Molecular Imaging of Gene Therapy

Abstract

Molecular imaging techniques that emerged in biology as a means to monitor intracellular trafficking and interaction of macromolecules have lately become a powerful tool also for detection of transgene delivery by viral vectors. The necessity of monitoring and quantification of vectordelivered transgene expression prompted development of new generation viral vectors. Those encoded a special class of reporter genes whose expression in vector-targeted cells and tissues allowed quantitative assessment of vectormediated gene transfer and thereby a noninvasive real-time tracking of the viral vectors at the tissue and the whole-body levels. Those imaging reporters are classified in this review according to their biochemical nature, type of the generated imaging signal, substrate requirements, and type of tracer/substrate used for signal generation. This chapter reviews imaging strategies, used for adenoviral vectors, as a major class of gene therapy vectors, as well as other (nonadenoviral) common virus-based vector systems. Special attention is given to imaging strategies, used to monitor replicative vectors for oncolytic therapy applications. One of those is a new approach of genetic capsid labeling that potentially allows for direct monitoring of the viral progeny particles, as opposed to reporter transgene expression, typically used in vector imaging. The major advancements in imaging vector development are reviewed in the context of their applications for research and clinical purposes.