Gene Therapy is the transfer of genetic material (gene transfer) to dysfunctional cells to correct a deficiency in the DNA or genome of a patient. Cell Therapy, such as stem cell therapy, is the transfer of normal or genetically modified cells to a diseased tissue in order to restore proper tissue function.
These approaches have been historically applied to treat genetic disorders, but they can also be used to treat diseases acquired over the lifetime of an individual, such as cancer or infection, where genes are transferred to confer a specific property to the cell allowing it to combat the disease.
Effective transfer of genetic material into human cells is perhaps the biggest challenge in Gene Therapy. A gene transfer agent has to be safe, introduce its DNA cargo into a sufficiently large population of cells to produce a biological effect and mediate expression of the desired gene for a sustained period of time. Identifying a gene transfer tool that meets all of these criteria has proven to be a difficult task.
Gene Therapy is normally used in diseases where the cells of a particular organ or system cannot function correctly due to the fact that they do not have an essential protein that is required to perform a specific task. In order to replace the malfunctioning protein, a gene transfer vector (such as a disabled adenovirus in the diagram above) is modified so that it contains the gene that encodes for this protein. The modified vector is then given to the patient where it enters the affected cells. The gene tranfer vector then transfers the therapeutic gene to the cell and the cell's own machinery turns the therapeutic gene into correct version of the protein, which in essence fixes the malfunctioning cell.
In gene transfer vector our section on we provide more information on the most widely used gene transfer systems studied to date. The information provided in those pages is targeted to non-experts in the field, with some knowledge in biology, and aims to provide a further educational tool for those wishing to learn about gene therapy.