ADDITION OF A SHORT PEPTIDE LIGAND TO THE ADENOVIRUS FIBER PROTEIN

A major concern associated with We use of recombinant adenoviral vecto rs is that viral receptors are found on the surface of many cell types and systemic in vivo delivery of the viral vector could result in unc ontrolled and widespread expression of therapeutic molecules in many t issues, To construct a cell-type specific recombinant adenoviral vecto r a new binding specificity must be added to the virus, and the endoge nous binding specificity of We virus must be ablated. In order to intr oduce a new binding specificity to recombinant adenoviral vectors, We coding sequence of a physiological ligand, the terminal decapeptide of the gastrin releasing peptide (GRP), was placed at the 3' end of the coding sequence of the adenovirus type 5 fiber gene. The resulting fib er-GRP fusion protein was expressed using a T7 vaccinia expression sys tem and has been shown to assemble protein trimers whose quaternary st ructure is indistinguishable from that of wild-type protein. The fiber -GRP fusion protein was correctly transported to the nucleus of HeLa c ells immediately after synthesis. The added GRP ligand in the fiber-GR P fusion protein was accessible to binding by an anti-GRP antibody in both the monomeric and trimeric forms of We chimeric protein. These st udies suggest that new cell type specificities for adenovirus binding might be introduced by genetic fusion of peptide ligands on to the car boxyl terminus of the adenovirus fiber protein.