The definition of gene therapy is a "technique where the genes causing a defect are themselves substituted by correct genes in the patient to cure a disease" (Macer, 1990).
At birth each of us receives a set of chromosomes that contain the genes that code for our personality, appearance, and long term-health (Becker,1996). When one of those genes has a mutation or flaw in the DNA structure it can lead to disease. Some diseases related to genetic inheritance are diabetes, sickle cell anemia, and some cancers. With gene therapy we can eliminate these diseases before they even show their fist symptom.
There are two types of gene therapy treatments. They differ in the consequences they have for the patients. The first is somatic cell gene therapy. In this process faulty genes are replaced by the correct sequence of genes. The body can then make the correct protein and ultimately eliminate the faulty gene causing the disease. It is only necessary to treat enough cells to provide adequate amounts of the correct protein so that some reach the site of action (Macer, 1990).
Somatic gene therapy is only corrective to the patient and cannot be passed on to the net generation. This is because any rearranging of genes happens in the somatic or non-reproductive cells (BIO, 1990).
The net type of gene therapy takes place in the reproductive cells or germline cells. The term germline therapy is used to describe the form of gene therapy where the correct gene is inserted into the reproductive cells. Therefore when the treated individual reproduces his or her offspring will have the correct gene instead of the defected one. This treatment affects both the parent and the offspring. It is also possible to insert a manipulated gene into an early embryo so this new individual will have the correct gene sequence. This treatment only affects the embryo. One thing to remember is that germline therapy not only affects the individual but their potential offspring as well (BIO, 1990). Thus germline therapy is passed on into the gene pool of future generations.
The challenge in gene therapy is how to get the correct genetic material to the appropriate cells. According to Encyclopedia Britannica online 1998 there are three types of delivery systems- a viral vector, a chemical method or a physical method. The most common and accurate is a viral vector. Technology has developed vectors, which encapsulate therapeutic genes, in order for delivery to defected cells.
Many vectors are actually viruses. Viruses are efficient in targeting cells and delivering information. According to PBS online 1998, viruses are actually genes wrapped in a protein coat. This protein coat is unique since it has special proteins that bind to the surfaces of cells. Once bonded they either force their way in or are sucked into the cell itself. The virus can either be mixed with cells taken out of the body or they can be injected directly into the body.
One type of virus actually inserts its genetic code directly into the chromosome of the host cell. This classification of virus is called a retrovirus. The retrovirus infects the cell and changes the cells defective genes with the new substituted genes. By integrating the old and new genes it is possible for the new "good" genes to take over the chosen cells. These cells are taken out of the body, allowed to grow and then reinserted into the body (Becker, 1996). The result is hopefully the new gene takes over the body and all that remains are cells with the correct gene.
One consequence of using a virus, as a vector is the body can not tell the difference between a good virus and a bad one. So the immune system attempts to wipe out the virus. Thus the immune system must be weakened before the gene therapy can take place. Another approach besides the retrovirus is to encapsulate the DNA in a fatty liposome. This works as a vector since the cell wall is made of fatty lipids and the liposome can move across the membrane into the cell where it releases the DNA. This approach is less efficient than the retrovirus since the encapsulated DNA does not target a specific cell.
Ethical as well as legal issues are concerns when discussing gene therapy. A review board know as the Recombinant Advisory Committee (RAC) has been developed to address the concerns related to gene therapy (Becker, 1995).
The positive aspect of gene therapy is apparent. It can wipe out genetic disease before they can begin and eliminate suffering for future generations. Gene therapy is also a good technique for diseases not researched yet. All of us carry defected genes and may not know it. Gene therapy is a 'medicine" for the future since it can control or eliminate hereditary diseases.
The consequences of gene therapy are numerous at this time. As with anything not researched there are critics. The first issue targets putting human fate in our own hands - giving us the ability to manufacture future generations. Some people are concerned that gene therapy will be used to create a superior race. This is termed eugenics. This is not the goal of geneticists. The idea of gene therapy is to cure hereditary diseases not make any one person or race superior.
Another consideration is religion. Some consider it sinful to manipulate DNA. In reality gene therapy is just that- a therapy. It is a new form of advanced medicine. Gene therapy is completely up to the individual in question. If religion is a factor then somatic cell therapy should be applied. This allows the next generation to make their own decision.
Some groups claim that regulations will be hard to control, even with laws there is the possibility gene therapy could become available on the black market. It could be used for any genetically linked trait such as eternal appearance, personality, or physical enhancement. These concerns will have to be dealt with in time.
The cost of gene therapy is high at this time and could be a concern for families with that need lifelong treatment and do not have health care. Gene therapy will probably be cheaper in the ling run since it is a one time only procedure. It will eliminate suffering for the individual and possibly their children.
Invasion of privacy is also a concern for many. Insurance companies could make it mandatory to have genetic screening before a policy before they issue a policy. This could cause discrimination to families with genetic diseases. Or potential employers could question a person's genetic background and pass them up for a promotion or job. These are all good reasons to use gene therapy and eliminate the controversy before it starts.
The last and most important concern is the risk of the procedure. It is still in the developmental stage. Finding the precise location of the defected gene is still under research. Any miscalculation could cause a risk of a new disease such as cancer to form.
2. PBS On-Line. 1998. What is Gene Therapy. Obtainined fromn the WWW: http://www.pbs.org/wnet/innovation/show1/html/2sb-therapy.html
3. Macer, DRJ. 1990. Shaping Genes: Ethics, Law and Science of Using New Genetic Technology in Medicine and Agriculture. Obtained from the WWW: http://www.biol.tsukuba.ac.jp/~macer/SG14.html
4. Wilson, J. What is Gene Therapy. 1997. Obtained from the WWW: http://www.med.upenn.edu/ihgt/info/whatisgt.html