Gene Therapy

Michelle Nimsgern

Copyright 1998

The Human Genome Project began around 1986. The main goal of the project is to locate and sequence all genes found in human DNA. The objectives for this ambitious effort are to learn more about heredity of disease and to discover the genes that would aid in gene therapy. Advances in gene therapy strive to treat hereditary diseases and possibly eliminate disease from the genome.

The definition of gene therapy is the introduction of genes into existing cells to prevent or cure a wide range of diseases (Jaroff, 1996). Gene therapy has two possibilities of disease treatment, somatic gene therapy and germline gene therapy. Somatic gene therapy involves the manipulation of gene expression in cells that will be corrective to the patient but not inherited to the next generation. Germline gene therapy involves the genetic modification of germ cells, which pass the change on to the next generation (Wilson, 1998). Somatic gene therapy is currently being researched more aggressively due to ethical and technical complications with germline gene therapy.

Technical Aspects

Gene therapy began with the Human Genome Project. The Human Genome Project has found gene locations for many diseases. Among the diseases that have been found Huntingtonís disease, cystic fibrosis, ADA deficiency, and two genes for breast cancer are just a few examples. After a disease-causing gene is found, correcting it is the next logical step. This can be achieved through various methods. One of the first tested methods was to obtain the faulty gene from the patient, introduce the corrected gene into cells, and finally inject the altered cells back into a blood vessel.

Blood is taken from the affected individual to obtain cells with DNA carrying the faulty gene. A vector is then used to carry a healthy copy of the gene into the affected cells. Possible vectors are retroviruses. Retroviruses are specialized virus containing RNA that has a knack for finding its way into a cellís genome and making itself at home (Elmer-Dewitt, 1994). This vector is optimal because it can be genetically engineered to not infect the patient with the virus, but it will carry the corrected gene in the RNA. When the retrovirus attacks affected cells, it will commence replication, replacing the affected gene with the corrective gene. The healthy cells are then injected into the patient to continue replication in the body.

An example of this procedure was first demonstrated in 1990. The patient was a four-year-old girl. She had severe immune-deficiency disease caused by a faulty gene that failed to order the production of a vital enzyme. (Jaroff, 1996) Some of the white blood she carried were extracted and introduced to genetically engineered viruses containing healthy copies of the gene. The viruses performed as expected and attacked her white blood cells. The cells were then injected back into her bloodstream. The newly corrected genes began producing the proper enzyme. The problem that arose with this particular procedure was she was not cured, because the altered cells did not reproduce and eventually died. They young girl needed treatment to be administered every one to two months, based on the lifespan of the cells containing the corrected gene. Treatment did make it possible for this child to lead a relatively normal childhood.

To achieve a cure, bone-marrow stem cells are necessary. Bone-marrow stem cells make all the bloodís white blood cells, which means the genetic information is passed on to the new cells. The major complication with this procedure is that vectors can insert genetic information only into dividing cells, and stem cells divide infrequently. The infrequency makes it difficult to pinpoint when the vector should be introduced.

It is speculated that genes of an organ can also be altered. One strategy is to take a piece of the organ and divide it into individual cells. Insert the corrected gene into the cells and transplant the cells into the patient. A second strategy is to develop vectors that can find their own way to diseased tissue inside the body. The vectors would be referred to as smart vectors. This type of procedure would consist of directly injecting the new generation of vectors into affected patients. The smart vectors would then carry corrected genes to their targets, similar to the action of guided missiles. This could be achieved by attaching molecules to the vector, which recognize specific proteins found on the surface of cells in the target organ (Grace 1998).

The methods discussed above involve replacing bad genes with good genes. Another method of gene therapy is antisense therapy, which would add a gene that mirrors the target gene. This strategy would be effective if the cells produce unwanted proteins. In antisense therapy, the engineered gene produces RNA that complements the RNA of the troublesome gene, binding onto it and blocking its action (Grace 1998). Blocking the faulty gene action allows proper protein production.

The procedures mentioned above have been discussed throughout the medical profession and a few have even been proven as treatments, but there is a lot of work that still needs to be done in this field. The stage of identifying genes associated with disease has been established through research in the Human Genome Project. The next step is to put this knowledge to use by delivering corrective genes to their target areas in the body and controlling gene expression in the altered cells.

Good Advancement or Bad Advancement

Will my child be healthy? This is the main concern for many soon-to-be mothers. Everybody wants assurance their children will be born healthy and live long healthy lives. With the Human Genome Project, the knowledge is now accessible. All that is needed is a little drop of blood from the developing fetus, or if the question should arise after the child is born, a simple schwab from the inside of the childís mouth would acquire the necessary cells to discover what types of disease the child is predisposed to later in life.

Advantages of gene therapy are quite numerous. First of all, advances in the field have introduced treatments to various diseases that were previously thought to be hopeless. Secondly, gene therapy has brought about the production of medicines in mass quantities. The medicines are pure and much cheaper if technology allows it to be produced in large amounts. An example of this advancement is production of the interferon. Discovered in 1957, interferon is produced by cells in the human body in response to viral attack. It promotes production of a protein that stimulates the immune system, interfering with the spread of infection (Grace 1998). The insight was great for science but the downfall was the body produces the chemical in tiny amounts and to accumulate just one gram would take 90,000 donors. Even after all this effort, the product would only be 1% pure. In 1980, an experiment was conducted that allowed interferon to be produced in mass quantities. The interferon was introduced into bacteria. Cloning the altered bacteria made it possible to make millions of copies of the interferon at the low cost of just $1 per dose. This technique has also been applied to making insulin more compatible with people than the insulin from cattle and pigs, which caused allergic reactions in some patients.

What seems to be the most concerning aspect is the fact that technology is making it so easy to find out a personís genome. There have already been cases where insurance companies have obtained the information and then refused to insure the individual. One case was of a woman that discovered her unborn child had the gene for cystic fibrosis. Her insurance company informed her they would fund an abortion, but if she chose to have the child, they would not pay for treatments the child may require. This type of case is becoming more evident because there are no present laws protecting the patientsí privacy and rights.

Various ethics debates involved in gene therapy are controlling fate by altering germline cells and the effect of knowing oneís fate. Many debates are about altering germline cells. When germline cells are altered, they are altered to better the fate of the child. Many people do not believe it is right to take control of fate. Others believe we were given the knowledge and ability to better a childís fate. Another debate concerns the devastating affects of knowing oneís ill fate. Depending on the person, they may either decide to live life to the fullest, or they may just give up. Is it in the patientís best interest to tell them their fate? It depends on the person.

My Opinion

I believe we were given the ability to better the human race by gaining the knowledge of how to use gene therapy. This ability was given to us so that we would use it. The only aspect I am concerned about is the possibility that we may limit our ability to adapt to ecological and environmental changes. In spite of this, I am enthusiastic about gene therapy. I want to live a healthy life and I want my children to be able to live happy, healthy lives. With gene therapy, the use of human cells to treat disease looks very promising. Who knows, by the time the environment does change, gene therapy may be so advanced that a simple injection could make us adapt to this change.

References

Elmer-Dewitt, Philip. The Genetic Revolution. Time. January 17, 1994. V 143. N 3. P (46-44).
Grace, Eric S. Better Health Through Gene Therapy. The Futurist. Jan-Feb 1998. V 32. N 1. P (39-43).
Jaroff, Leon. Keys to the Kingdom. Time. Fall 1996. V 148. N14. P (24-29).
Wilson, Jim. The Institute for Human Gene Therapy. Obtained from the WWW November 1, 1998:http://www.med.upenn.edu/~ihgt/info/whatisgt.html


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