THURSDAY, Sept. 5, 2002 (HealthDayNews) -- Federal researchers say they're on the road to creating a vaccine that could tweak the linings of blood vessels so they can't begin the process that leads to a stroke.
While the new study suggests the vaccine works in rats, no one knows whether it will have similar effects in humans. However, if it works, the vaccine could offer a "new dimension" in stroke prevention, says Dr. John M. Hallenbeck, the study's senior author and chief of the Stroke Branch at the National Institute of Neurological Disorders and Stroke.
Strokes happen in one of two ways: either a blood clot forms and cuts off circulation to part of the brain or a blood vessel ruptures and leaks blood into the brain. In both cases, a stroke can lead to permanent disability or death.
Half a million Americans have strokes each year, and about 150,000 die from stroke-related causes. Only heart disease and cancer claim more lives.
In his study, Hallenbeck and colleagues sprayed a protein known as E-selectin into the noses of rats that were genetically designed to suffer from high blood pressure and be susceptible to strokes. Other rats received two other treatments for the sake of comparison.
The results appear in the September issue of Stroke.
During the year-long study, rats that received repeated treatment with the protein had 16 times fewer strokes caused by blood clots than those that received other treatments. And the strokes that did occur were less severe.
None of the rats that had repeated treatment suffered from a hemorrhagic stroke, in which blood vessels rupture.
Unlike most vaccines, the treatment appears to dampen down the immune system instead of gearing it up, Hallenbeck says. The protein primes blood vessels so they're ready to attack inflammation when it occurs, Hallenbeck says.
Strokes begin when inflammation occurs on a molecular level in blood vessels as part of a response by the immune system. "It's not a big, red, swollen and hot joint. It's more subtle," he says. "That process can be interrupted by this approach."
The key appears to be giving the treatment often enough to make it work properly, he says. Rats that received the protein less frequently were more likely to suffer strokes.
Hallenbeck says the next step is to study whether the vaccine will work in humans. Researchers will first have to study side effects, and figure out how to safely give the vaccine to people. Protein derived from people may not work, so researchers may turn to cow-derived protein, he says.
The vaccine would most likely be targeted to people who are susceptible to strokes because they've already had them, he says. "You would take it once every other day for five days about once a month."
Dr. James Grisolia, a neurologist at Scripps Mercy Hospital in San Diego, cautions that tinkering with the immune system could create problems in elderly people.
"Are you going to increase their risk of pneumonia, of urinary tract infections, of septic shock with this vaccine?" Grisolia asks. "How long will the immunity (to strokes) last in humans? Maybe the risks will be acceptable for high-risk patients, but would not make the treatment desirable for the general population, at least not until they've had one or more strokes already."
However, he adds there's reason for hope: "These worries aside, the vaccine concept offers a lot of promise for stroke, the nation's number one crippling disease. More research will answer the practical questions."
What To Do
For a range of information on strokes, visit the National Stroke Association or the American Heart Association.
