The reason that we decided to research genome therapy was because we very interested in this project and had a lot of questions concerning this topic. Some of the questions that we had were: what is normal and what is a disability or disorder, and who decides? Are disabilities diseases? Do they need to be cured or prevented? Does searching for a cure degrade the lives of individuals presently affected by disabilities? Is somatic gene therapy more or less ethical than germline gene therapy? In cases of somatic gene therapy, the procedure may have to be repeated in future generations.
Preliminary attempts at gene therapy are extremely expensive. Who will have access to these therapies? Who will pay for their use? The Human Genome project experienced many setbacks, including the death of an 18 year old boy. He died from multiple organ failures 4 days after starting the gene therapy treatment. His death is believed to have been activated by a severe immune response to the adenovirus carrier. Another major blow came in January 2003, when the FDA placed a temporary stop on all gene therapy trials using retroviral vectors in blood stem cells.
FDA took this action after it learned that a second child treated in a French gene therapy trial had developed a leukemia-like condition. This figure demonstrates the genetic similarity (homology) of the superficially different mouse and human species. The similarity is such that human chromosomes can be cut (schematically at least) into about 150 pieces (only about 100 are large enough to appear here), then reassembled into a reasonable approximation of the mouse genome.
The colors and corresponding numbers on the mouse chromosomes indicate the human chromosomes containing homologous segments. A molecular Trojan horse that can slip past the brain’s defenses has proved to be very effective at delivering genes to the brains of primates. It could be used to treat a host of brain disorders, from Parkinson’s to epilepsy. The viruses most gene therapists use to deliver genes are too big, and have to be injected directly instead.
Even then, the genes are not expressed widely and evenly throughout the brain. First the team coats the liposomes with a polymer called polyethylene glycol (PEG), without which they would be purged from the blood within minutes. Next, antibodies that latch on to some of the brain-capillary receptors are tethered to a few of the PEG strands. The antibodies trick the receptors into letting the liposomes pass, where they can deliver their cargo to brain cells.