Viral imaging in gene therapy: Noninvasive demonstration of gene delivery and expression

Gene therapy is a rapidly developing modality of treatment, with applications in acquired and inherited disorders. Gene delivery vehicles ("vectors") are the main impediment in the evolution of gene therapy into a clinically acceptable mainstream therapy. Vectors based on viral particles are the most commonly used vehicles to carry genes to the organs and tissues of interest. Despite initial promise and substantial progress in the development of experimental gene therapy protocols, human gene therapy still is based on technologies that so far do not allow for routine clinical use. Recent progress in viral vector production and better understanding of molecular aspects of vector delivery and targeting issues has created the need for imaging techniques that would be useful in addressing the problems and opportunities inherent in viral gene therapy development. Two integral components of gene therapy monitoring, the imaging of gene delivery and the imaging of resultant exogenous gene expression, are recognized. These molecular imaging components provide a realistic means for assessment of safety and efficacy of preclinical and clinical development of gene therapy.