Basically gene therapy is an intracellular delivery of genomic materials (transgene) into specific cells to generate a therapeutic effect through correcting an existing abnormality or providing the cells with a new function. Many types of gene delivery systems have been applied in gene therapy to restore a specific gene function or turning off a special gene. The ultimate goal of gene therapy is single administration of an appropriate material to replace a defective or missing gene.
Figure 1. The gene therapies utilize modified AAV.
One of the successful gene therapy systems available today are viral vectors, such as retrovirus, adenovirus, lentivirus, adeno‑associated virus, herpes virus, human foamy virus (HFV), and pox virus. All viral vector genomes can be modified by deleting some areas of their genomes so that their replication becomes deranged and it makes them safer, but the system has some problems, such as their marked immunogenicity that causes induction of inflammatory system resulting in degeneration of transduced tissue. During the past few years some viral vectors with specific receptors have been designed that could transfer the transgenes to some other specific cells, which are not their natural target cells.