Gene therapy is a very different type of genetic biotechnology application which involves the manipulation of genetic material, and the genetic manipulation of organisms, in the attempt to cure specific diseases. Gene therapy involves using normal, unmutated genes to replace copies of defective disease-causing genes, or in some cases to initiate or bolster an immune response to a specific disease (such as cancer).
Gene therapy treatments can be implemented in an individual in one of two ways.
The ex vivo method of treatment involves removing a sample of a patient’s blood or bone marrow, and growing the cells in a laboratory. The cells are then exposed to a virus which carries a normal copy of the relevant disease-causing gene. The virus then enters cells, and introduces the normal gene into cellular DNA. Next, the cells go through a second growth period before being injected back into the patient. After a successful gene therapy treatment, the patient has a normal copy of the relevant gene and is able to successfully make the protein the gene codes for.
In the in vivo method of treatment, cells are not removed. Instead, the patient is ‘infected’ with a non-infectious virus which has been genetically engineered to carry the required genetic material. The virus infects cells and introduces the gene into cellular DNA.
Currently the use of gene therapy is largely experimental, with well over five hundred clinical trials having been initiated in the last one or two decades. Many of these focus on treating various types of cancer, as well as genetic disorders.
There are problems and controversies associated with gene therapy, as with genetic testing. Perhaps the most controversial issue is that while non-infectious viruses are used as vectors, there have been very rare occasions where a virus has caused serious infection in patients.
Other problems include the fact that many genetic disorders are caused by disruptions in multiple genes, making it difficult, if not impossible, to devise effective treatment using current methods. In addition, there are many diseases which have environmental as well as genetic causes, such as cancers which are affected by diet and lifestyle choices.