Targeting adenoviral vectors to cells expressing EGFRvIII using a single chain antibody fused to pIX

Current adenovirus retargeting strategies are unable to target the virus to specific cell types. In this study, we investigated whether fusion of a single-chain antibody, MR1, to the capsid protein IX (pIX) could target the virus to cancer cells expressing EGFRvIII. We show that addition of an endoplasmic reticulum signal peptide to pIX-MR1 significantly increased the ability of the fusion protein to bind its ligand. Use of the human CMV promoter rather than the native pIX promoter permitted a greater accumulation of the protein within the cell. Finally, addition of the HIV-1 Tat NLS caused pIX-MR1 to relocalize to the nucleus, the site of capsid assembly. Taken together, these results provide a foundation to design Ad vectors targeted to specific cells through the use of single-chain antibodies. Ultimately, the development of a tropism modified Ad vector would result in a tailored treatment for a particular acquired genetic disease