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
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
Much more study will be needed before the vaccine can be tested in humans.
During suggests that the first patients to test should be those with an
exceptionally high risk of brain damage from a stroke because they have
inoperable brain aneurysms -- small blood vessels that balloon out and threaten
"If it works in that group of patients, we would do it with surgery
patients who run a high risk of stroke [such as patients having heart bypass
surgery] and then step by step move back into a broader population group until
we include anyone at a higher risk of stroke [such as patients with elevated
cholesterol, diabetes, or high blood pressure]," During says.