Via newscientist.com -
Exposure to the saliva of biting insects could later protect people against infection by insect-borne parasites. If the components of saliva that confer protection can be isolated, they could be used to boost the strength of future vaccines against malaria and other deadly diseases.
The phenomenon has previously been documented in leishmaniasis - a skin disease spread by sandflies that currently afflicts many soldiers returning from Iraq. Now a study in mice has shown mosquito saliva can protect against malaria.
People who live in regions where insect-borne parasitic diseases are widespread, such as Africa and the Middle East, often show greater resistance to infection than people from other parts of the world. It had been assumed that the protection comes from repeated exposure to the parasite over a person's lifetime, but now it seems that repeated exposure to uninfected saliva could also play a part in generating immunity.
"In some areas people can get up to a thousand mosquito bites a day," says Mary Ann McDowell, an immunoparasitologist at the University of Notre Dame in Indiana. "That's a lot of mosquito spit."
After animal studies showed that prior exposure to sandfly saliva conferred protection against leishmaniasis, McDowell decided to test for the same effect in malaria. Working with researchers at the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, her team exposed mice to mosquitoes carrying the malaria parasite, some of which had previously been bitten by uninfected mosquitoes.
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