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

The feasibility of in vivo gene therapy for hemophilia B by VSV-G pseudotyp ed retroviral vector was introduced. The novel packaging cell line 293GPG w as used to produce VSV-G/G1NaBAIX pseudotyped virus with the highest titers up to 8.5 x 10(8) cfu . mL(-1). In contrast to the conventional retrovirus , VSV-G pseudotyped virus was more resistant to inactivation by serum compl ements (P<0.001). Our results also demonstrated that VSV-G pseudotyped viru s 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 s ome extent in all hFIX-treated mice, the most remarkable improvement was ob served in the mice treated with higher dose of virus whose clotting activit y increased to (3.4 +/- 1.5) % and APTT (activated partial thromboplastin t ime) reduced to (43.2 +/- 7.2) s. The anti-hFIX antibody was not detected b y the method of Bethesda, no germ line transmission and any side effects as sociated with gene transfer were found. Our results indicated that neonatal gene therapy for hemophilia B mice by VSV-G pseudotyped retrovirus is prom ising.