. J Biol Chem 2005; 280:36952-61. [PMID: 16120607 DOI: 10.1074/jbc.m502449200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhinovirus (RV) is a common cause of asthma exacerbations. The signaling mechanisms regulating RV-induced airway epithelial cell responses have not been well studied. We examined the role of phosphatidylinositol (PI) 3-kinase in RV-induced interleukin (IL)-8 expression. Infection of 16HBE14o- human bronchial epithelial cells with RV39 induced rapid activation of PI 3-kinase and phosphorylation of Akt, a downstream effector of PI 3-kinase. RV39 also colocalized with cit-Akt-PH, a citrogen-tagged fluorescent fusion protein encoding the pleckstrin homology domain of Akt, indicating that 3-phosphorylated PI accumulates at the site of RV infection. Inhibition of PI 3-kinase and Akt attenuated RV39-induced NF-kappaB transactivation and IL-8 expression. Inhibition of PI 3-kinase also blocked internalization of labeled RV39 into 16HBE14o- cells, suggesting that the requirement of PI 3-kinase for RV39-induced IL-8 expression, at least in part, relates to its role in viral endocytosis.
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Affiliation(s)
- Dawn C Newcomb
- Department of Pediatrics, Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, USA
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136
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Bleker S, Sonntag F, Kleinschmidt JA. Mutational analysis of narrow pores at the fivefold symmetry axes of adeno-associated virus type 2 capsids reveals a dual role in genome packaging and activation of phospholipase A2 activity. J Virol 2005; 79:2528-40. [PMID: 15681453 PMCID: PMC546590 DOI: 10.1128/jvi.79.4.2528-2540.2005] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated virus type 2 (AAV2) capsids show 12 pores at the fivefold axes of symmetry. We mutated amino acids which constitute these pores to investigate possible functions of these structures within the AAV2 life cycle. Mutants with alterations in conserved residues were impaired mainly in genome packaging or infectivity, whereas few mutants were affected in capsid assembly. The packaging phenotype was characterized by increased capsid-per-genome ratios. Analysis of capsid-associated DNA versus encapsidated DNA revealed that this observation was due to reduced and not partial DNA encapsidation. Most mutants with impaired infectivity showed a decreased capability to expose their VP1 N termini. As a consequence, the activation of phospholipase A2 (PLA2) activity, which is essential for efficient infection, was affected on intact capsids. In a few mutants, the exposure of VP1 N termini and the development of PLA2 activity were associated with enhanced capsid instability, which is obviously also deleterious for virus infection. Therefore, PLA2 activity seems to be required on intact capsids for efficient infection. In conclusion, these results suggest that the pores at the fivefold axes function not only as portals for AAV2 single-stranded DNA packaging but also as channels for presentation of the PLA2 domain on AAV2 virions during infection.
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Affiliation(s)
- Svenja Bleker
- Tumor Virology, German Cancer Research Center, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany
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137
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Abstract
In recent years, significant efforts have been made on studying and engineering adeno-associated virus (AAV) capsid, in order to increase efficiency in targeting specific cell types that are non-permissive to wild type (wt) viruses and to improve efficacy in infecting only the cell type of interest. With our previous knowledge of the viral properties of the naturally occurring serotypes and the elucidation of their capsid structures, we can now generate capsid mutants, or hybrid serotypes, by various methods and strategies. In this review, we summarize the studies performed on AAV retargeting, and categorize the available hybrid serotypes to date, based on the type of modification: 1) transcapsidation, 2) adsorption of bi-specific antibody to capsid surface, 3) mosaic capsid, and 4) chimeric capsid. Not only these hybrid serotypes could achieve high efficiency of gene delivery to a specific targeted cell type, which can be better-tailored for a particular clinical application, but also serve as a tool for studying AAV biology such as receptor binding, trafficking and genome delivery into the nucleus.
