Human Gene Therapy

Melissa Gross

Copyright 1999

Image what it would be like if doctors could cure Huntington's disease, muscular dystrophy, or even hemophilia. Could this be possible? With gene therapy this all could be reality in the near future. Gene therapy is a potential approach to the treatment of genetic disorders in humans. This is a technique where the absent or faulty gene is replaced by a working gene, so the body can make the correct enzyme or protein and consequently eliminate the root cause of the disease (BIO, 1990).

There are two types of gene therapy treatment: Somatic cell gene therapy and germline therapy. Somatic cell gene therapy involves obtaining blood cells from a person with a genetic disease and then introducing a normal gene into the defective cell (Coutts, 1998). This type of gene therapy does not prevent the disease from occurring in the next generation because it does not affect the sperm and egg cells. Somatic cell gene therapy only effects the other body cells. Somatic cell gene therapy has to be done several times over the coarse of the patient's life because the effects do not last very long.

The contrast of somatic cell gene therapy is germline therapy. Germline therapy takes place in the reproductive cells. It involves the genetic modification of germ cells that will pass the change on to the next generation (Wilson, 1997). This type of gene therapy only has to be done one time to be permanent. One type of germline therapy is to treat a pre-embryo that carries a serious genetic defect before it is placed back in the mother by in vitro fertilization. Another germline therapy is to treat adult sperm and egg cells so the genetic defect is not passed on to children (Coutts, 1998). If a genetic change occurs, it will effect the next generation. This raises many ethical questions. The next question in gene therapy is how is the genetic material delivered to the appropriate cells in the patient? And also how do you make the delivery specific and safe? The first step in gene therapy is an accurate diagnosis of the genetic defect. This is done by using a DNA probe. The DNA probe is specific to a complementary piece of DNA. This technique using DNA probes is more specific then other conventional methods of diagnosing genetic defects in humans (BIO, 1990). After the correct diagnosis is made, healthy DNA can be inserted into a virus, which has had infectious genes stripped out of it. The virus is then mixed with cells taken out of a patient and then injected back into that patient. Viruses are used because they are like genes, but wrapped in a special protein coat. On the surface of this protein coat are specialized proteins that bind to the surface of cells. Once these viruses are in the body they lock in place on specific cells. The cells then suck the viruses in or the viruses force their way into the cells (PBS).

A retrovirus is a type of virus that is used in gene therapy. This is a virus that inserts its genetic code directly into the chromosomes of the host cell (PBS). Other viruses are used for different kinds of genetic problems. One of these is the adenovirus which is used for cystic fibrosis patients (Coutts, 1998). To use a virus in gene therapy, the patient's immune system has to be weakened so it will not fight off the virus. If weakening the patient's immune system is not an option then there are other vectors that can be used instead of viruses to perform gene therapy. An other gene therapy technique that doesn't use viruses is to encapsulate the DNA into fatty liposomes. This process works because the cell's membranes are made up of fatty materials so the liposomes can move across the membranes into the center of the cell. Then the liposomes will release their DNA material into the cell. Also the new DNA can be introduce directly into the skin cells or tumor cells. Neither liposomes or direct DNA injections are as effective as viruses used in gene therapy (PBS).

There are several ethical and legal issues involved in gene therapy. The Recombination DNA Advisory Committee (RAC) is a review board that was created to regulate research projects involving recombinant DNA, handle gene marking research, and review all gene therapy protocols. The Food and Drug Administration (FDA) works with the RAC on guidelines involved on human experiments (Coutts, 1998). Some of the ethical issues in gene therapy stem from germline therapy techniques. This is because germline gene therapy involves too much scientific uncertainty and risks. The long-term effects of this type of therapy are unknown. Also this type of gene therapy could bring about altering other human traits that are not associated with the disease. With germline therapy, the next generation of offspring from the parents does not consent to the treatment. The cost for this germline gene therapy would be so high that only the upper class of society would be able to even afford it (Coutts, 1998).

