Adenovirus vectors are employed in a wide range of gene therapy and vaccine applications due to several attractive features such as high titers, structural stability, broad infectivity, established protocols for genetic manipulation and high levels of transgene expression with lack of host genome integration. However development of these vectors in the clinical context has highlighted that vector efficacy would be improved by cell specific targeting and by shielding against host humoral responses. As a means to optimize Ad vector utility in this manner we have technology that allows non-covalent attachment of functional moieties in a pharmacological manner. Specifically we have the ability to genetically incorporate IgG binding domains into the adenoviral capsid permitting interaction with ligands that can provide the duality required such as Fc- fusion proteins or humanized antibodies. We have identified the minor capsid protein, pIX, embodying such genetic incorporation utility. This protein is of high valency within the adenovirus capsid and would therefore provide numerous but defined attachment sites to interact with a targeting protein, and thus confer a concealing effect on an Ad vector. The resulting targeted shielded Ad vector would therefore have uniformity in the quantity of Fc-fusion proteins or humanized antibodies, an essential element in the scaling up of a clinical product. The development of our targeted shielded Ad vector would involve genetic incorporation of a modified IgG binding domain from Staphylococcus aureus protein A into the pIX capsid protein, and demonstrate that targeted gene transfer can be achieved utilizing Fc-fusion proteins. We would modulate fiber to optimize the spatial array of this locale and improve accessibility of pIX-ligand interactions with target cells. Finally we will explore the capacity of our Ad vector to conjugate with humanized antibodies and examine the stability of this complex and the ability of our Ad vector, to evade neutralizing antibodies by retained targeted gene transfer in in vitro systems. Our studies will establish the employment of Fc-fusion proteins or humanized antibodies conjugated to a genetically incorporated attachment moiety in a specific capsid protein to improve Ad vector capacity. We view the creation of our targeted shielded Ad vector as a major progression forward to furthering the utility of Ad in vivo for vaccine and gene therapy applications. ? ? ? ?
