Mosquito immunity to fight malaria
doi:10.1038/nindia.2010.47 Published online 15 April 2010
Malaria researchers have uncovered that a complex of substances secreted inside the midgut of the malaria vector Anopheles gambiae actually helps protect its gut microbes. This could be promising in the development of a vaccine that activates the mosquito's immune system to fight the malarial parasite and prevent transmission of the deadly disease.
The mosquito, like most insects, harbours large number of commensal bacteria within its guts. When A. gambiae feeds on blood, the midgut secretes a peritrophic matrix in response. This matrix is a semipermeable layer of chitin polymers that surrounds the blood meal and prevents blood cells and gut bacteria from coming into direct contact with midgut epithelial cells.
The researchers characterised a heme peroxidase—immunomodulatory peroxidase (IMPer) secreted by A. gambiae midgut epithelial cells in response to blood feeding. This enzyme, together with a dual oxidase (Duox), forms a protective protein network barrier around the ingested blood. The barrier protects Plasmodium parasites by preventing mosquitoes from mounting an immune response to kill them.
"It might be possible to prevent the formation of the protein barrier by immunising people with IMPer or Duox. Such a vaccine would generate antibodies that, after a mosquito feeds on a human, could disrupt the barrier and activate the mosquito's immune system to fight the parasite and prevent malaria transmission," says lead researcher Carolina Barillas-Mury.
This is a previously unrecognised function of the peroxidase/Duox system.
The authors of this work are from: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Maryland, USA and presently the Biological Sciences Group, Faculty Division III, Birla Institute of Technology and Science, Pilani, Rajasthan, India.