The present invention provides delivery vectors for transferring a nucleic acid sequence to a cell in vitro, ex vivo or in vivo. The delivery vector comprises a segment encoding a secretory signal peptide. In embodiments of the invention, the delivery vector is an adeno-associated virus (AAV) vector. In other embodiments, the secretory signal peptide is a fibronectin secretory signal peptide (including variations and modifications, thereof). The delivery vectors of the invention may further comprise a heterologous nucleic acid sequence encoding a polypeptide of interest for transfer to a target cell, where the polypeptide of interest is operably associated with the secretory signal. Also disclosed are methods of transferring a nucleic acid of interest to a cell using the delivery vectors of the invention.