IN-VIVO CORRECTION OF LOW-DENSITY-LIPOPROTEIN RECEPTOR DEFICIENCY IN THE WATANABE HERITABLE HYPERLIPIDEMIC RABBIT WITH RECOMBINANT ADENOVIRUSES

A rabbit animal model of the human disease familial hypercholesterolem ia (FH), which is the result of low density lipoprotein (LDL) receptor deficiency, was used to develop an in vivo approach to gene therapy b ased on recombinant adenoviruses. Recombinant, replication-defective a denoviruses expressing the lacZ gene under the control of different pr omoters were infused into the portal circulation of New Zealand White (NZW) rabbits. Expression of lacZ could be obtained in virtually all h epatocytes within 3 days post infusion, but was undetectable by 3 week s. This was not associated with liver pathology, An LDL receptor expre ssing adenovirus was constructed using the most active promoter and wa s infused into the portal vein of rabbits deficient in LDL receptor. A nalysis of liver tissues harvested 3 days after virus infusion demonst rated human LDL receptor protein in the majority of hepatocytes that e xceeded the levels found in human liver by at least 10-fold. Transgene expression was stable for 7-10 days and diminished to undetectable le vels within 3 weeks. Infusion of LDL receptor expressing virus led to substantial reductions in serum cholesterol that returned to base line within 3 weeks; this acute reduction in serum cholesterol was associa ted with accumulations of lipid in hepatocytes. The development of neu tralizing antibodies to the recombinant adenovirus markedly diminished the effectiveness of a second dose. These studies illustrate the adva ntages of recombinant adenoviruses for the treatment of liver metaboli c diseases and define issues, such as viral genome instability and blo cking immune response, that need to be overcome before the promise of this technology can be fully realized.