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Affiliation(s)
- Vivian W. Choi
- Department of Pharmacology and
- Gene Therapy Center, University of North Carolina at Chapel Hill. Chapel Hill. NC 27599, USA
| | - Douglas M. McCarty
- Columbus Children’s Research Institute, Center for Gene Therapy, Columbus Children’s Hospital, and Department of Pediatrics, College of Medicine and Public Health, The Ohio State University, Columbus, Ohio 43205, USA
| | - R. Jude Samulski
- Department of Pharmacology and
- Gene Therapy Center, University of North Carolina at Chapel Hill. Chapel Hill. NC 27599, USA
- *Address correspondence to this author at the 7119 Thurston Bowles CB#7352, University of North Carolina at Chapel Hill, NC 27599, USA; Tel: 1-919-962-3285, Fax 1-919-966-0907; E-mail:
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138
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Hendrie PC, Russell DW. Gene Targeting with Viral Vectors. Mol Ther 2005; 12:9-17. [PMID: 15932801 DOI: 10.1016/j.ymthe.2005.04.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Revised: 04/06/2005] [Accepted: 04/06/2005] [Indexed: 10/25/2022] Open
Abstract
Genetic manipulation of cells for scientific and therapeutic goals can be achieved by both gene-addition and gene-targeting methods. Gene targeting precisely alters a gene in its natural chromosome location, providing distinct advantages over gene-addition approaches. Classic gene-targeting delivery systems (microinjection, electroporation, or calcium phosphate transfection) have led to major scientific advances, but are too inefficient in their current state to be used for some applications, including gene therapy. This review describes the development of gene-targeting vectors based on three types of viruses (retrovirus, adenovirus, and adeno-associated virus) and discusses the design, possible mechanisms of action, and applications of gene-targeting vectors based on adeno-associated virus.
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Affiliation(s)
- Paul C Hendrie
- Division of Hematology, Department of Medicine, University of Washington, Seattle, WA 98195, USA
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139
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Kronenberg S, Böttcher B, von der Lieth CW, Bleker S, Kleinschmidt JA. A conformational change in the adeno-associated virus type 2 capsid leads to the exposure of hidden VP1 N termini. J Virol 2005; 79:5296-303. [PMID: 15827144 PMCID: PMC1082756 DOI: 10.1128/jvi.79.9.5296-5303.2005] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The complex infection process of parvoviruses is not well understood so far. An important role has been attributed to a phospholipase A2 domain which is located within the unique N terminus of the capsid protein VP1. Based on the structural difference between adeno-associated virus type 2 wild-type capsids and capsids lacking VP1 or VP2, we show via electron cryomicroscopy that the N termini of VP1 and VP2 are involved in forming globules inside the capsids of empty and full particles. Upon limited heat shock, VP1 and possibly VP2 become exposed on the outsides of full but not empty capsids, which is correlated with the disappearance of the globules in the inner surfaces of the capsids. Using molecular modeling, we discuss the constraints on the release of the globularly organized VP1-unique N termini through the channels at the fivefold symmetry axes outside of the capsid.
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Affiliation(s)
- Stephanie Kronenberg
- Applied Tumor Virology, German Cancer Research Centre, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany
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140
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Zhong L, Li W, Yang Z, Qing K, Tan M, Hansen J, Li Y, Chen L, Chan RJ, Bischof D, Maina N, Weigel-Kelley KA, Zhao W, Larsen SH, Yoder MC, Shou W, Srivastava A. Impaired nuclear transport and uncoating limit recombinant adeno-associated virus 2 vector-mediated transduction of primary murine hematopoietic cells. Hum Gene Ther 2005; 15:1207-18. [PMID: 15684697 DOI: 10.1089/hum.2004.15.1207] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Controversies abound concerning hematopoietic stem cell transduction by recombinant adeno-associated virus 2 (AAV) vectors. For human hematopoietic cells, we have shown that this problem is related to the extent of expression of the cellular receptor for AAV. At least a small subset of murine hematopoietic cells, on the other hand, does express both the AAV receptor and the coreceptor, yet is transduced poorly. In the present study, we have found that approximately 85% of AAV genomes were present in the cytoplasmic fraction of primary murine c-Kit(+)Lin- hematopoietic cells. However, when mice were injected intraperitoneally with hydroxyurea before isolation of these cells, the extent to which AAV genomes were detected in the cytoplasmic fraction was reduced to approximately 40%, with a corresponding increase to approximately 60% in the nuclear fraction, indicating that hydroxyurea facilitated nuclear transport of AAV. It was apparent, nonetheless, that a significant fraction of the AAV genomes present in the nuclear fraction from cells obtained from hydroxyurea-treated mice was single stranded. We next tested whether the single-stranded AAV genomes were derived from virions that failed to undergo uncoating in the nucleus. A substantial fraction of the signal in the nuclear fraction of hematopoietic cells obtained from hydroxyurea-treated mice was also resistant to DNase I. That AAV particles were intact and biologically active was determined by successful transduction of 293 cells by virions recovered from murine hematopoietic cells 48 hr postinfection. Although hydroxyurea facilitated nuclear transport of AAV, most of the virions failed to undergo uncoating, thereby leading to only a partial improvement in viral second- strand DNA synthesis and transgene expression. A better understanding of the underlying mechanism of viral uncoating has implications in the optimal use of recombinant AAV vectors in hematopoietic stem cell gene therapy.
