BBC Monday, 6 August, 2001, 23:43 GMT 00:43 UK Vaccine from sand fly spit Leismaniasis is common in parts of Africa The saliva of a fly which carries a dangerous parasitic illness has provided the unusual source for a vaccine.

Leishmaniasis affects an estimated 12 million people worldwide, most of them in south or central America, Africa and the Middle East.

It causes "flesh-eating" nose, throat and mouth infections, skin lesions, or even fatal infestations of the internal organs.

Normally, the vaccine might be expected to target the single-celled parasite which causes the damage, which is transmitted when a carrier sand fly bites its victim in order to take blood.

Scientists from the National Institute of Allergy and Infectious Diseases in America decided instead to look at the saliva in which the parasites make their way into the human body.

They looked at the saliva closely, trying to identify body proteins specific only to it.

The gene which helped produce one of them, called SP15, appeared to already provoke a smaller immune response in mice.

They used it to make a DNA vaccine, so that that immune response could be reproduced in humans.

When this vaccine was used to immunise specially-created mice with no immunity of their own, they were protected against the parasite.

Further tests

There are now plans to test the vaccine in dogs and monkeys, and to try to work out if the body's natural ability to produce an immune response to sand fly saliva is the reason why some people do not get leishmaniasis, despite getting bitten by infected flies.

Dr Jose Ribeiro, who led the team, said: "People get bitten by sand flies all the time without developing leishmaniasis.

"It could be that those who develop disease are merely unlucky - they are bitten by a Leishmania-carrying fly before uninfected flies have had time to naturally immunise them."

Unfortunately, there is not a single vaccine which will protect the world against the disease, as there are many different types of leishmaniasis which plague different regions.

Separate vaccines would have to be developed for all of them.

This is not the first time that the saliva of this particular insect has yielded a protein useful to medical science.

In the 1980s, scientists discovered a protein called maxadilan which appeared to open up blood vessels, increasing blood flow.

It was hoped this would contribute to a baldness treatment, and investigations continue into its possible use as an immune system suppresser and cardiovascular drug.

-- Anonymous, August 06, 2001