Exposure to Saliva of Uninfected Mosquitoes Could Protect Against Malaria, Study Says

Exposing people to the saliva of mosquitoes that are not carrying malaria parasites could later trigger immune system responses that protect again the disease, according to a study published in the March 5 issue of the journal Infection and Immunity, the New Scientist reports. For the study, Mary Ann McDowell of the University of Notre Dame and colleagues in collaboration with NIH's National Institute of Allergy and Infectious Diseases exposed mice to mosquitoes carrying malaria parasites. Some of the mice previously had been bitten by uninfected mosquitoes. The mice that previously had been exposed to uninfected mosquito saliva had lower levels of malaria parasites in their liver and blood, the researchers found. The infected saliva prompted their immune systems to produce infection-fighting chemicals called cytokines, which usually are associated with CD4+ T cells. McDowell said additional research is needed before components of insect saliva can be used in a potential malaria vaccine developed for humans. Her team currently is studying the specific salivary protein that could have prompted the immune system to produce CD4 cells, and it then plans to test whether that protein prompts a similar immune response in humans, the New Scientist reports. Previous studies have shown a link between exposure to sandfly saliva and resistance to leishmaniasis, a skin disease that is spread by sandflies. "In some areas people can get up to a thousand mosquito bites a day," McDowell said, adding, "That's a lot of mosquito spit" (Pearson, New Scientist, 3/24).

The study is available online.