Stable delivery of physiologic levels of recombinant erythropoietin to the systemic circulation by intramuscular injection of replication-defective adenovirus.

A number of inherited and acquired serum protein deficiencies including hemophilias A and B, diabetes mellitus, and the erythropoietin-responsive anemias are currently treated with repeated subcutaneous or intravenous infusions of purified or recombinant proteins. The development of an in vivo gene-transfer approach to deliver physiologic levels of recombinant proteins to the systemic circulation would represent a significant advance in the treatment of these disorders. Here we describe the construction of a replication-defective adenovirus (AdEF1hEpo) containing the human erythropoietin (hEpo) cDNA under the transcriptional control of the cellular elongation factor 1 alpha (EF1 alpha) promoter and the 4F2 heavy chain (4F2HC) enhancer. Neonatal CD-1 and adult SCID mice injected once intramuscularly (i.m.) with 10(7) to 10(9) plaque-forming units (pfu) of this virus displayed significant dose-dependent elevations of serum hEpo levels and increased hematocrits, which were stable over the 4-month time course of these experiments. Adenovirus injected i.m. remained localized at the site of injection and there was no evidence of either systemic infection or a localized inflammatory response. These results suggest that i.m. injection of recombinant replication-defective adenovirus vectors may serve as a paradigm for the treatment of human serum protein deficiencies.