Studies point to immune system role in Huntington's

By Michael Kahn

LONDON (Reuters) - Immune system proteins in the blood may reflect how abnormal proteins destroy brain cells in people with Huntington's disease, an incurable, inherited condition, British researchers said on Monday.

And in a separate study, U.S. researchers said similar findings suggest a previously unsuspected role for the immune system in the brain-destroying disease.

The findings point to a better understanding of how the disease damages nerve cells in the brain and could lead to treatments to delay symptoms, said Sarah Tabrizi, a neurologist at University College London who led one study.

"We appear to have detected something that may mirror what is going on in the brain," she said in a telephone interview. "This can contribute to the huge body of work trying to develop therapies to delay the disease onset into old age."

In their studies published in the Journal of Experimental Medicine, the researchers looked at mouse models, blood samples of volunteers with the defective gene and brain tissue taken from people with Huntington's after they had died.

In all cases they found high levels of cytokines -- signaling proteins produced by white blood cells -- that could be damaging nerve cells in the brain before people develop the disease.

"When we found increased levels of cytokines in the brains of Huntington's disease patients, we were very excited," said Dr. Thomas Moeller of the University of Washington, who led one study.

"Inflammation in the brain has been increasingly recognized as an important component in other neurodegenerative diseases such as Alzheimer's or Parkinson's disease. These findings might open the door to novel therapeutic approaches for Huntington's disease that target inflammation."

STUTTERING GENE

Huntington's disease affects up to one person in every 10,000 in the Western world. It is a progressive, degenerative condition marked by uncontrolled movements, emotional disturbances and mental deterioration.

Drugs can help manage symptoms but do not stop the physical and mental decline. Patients typically die within 10 to 15 years after symptoms arise.

Children of people with the disease have a 50 percent chance of inheriting the faulty gene that causes it, and if they get even one copy of the damaged gene, they will develop Huntington's at some point.

The mutation causes a "stutter" in a gene called "huntingtin" -- a seemingly sesne repeat of DNA sequence. No one quite knew what this did to cells, however.

"It looks like the mutant gene is causing people's white blood cells to become abnormal," Tabrizi said in a telephone interview.

"The protein could be causing damage through an abnormally overactive immune system in both the blood and the brain. While damage from Huntington's is typically seen in the brain, this new pathway is quite easy to detect in the blood of patients, so we may have found a unique window from the blood into what the disease is doing in the brain," added Moeller.