The goal of gene therapy is introduce the correct genetic code into a cell so that enzyme production can occur. The correct genetic code may be delivered in various ways, but the most common approach is using a viral vector. Typically, when a virus enters the human body, it injects its own genetic material into the nucleus of the human cell, so the viral genetic material will be then be replicated in the human body when the cell divides. In gene therapy, the DNA of the non-disease causing virus is altered so that it carries the correct genetic code which the person needs. Therefore, when the virus enters the cell and injects the genetic material into the cell's nucleus, the cell will be given the correct information to produce the enzyme which it is missing.
There are many challenges to safe and effective gene therapy. Some of these include
However, this is an exciting and progressing research area.
Adeno-associated viruses (AAV) are an example of a viral vector which is showing promising results in gene therapy trials in animal models. It is a harmless virus which most people carry, so is believed to be a safe way to insert new genetic material into humans. Read more about the delivery approaches here.
Research into gene therapy in animals with Tay Sachs and Canavan has also been using the AAV gene therapy, as is described on the Research by Disease page.