There are arguments for germline therapy because it truly is a cure for patients that have no hope of living a "normal" life. Germline therapy also may be the only way to deal with some genetic problems. Since germline therapy cures genetic problems generation after generation there is no need to do somatic cell gene therapy in every generation. Parents with a genetic disease will not have to worry about passing their defective genes on to their children (Coutts, 1998). Germline gene therapy has caused a conflict in the medical community on whether or not it should be used.

There are other problems with gene therapy that involve the right to privacy of people with genetic diseases. Insurance companies may want to know in the future if clients have genetic defects. The insurance companies could then turn down people because gene therapy is a very costly procedure. The cost of caring for a child with a genetic defect is a burden to society so should we allow germline gene therapy so our medical costs will go down. Also how can one say whether the gene modification is "good" or "bad"? There is also the potential that this therapy will be abused in the future if it is not closely regulated. Once gene therapy has been done, the patient will have to be monitored for several decades to make sure this is not harmful to other generations having the same therapy. This could be hard to do because once the patient believes the problem is gone they may not feel the need not to go to the doctor or may not have the resources to go to the doctor for a long period of time. Gene therapy would also be done on many children who might be too young to understand the ramifications of the procedure (Coutts, 1998).

A very limited number of patients now receive gene therapy. There are several regulations involved in the process of selecting who can receive gene therapy. Some of these rules are that the disease has to be a life threatening and incurable. The cells affected by the disease have to be identified. The defective gene has to have its normal counterpart isolated and cloned. This normal gene has to be able to be introduced into the cells of the effected tissue, and these cells should somehow alter the disease. The gene has to be expressed properly so it will be able to direct the normal protein and make a difference in the disease. All of the techniques in the procedure have to be verified for safety (Coutts, 1998). What will happen when more people learn about this therapy and want to have it done? The regulation could become easier so more people will be able to take advantage of this procedure. This could cause a problem if people think they can start changing their genes for cosmetic reasons.

There are many issues to think about when dealing with gene therapy. My opinion is that somatic cell gene therapy could be a very useful device in helping people with serious genetic diseases. People that have a life threatening genetic disease should be allowed to have a cure. Even though somatic cell gene therapy is a life-long treatment plan, I feel people would do this if it would make their life better and longer. I don't feel as strongly about germline therapy because the effects will effect future generations to come. This could have very danger effects on the future if it was used wrongfully. No one knows the long-term effects either of these treatments could have so I think the medical community should proceed with caution. I do think there needs to be very strict regulations on these types of therapies. If there is no strict regulations, I believe down the road there could be negative effects on the human species. These regulations would stop people from changing their appearance or IQ which I feel should never be altered because this is not life threatening. If people get the opportunity to change these traits, then the population would have less genetic diversity. This could be devastating to humans.

I also feel that insurance companies do not have the right to find out if people have genetic defects. This would be devastating for several people because they could be denied benefits. People have the right to privacy and insurance companies don't need to know this information. I also believe that the cost of this treatment should not be out of reach for the average person. If only the rich are able to have access to this treatment, its impacts will not be as great as they could be. Everyone should be allowed access to gene therapy if they have a serious genetic disease. Parents of children with genetic diseases should be able to decide if their children should undergo this procedure. When the children get up to a certain predetermined age where they will be able to understand the effects of the therapy, they should then be allowed to make their own decision. There are many thoughts that have to go into this procedure, and I think people should be careful when considering a life altering gene therapy.


1. Biotechnology Industry Organization, 1990. Gene Therapy An - Overview. Obtained from TheWWW.10/16/99:
2. Coutts, M.C., Human Gene Therapy. Obtained from the WWW. 10/16/99:
3. PBS On-Line. What is Gene Therapy. Obtained from the WWW. 10/16/99:
4. Wilson, J. IHGT The Institute for Human Gene Therapy. Obtained from the WWW. 10/16/99:

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