Global Health: Sand Fly Saliva Proves a Good Monkey Vaccine for Leishmaniasis

A vaccine against leishmaniasis based on the saliva of sand flies has worked well in monkeys and may have potential to work in humans, according to a new study.

Leishmanias, caused by a parasite injected by the bite of bloodsucking sand flies, infects about one million people a year, mostly in the Middle East and South America. It can cause long-lasting skin sores — known to American troops in Iraq as the “Baghdad boil.” Another form, called kala azar, found in India and Africa, is caused by a related parasite that attacks internal organs and can be fatal.

There is currently no human vaccine, and the drugs that kill the parasites have harsh side effects.

The new study, led by researchers at the National Institutes of Health and published this month in Science Translational Medicine, found that monkeys bitten by sand flies that carried no leishmaniasis parasites developed some immunity to the disease — suggesting that the saliva itself was somehow involved in the infection process.

The researchers isolated one saliva protein, now known as PdSP15, and found that it alone set off some immunity to the parasites in seven of 10 monkeys that were injected with it. Cells from humans bitten by sandflies also reacted to PdSP15, suggesting the protein might protect people.

Dr. Peter J. Hotez, the president of the Sabin Vaccine Institute, who was not part of the study but whose institute has helped the N.I.H. team increase its production, said the work could open a new route to a vaccine, but much remained to be learned.

“Exactly how the saliva does this is a bit of a a mystery,” he said.

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(via NY Times)