Ad Vector Targeting Utilizing Capsid-Incorporated Single Domain Antibodies

DESCRIPTION (provided by applicant): Adenovirus vectors are employed in a wide range of gene therapy and vaccine applications due to several attractive features such as high titer attainment, 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. Essentially this embodies the genetic modification of adenoviral capsid proteins to allow the incorporation of suitable targeting moieties to re-direct tropism. As a means to optimize Ad vector utility in this manner we have technology that allows radical genetic modification of fiber. Specifically we have the ability to genetically de-knob the fiber and re-trimerize with fibritin motifs. The removal of the constraining knob allows the chimeric fiber to incorporate complex ligands that can re-direct tropism of the Ad vector. Targeting motifs of interest include antibody-related molecules as they embody unparalleled affinity and specificity for recognition and binding to target cell surface markers as well as embracing a wide spectrum of characterized targets. In this regard, the emerging class of humanized single domain antibodies (dAbs), based on the variable regions of heavy or light chains of immunoglobulins, are of interest as they are small, robust and soluble, a factor which potentially overcomes cytosolic redox problems, i.e. misfolding of antibody fragments, that derive from being incorporated into fiber, a protein that is routed through the cytosol. The development of a tropism modified Ad vector will involve genetic incorporation of a dAb species into fibritin modified fibers, and demonstrate that the dAb retains the function of antigen recognition within the constraints of an Ad capsid protein. We will explore the capacity of the Ad vectors to target and deliver genes in a CAR-independent, receptor specifc manner in in vitro systems. Our studies will establish the employment of genetically incorporated dAbs into the fiber as a means to improve Ad vector capacity through cell specific targeting. We view the creation of our dAb targeted Ad vector as a major progression forward to furthering the utility of Ad in vivo for vaccine and gene therapy applications.