179. Helper-Dependent Adenovirus-Mediated Gene Transfer of an LDL Receptor/Transferrin Chimeric Protein Reduces Aortic Atherosclerosis in LDL Receptor-Deficient Mice

Familial hypercholesterolemia (FH) is a well-characterized genetic hyperlipidemia due in most of the cases to mutations in the LDL receptor (LDLR) gene; FH is characterized by elevated concentration of plasma LDL cholesterol (LDL-C) with consequent deposition of LDL-C in tendons, skin and arteries. Statins can lower cholesterol levels but are not effective in all patients whose prognosis is still quite poor. In the past, we have developed safe and effective gene-therapy strategies for hepatocytes transduction and consequent expression of anti-atherogenic proteins using PEGylated helper-dependent adenoviral (HD-Ad) vectors. We have recently devised a therapeutic strategy for reducing LDL using a secreted protein that can potentially be expressed in non-hepatic tissues used as bioreactors. At this aim, we developed an HD-Ad vector for the expression of the soluble form of the extracellular portion of the human LDLR fused with transferrin (LDLR/Tf). We evaluated the efficacy of LDLR/Tf in cellular models such as CHOldla7 in which we restored the cell ability to uptake of labeled LDL; subsequently, we administered intravenously 1X10E11 vp/kg of the HD-Ad vector expressing LDLR/Tf in LDLR-deficient mice and demonstrated the efficacy of the above-mentioned vector in reducing total and LDL cholesterol levels; in addition, expression of LDLR/Tf significantly reduced aortic atherosclerotic lesions in treated LDLR-deficient mice compared to controls 1.78±0.48 vs. 5.38±0.54 sq.mm.). We therefore demonstrated the efficacy of serum secretion of LDLR/Tf in reducing aortic atherosclerosis in FH mice. These results will allow the evaluation of HD-Ad vector-mediated expression of LDLR/Tf in non-hepatic tissues using alternative routes of administration in order to develop safer gene transfer protocol more compatible with clinical applications.