Gene transfer represents a relatively new possibility for the treatment of rare genetic disorders and common multifactorial diseases by changing the expression of a person's genes. Typically gene transfer involves using a vector such as a virus to deliver a therapeutic gene to the appropriate target cells. The technique, which is still in its infancy and is not yet available outside clinical trials, was originally envisaged as a treatment of monogenic disorders, but the majority of trials now involve the treatment of cancer, infectious diseases and vascular disease. Human gene transfer raises several important ethical issues, in particular the potential use of genetic therapies for genetic enhancement and the potential impact of germline gene transfer on future generations.
Scientific Issues
Gene transfer can be targeted to somatic (body) or germ (egg and sperm) cells. In somatic gene transfer the recipient's genome is changed, but the change is not passed on to the next generation. In germline gene transfer, the parents' egg and sperm cells are changed with the goal of passing on the changes to their offspring. Germline gene transfer is not being actively investigated, at least in larger animals and humans, although a great deal of discussion is being conducted about its value and desirability.
Many people falsely assume that germline gene transfer is already routine. For example, news reports of parents selecting a genetically tested egg for implantation or choosing the sex of their unborn child may lead the public to think that gene transfer is occurring, when actually, in these cases, genetic information is being used for selection, with no cells being altered or changed. In addition, in 2001 scientists confirmed the birth of 30 genetically altered children whose mothers had undergone a procedure called ooplasmic transfer. In this process, doctors injected some of the contents of a healthy donor egg into an egg from a woman with infertility problems. The result was an egg with two types of mitochondria, cellular structures that contain a minuscule amount of DNA and that provide energy for the cell. The children born following this procedure thus have three genetic parents, since they carry DNA from the donor as well as the mother and father. Although the researchers announced this as the "first case of human germline genetic modification," the gene transfer was an inadvertent side effect of the infertility procedure.