Gene Transfer
The purpose of Gene Transfer is to transport a functioning dystophin gene into muscle cells. There are two main forms - viral vectors and non viral methods. There is evidence in the mdx mouse model that delivering a new gene into muscle cells would prevent, halt and at least partially reverse damage in muscle cells.
The most commonly used vectors in animal studies for DMD are based on adenovirus and adeno-associated virus(AAV). These viruses are associated with the common cold but have been stripped or gutted to remove harmful effects. Adenoviruses have been used as vectors which are large enough to carry all the active genetic sequences for full length dystrophin. There are concerns over the safety and immune response to the use of viral vectors. To overcome some of these problems smaller AAV's are preferred but can only carry shorter versions of dystrophin or mini or micro genes. The major problem will be to make the most effective micro genes that can offer a DMD patient more benign Becker type symptoms of the disease.
Non viral vector methods of Gene Transfer involve using plasmids. Plasmids are short circular pieces of DNA to which the gene of interest is added and then the construct is injected directly into the muscle cells. Results have been positive for work in animals where the dystrophin gene as a plasmid has been forced under pressure into the blood circulation of limbs. Up to 40% of the muscle fibres of the limbs of these animals were found to have dystrophin.