- WASHINGTON (UPI) -- Researchers
have developed a new vaccine that interferes with the inflammation of blood
vessels and has reduced the risk of stroke significantly in animal studies,
a finding that could lead to drugs that prevent thousands of strokes in
humans.
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- The researchers, led by John Hallenbeck, chief of the
stroke branch at the National Institute of Neurological Disorders and Stroke,
administered a nasal spray carrying an important protein called E-selectin.
Under normal circumstances, E-selection contributes to inflammation in
the cells of the interior walls of blood vessels, a natural response by
the body when the immune system is repelling an invading organism.
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- When Hallenback and colleagues exposed rats to E-selectin,
however, they found the animal's bodies tended to trigger cells called
lymphocytes that monitor the blood vessels for signs of this particular
protein. When the lymphocytes found it, they attacked and suppressed the
inflammation that potentially could lead to a stroke.
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- In other words, E-selectin acted like a vaccine against
stroke.
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- The researchers administered the protein, as well as
two other substances, randomly to 113 rats genetically altered to have
high blood pressure and be susceptible to stroke. Some rats received E-selectin
through the nasal spray every other day for 10 days while the remaining
animals received the 10-day course of treatment every three weeks until
they died or the study, which lasted more than a year, concluded.
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- Results showed rats receiving E-selectin suffered only
one-sixteenth as many ischemic strokes, in which a blood vessel becomes
blocked, compared to the other animals who had received different substances.
None of the rats suffered a hemorrhagic stroke, where a clot bursts and
causes internal bleeding.
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- Strokes that did occur among the rats taking E-selectin
produced significantly less brain damage than strokes in the rats not receiving
this critical protein, the researchers reported. Testing revealed E-selectin
among the treated rats produced a type of chemical called a cytokine that
prevented inflammation in the blood vessels.
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- "Normally with a vaccine, what you want to do is
activate the immune system," Hallenbeck told United Press International.
"Here, the reason it was called a vaccine was that we were giving
a protein ... but instead of developing an immune response, the lymphocytes
(became) immosuppressive." They suppressed part of an immune system
reaction.
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- Although a single shot will not protect against stroke,
the researchers said the findings suggest repeated doses of the E-selectin
vaccine could assist in preventing stroke for the long-term.
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- Hallenbeck said the findings are so encouraging an E-selectin
vaccine should be tested in human studies. A Phase I clinical trial is
planned to test the effects of human and bovine E-selectin vaccines in
patients at high risk for stroke. That study will assess whether the vaccines
are safe to use and what the side effects may be.
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- Bovine E-selectin will be tested in addition to the human
protein because there is a chance it may produce a stronger response. The
two vaccines are being produced by Novavax Inc. of Columbia, Md., under
a cooperative agreement with NINDS.
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- "The important thing about this work is that the
majority of effort that's gone into preventing stroke and prevent heart
attacks has gone into preventing platelets and in preventing clotting,"
Hallenbeck said. "This is a new dimension that hasn't been explored
perhaps as much as it deserves."
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- Hal Unwin, director of the stroke program at the University
of Texas Southwestern Medical Center in Dallas and a neurologist, called
the research exciting.
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- "To basically have 16 times fewer strokes, I mean,
is just incredible," Unwin told UPI. "That's a big response.
Now, whether that can be translated into humans isn't known."
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- Stroke prevention requires high-risk patients to exercise,
eat healthy, and in some cases, adhere to their medication treatments.
One of the big advantages of a vaccine, Unwin said, is it would help people
who might have difficulty complying with traditional stroke therapies and
prevention strategies.
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- "Clearly the best chance we have in stroke is prevention,"
he said. "And stroke is pretty much a preventable disease. And with
a vaccination, basically it doesn't require the patient to do much of anything."
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- Stroke is the third-leading cause of death among Americans
with more than 500,000 new cases every year and about 150,000 deaths annually
from stroke-related causes.
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- The study is published in the September issue of Stroke.
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- Copyright © 2002 United Press International. All
rights reserved.
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