Establishment of a recombinant adeno-associated virus expressing hVEGF165*☆

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BACKGROUND:Because certain gene vectors could have deleterious effects in the central nervous system, the choice of a safe and effective vector system has become more important for gene therapy of nerve regeneration.OBJECTIVE:To construct a non-pathogenic, recombinant adeno-associated virus (AAV) simultaneously expressing human vascular endothelial growth factor 165 (hVEGF165) and green fluorescent protein (GFP).DESIGN, TIME AND SETTING:A randomized controlled experiment was performed at the Virology Laboratory of Shaanxi Provincial Center for Disease Control and Prevention between March and September 2007.MATERIALS:AAV helper-free system, AAV–293 packaging cell line, and AAV HT–1080 cells were purchased from Stratagene, USA. E. coli DH was a stocked strain from Centers for Disease Control and Prevention of Shaanxi, China. Plasmid pUC18-hHVEGF165 was a gift from Zhibin Shi.METHODS:The hVEGF165 gene was amplified by PCR from pUC18-hHVEGF165 and inserted into plasmid pAAV-IRES-hrGFP to construct recombinant plasmid pAAV-hVEGF165-IRES-hrGFP. Subsequently pAAV-hVEGF165-IRES-hrGFP, pAAV-RC (the rep/cap-gene containing plasmid), and pHelper were co-transfected into AAV–293 cells to complete rAAV-hVEGF165-IRES-hrGFP packaging through homologous recombination. The efficiency of AAV packaging was monitored under a fluorescent microscope, and the recombinant viral particles were harvested from infected AAV–293 cells, and further concentrated and purified. AAV HT–1080 cells were infected with the recombinant virus AAV-hVEGF165-IRES-hrGFP.MAIN OUTCOME MEASURES:Recombinant virus titer was measured by fluorescent cell counting, and infection efficiency was detected by Fluorescence Activated Cell Sorter (FACS) upon infecting AAV-HT1080 cells. The recombination with the exogenous gene was verified by PCR.RESULTS:The PCR amplified products were verified as hVEGF165 gene by DNA sequencing, and the recombinant pAAV-hVEGF165-IRES-GFP was confirmed by double digestion. The system provided a high packaging ratio of 95%, and the purified recombinant virus had a high titer of 5.5×1011 virus particles/mL. The AAV-HT1080 cells were infected at a ratio of 90.4%. The recombinant virus was confirmed by PCR to contain the exogenous hVEGF165 gene.CONCLUSION:The non-pathogenic rAAV-hVEGF165-GFP vector, carrying hVEGF165 and GFP reporter gene, was successfully constructed with a high titer and infection efficiency.

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