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Affiliation(s)
- Li Zhong
- Department of Microbiology and Immunology, Walther Oncology Center, Walther Cancer Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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141
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Rohr UP, Heyd F, Neukirchen J, Wulf MA, Queitsch I, Kroener-Lux G, Steidl U, Fenk R, Haas R, Kronenwett R. Quantitative real-time PCR for titration of infectious recombinant AAV-2 particles. J Virol Methods 2005; 127:40-5. [PMID: 15893564 DOI: 10.1016/j.jviromet.2005.03.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Revised: 03/03/2005] [Accepted: 03/08/2005] [Indexed: 11/29/2022]
Abstract
In this report, we present a fast, reliable and easy to perform method to quantify infectious titers of recombinant AAV-2 (rAAV-2) particles using the LightCycler technology, which is independent from the therapeutic transgene and without the presence of a marker gene. The method is based on the life cycle of AAV-2: after infection of the host cell, the single stranded (ss) AAV-2 genome is converted into a double stranded (ds) form. Following infection with rAAV-2, HeLa cells were lysed and ssDNA of transcriptionally inactive particles were efficiently removed by ssDNA-specific S1 nuclease digestion. The remaining viral dsDNA can be quantified by quantitative real-time PCR (qPCR). For validation of the new method, rAAV-2 preparations were analyzed by two other standard methods for titration of infectious particles in parallel, i.e. the infectious center assay (ICA) as well as flow cytometry using GFP as a marker. Comparing the infectious titers of 40 different AAV-2 fractions assessed by qPCR with the titers determined by FACS analysis a significant correlation (r=0.87, p<0.001) with a mean ratio of the titers assessed by qPCR and FACS of 1.92 (S.D.+/-1.59) was found. Further, the titers of seven rAAV-2 fractions using qPCR and ICA covering 5 log ranges were compared and a significant correlation was found between the results (r=0.80, p<0.001) with a mean ratio of 3.38 (S.D.+/-1.79), respectively.
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Affiliation(s)
- Ulrich-Peter Rohr
- Klinik für Haematologie, Onkologie und klinische Immunologie, Heinrich-Heine-Universitaet Duesseldorf, Moorenstrasse 5, D-40225 Duesseldorf, Germany.
