Epilepsy, Stroke Vaccine Shows Promise
Feb. 24, 2000 (Atlanta) -- Epilepsy, stroke, Parkinson's disease, chronic pain, depression -- all might one day be treated and/or prevented with a new vaccine. Studies published in Thursday's issue of the journal Science show that the vaccine prevents seizures in laboratory animals and protects them against brain damage caused by stroke.
"We saw 78% fewer seizures and 70% less stroke [brain] damage in vaccinated mice, which is pretty dramatic," Matthew J. During, MD, lead author of the study, tells WebMD. "We are very excited. We obviously want to take it to the next step in humans."
The oral vaccine contains a harmless virus genetically engineered to produce part of an important protein in the brain known as NMDA. This protein is a key link in the chain of events leading to brain damage from stroke, epilepsy, head injury, dementia, and degenerative diseases such as Parkinson's and Alzheimer's. But it also plays a major role in normal brain function, which is why drugs that block the protein have a wide range of unwanted side effects.
Animals respond to the vaccine by making antibodies that block NMDA, but antibodies normally have trouble getting into the brain: they're mostly kept out by a protective system known as the blood-brain barrier, which acts as a shield. However, when damage to the brain occurs, this barrier relaxes, letting the NMDA antibodies go exactly where they are needed, almost exactly when they are needed. During and his co-workers hoped such precise timing would decrease the negative side effects of the vaccine because the antibodies can't get through the barrier to affect the brain at other times. And two different experiments that they conducted did show a decrease in side effects.
The first test simulated human epilepsy. Far fewer vaccinated than unvaccinated animals developed seizures, and those that did suffered much less brain damage. The second test simulated a human stroke caused by a blood clot. Although vaccination did not prevent stroke itself, the strokes were much smaller in the vaccinated animals. This latter study was particularly dramatic -- not only because of the extent to which the antibodies were able to protect the brain -- but also because the vaccine protected the animals against the effects of the stroke even five months after it was given. None of the vaccinated animals showed any sign of damage to their normal brain functions.