New nasal vaccine blocks parasite transmission to mosquitoes

An experimental nasally administered malaria vaccine prevented parasite transmission from infected mice to mosquitoes and could play an important role in the fight against human malaria, ScienceDaily reported Dec. 20.

Researchers from Japan report their findings in the December issue of the journal Infection and Immunity.

Malaria is one of the most significant infectious diseases affecting developing countries. Mortality and morbidity levels are high and although anti-malarial drugs and insecticide-treated bed nets have somewhat reduced the number of malaria infections; additional prevention and treatment methods such as vaccines are needed.

Prior studies show that the ookinete-to-oocyst phase in the malaria life cycle, when the malarial parasite is fertilized in the mosquito's body, is one of the most vulnerable stages making it an ideal target for anti-transmission vaccines.

In the study researchers developed a nasal vaccine based on ookinete-surface proteins (also known as parasite antigens) and intranasally vaccinated mice infected with malaria. When given in conjunction with the cholera toxin adjuvant, vaccinated mice developed a robust antibody response and prevented transmission of the parasite to mosquitoes that were allowed to feed on them after infection.

"To our knowledge, this is the first time that mucosal vaccination has been demonstrated to be efficacious for directly preventing parasite transmission from vaccinated animals to mosquitoes, and the results may provide important insight into rational design of nonparenteral vaccines for use against human malaria," the researchers say.