Gene Therapy Facts

The challenge of gene therapy is to send a functioning gene into a nucleus, and to have it land in the desired spot so that it will be reproduced normally during cell division and have a lasting effect. Various methods have been developed to get genes to their targets and these include: -

• Packing genes into non-virulent viruses or inactivated viruses and injecting the gene-virus complex into the patient
• Placing the gene of interest inside a liposome - a fatty type molecule that can traverse cell membranes

A whole host of viral vectors are at the disposal genetic scientists and these include adenoviruses, retro-viruses, and adeno-associated viruses.

There are a number of risks associated with the use of viral vectors and these include a concern that once inside a cell a virus might 're-discover' its pathogenic abilities. In addition, a virus could cause a number of problems such as provoking a strong immune and inflammatory reaction.

In 1999 teenager Jesse Gelsinger became the first person to die whilst undergoing a gene therapy treatment.

• The first use of gene therapy in humans was in 1990. Dr French Anderson (often called 'the father of gene therapy') treated a 4 year old girl, Ashanti DeSilva who was suffering from the immune disorder adenosine deaminase deficiency (ADA). It is caused by a defective ADA gene and Anderson was able to introduce functioning copies.

• Somatic gene therapy is the transfer of genes into somatic cells (non-sex cells) of an individual. Any subsequent genetic modifications are restricted to the individual only.

• Germline gene therapy is the transfer of genes into the sperm or eggs. Any subsequent genetic modification will be passed on to the succeeding generations. This application is banned in many countries. The consensus is that the risks outnumber the perceived benefits.

• One of the reasons as to why gene therapy is not yet a conventional treatment is its short-lived nature. To become truly effective the benefits have to be long lasting and not involve multiple rounds of gene therapy for a patient.

• Gene therapy has been proposed as a treatment for a number of disorders and diseases including cancers, Alzheimer's, Parkinson's and AIDS.

• Notable gene therapy wins include successful gene therapy trials in the United States and the United Kingdom to cure Leber's congenital amaurosis (LCA), an inherited degeneration of the retina. Working copies of the defective RPE65 gene have been injected into several patients who had some of their sight restored.

• Gene therapy is still considered to be an experimental technology.