In the 1980s, advances in
molecular biology had already enabled human genes to be
sequenced and
cloned. Scientists looking for a method of easily producing
proteins ！ such as
insulin, the protein deficient in
diabetes mellitus type 1 ！ investigated introducing human genes
to
bacterial DNA. The modified bacteria then produce the
corresponding protein, which can be harvested and injected in people
who cannot produce it naturally.On
September 14,
1990 researchers at the
U.S.
National Institutes of Health performed the first approved gene
therapy procedure on four-year old Ashanti DeSilva. Born with a rare
genetic disease called
severe combined immunodeficiency (SCID), she lacked a healthy
immune system, and was vulnerable to every passing germ. Children
with this illness usually develop overwhelming infections and rarely
survive to adulthood; a common childhood illness like chickenpox is
life-threatening. Ashanti led a cloistered existence--avoiding
contact with people outside her family, remaining in the sterile
environment of her home, and battling frequent illnesses with
massive amounts of antibiotics.
In Ashanti's gene therapy procedure, doctors
removed white blood cells from the child's body, let the cells grow
in the lab, inserted the missing gene into the cells, and then
infused the genetically modified blood cells back into the patient's
bloodstream. Laboratory tests have shown that the therapy
strengthened Ashanti's immune system; she no longer has recurrent
colds, she has been allowed to attend school, and she was immunized
against whooping cough. This procedure was not a cure; the white
blood cells treated genetically only work for a few months, and the
process must be repeated every few months. (VII, Thompson [First]
1993).
Although this simplified explanation of a
gene therapy procedure sounds like a happy ending, it is little more
than an optimistic first chapter in a long story; the road to the
first approved gene therapy procedure was rocky and fraught with
controversy. The biology of human gene therapy is very complex, and
there are many techniques that still need to be developed and
diseases that need to be understood more fully before gene therapy
can be used appropriately. The public policy debate surrounding the
possible use of genetically engineered material in human subjects
has been equally complex. Major participants in the debate have come
from the fields of biology, government, law, medicine, philosophy,
politics, and religion, each bringing different views to the
discussion.
Scientists took the logical step of trying
to introduce genes straight into human cells, focusing on diseases
caused by single-gene defects, such as
cystic fibrosis,
hemophilia,
muscular dystrophy and
sickle cell anemia. However, this has been much harder than
modifying simple bacteria, primarily because of the problems
involved in carrying large sections of DNA and delivering it to the
right site on the genome.
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