The vaccine works by dampening down the immune system

levels of immune cells that target myelin sheaths fell

The first human trial of a DNA-based vaccine to combat multiple sclerosis has been declared a success by doctors in America after tests on patients revealed signs that their condition had improved.

However, the trial is only the first small step in developing an effective treatment against the debilitating degenerative disease.

Immune system

The vaccine works by dampening down the immune system, which is believed to become overactive in people who develop multiple sclerosis.

The disease is caused by a small group of immune cells that start to attack the body by targeting the fatty sheaths of myelin that coat nerves in the central nervous system. After waves of attacks, the nerves are eventually destroyed. The myelin coating helps to ensure that signals passed along the nerves travel quickly.

Doctors led by Amit Bar-Or at the Montreal Neurological Institute in Canada developed a vaccine which contains the strands of DNA that produce myelin.

Drug boost

In the trial, 30 patients had the vaccine injected into their muscles over one, three, five and nine weeks, with half also receiving a statin drug to boost the effect of the vaccine. All of the patients in the study had the most common form of the disease, known as relapsing and remitting multiple sclerosis, in which symptoms come and go over long periods, or steadily worsen with spells of remission in between. The main purpose of the trial was to test the safety of the vaccine, the first to be tested in humans to treat an autoimmune disease such as MS.

Any side effects were brief and were considered to be mild or moderate, according to a report in the US journal Archives of Neurology.

The doctors went on to test blood from the patients to see how their immune systems had responded to the vaccine.

Eight relapses

They found that levels of immune cells that specifically attack myelin sheaths had fallen, along with levels of antibodies which are also implicated in the disease.

The doctors recorded eight relapses, though only one occurred in a patient who was receiving the experimental vaccine.

After treatment, the patient continued on the trial and experienced no further relapses.

All of the other relapses happened five to 29 weeks after the patients received their final dose of vaccine.

The patients were later given magnetic resonance imaging brain scans to examine the damage caused by the disease.

Size of lesions

As the disease progresses, it produces lesions which can be counted and measured. In the trial, the researchers saw the number of lesions fall by 18 per cent to 64 per cent in patients who were given the DNA vaccine alone. The size of the lesions also dropped, by between 38 per cent and 83 per cent.

The statin drug did not seem to improve the vaccine’s effectiveness. The researchers were excited by the results, but cautioned against reading too much into the trial’s findings.

“We have demonstrated in this first, to our knowledge, in-human trial of a DNA vaccine for autoimmune disease that the approach is safe and well-tolerated.

“We describe evidence for induction of favourable trends on brain MRI, indicating a reduction in the inflammatory response in the central nervous system,” they wrote.

The team has now begun a 12-month trial of 290 patients. If that is a success, it could pave the way for DNA vaccines for a range of other diseases caused by an over-active immune system, such as type I diabetes and rheumatoid arthritis. — Guardian Newspapers Limited 2007

The vaccine works by dampening down the immune system

levels of immune cells that target myelin sheaths fell