Researchers Find Promising Brain Injury Vaccine in Rat Study

5:44 PM EST; February 24, 2000; Washington, D.C. (AP) -- An oral vaccine that protects brain neurons from injury caused by epilepsy seizure or by stroke has been tested successfully in rats, U.S. researchers report. In a study to be published Friday in the journal Science, researchers at the medical school of Thomas Jefferson University in Philadelphia report that a vaccine given to rats caused their immune system to develop antibodies that prevented the action of a protein that causes damage after brain injury. Dr. Matthew During, Professor of Neurosurgery at Jefferson and lead author of the study, said the vaccine works against a brain protein, called the NMDA receptor, that has been shown to aggravate brain damage after a stroke and to play a role in epileptic seizures.

Other researchers have tried to block the action of the NMDA receptor using drugs, but these drugs often fail to effectively cross the blood-brain barrier, a natural barrier that protects the brain from most destructive substances in the blood. By using a vaccine, the researchers prompt the body, in effect, to make its own NMDA blocker by creating antibodies that neutralize the protein after brain injury.

In the study, some rats were immunized with the anti-NMDA antibody while others were not. A month later, the rats were injected with a neurotoxin, kainate, which causes seizures similar to those in epilepsy. Among the control rats, which were not immunized, there was a seizure rate of 70 percent. Among those with the anti-NMDA antibody, the seizure rate was 20 percent.

In another study, immunized and nonimmunized rats were tested after five months for protection from stroke damage. An artificial stroke was induced in the animals using a drug. Among the immunized rats, said During, "We found dramatic protection in the rats' brains. ... It doesn't stop the stroke from occurring, but the amount of brain damage is diminished by 70 percent." None of the studied rats showed abnormal behavior from the vaccine, he said.

The study has been conducted only in rats, and During said a vaccine may cause unknown effects that are not reversible. "We are continuing to look at long-term effects," the authors said in the Science study. "These experiments and additional safety studies need to be investigated before any translation of this technology to the clinic."