Chapter 12 : Genetics, Intervention, Control, and Research
|Section 1. Case Presentation|
Case Presentation 1
The Birth of Gene Therapy
prepared and written by Mark Riddagh (SCCC, 2006) using Ronald Munson's
Intervention and Reflection as a guide.
On Sept. 14, 1990, gene therapy was essentially born with the effective treatment of a four-year-old girl from Bethsaida Maryland. Her name is Ashanthi Desilva and she was born without the gene that produces adenosine deaminase or ADA, an enzyme necessary for proper immune functioning. Her prognosis was poor in 1990, as she would almost assuredly build up cancers and infection that current medicine could not effectively treat. Without ADA, she would certainly not survive for very long.
Treatment came in the way of replacing the gene that Ashanthi lacked. By removing some blood cells and infecting them with a weakened retrovirus spliced with a copy of the gene that controlled ADA production, the re-injected cells would theoretically carry the gene to the DNA of neighboring cells and hence the production of ADA would occur naturally. If enough ADA could be produced, Ashanthi’s prognosis would drastically change for the better. However, the short lifespan of the T-cells, from weeks to months at best, meant that the process would need to be repeated regularly. Nevertheless, nine-years after her initial treatment, Ashanthi is alive and healthy.
The following January, a nine-year-old named Cynthia Cutshell became the second person to receive gene therapy for lack of the ADA producing gene. Like Ashanthi, Cynthia was also given retrovirus-infected cells containing a copy of the ADA producing gene, which seemed to sustain her as long as the regular injections continued. Soon her treatment took a slightly new direct from that which Ashanthi had received. By isolating stem cells from the bone marrow, their genetic alteration might produce enough T-cell to permanently correct the lack of ADA production and thereby cure Cynthia of the defect.
In May of ’93, Cyhthia’s stem cells were harvested and infected with the retrovirus containing the ADA producing gene. After injected back into the child, she showed no sign of negative reaction to the procedure. Additionally, after years of what appeared to be effective ADA production for Cynthia, Ashanthi received the same procedure. Both girls currently experience normal immune system functioning, however assessment of the final procedure has not been determined since both girls also receive treatment in the form of standard drug regimens. Supporters of the therapy, however believe that Ashanthi and Cynthia have been successfully and genetically cured of a condition that would have previously proved fatal.
Case Presentation 2 Huntington’s Disease: The Fulfilled promise and Consequences of Genetic Research prepared and written by Mark Riddagh (SCCC, 2006) using Ronald Munson's Intervention and Reflection as a guide.
Huntington’s disease (HD) affects up to 30,000 people in the United States and another 150,000 can possess the gene responsible for it at any given time. Although the incidence of the disease is only 1 out of every 10,000 people, every child born to a parent who carries the gene has a 50% chance of developing the disorder.
A particularly vicious condition, Huntington’s disease originally manifests in mild clumsiness accompanied by facial twitches and a slight slurring of speech. As it progresses however, the victim becomes more disoriented, engages in unfounded outbursts of emotion and eventually loses the ability to speak. Furthermore, advanced mental deterioration and death will soon follow, provided the victim does not commit suicide from depression, a common occurrence with victims of the merciless disease.
There is currently no effective treatment for HD, which makes diagnosis all the more bleak for its victims. In 1993, however, due to the miracle of genetic research, the gene which causes HD was successfully identified. The process took 10 years of extensive research in genetic laboratories in England, Wales and the United States but success eventually came in the form of genetic markers, which pointed to a gene at the tip of chromosome 4. When the nucleotides were sequenced, a trinucleotide repeat (mutation) was discovered. A healthy person will have the nucleotide CAG repeated anywhere from eleven to thirty-four times. A person with HD however, will have the same repeated from thirty-seven to eighty-six times. Additionally, they found some evidence to suggest that higher repetitions are correlated with an earlier onset. Commonly, the initial symptoms of HD occur in people between 35 and 45 years of age. Tragically, this means that many have already passed on the gene to their children before realizing that they themselves are carriers.
When originally identified, researchers expected that the responsible gene would function only in the brain, but radioactive tagging shows it functioning in the colon, liver, pancreas, testes and virtually in every tissue of the body. This misunderstanding of the gene’s functioning has resulting in the delay of an effective treatment. Moreover, the gene has been found to code for a toxic plaque producing protein, which destroys neural development. Unfortunately, this precise protein has yet to be isolated.
Since the gene is commonly passed on, undetected to the following generation, a genetic test for gene identification would be an essential tool in HD prevention. The discovery of the "genetic marker," indicating the gene’s presence, has been instrumental in a successful realization of this goal. James Gusell of Massechusetts General Hospital and his team of researchers successfully located the markers that pointed to the HD gene in 1983. By studying a family with an HD history, DNA segments, containing the HD gene were finally located. With support from the Hereditary Disease Foundation, Gusella’s "genetic marker" was additionally tested in a much large population and the results further supported his findings. Additional work by Susan Naylor indicated the marker to be on chromosome 4 and when the actual gene was identified in 1993, both researchers’ findings were substantiated.
After the location of the HD gene was established, a test to detect its presence soon followed. Unfortunately, the successful creation of the test gave birth to many ethical and social dilemmas. Studies show that those with HD parents did not want to know if they themselves possessed the deadly gene. Since the disease is fatal with no effective treatment, those at high risk had no desire to be aware of their potential fate. Because of the prospective trauma associated with receiving a positive test result, many have decided the tragic condition would not be worth knowing. The other end of this ethical spectrum focuses on one’s duty to their future spouse and children if they are indeed a carrier. Are high-risk individuals obligated to inform their potential spouses of the possible future they may face together? Without this knowledge, one is robbed of the opportunity to avoid a life of anxiety and emotional turmoil and even more so, one does not have the option to avoid giving his or her children a 50% chance of contracting the disease themselves. In addition, the test in conjunction with amniocentesis can be used to determine whether a fetus is a carrier of the gene. This would be instrumental in assisting one’s decision to abort and thus avoid giving birth to a high-risk child.
There are other moral issues connected with the ability to perform such a test. Life and health insurance companies may require testing for those with a family history. They additionally, may opt to refuse coverage unless one can prove conclusively that he or she is not a carrier of the gene. What's more, adoption agencies have requested testing for infants in their care in an effort to avoid providing an HD carrier to an adopting family. Since the gene provides only a 50% that a child will later develop the disease, then theoretically, the 50% who will never have HD will be at a disadvantage without ever having the disease.
Furthermore, the high rate of suicide among HD victims must be considered when contemplating testing. Ten to twelve percent of HD victims eventually take their own lives. In many circumstances, the devastating news is more than the victims can bear and 30% of those found to have the gene claim that they will commit suicide if they do indeed contract the disease. This theoretically makes the knowledge of the disease a threat to life.
Siu Hei Szeto : Reproduction
This is a case study providing information of basic introduction of basic reproductive techniques and ethical issues surrounding the issue.
url's for the Articles Describing case:
Infertility and assisted reproductive technologies
url's for Articles with Ethical Position: Philosophers, Theologians, Lawyers, Medical Doctors
A religious view of the issue.
A bibliography with abstracts of articles on the subject.
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© Copyright Philip A. Pecorino 2002. All Rights reserved.
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