A new study suggests that bites from mosquitoes not infected with malaria may trigger an immune response limiting parasite development following bites from infected mosquitoes. The researchers from the Center for Global Health and Infectious Diseases, University of Notre Dame, Indiana and the National Institute of Allergy and Infectious Diseases, Bethesda, Maryland report their findings in the May 2007 issue of the journal Infection and Immunity.
Malaria, a major public health threat resulting in 3 million deaths annually, is transmitted to humans through mosquito bites. Emerging drug and insecticide resistance emphasize the urgent need for effective new vaccines.
In the study researchers compared immune responses of mice preexposed to uninfected mosquito bites followed by bites from mosquitoes infected with the malaria parasite, Plasmodium spp. and those of mice only exposed to infected mosquitoes. Results showed that in the early stages, mice preexposed to uninfected bites exhibited reduced parasite burdens in the liver and they remained lower during the blood-stage of the life cycle of infection.
"These data suggest that the addition of mosquito salivary components to antimalaria vaccines may be a viable strategy for creating a Th1-biased environment known to be effective against malaria infection," say the researchers. "Futhermore, this strategy may be important for the development of vaccines to combat other mosquito-transmitted pathogens."
(M.J. Donovan, A.S. Messmore, D.A. Scrafford, D.L. Sacks, S. Kamhawi, M.A. McDowell. 2007. Uninfected mosquito bites confer protection against infection with malaria parasites. Infection and Immunity, 75. 5: 2523-2530).
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