Browsing by Author "Zhong, Li"

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    High-Efficiency Transduction of Primary Human Hematopoietic Stem Cells and Erythroid Lineage-Restricted Expression by Optimized AAV6 Serotype Vectors In Vitro and in a Murine Xenograft Model In Vivo
    (Public Library of Science, 2013) Song, Liujiang; Li, Xiaomiao; Jayandharan, Giridhara R.; Wang, Yuan; Aslanidi, George V.; Ling, Chen; Zhong, Li; Gao, Guangping; Yoder, Mervin C.; Ling, Changquan; Tan, Mengqun; Srivastava, Arun; Pediatrics, School of Medicine
    We have observed that of the 10 AAV serotypes, AAV6 is the most efficient in transducing primary human hematopoietic stem cells (HSCs), and that the transduction efficiency can be further increased by specifically mutating single surface-exposed tyrosine (Y) residues on AAV6 capsids. In the present studies, we combined the two mutations to generate a tyrosine double-mutant (Y705+731F) AAV6 vector, with which >70% of CD34(+) cells could be transduced. With the long-term objective of developing recombinant AAV vectors for the potential gene therapy of human hemoglobinopathies, we generated the wild-type (WT) and tyrosine-mutant AAV6 vectors containing the following erythroid cell-specific promoters: β-globin promoter (βp) with the upstream hyper-sensitive site 2 (HS2) enhancer from the β-globin locus control region (HS2-βbp), and the human parvovirus B19 promoter at map unit 6 (B19p6). Transgene expression from the B19p6 was significantly higher than that from the HS2-βp, and increased up to 30-fold and up to 20-fold, respectively, following erythropoietin (Epo)-induced differentiation of CD34(+) cells in vitro. Transgene expression from the B19p6 or the HS2-βp was also evaluated in an immuno-deficient xenograft mouse model in vivo. Whereas low levels of expression were detected from the B19p6 in the WT AAV6 capsid, and that from the HS2-βp in the Y705+731F AAV6 capsid, transgene expression from the B19p6 promoter in the Y705+731F AAV6 capsid was significantly higher than that from the HS2-βp, and was detectable up to 12 weeks post-transplantation in primary recipients, and up to 6 additional weeks in secondary transplanted animals. These data demonstrate the feasibility of the use of the novel Y705+731F AAV6-B19p6 vectors for high-efficiency transduction of HSCs as well as expression of the b-globin gene in erythroid progenitor cells for the potential gene therapy of human hemoglobinopathies such as β-thalassemia and sickle cell disease.
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    Optimizing the transduction efficiency of human hematopoietic stem cells using capsid-modified AAV6 vectors in vitro and in a xenograft mouse model in vivo
    (Elsevier, 2013) Song, Liujiang; Kauss, M. Ariel; Kopin, Etana; Chandra, Manasa; Ul-Hasan, Taihra; Miller, Erin; Jayandharan, Giridhara R.; Rivers, Angela E.; Aslanidi, George V.; Ling, Chen; Li, Baozheng; Ma, Wenqin; Li, Xiaomiao; Andino, Lourdes M.; Zhong, Li; Tarantal, Alice F.; Yoder, Mervin C.; Wong, Kamehameha K., Jr.; Tan, Mengqun; Chatterjee, Saswati; Srivastava, Arun; Pediatrics, School of Medicine
    Background aims: Although recombinant adeno-associated virus serotype 2 (AAV2) vectors have gained attention because of their safety and efficacy in numerous phase I/II clinical trials, their transduction efficiency in hematopoietic stem cells (HSCs) has been reported to be low. Only a few additional AAV serotype vectors have been evaluated, and comparative analyses of their transduction efficiency in HSCs from different species have not been performed. Methods: We evaluated the transduction efficiency of all available AAV serotype vectors (AAV1 through AAV10) in primary mouse, cynomolgus monkey and human HSCs. The transduction efficiency of the optimized AAV vectors was also evaluated in human HSCs in a murine xenograft model in vivo. Results: We observed that although there are only six amino acid differences between AAV1 and AAV6, AAV1, but not AAV6, transduced mouse HSCs well, whereas AAV6, but not AAV1, transduced human HSCs well. None of the 10 serotypes transduced cynomolgus monkey HSCs in vitro. We also evaluated the transduction efficiency of AAV6 vectors containing mutations in surface-exposed tyrosine residues. We observed that tyrosine (Y) to phenylalanine (F) point mutations in residues 445, 705 and 731 led to a significant increase in transgene expression in human HSCs in vitro and in a mouse xenograft model in vivo. Conclusions: These studies suggest that the tyrosine-mutant AAV6 serotype vectors are the most promising vectors for transducing human HSCs and that it is possible to increase further the transduction efficiency of these vectors for their potential use in HSC-based gene therapy in humans.
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    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
    (Elsevier, 2004-11-01) Zhong, Li; Chen, Linyuan; Li, Yanjun; Qing, Keyun; Weigel-Kelley, Kirsten A.; Chan, Rebecca J.; Yoder, Mervin C.; Medicine, School of Medicine
    Recombinant vectors based on adeno-associated virus type 2 (AAV) target the liver efficiently, but the transgene expression is limited to ∼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.