Healthwatch: Breaking Down Barriers

West Nile virus is one of many mosquito-spread diseases that attack the brain. Researcher Priti Kumar explains that a big reason there's no cure for deadly brain infections, is a natural barrier.

The so-called "blood-brain barrier", tightly-packed cells around the blood vessels, prevents drugs in the bloodstream from passing into the brain.

"The only way you can do it is by complex surgery where, which would involve direct injections into the brain," said Kumar of the CBR Institute for Biomedical Research.

Kumar and her colleagues at Harvard's CBR Institute set out to stop brain- attacking viruses using a new type of medicine called RNA interference. It uses small pieces of genetic code to switch off specific disease-causing genes.

When the researchers injected their RNA drug into the brains of mice, they found it could both prevent and cure the viruses.

"When we used the small RNA molecules, we found that more than 80 percent of the mice survived in all the experiments that we did repeatedly," said Kumar.

But to use it in people, they needed a better way to deliver the new drug. So they stole a trick from another virus that breaks through the blood-brain barrier, rabies.

As they wrote in the journal "Nature," they attached their drug to a harmless protein that carries rabies into the brain. That let them give the drug with a simple IV injection.

"This also shows us that this molecule is capable of carrying any kind of cargo across into the brain," Kumar said.

Meaning the strategy could also speed new drugs for other brain diseases from Alzheimer's to cancer.

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