| Gene therapy is an experimental medical procedure | | | | Another setback to gene therapy occurred in 1999. |
| that attempts to correct a genetic mutation (missing | | | | An eighteen-year-old patient named Jesse Gelsinger |
| or changed genes) so that properly functioning genes | | | | was involved in a gene therapy trial for a genetic |
| are restored to cells. When gene therapy works, the | | | | disease called ornithine transcarboxylase deficiency |
| correct instructions for building proteins (chemicals | | | | (OTCD). This rare disease prevents the liver from |
| that direct and control chemical reactions in the body) | | | | breaking down ammonia, which can build up in the |
| are once again available to cells, and the body returns | | | | body and become toxic. Gelsinger died from organ |
| to normal or healthier function. | | | | failure four days after starting treatment. |
| Scientists first began discussing the possibility of this | | | | Researchers believe his immune system reacted to |
| method to cure diseases in the 1960s. In 1970, | | | | the virus that carried the new gene into his cells. |
| American doctor Stanfield Rogers at Oak Ridge | | | | In 2000, French researcher Alain Fischer was able to |
| National Laboratory in Tennessee tried to use gene | | | | cure children of a similar kind of immune system |
| therapy to treat two sisters who had a genetic | | | | disorder. Fischer used retroviruses as gene carriers. |
| disorder called argininemia. With this genetic disorder, | | | | Retroviruses are a type of virus that uses ribonucleic |
| the body lacks an enzyme (a type of protein) called | | | | acid (RNA) as its genetic material, instead of DNA. |
| arginase. People with this disorder can have seizures | | | | Retroviruses produce an enzyme (a protein that |
| and mental impairment. Rogers tried to treat the | | | | controls a biochemical reaction) that builds DNA upon |
| sisters by using a virus to carry the healthy gene into | | | | a strand of RNA. The most well known of these |
| their cells. In this case, the gene therapy was | | | | retroviruses is the human immunodeficiency virus |
| unsuccessful. | | | | (HIV), the virus responsible for acquired immune |
| In 1977, scientists were able to use gene therapy | | | | deficiency syndrome (AIDS). Fischer inserted a |
| techniques to deliver a gene into the cells of | | | | retrovirus carrying the normal gene into the children's |
| mammals. American doctor W. French Anderson | | | | blood stem cells. Several months later, two of the |
| performed one of the first studies of gene therapy | | | | children in the trial developed a disease similar to |
| in humans in 1990 on a four-year-old girl who had a | | | | leukemia (a type of cancer that starts in the cells |
| rare genetic immune system disorder called severe | | | | that make blood cells). As a result, the U.S. Food and |
| combined immunodeficiency (SCID). The immune | | | | Drug Administration (FDA) halted the use of |
| system fights off infections from bacteria and | | | | retroviruses in the United States. |
| viruses, and the disorder made it difficult for her | | | | Although research in this field has moved slowly, it still |
| body to stay healthy. Anderson and his team | | | | moved forward. In 2003, the first officially licensed |
| genetically altered her white blood cells and then | | | | gene therapy was available in China. Several types of |
| returned them to her body. The new white blood | | | | gene therapy are waiting for approval from the U.S. |
| cells strengthened the girl's immune system and made | | | | Food and Drug Administration. |
| it possible for her to survive. | | | | |