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142
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Burger C, Gorbatyuk OS, Velardo MJ, Peden CS, Williams P, Zolotukhin S, Reier PJ, Mandel RJ, Muzyczka N. Recombinant AAV viral vectors pseudotyped with viral capsids from serotypes 1, 2, and 5 display differential efficiency and cell tropism after delivery to different regions of the central nervous system. Mol Ther 2005; 10:302-17. [PMID: 15294177 DOI: 10.1016/j.ymthe.2004.05.024] [Citation(s) in RCA: 562] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 05/13/2004] [Indexed: 12/14/2022] Open
Abstract
Recombinant adeno-associated virus 2 (rAAV2) has been shown to deliver genes to neurons effectively in the brain, retina, and spinal cord. The characterization of new AAV serotypes has revealed that they have different patterns of transduction in diverse tissues. We have investigated the tropism and transduction frequency in the central nervous system (CNS) of three different rAAV vector serotypes. The vectors contained AAV2 terminal repeats flanking a green fluorescent protein expression cassette under the control of the synthetic CBA promoter, in AAV1, AAV2, or AAV5 capsids, producing the pseudotypes rAAV2/1, rAAV2/2, and rAAV2/5. Rats were injected with rAAV2/1, rAAV2/2, or rAAV2/5 into selected regions of the CNS, including the hippocampus (HPC), substantia nigra (SN), striatum, globus pallidus, and spinal cord. In all regions injected, the three vectors transduced neurons almost exclusively. All three vectors transduced the SN pars compacta with high efficiency, but rAAV2/1 and rAAV2/5 also transduced the pars reticulata. Moreover, rAAV2/1 showed widespread distribution throughout the entire midbrain. In the HPC, rAAV2/1 and rAAV2/5 targeted the pyramidal cell layers in the CA1-CA3 regions, whereas AAV2/2 primarily transduced the hilar region of the dentate gyrus. In general, rAAV2/1 and rAAV2/5 exhibited higher transduction frequencies than rAAV2/2 in all regions injected, although the differences were marginal in some regions. Retrograde transport of rAAV1 and rAAV5 was also observed in particular CNS areas. These results suggest that vectors based on distinct AAV serotypes can be chosen for specific applications in the nervous system.
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Affiliation(s)
- Corinna Burger
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville 32610, USA
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143
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Zhong L, Chen L, Li Y, Qing K, Weigel-Kelley KA, Chan RJ, Yoder MC, Srivastava A. Self-complementary adeno-associated virus 2 (AAV)-T cell protein tyrosine phosphatase vectors as helper viruses to improve transduction efficiency of conventional single-stranded AAV vectors in vitro and in vivo. Mol Ther 2005; 10:950-7. [PMID: 15509512 DOI: 10.1016/j.ymthe.2004.07.018] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Accepted: 07/15/2004] [Indexed: 10/26/2022] Open
Abstract
Recombinant vectors based on adeno-associated virus type 2 (AAV) target the liver efficiently, but the transgene expression is limited to approximately 5% of hepatocytes. The lack of efficient transduction is due, in part, to the presence of a cellular protein, FKBP52, phosphorylated forms of which inhibit the viral second-strand DNA synthesis. We have documented that dephosphorylation of FKBP52 at tyrosine residues by the cellular T cell protein tyrosine phosphatase (TC-PTP) enhances AAV-mediated transduction in primary murine hematopoietic cells from TC-PTP-transgenic mice. We have also documented that AAV-mediated transduction is significantly enhanced in hepatocytes in TC-PTP-transgenic as well as in FKBP52-deficient mice because of efficient viral second-strand DNA synthesis. In this study, we evaluated whether co-infection of conventional single-stranded AAV vectors with self-complementary AAV-TC-PTP vectors leads to increased transduction efficiency of conventional AAV vectors in established human cell lines in vitro and in primary murine hepatocytes in vivo. We demonstrate here that scAAV-TC-PTP vectors serve as a helper virus in augmenting the transduction efficiency of conventional AAV vectors in vitro as well as in vivo which correlates directly with the extent of second-strand DNA synthesis of conventional single-stranded AAV vectors. Toxicological studies following tail-vein injections of scAAV-TC-PTP vectors in experimental mice show no evidence of any adverse effect in any of the organs in any of the mice for up to 13 weeks. Thus, this novel co-infection strategy should be useful in circumventing one of the major obstacles in the optimal use of recombinant AAV vectors in human gene therapy.
