ABSTRACT
Gene therapy can be broadly defined as the transfer of genetic material to cure a disease or at least to improve the clinical status of a patient. One of the basic concepts of gene therapy is to transform viruses into genetic shuttles, which will deliver the gene of interest into the target cells. Gene therapy has progressed from a dream to a bedside reality in quite a few human diseases. From its first application in adenosine deaminase deficiency, through the years, its application has evolved to wide variety of diseases. Based on the nature of the viral genome, these gene therapy vectors can be divided into RNA and DNA viral vectors. The majority of RNA virus-based vectors have been derived from simple retroviruses. A major shortcoming of these vectors is that they are not able to transducer nondividing cells. This problem may be overcome by the use of novel retroviral vectors, such as human immunodeficiency virus [HIV]. The most commonly used DNA virus vectors are based on adenoviruses and adeno-associated viruses. Although the available vector systems are able to deliver genes in vivo into cells, the ideal delivery vehicle has not been found. Thus, the present viral vectors should be used only with great caution in human beings and further progress in vector development is necessary. The Food and Drug Administration [FDA] has not yet approved any human gene therapy product for sale. Current gene therapy is still in experimental stage and has not proven very successful in clinical trials