Gene therapy is a treatment method for hereditary disorders in which genes containing faults (= mutations) found in patients are replaced with healthy copies or these healthy copies are added to cells containing faults. The replacement genes produce again the proteins that as a result of the mutations were no longer produced. This should stop the deterioration of the functioning of the retina or cochlea.
GENE THERAPY STUDY FOR USHER
Various research institutes are doing studies into gene therapy for Usher Syndrome. Gene therapy is really promising and the developments are going quite fast.
We have an overview of all studies into gene therapy for the various Usher genes.
GENE THERAPY FOR EYE DISEASES
An important advantage of gene therapy for Usher Syndrome is that the retina can be reached with one syringe and the AVV vector can be applied very locally and specifically. Besides, only a small quantity is needed. Another advantage is that the immune system in the eye is less responsive. This reduces the chance of an immune response and infection that would block the effect of the treatment.
Research has shown that after gene therapy, the retina (part of the eye) can despite the presence of dead cells make normal connections with other cells, which leads to a normal response to light.
Also take a look at the fact sheet about gene therapy of the Life Sciences and Society Foundation (BWM = Biowetenschappen en Maatschappij). (Unfortunately only in Dutch)
A VIRUS AS A MEANS OF TRANSPORT
With this therapy a healthy copy of a required gene is delivered at a specific place in the body, for instance the eye. This is usually done with the help of a molecular vehicle or means of transport: a virus. Not any virus can simply be used as a means of transport. A suitable virus is first deactivated, so that it cannot multiply itself and cause any other disease. This type of virus is called a vector, a kind of ‘packaging’. Then the required gene is inserted into the DNA of the virus. Finally, the vector with its new content is injected into a certain area in the eye, after which the new gene in the particular cells are translated into a functional protein. The most commonly used vector is the adeno-associated viral vector (AAV).
Gene therapy utilizing DNA plasmids can have additional benefits, including multiple applications with limited immune response. DNA plasmids are also larger and can package and deliver an entire Usher gene.
Researchers have previously developed new vectors capable of accommodating very large genes, known as High Capacity Adenoviral Vectors (HcAdV). The large USH2A gene fits entirely within this vector, allowing it to serve as a molecular truck and be used as a vector for gene therapy.