An alternative approach to somatic cell gene therapy.

Mouse primary skin fibroblasts were infected with a recombinant retrovirus containing human factor IX cDNA. Bulk infected cells capable of synthesizing and secreting biologically active human factor IX protein were embedded in collagen, and the implant was grafted under the epidermis. Sera from the transplanted mice contain human factor IX protein for at least 10-12 days. Loss of immunoreactive human factor IX protein in the mouse serum is not due to graft rejection. Instead, the mouse serum contains anti-human factor IX antibodies, which react with the protein. We suggest that retroviral-infected primary skin fibroblasts offer an alternative approach to somatic cell gene therapy.