Corneal grafting is the most common form of transplantation and a major way of treating and reversing blindness, with 60-80,000 operations performed worldwide each year. About a quarter of all these grafts fail within 5 years, and in some groups of patients (such as children or those with eye infections) the majority are rapidly rejected. This team is working to prevent such corneal rejection by using molecules which are normally used by viruses to protect themselves from the immune system. (The molecules confuse the immune system and prevent it from attacking the virus.) The aim of this study is to cause the corneas to make these particular molecules, in order to similarly confuse the immune system and thereby stop it from attacking the graft.