[Optimized AAV package and experimental application of recombinant AAV8/hFⅧ for gene therapy on hemophilia A mice]

Objective: To evaluate the effects of adeno-associated virus (AAV) carrying hFⅧ by serotype 8 (AAV8/hFⅧ) on hemophilia A (HA) mice by gene therapy strategy. Methods: pAAV-CB-EGFP, pH22 (serotype 2) and pfΔ6 (adenovirus helper) were used to package AAV into HEK-293 cells in different conditions (ratios of cells to plasmids). The efficiency of transfection and infection were evaluated using immunofluorescence microscope to seek an optimized package condition. pAAV-TTR-hFⅧ, pH 28 (serotype 8) and pfΔ6 were applied to package AAV8/hFⅧ in HEK-293 cells using the optimized package condition. The purified AAV8/hFⅧ were intravenously injected into HA mice and the effects of gene therapy were estimated. Results: The efficiency of package was evaluated according to the amount and intensity of enhanced green fluorescent protein (EGFP) under immunofluorescence microscope. Four package conditions including 10 cm-dish to transfect 10 μg plasmids, 20 cm-dish to 20 μg, 30 μg and 40 μg plasmids were employed, and the condition of 20 cm-dish to transfect 20 μg plasmids reached the highest transfection efficiency at 24 h, 48 h and 72 h after transfection. The small scale AAV-EGFP was packaged using the optimized condition and an AAV crude extract was harvested by a freeze-thaw method. HEK-293 and 16095 cells were infected by the AAV crude extract, and the preferential infection efficiency was recognized in 16095 cells under immunofluorescence microscope. Then, AAV8/hFⅧ was packaged and purified based on the optimized transfection condition, and the high purity of AAV8/hFⅧ was detected by Western blot. Fractions of AAV8/hFⅧ at the dose of 8×10(12) vg/kg were injected into HA mice through tail vein, an eye-bleeding was performed at every two weeks, and the activity of FⅧ was measured by aPTT assay. Results showed that the activity of FⅧ maintained at the therapeutic level and lasted up to 12 weeks after injection. Conclusion: The purified AAV8/hFⅧ based on the optimized package condition could play a role in HA mice gene therapy, and the long-term therapeutic effects of AAV8/hFⅧ were observed in vivo.