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Wednesday, 24 January, 2001, 01:35 GMT
GM corneas could boost transplants
Corneal defects are a leading cause of blindness
A subtle genetic modification to corneas could increase the chances of a graft operation being successful, scientists hope.

The research project, based jointly between Moorfields Eye Hospital and Hammersmith Hospital in London, is looking at ways of reducing the hundreds of corneal grafts which fail each year in UK.

They believe that by changing the cells of the cornea so that they behave more like an invading virus, the chances of success will be boosted.

Essentially we want to hijack a method that viruses use to protect themselves

Dr Andrew George, Hammersmith Hospital
The cornea is the layer of cells which lie across the surface of the eye, and defects in it are one of the leading causes of blindness in the developed world.

The most common way of treating the condition is through corneal grafting, in which a cornea taken from a dead body is transplanted onto the patient to restore sight.

However, up to a quarter of these are rejected, many because the body's immune system decides they are foreign and launches an attack.

The new project, funded by Action Research to the tune of 125,000, believes it knows a way of heading off this immune system attack.

Dr Andrew George, an immunologist who is leading the team, said: "Essentially we want to hijack a method that viruses use to protect themselves.

"If it works, it might be used to help those who are at high risk of rejecting their grafts - and this includes children, among whom failure is more likely."

eye test
A quarter of corneal grafts fail
The method relies on blunting the process by which the body is traditionally alerted to the possible presence of foreign intruders so that an immune system defence can be mounted.

In this case, the damage to tissues caused by the cutting away of the defective cornea, and the grafting of the new one, causes the release of molecules called chemokines.

These in turn alert dendritic cells - the part of the immune system whose role is to sound the alert if an immune response may be needed.

Viruses get round this by sending out slightly mutated chemokines, which, instead of ringing the alarm bells, actually have the reverse effect on dendritic cells.

Dr George said: "In effect, what they tell the immune system is: 'It's all quiet on the Western Front'."

He also believes the same principle could in theory lead to genetic modifications which protect transplanted hearts from the rapid hardening of the arteries which often follows transplantation.

He is hopeful that human trials of modified corneas, provided laboratory work proves successful, could be held within five years.

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