Gene therapy is a new approach to treat, cure, and ultimately prevent disease by changing the expression of a person's genes. Gene therapy is in its infancy, and primarily experimental, with most human clinical trials only in the research stages. It is being studied for many different types of cancer and some other diseases.

Gene therapy is also being studied as a way to change how a cell functions; for example, by stimulating immune system cells to attack cancer cells or by introducing resistance to human immunodeficiency virus (HIV), the virus that causes AIDS.

In general, a gene cannot be directly inserted into a person's cell. It must be delivered to the cell using a carrier known as a "vector. The most common types of vectors used in gene therapy are viruses. Scientists use viruses because they have a unique ability to enter a cell's DNA. Viruses used as vectors in gene therapy are genetically disabled; they are unable to reproduce themselves.

In other studies, vectors or liposomes (fat particles) are used to deliver the desired gene to cells in the patient's body. This form of gene therapy is called in vivo, because the gene is transferred to cells inside the patient's body.

In addition, when DNA is injected directly into a tumour, or when a liposome delivery system is used, there is a slight chance that this DNA could unintentionally be introduced into reproductive cells, producing inheritable changes. Other concerns include the possibility that transferred genes could be "overexpressed," producing so much of the missing protein as to be harmful; that the viral vector could cause inflammation or an immune reaction; and that the virus could be transmitted from the patient to other individuals or into the environment.

However, scientists use animal testing and other precautions to identify and avoid these risks before any clinical trials are conducted in humans.

Other advances that are needed include the ability to deliver genes consistently to a precise location in the patient's DNA (thus diminishing the risk of causing cancer), and ensure that transplanted genes are precisely controlled by the body's normal physiologic signals.

One such question is related to the possibility of genetically altering human eggs or sperm, the reproductive cells that pass genes on to future generations. Since reproductive cells are also called germ cells, this type of gene therapy is referred to as germ-line therapy. Another question is related to the potential for enhancing human capabilitiesfor example, improving memory and intelligenceby genetic intervention. Although both germ-line gene therapy and genetic enhancement have the potential to produce benefits, possible problems with these procedures worry many scientists.

Germ-line gene therapy would forever change the genetic make-up of an individual's descendants. Thus, the human gene pool would be permanently affected. Although these changes would presumably be for the better, an error in technology or judgment could have far-reaching consequences. In the case of genetic enhancement, there is anxiety that such manipulation could become a luxury available only to the rich and powerful. Some also fear that widespread use of this technology could lead to new definitions of "normal" that would exclude individuals who are, for example, of merely average intelligence. And, justly or not, some people associate all genetic manipulation with past abuses of the concept of "eugenics," or the study of methods of improving genetic qualities through selective breeding.

Scientists working on the Human Genome Project, which is mapping and sequencing all of the human DNA, have recognized that the information gained from this work will have profound implications for individuals, families, and society. The Ethical, Legal, and Social Implications (ELSI) Programe was established in 1990 to address these issues. The ELSI Programme is designed to identify, analyze, and address the ethical, legal, and social implications of human genetics research at the same time that the basic scientific issues are being studied. In this way, problem areas can be identified and solutions developed before the scientific information becomes part of standard health care practice.

More:
Gene therapy - Doctor.ndtv.com

Comments are closed.