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Malaria-Transmitting Mosquito Has Immunological Memory, NIAID Study Suggests

Photo of annopheles gambiae mosquito being injected with hemolymph for malaria study
An Anopheles gambiae mosquito is shown being injected with hemolymph, the insect's primary circulatory fluid, as part of a malaria study.
Credit: NIAID/J. Rodrigues

A new study by NIAID scientists proposes that Anopheles gambiae—the mosquito that most commonly spreads malaria—has an immune “memory” that could one day be taught to resist infection by malaria parasites.

Humans have an adaptive immune memory—for example, people exposed to measles virus only are infected once, and thereafter their immune system recognizes the virus and prevents re-infection. For decades, scientists believed that insects could not learn how to respond better to re-infection because they lacked adaptive immune responses.

NIAID scientist Carolina Barillas-Mury, M.D., Ph.D., and her research group found that A. gambiae mosquitoes experience enhanced immune surveillance after the malaria-causing parasite Plasmodium invades the mosquito midgut and mingles with gut flora and cells. When mosquitoes are exposed a second time to the parasite, the insect’s immune response is more robust and efficient at fighting off infection. Their studies suggest that the first exposure releases a long-lasting immune substance into the midgut, triggering changes in hemocytes—the mosquito’s equivalent of white blood cells in humans. These changes permanently increase the number of disease-fighting granulocytes in the blood of mosquitoes. Transferring blood from primed mosquitoes to mosquitoes that had not been infected also resulted in more granulocytes and enhanced the immune response to Plasmodium infection.

Dr. Barillas-Mury said her group is trying to identify the specific substance in the mosquito blood that enhances immunity to Plasmodium parasites. Once this substance is known, scientists will explore the possibility of using it to identify mosquito pathogens or chemicals that can prime the mosquito immune system to resist malaria-causing parasites, thereby reducing the ability of A. gambiae mosquitoes to transmit these parasites to humans.

The study is published in Science.

Reference: Rodrigues J et al. DOI: 10.1126/science.1190689 (2010)

Last Updated September 09, 2010

Last Reviewed September 07, 2010