Gene therapy via primary myoblasts: long-term expression of factor IX protein following transplantation in vivo.

We have explored the use of primary myoblasts as a somatic tissue for gene therapy of acquired and inherited diseases where systemic delivery of a gene product may have therapeutic effects. Mouse primary myoblasts were infected with replication-defective retroviruses expressing canine factor IX cDNA under the control of a mouse muscle creatine kinase enhancer and human cytomegalovirus promoter. The infected myoblasts were injected into the hindlegs of recipient mice and levels of secreted factor IX protein were monitored in the plasma. We report sustained expression of factor IX protein for over 6 months without any apparent adverse effect on the recipient mice.