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Sand Fly Spit Vaccine

© Neal Rolfe Chamberlain

Truth is oftentimes stranger than fiction. Some of the best stories come from the real world. In fact many authors use real life stories to jump start their novels. Usually vaccines consist of components from the microbe that causes the disease you what to be protected against. However, in the world of Leishmania sand fly spit (saliva) may actually work best at preventing Leishmaniasis than components from the parasites themselves.

Leishmaniasis infections occur in over 2 million people each year in Asia, Africa, Europe, Central America, and South America. There are three different forms of leishmaniasis caused by three different species of Leishmania (L. tropica, L. braziliensis, L. donovani). Leishmania is a parasite that is transmitted from animals (dogs, rats, mice) to humans by the bite of a sand fly. These parasites infect our blood and tissues.

Leishmania donovani causes the most severe form of this disease. It infects the organs (liver, kidney, spleen, large intestine) causing fever, diarrhea, anemia. If not treated this disease called Kala-azar or dum dum fever is fatal. Click here to find where Kala-azar is found in the world.

Leishmania tropica only infects the skin. Our bodies can eliminate it without any treatments however is causes disfiguring scars in the skin at the site the sand fly has bitten. This disease is called cutaneous leishmaniasis. It is also called by many other names (Oriental sore, Jericho boil, Aleppo boil, or Dehli boil; image of sore). Click here to find were this disease is located in the world.

Leishmania braziliensis causes the same sort of scars as does L. tropica except that it can also spread and infect mucous membranes (areas inside the nose and mouth). This disease is called mucocutaneous leishmaniasis. It is also called espundia, chilero ulcer, and uta. If left untreated it can also be fatal. Mucocutaneous leishmaniasis is found primarily in Central and South America.

While working with this parasite a team of researchers lead by Jose Ribeiro found that if they purified the parasite and tried to infect another mouse the parasite could not cause any damage to the new mouse. If they fed the purified parasites to sand flies and allowed them to bite uninfected mice the mice would soon develop skin damage from the parasites. Thinking that there may be something in the sand fly saliva that helps the parasites to infect the mice Ribeiro's team mixed sand fly saliva with purified parasites and found when mixed with saliva the parasites could cause damage to the skin of the mice.

After much hard work they identified a protein called SP-15 in the sand fly saliva that was helping the parasite infect the mice. The researchers