Gene therapy is based on the concept that genetic disorders and acquired diseases can be treated by replacing abnormal or absent genes or by modifying their functions. Inherited disorders such as cystic fibrosis and haemophilia, as well as catastrophic diseases such as cancer and AIDS, are prospective candidates for gene therapy. Although cures for these ailments would be welcome, some medical researchers suggest that the range of diseases that can be treated with gene therapy may be limited. In 2000, researchers used gene therapy techniques to help mice with haemophilia produce high levels of the protein needed to restore and maintain the clotting property of blood. For advocates, knocking out this disease in the human population makes gene therapy—despite its limitations— a worthwhile pursuit. Gene therapy is the use of DNA as a pharmaceutical agent to treat disease. It derives its name from the idea that DNA can be used to supplement or alter genes within an individual's cells as a therapy to treat disease. The most common form of gene therapy involves using DNA that encodes a functional, therapeutic gene to replace a mutated gene. Other forms involve directly correcting a mutation, or using DNA that encodes a therapeutic protein drug (rather than a natural human gene) to provide treatment. Gene therapy is composed of two categories: somatic gene therapy and germ line gene therapy. In somatic gene therapy, therapeutic genes are introduced to the diseased cells of a patient in hopes that they will genetically alter them to function normally. In germ line gene therapy, therapeutic genes are introduced to reproductive cells (egg and sperm cells) to prevent the manifestation of a genetic disorder before the patient is born. This approach would alter the patient’s genetic makeup and the genes he or she passes on to succeeding generations. Additionally, therapeutic genes can be introduced to cells in several ways. In ex vivo gene therapy, a patient’s blood or bone marrow cells are removed and cultivated in a laboratory, exposed to a virus carrying therapeutic genes, and returned to the patient. In in-vivo gene therapy, a virus or other particle carrying genes is inserted directly into the patient’s body. The particle that carries genes to cells is known as a vector. Usually modified viruses are used as vectors in clinical trials, but the use of non-viral vectors, such as liposomes (microscopic fatty particles), are also under investigation. When genetic material is inserted without a vector, it is known as naked DNA. The first human gene therapy clinical trial occurred in 1990, in which Ashanti DeSilva, then four years old, was treated for adenosine deaminase (ADA) deficiency, a rare genetic disorder that severely limits the functions of the immune system. Today, she leads a normal life and receives weekly injections of synthetic DNA to maintain her immune system. Some researchers herald the outcome of DeSilva’s clinical trial as gene therapy’s first success story, spurring interest and support for gene therapy research in the 1990s. However, hundreds of unsuccessful gene therapy clinical trials followed thereafter, dimming the initial optimism. But it was the death of a young patient that subjected gene therapy research to intense scrutiny.
One common form of gene therapy is recombinant DNA. Recombinant DNA is defined as a novel DNA sequence produced by artificially joining pieces of DNA from different organisms together in the laboratory. Therefore, recombinant DNA is DNA that could cure a host body when it is combined with the DNA of a pathogen. The recombined pathogen is reinserted into the host where the genetically improved DNA is absorbed by the host. The hope is for successful treatment of the malady. In opposition to continued gene therapy research, critics of recombinant DNA fear that the pathogenic, or disease-producing, organisms used in some recombinant DNA experiments might develop extremely...
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