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Affiliation(s)
- Li Zhong
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis 46202, USA
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144
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Nakai H, Fuess S, Storm TA, Muramatsu SI, Nara Y, Kay MA. Unrestricted hepatocyte transduction with adeno-associated virus serotype 8 vectors in mice. J Virol 2005; 79:214-24. [PMID: 15596817 PMCID: PMC538708 DOI: 10.1128/jvi.79.1.214-224.2005] [Citation(s) in RCA: 261] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Recombinant adeno-associated virus (rAAV) vectors can mediate long-term stable transduction in various target tissues. However, with rAAV serotype 2 (rAAV2) vectors, liver transduction is confined to only a small portion of hepatocytes even after administration of extremely high vector doses. In order to investigate whether rAAV vectors of other serotypes exhibit similar restricted liver transduction, we performed a dose-response study by injecting mice with beta-galactosidase-expressing rAAV1 and rAAV8 vectors via the portal vein. The rAAV1 vector showed a blunted dose-response similar to that of rAAV2 at high doses, while the rAAV8 vector dose-response remained unchanged at any dose and ultimately could transduce all the hepatocytes at a dose of 7.2 x 10(12) vector genomes/mouse without toxicity. This indicates that all hepatocytes have the ability to process incoming single-stranded vector genomes into duplex DNA. A single tail vein injection of the rAAV8 vector was as efficient as portal vein injection at any dose. In addition, intravascular administration of the rAAV8 vector at a high dose transduced all the skeletal muscles throughout the body, including the diaphragm, the entire cardiac muscle, and substantial numbers of cells in the pancreas, smooth muscles, and brain. Thus, rAAV8 is a robust vector for gene transfer to the liver and provides a promising research tool for delivering genes to various target organs. In addition, the rAAV8 vector may offer a potential therapeutic agent for various diseases affecting nonhepatic tissues, but great caution is required for vector spillover and tight control of tissue-specific gene expression.
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Affiliation(s)
- Hiroyuki Nakai
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California 94305, USA.
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145
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Hsu PYJ, Yang YW. Effect of polyethylenimine on recombinant adeno-associated virus mediated insulin gene therapy. J Gene Med 2005; 7:1311-21. [PMID: 15906397 DOI: 10.1002/jgm.779] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND Recombinant adeno-associated virus (rAAV) is becoming a promising vector for gene therapy for type I diabetes. The objective of this study was to investigate the effect of incorporation of polyethylenimine (PEI) on rAAV-mediated insulin gene therapy in vitro and in vivo. METHODS Recombinant AAV vector, harboring the furin-mutated human insulin and enhanced green fluorescent protein (EGFP) genes, was constructed. The effect of complexation with PEI on rAAV-mediated gene transfer was examined in Huh7 human hepatoma cells. The transgene expression was also examined in streptozotocin (STZ)-induced diabetic C57BL/6J mice by direct administration of rAAV into the livers of the animals, followed by monitoring changes in body weight and blood glucose levels. Secretion of human insulin was determined by radioimmunoassay (RIA) and immunohistochemical staining in the livers. RESULTS Complexation with PEI was shown to enhance rAAV-mediated transgene expression in Huh7 cells, resulting in higher transduction efficiency and enhanced production of immunoreactive human insulin. Heparin competition assay demonstrated that endocytosis of rAAV-PEI was partially inhibited by heparin. The enhancement of rAAV-mediated transgene expression was also demonstrated in the animals, showing lowering of blood glucose and longer duration of normoglycemia. Immunofluorescent staining of the liver sections demonstrated that PEI increased the uptake of rAAV and enhanced insulin secretion. The enhancement of PEI on rAAV-mediated insulin gene therapy was further confirmed by glucose challenge and a 10-h fasting blood glucose test. CONCLUSIONS Results obtained in this study demonstrated that incorporation of PEI augmented rAAV-mediated insulin gene transfer and enhanced amelioration of hyperglycemia in the STZ-induced diabetic animals.
