Tackling Corneal Transplant Rejection
First Published: Investigator - April 2006
A new research project currently underway at Flinders Medical Centre is focused on reducing the risk of corneal transplant rejection. Transplant rejection occurs when the immune system attacks the transplanted organ or tissue because it is foreign to the body.
Each year in Australia up to 1,500 corneal transplants are performed to correct visual impairment, around 50 of these take place at Flinders Medical Centre. The cornea is the curved, transparent layer that covers the front part of the eye and protects its inner structures. When the cornea becomes opaque due to either trauma or disease, light is unable to reach the retina at the back of the eye which significantly reduces sight.
The surgery involves removing the damaged part of the cornea and replacing it with a piece of normal cornea taken from the eye of a donor. The Eye Bank of South Australia, situated at Flinders Medical Centre, is responsible for collecting the donated corneas which are then stored for up to four days. It is this four day window of opportunity that is of particular interest to the research team Associate Professor Keryn Williams, Professor Doug Coster and Dr Helen Brereton are involved in.
While it is unusual to see early rejection with corneal grafts, as opposed to major organ transplants, this can still occur over a much longer period. The Australian Corneal Graft Register indicates that the success rate in terms of restoration of vision is less than 60% after 10 years – that is six in every 10 patients will retain good vision for up to 10 years.
Rejection is the major cause of the failure for the other 40% of recipients. The researchers want to develop a simple intervention directed at the donor cornea before it is transplanted to minimise this risk of rejection.
“A major part of the research is identifying the right protein that will help stop rejection, currently we have identified a protein that works in two thirds of our experimental cases,” says Associate Professor Williams.
Using a gene therapy approach, they will insert a gene which has been programmed to produce an identified anti-rejection protein into the donor cornea. This gene will cause the cornea to express more of the desired protein helping to minimise the risk of rejection.
Professor Williams acknowledges that the research is in the very early stages but their aim to reduce the number of recipients who experience rejection will be an extremely worthwhile outcome.