Sustained high-level expression of full-length human factor VIII and restoration of clotting activity in hemophilic mice using a minimal adenovirus vector

The successful prophylactic treatment of hemophilia A by frequent infusions of plasma concentrates or recombinant factor VIII (hFVIII) indicates that gene therapy may be a potential alternative for the treatment of the diseas e. For efficient delivery and long-term expression of the hFIII gene, a nov el minimal adenovirus (mini-Ad) vector, MiniAdFVIII, has been developed. Th e Vector is devoid of all viral genes and carries the full-length hFVIII cD NA under the control of the human 12.5-kb albumin promoter. The MiniAdFVIII vector was propagated with the assistance of an ancillary vector in 293 ce lls and was purified by CsCl banding. Sustained expression of hFVIII at phy siologic levels (100-800 ng/mL) was achieved in mice after a single intrave nous injection of MiniAdFVIII, The expressed hFVIII had a structure identic al to that of recombinant hFVIII, as determined by Western blot analysis, T he functionality of the protein was confirmed by the restoration of blood c oagulation capacity in MiniAdFVIII-treated hemophilic mice, as determined b y tail clipping observations. Although antivector or antihuman FVIII antibo dies at various levels were detected, long-term expression of the transgene was observed in the mice that did not generate antibodies against the tran sgene product. The vector DNA persisted in the liver tissues of the mice wi th long-term expression, No significant histopathologic findings or toxicit ies were observed to be associated with the vector in the MiniAdFVIII-treat ed C57BL/6 mice. These results support the further development of MiniAdFVI II for clinical trials toward the treatment of hemophilia A. (C) 2000 by The American Society of Hematology.