Researchers Unlock Meningitis' Secrets

A cellular 'key' helps bacteria pierce brain's defenses

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By Randy Dotinga
HealthDay Reporter

FRIDAY, Sept. 2, 2005 (HealthDay News) -- Scientists believe they're getting a better handle on how some meningitis germs make the difficult trip from the bloodstream into the brain, potentially paving the way for better treatments.

"We hope this will eventually lead to different therapies, although it's hard to say how many years it would take," said Kelly Doran, assistant adjunct professor of pediatrics at the University of California at San Diego and co-author of a study that appears in the September issue of the Journal of Clinical Investigation.

Meningitis refers to diseases that strike the lining of the brain, known as the meninges. Antibiotics are often an effective treatment for the bacterial streptococcus form of meningitis, but untreated cases can lead to deafness, seizures, epilepsy and cerebral palsy. "It's due to the damage you incur by having the bacteria in your brain, and by your own inflammatory (swelling) response," Doran explained.

One of the mysteries of meningitis is how the germ manages to pass through the "blood-brain barrier," which normally protects the brain from all kinds of germs and other invaders that live in the blood. According to Doran, "It's been important to figure out how some of these bacteria have developed the ability to get in there."

Her team looked for the answer by studying mice, pinpointing which strains of streptococcus meningitis were able to infect them. They discovered that some strains had more trouble getting through than others.

Later research confirmed that these weaker strains lacked a molecule that usually sticks out from the bacterium's cell, poking through the blood-brain barrier. Essentially, Doran said, it's a kind of key.

Ninety percent of mice managed to survive after they were infected with a genetically engineered meningitis strain lacking this key, the researchers reported. On the other hand, mice infected with a normal strain died within days.

What does this mean for treatment? One approach might be to use a drug or vaccine to change the "locks" in the blood-brain barrier, making it impossible for meningitis germs to get through even if they have the key, Doran said.

The study results are promising, said Dr. Allan R. Tunkel, a professor of medicine at Drexel University who studies meningitis. While a new drug treatment won't help people already infected with meningitis -- including very young babies, who are especially vulnerable to the streptococcus strain -- it could help prevent germs from working their way into the brain, he said.

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SOURCES: Kelly S. Doran, Ph.D., assistant adjunct professor, pediatrics, University of California at San Diego; Allan R. Tunkel, M.D., Ph.D., professor, medicine, Drexel University, Philadelphia; September 2005 Journal of Clinical Investigation

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