A new study adds to mounting evidence that HHV-6 can trigger the chronic muscle weakness and neurologic impairment of multiple sclerosis. The study, which appears in the December issue of the journal Nature Medicine, found that a strain of the common herpes virus may be associated with the unforgiving multiple sclerosis disorder in which the body attacks its own tissues.
The study, the first to suggest a link between herpes and MS, points to the potential role of anti-herpes drugs in treating the often untreatable disorder, experts said. "We expect that currently available anti-viral treatments for example, valtrex might one day be applied successfully to MS," said Steven Jacobson, chief of viral immunology at the National Institute of Neurological Disorders and Stroke in Bethesda, Md., and the study's principal investigator. "We've suspected a possible role for a virus in MS for quite some time, and these results certainly point to this particular virus."
In the study, more than one-third of MS patients had detectable levels of active human herpes virus-6 in their blood, Jacobson reported. As many as 350,000 Americans are affected by MS, which most often strikes between the ages of 20 and 40 and is characterized by muscle weakness, visual disturbances and, eventually, disability and paralysis.
MS is characterized by the inflammation and eventual destruction of myelin tissue, the protective covering of the nerve cells in the brain and spinal cord. HHV-6 appears to speed up the breakdown of the protective myelin covering, Jacobson said, causing symptoms to worsen.
The next step, he believes, is to figure out why infection with such a common virus causes disease in so few people. HHV-6, one of eight human herpes virus, causes the common childhood illness roseola. It is not sexually transmitted. "HHV-6 sub-variant A is present in more than 90 percent of the adult population as a result of infection during the first few years of life. In MS, HHV-6, which has been dormant for years, is somehow reactivated," says Jacobson.
In the new study, the investigators detected HHV-6 DNA – a marker of active virus infection in the blood of 15 of 50 MS patients. All 47 healthy volunteers tested negative for the presence of active HHV-6 viral infection. Additional testing for the presence of HHV-6 virus in larger numbers of MS patients, as well as those with other autoimmune disorders, is under way.