PARASITOLOGY

Mosquitoes Complement Malaria

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Science  19 Mar 2004:
Vol. 303, Issue 5665, pp. 1733
DOI: 10.1126/science.303.5665.1733b

Not all strains of the mosquito Anopheles gambiae are able to host or transmit malaria parasites with equal efficiency. Even in susceptible strains, most parasites are killed and cleared before they can be passed on to the next host. Blandin et al. have investigated a thioester-containing protein (TEP1) that was previously discovered to be important in mosquito immune responses to bacterial pathogens and that has homology to mammalian complement factors. Double-stranded RNA knockdown experiments rendered both susceptible and refractory strains of mosquito highly vulnerable to parasite establishment. Blandin et al. realized there were two alleles: TEP1r, which occurs in the refractory strains of mosquito that encapsulate parasites in melanin, and TEP1s, which regulates the resistance to parasites observed in susceptible mosquitoes. The difference probably lies in the kinetics of binding to the parasite, with TEP1r being faster than TEP1s. It is known that TEP1 is a glycoprotein secreted into the hemolymph by hemocytes, and in bacterial infections TEP1 apparently tags the pathogen surface with its C-terminal domain via the thioester bond, rendering it liable to phagocytosis. Something similar probably happens to the malaria parasites. — CA

Cell 116, 661 (2004).

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