This is a very important discovery

Professor Alejandro Madrigal

CML affects mainly adults over the age of 30. It claims about 1,000 victims a year in the UK. Without a bone marrow transplant and chemotherapy, survival is normally less than five years.

The international scientific community has been looking for something on which to base a vaccine against the disease.

Protein

A US group has synthesised an artificial peptide - a piece of a protein - which shows promise.

But the British team is the first to identify the actual peptide produced by leukaemic cells that is targeted by the immune system.

This will greatly accelerate work to develop the first practical vaccine against CML.

Professor Alejandro Madrigal, scientific director at the Anthony Nolan Bone Marrow Trust, who led the research, said: "This is a very important discovery.

"In just a few years there could be a vaccine for CML. It could be used to treat individual patients, but there's no reason why you couldn't extend it to the general population to prevent the disease."

Natural reaction

Scientists know that the immune system naturally reacts to CML - but usually the response is not strong enough to conquer the leukaemia.

White blood cells called T-cells, which attack foreign bodies, lock on to a specific peptide which appears on the surface of the cancerous cells.

It took seven years of work before the peptide, made up of a small number of linked amino acids, was identified.

Professor Madrigal's team at the Anthony Nolan Research Institute laboratories in Hampstead, north London, collaborated with scientists at Nottingham Trent and Liverpool universities.

A simple vaccine could be made using the peptide to trigger an immune system reaction against the cancer.

Alternatively, said Prof Madrigal, T-cells could be grown in the laboratory and "trained" to recognise the molecule.

They could then be used as a treatment in their own right. The cells would not have to be returned to the patient they came from.

They could be stored and given to any patient who provides a close enough match, just as bone marrow transplants are carried out today.

Professor Robert Rees, from Nottingham Trent University, said: "These results demonstrate that we have identified key components of leukaemia cells against which we might be able to develop a vaccine."