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Vaccine Against Sand Fly Saliva Prevents Leishmaniasis in Mice

By Kate Wong

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A vaccine containing components of sand fly saliva may one day offer people protection against a devastating tropical illness, according to new research. In a report published today in the Journal of Experimental Medicine, scientists describe how their vaccine prevents leishmaniasis in mice.

Leishmaniasis, which comprises a group of related diseases caused by the parasite Leishmania, is transmitted through the bite of a sand fly. Earlier research had shown that lab animals immunized with sand fly saliva commonly resist infection when later bitten by Leishmania-carrying flies. With that in mind, Jos Ribeiro of the National Institute of Allergy and Infectious Disease and colleagues decided to try developing a vaccine against leishmaniasis. Specifically, the team worked with saliva from the sand fly that carries a skin-lesion-causing variant of the parasite. Analyses of the saliva revealed that one of its protein components, known as SP15, appeared to elicit a natural immune response in mice. Subsequent identification of the SP15 gene enabled the researchers to construct a DNA vaccine.

The team's unconventional vaccine worked. Mice that received it fared much better than mice that didn't when challenged with an injection containing parasites mixed with saliva. Indeed, whereas immunized mice exhibited only small lesions and cleared the infection within six weeks, unvaccinated mice suffered large ulcers and failed to get rid of the parasites.

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Next Ribeiro plans to test the vaccine in dogs and monkeys, and work on developing vaccines against the other leishmaniasis variants. It won't be easy. "Different sand fly species, each with its unique collection of salivary proteins, transmit different Leishmania species," he notes. "If anti-saliva vaccines are to work in people, they will have to be specifically engineered for the problem insects of each region."

Kate Wong is an award-winning science writer and was formerly senior editor for features at Scientific American, where she focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

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