Efficient transfer and expression of human clotting factor IX cDNA in neonatal hemophilia B mice mediated by VSV-G pseudotyped retrovirus

The feasibility ofin vivo gene therapy for hemophilia B by VSV-G pseudotyped retroviral vector was introduced. The novel packaging cell line 293GPG was used to produce VSV-G/GlNaBAIX pseudotyped virus with the highest titers up to 8.5×10⁸ cfu · mL⁻¹. In contrast to the conventional retrovirus, VSV-G pseudotyped virus was more resistant to inactivation by serum complements (P<0.001). Our results also demonstrated that VSV-G pseudotyped virus was more stable in neonatal mice serum than in adult mice serum (P<0.01). After intraperitoneal injection of different doses of virus, hFIX antigen was detected and lasted for more than 120 d, the highest level reached (72.5±6.1) ng · mL⁻¹. Moreover, the functional activity was improved to some extent in all hFIX-treated mice, the most remarkable improvement was observed in the mice treated with higher dose of virus whose clotting activity increased to (3.4±1.5)% and APTT (activated partial thromboplastin time) reduced to (43.2±7.2) s. The anti-hFIX antibody was not detected by the method of Bethesda, no germ line transmission and any side effects associated with gene transfer were found. Our results indicated that neonatal gene therapy for hemophilia B mice by VSV-G pseudotyped retrovirus is promising.