Gene Therapy

3. Production Process

3.2. Production process - Viral vectors

Viruses are commonly used as vectors. They have had specific modifications made to render them non-infective. Often they are designed to last a long time inside the affected cell, either by integrating into the cell’s DNA or staying inside the cell. This reduces the requirement for repeated treatments. The main safety concern when using these agents is the risk of insertional mutagenesis. This is when a piece of DNA enters the nucleus and causes disruption of the surrounding genes, such as those that normally suppress tumour growth. In several gene therapy trials, some patients have developed leukaemia as a result of insertional mutagenesis. In these cases, the gene therapy DNA inserted itself close to a gene, which can cause cancer if switched on.

Additionally, the introduction of viral proteins into the body can activate the immune system too as if the body has been infected, which can make the patient receiving gene therapy ill. Owing to these safety concerns, and other issues surrounding genetic engineering in humans, the European Medicines Agency has published guidelines for the development and use of gene therapy vectors in humans.