von Willebrand disease (VWD), the most common
hereditary coagulation disorder, results from mutations in the 52-exon gene for
von Willebrand factor (VWF), which encodes an 8.4-kB
cDNA. Studies with VWF
cDNA plasmids have demonstrated that in vivo gene transfer to the liver will correct the coagulation dysfunction in VWF(-/-) mice, but the correction is transient. To develop gene therapy for VWF that would mediate long-term expression of the VWF
cDNA in liver, we first evaluated segmental
pre-mRNA trans-splicing (SPTS) with two adeno-associated virus (AAV) serotype 8 vectors, each delivering one-half of the VWF
cDNA. However, although the two vectors functioned well to generate VWF multimers after
infection of cells in vitro, the efficiency of SPTS was insufficient to correct the VWF(-/-) mouse in vivo. As an alternative, we assessed the ability of a lentiviral vector to transfer the intact murine VWF
cDNA in vivo directly to the neonatal liver of VWF(-/-) mice, using generation of VWF multimers, bleeding time, and
bleeding volume as efficacy parameters. The VWF lentivirus generated VWF multimers and partially or completely corrected the coagulation defect on a persistent basis in 33% of the treated VWF-deficient mice. On the basis of the concept that partial persistent correction with gene transfer could be beneficial in VWD patients, these observations suggest that lentiviral delivery of VWF
cDNA should be explored as a candidate for gene therapy in patients with a severe form of VWD.