Gene Therapy to Treat Disease - Biotechnology and Your Health: Pharmaceutical Applications - page 84

to HIV. Ashanti has an inherited defect in the production of mature
immune system cells, so she is dangerously vulnerable to viruses
that would be nothing more than a nuisance to a healthy child.
Children with severe combined immunodeficiency , the condition that
affects Ashanti, can die, and have died, from a chicken pox vacci-
nation. Ashanti's father has read about HIV, but the doctors have
told him that this virus will not hurt Ashanti. The treated cells are
supposed to be little factories to produce the protein that Ashanti
needs to make her immune system work. All those blood transfusions
and other injections she had in the past did not help her for very
long. Despite the treatments, she could not go to nursery school or
even play with her cousins when they came to visit because she
might get a cold or a case of chicken pox that could kill her. This
new treatment is called gene therapy , and the doctors think it might
cure Ashanti.
Proteins are the workhorses of the body. Genes carry informa-
tion in their DNA sequence about the structure of the protein, as
well as instructions for when and where to make it. Errors in the
DNA sequence coding for a particular protein can make the protein
fail to do its job or be missing entirely, as in people with hemophilia.
The first uses of recombinant technology in medicine replaced a
missing protein or a protein that did not work correctly, but scien-
tists soon got the idea that they could replace a miscoded gene with
a correct one. In fact, the possibility was first discussed in 1966, just
13 years after James Watson and Francis Crick reported that they
had determined the structure of DNA, and nearly a decade before
anyone learned how to move a gene from one organism to another.
It took a long time to work out how gene therapy might safely be
tried in human patients; the first government-approved clinical trial
of gene therapy began in 1990, with 4-year-old Ashanti.
More than 15 years and hundreds of clinical trials later, the
FDA has not yet approved any gene therapy product. It has not
been for lack of trying. By 2004, there were more than 600 human