Abstract

In lieu of an abstract, here is a brief excerpt of the content:Human Gene TherapyMary Carrington Coutts (bio)On September 14, 1990, researchers at the U.S. National Institutes of Health (NIH) performed the first approved gene therapy procedure on a four-year-old girl named Ashanti DeSilva. Born with a rare genetic disease, severe combined immune deficiency (SCID), Ashanti lacked a healthy immune system and was extremely vulnerable to infection. Children with SCID usually develop overwhelming infections and rarely survive to adulthood; even a common childhood illness like chicken pox 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, her own white blood cells were genetically modified and then infused back into her bloodstream. Laboratory tests show that the therapy has strengthened Ashanti's immune system. She no longer has recurrent colds, has been allowed to attend school, and has been immunized against whooping cough. This gene therapy procedure is not a cure, however. The genetically-treated white blood cells only survive for a few months and must then be replaced, but Ashanti's future is much brighter because of the new therapy (VI, Thompson [The First] 1993).Although this simplified description of Ashanti's gene therapy procedure sounds like a happy ending, it is little more than an optimistic 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 still many techniques that need to be developed and diseases that need to be understood more fully before gene therapy is well established. The public policy debate surrounding the possible use of genetically engineered material in human subjects is equally complex. Major participants in the debate come from the fields of biology, government, law, medicine, philosophy, politics, and religion, each bringing different views to the discussion.In studying the ethics of gene therapy, one should draw a distinction between [End Page 63] therapy on somatic (non-reproductive) cells and germ (reproductive) cells. Only the germ cells carry the genes that will be passed on to the next generation. Reactions to gene therapy have varied widely. Some commentators on gene therapy object to any form of genetic manipulation, no matter how well-intentioned (VI, Rifkin 1983). Another reaction is to allow the use of somatic-cell therapy, but not to approve the use of germ-line therapy, which could have unforeseeable effects on future generations. A different stance is that, with proper regulation and safeguards, germ-line gene therapy is a logical extension of the progress made to date and that it is an ethically acceptable procedure.TechniquesTo date, 43 research protocols have been approved for somatic-cell gene therapy in the United States. The techniques employed in each protocol vary, but in general a virus is used as a "vector" to insert the desired gene into the DNA of the patient's cells, in order to compensate for a defective gene. For Ashanti's gene therapy, this technique involved obtaining white blood cells and introducing properly functioning genes into as many of the cells as possible. The normal genes were delivered through the use of a specially-engineered virus.Although similar techniques are used in germ-line gene therapy, the procedure is more difficult. There are two basic ways to perform germ-line gene therapy: (1) to treat a preimplantation embryo that carries a serious genetic defect before its implantation in the mother, which necessitates the use of in vitro fertilization techniques; or (2) to treat the germ cells (sperm or egg cells) of afflicted adults so that the genetic defects would not be passed on to their offspring, which requires the technical expertise to delete the defective gene and insert a properly functioning replacement. Because of the complexity of the procedures involved and the attendant ethical controversy, germ-line therapy is not currently performed.Candidate Diseases for Gene TherapyAt present, gene therapy is likely to be most successful in treating diseases that are caused by single-gene defects and has been approved for treating diseases such...