Alan McClelland

Phenotypic Correction of Hypercholesterolemia in ApoE-Deficient Mice by Adenovirus-Mediated In Vivo Gene Transfer

To investigate the potential use of apoE in gene therapy of hyperlipidemias, an adenoviral vector was constructed that contained the human apoE3 cDNA under the control of the RSV promoter (Av1RE). Transduction of HepG2 cells resulted in the overexpression of human apoE secreted into the culture medium. Intravenous injection of 5 x 10(11) Av1RE vector particles into apoE-deficient mice resulted in expression of human apoE3 in mouse plasma at levels of 1.2 +/- 0.4 micrograms/L (mean +/- SEM, n = 5) 7 days after injection. Mice injected with the control vector Av1Lacz4 did not express detectable levels of human apoE. Average plasma cholesterol concentrations were reduced approximately eightfold from 737.5 +/- 118 mg/dL (mean +/- SEM, n = 6) to 98.2 +/- 4.4 mg/dL (mean +/- SEM, n = 5) and were unaffected in the control vector group. Expression of human apoE resulted in a shift in the plasma lipoprotein distribution from primarily VLDL and LDL in the control mice to predominantly HDL in the Av1RE-treated group. Western blot analysis of fast protein liquid chromatography-fractionated mouse plasma showed that the human apoE protein was associated with VLDL, LDL, and HDL. Correction of the hyperlipidemic condition found in the apoE-knockout mouse strain by direct in vivo gene transfer establishes the potential of this approach for treatment of hyperlipidemia caused by apoE deficiency or malfunction in human disease.

Adenoviral Gene Delivery Approaches for Systemic Expression

Somatic cell gene therapy is being developed for many single gene disorders including hemophilia, cystic fibrosis, and familial hypercholesterolemia as well as for multifactorial disorders such as cancer and cardiovascular disease. Adenoviral-mediated gene delivery has been used to achieve the systemic expression of several transgenes in animal model systems. Systemic effects may be achieved either by expression of genes whose protein products are secreted into the bloodstream or by the local cellular expression of genes in organs such as the liver whose expression then produces systemic effects. This chapter will review recent developments in the use of adenoviral-mediated gene expression to influence cardiovascular risk factors. The adenovirus gene delivery approach will be considered both in terms of its use as a research tool, and as a potential clinical approach to understanding and treating cardiovascular disorders.