In a major breakthrough in the battle against multiple sclerosis (MS), scientists claim to have identified a chemical that triggers the devastating disease and also found a way to stop it in its tracks.

Researchers at the University of Zurich, Switzerland, found that an immune system chemical,
called GM-CSF, is the "driving force" behind the debilitating condition that affects over 2.5 million people worldwide.

MS is an autoimmune disease that affects the brain and spinal cord, or the central nervous system. The condition, which can cause blindness and paralysis, has no cure at present and drugs are not suitable for all.

But the Swiss researchers claimed that an antibody, which they tested on mice with a MS-like condition, was found to be very effective in countering GM-CSF and improved their health, the Daily Mail reported.

Although the experiments were on mice, the researchers said they were "quietly optimistic" that a similar approach would help people with MS. The first trials on patients are planned for later this year.

In the healthy body, the researchers said, GM-CSF is part of the defence against disease, attacking viruses and other invaders. But in MS, it triggers a series of reactions that culminate in "scavenger cells" destroying myelin -- the fatty protective sheath around nerve fibres in the brain and spinal cord -- which disrupts the transmission of messages from the brain.

Professor Burk-hard Becher, who led the study, said: "It is relatively easy to stop mice from getting the disease, so we waited until they had the disease and were pretty sick.

"This is similar to the clinical situation -- patients don't go to the doctor because they think they might get MS, they go when they have MS."

The drug was also given to mice whose disease was similar to the most common form of MS, in which relapses are followed by periods of remission. Mopping up the GM-CSF prevented any further relapses, the researchers reported in the journal Nature Immunology.

Prof Becher said: "We are extremely hopeful but whether this form of therapy will actually help MS patients remains to be seen. Quiet optimism is the way to go.

"I am not sure this is going to work in patients but, based on the mouse data, I believe GM-CSF is a good thing to target." Another study on MS, from Thomas Jefferson University in Philadelphia, also pointed the finger at GM-CSF.

Although the chemical was known to play a role in MS, its pivotal contribution was not understood until now. Dr Doug Brown, of the MS Society, said: "This is a very interesting development in research for a condition where there are limited treatment options and no cure.