QUANTITATIVE-EVALUATION OF LIVER-SPECIFIC PROMOTERS FROM RETROVIRAL VECTORS AFTER IN-VIVO TRANSDUCTION OF HEPATOCYTES

Hepatic gene therapy could be used to treat a number of inherited bloo d diseases such as hemophilia or thrombophilia. Although liver-directe d retroviral transduction can result in long-term gene expression in v ivo, the low level of protein production has limited its clinical appl ication. We reasoned that the insertion of liver-specific promoters in to retroviral vectors would increase gene expression in vivo. The 347- bp human alpha(1)-antitrypsin (hAAT), the 810-bp murine albumin (mAlb) , the 490-bp rat phosphoenolpyruvate carboxykinase (rPEPCK), and the 5 96-bp rat liver fatty acid binding protein promoters were inserted int o a Moloney murine leukemia retroviral backbone containing the hAAT re porter gene. Vectors that produced appropriately sized RNA and hAAT pr otein in vitro were tested in vivo by transducing regenerating rat liv ers. Long-term serum expression of the hAAT reporter gene was normaliz ed to retroviral transduction efficiency as determined by using a poly merase chain reaction-based assay of genomic DNA from transduced rat l ivers. The hAAT, mAlb, and rPEPCK promoters were, respectively, 35-, 8 -, and 0.02-fold as strong as the previously studied constitutive pol- II promoter. We conclude that the hAAT promoter resulted in the highes t expression from a retroviral vector and may result in therapeuticall y significant expression of other clinically significant blood protein s. (C) 1994 by The American Society of Hematology.