Gene therapy uses engineered viruses to carry a "normal" human gene to replace the missing function of an "abnormal", disease-causing gene in a patient's cells.
|The virus could potentially damage normal genes.|
However, the viruses carrying the therapeutic gene can become inserted into other genes and damage them, report researchers in the July issue of Nature Genetics
Adeno-associated virus (AAV) is commonly used to carry therapeutic genes. When this virus is injected into a cell it produces the therapeutic product without affecting the genetic material of the cell. However, in a few cases copies of the virus genome become integrated into the cell's chromosomes.
Drs Hiroyuki Nakai and Mark Kay studied AAV injected into the livers of mice.
They found that when the virus integrated, it preferred to do so inside functioning genes, rather than in DNA that did not code for genes. This means that the virus could potentially damage normal genes.
The Food and Drug Administration (FDA) has yet to approve any human gene therapy product.
A blow to gene therapy came in January 2003, when 2 children being treated for "bubble boy" disease in a French gene therapy trial developed leukemia.