Gene therapy for genetic diseases

Gene therapy provides the potential to permanently cure selected genetic diseases. However, a major obstacle is the effective delivery of the normal gene to specific target sites of pathology and continuous expression at therapeutic levels. A variety of viral and non-viral vectors have been developed to deliver genes to various cells, tissues and organs by ex vivo and in vivo strategies. Among the viral-based vectors, retroviruses, adenovirus, adeno-associated virus and herpes virus have been the most extensively studied. Among non viral-based vectors, liposomes have been used to introduce plasmid DNA directly into animals, and DNA protein conjugates are being developed to exploit receptor-mediated uptake pathways. Each of these gene delivery systems is reviewed here and their advantages and disadvantages compared. In addition, the current status and future prospects for human gene therapy trials for genetic diseases are discussed.