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Affiliation(s)
- Paul Yueh-Jen Hsu
- School of Pharmacy, College of Medicine, National Taiwan University, 1, Jen-Ai Road, Section 1, Taipei 100, Taiwan
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146
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Hauck B, Zhao W, High K, Xiao W. Intracellular viral processing, not single-stranded DNA accumulation, is crucial for recombinant adeno-associated virus transduction. J Virol 2004; 78:13678-86. [PMID: 15564477 PMCID: PMC533901 DOI: 10.1128/jvi.78.24.13678-13686.2004] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [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) is a unique gene transfer vector which takes approximately 4 to 6 weeks to reach its expression plateau. The mechanism for this slow-rise expression profile was proposed to be inefficient second-strand DNA synthesis from the input single-stranded (ss) DNA viral genome. In order to clarify the status of ss AAV genomes, we generated AAV vectors labeled with bromodeoxyuridine (BrdU), a nucleotide analog that can be incorporated into the AAV genome and packaged into infectious virions. Since BrdU-DNA can be detected only by an anti-BrdU antibody when DNA is in an ss form, not in a double-stranded (ds) form, ss AAV genomes with BrdU can be readily tracked in situ. Although ss AAV DNA was abundant by Southern blot analysis, free ss AAV genomes were not detectable after AAV transduction by this new detection method. Further Southern blot analysis of viral DNA and virions revealed that ss AAV DNA was protected within virions. Extracted cellular fractions demonstrated that viral particles in host cells remained infectious. In addition, a significant amount of AAV genomes was degraded after AAV transduction. Therefore, we conclude that the amount of free ss DNA is not abundant during AAV transduction. AAV transduction is limited by the steps that affect AAV ss DNA release (i.e., uncoating) before second-strand DNA synthesis can occur. AAV ss DNA released from viral uncoating is either converted into ds DNA efficiently or degraded by cellular DNA repair mechanisms as damaged DNA. This study elucidates a mechanism that can be exploited to develop new strategies to improve AAV vector transduction efficiency.
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Affiliation(s)
- Bernd Hauck
- Department of Pediatrics, University of Pennsylvania, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
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147
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Hamilton H, Gomos J, Berns KI, Falck-Pedersen E. Adeno-associated virus site-specific integration and AAVS1 disruption. J Virol 2004; 78:7874-82. [PMID: 15254160 PMCID: PMC446113 DOI: 10.1128/jvi.78.15.7874-7882.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [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) is a single-stranded DNA virus with a unique biphasic lifestyle consisting of both a productive and a latent phase. Typically, the productive phase requires coinfection with a helper virus, for instance adenovirus, while the latent phase dominates in healthy cells. In the latent state, AAV is found integrated site specifically into the host genome at chromosome 19q13.4 qtr (AAVS1), the only animal virus known to integrate in a defined location. In this study we investigated the latent phase of serotype 2 AAV, focusing on three areas: AAV infection, rescue, and integration efficiency as a function of viral multiplicity of infection (MOI); efficiency of site-specific integration; and disruption of the AAVS1 locus. As expected, increasing the AAV MOI resulted in an increase in the percentage of cells infected, with 80% of cells infected at an MOI of 10. Additional MOI only marginally effected a further increase in percentage of infected cells. In contrast to infection, we found very low levels of integration at MOIs of less than 10. At an MOI of 10, at which 80% of cells are infected, less than 5% of clonal cell lines contained integrated AAV DNA. At an MOI of 100 or greater, however, 35 to 40% of clonal cell lines contained integrated AAV DNA. Integration and the ability to rescue viral genomes were highly correlated. Analysis of integrated AAV indicated that essentially all integrants were AAVS1 site specific. Although maximal integration efficiency approached 40% of clonal cell lines (essentially 50% of infected cells), over 80% of cell lines contained a genomic disruption at the AAVS1 integration locus on chromosome 19 ( approximately 100% of infected cells). Rep expression by itself and in the presence of a plasmid integration substrate was able to mediate this disruption of the AAVS1 site. We further characterized the disruption event and demonstrated that it resulted in amplification of the AAVS1 locus. The data are consistent with a revised model of AAV integration that includes preliminary expansion of a defined region in AAVS1.
