DESCRIPTION (Verbatim from the application): The goal of these studies is to use in vivo panning methods with phage display libraries to identify homing peptide for the heart neovasculature, the coronary endothelium and the endocardium. We wish to use these peptides, especially the prototype RGD neovascular homing peptide, as ligands to target retrovirus and HIV lentivirus vectors to those tissues. We will also examine a method for selecting more efficient RGD-targeted vectors from a combinatorial retrovirus library. Finally, we propose to characterize the biodistribution of these targeted vectors by sensitive fluorescence methods and correlate vector attachment with sites of endothelial-specific gene expression.