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Affiliation(s)
- Henry Hamilton
- Molecular Biology Program, Weill Medical College of Cornell University, New York, NY 10021, USA
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148
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Sanlioglu AD, Karacay B, Benson PK, Engelhardt JF, Sanlioglu S. Novel approaches to augment adeno-associated virus type-2 endocytosis and transduction. Virus Res 2004; 104:51-9. [PMID: 15177892 DOI: 10.1016/j.virusres.2004.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2003] [Revised: 03/02/2004] [Accepted: 03/04/2004] [Indexed: 11/19/2022]
Abstract
Recombinant adeno-associated virus (rAAV) receptor binding, endocytosis, nuclear trafficking and second strand gene conversion have been described as potential rate-limiting steps in rAAV type-2 (rAAV-2) transduction. Several strategies have been developed to enhance rAAV-2 intracellular trafficking and gene conversion in an attempt to increase the efficiency of this virus as a gene therapy vector. To this end, the current study has investigated novel methods for augmenting rAAV transduction by enhancing endocytosis of rAAV-2. A selective trypsinization assay demonstrated that the abundance of internalized rAAV ssDNA was increased only in cells treated with both pyrrolidinedithiocarbonate (PDTC) and a genotoxic agent. Treating cells with each of these agents alone had no effect on rAAV endocytosis in comparison to controls. To investigate the mechanisms of this synergistic effect on rAAV transduction, the involvement of Rac1 protein was evaluated. Inhibition of the Rac1 pathway by expression of a dominant negative mutant of Rac1 (N17Rac1) decreased rAAV transduction. In contrast, expression of a dominant active form of Rac1 (V12Rac1) alone mimicked the up-regulated response seen in the presence of PDTC and genotoxic agents. These studies provide potential insights into the importance of the Rac1 pathway to enhance uptake of rAAV-2.
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Affiliation(s)
- Ahter D Sanlioglu
- The Human Gene Therapy Unit of Akdeniz University, Faculty of Medicine, Antalya, 07070 Turkey
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149
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Vihinen-Ranta M, Suikkanen S, Parrish CR. Pathways of cell infection by parvoviruses and adeno-associated viruses. J Virol 2004; 78:6709-14. [PMID: 15194745 PMCID: PMC421635 DOI: 10.1128/jvi.78.13.6709-6714.2004] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Maija Vihinen-Ranta
- Department of Biological and Environmental Science, University of Jyvaskyla, P.O. Box 35, FIN-40500 Jyvaskyla, Finland.
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150
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Zen Z, Espinoza Y, Bleu T, Sommer JM, Wright JF. Infectious Titer Assay for Adeno-Associated Virus Vectors with Sensitivity Sufficient to Detect Single Infectious Events. Hum Gene Ther 2004; 15:709-15. [PMID: 15298029 DOI: 10.1089/1043034041361262] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A highly sensitive assay for determination of infectious titers of recombinant adeno-associated virus (AAV) by limiting dilution analysis is described. This assay is capable of detecting single infectious events and can therefore provide an absolute rather than relative measure of infectivity. The assay utilizes a HeLa-derived AAV2 Rep/Cap-expressing cell line, D7-4, grown in 96-well plates and infected with replicate 10-fold serial dilutions of AAV2 vectors in the presence of adenovirus type 5. Forty-eight hours after infection, vector genome replication is determined by quantitative PCR (Q-PCR). A linear relationship between vector genome input and replicated copy number (slope = 2670 copies per vector genome) was determined, enabling detection of one infectious event per well by Q-PCR. The observed binomial distribution of the end-point data confirmed that single infectious events could be detected, and allowed calculation of infectious titers by the Kärber method. Analysis of an AAV2 reference vector, AAV-hFIX16, in 21 independent determinations gave an average ratio of AAV vector genomes (VG) to infectious units (IU) of 8.3 +/- 4.2 VG/IU, a value close to the theoretical limit. No significant differences in vector particle-to-infectious unit ratios were observed between vectors purified by column chromatography (9.3 +/- 5.0 VG/IU, n = 7) and cesium chloride gradient ultracentrifugation (6.4 +/- 3.2 VG/IU, n = 7).
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Affiliation(s)
- Zhu Zen
- Avigen, Alameda, CA 94502, USA.
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