A New Approach to Blocking Malaria Transmission

A promising new pathway to treating malaria focuses on potential targets to inhibit transmission of the parasite Plasmodium that causes the disease.

Researchers at the University of Illinois (UIC; Chicago, USA), hypothesized that if they could disrupt the function of a cell-surface transport protein known as Feline leukemia virus subgroup C receptor-related (FLVCR) that mosquitoes express after feasting on blood to protect cells from the toxicity of excess heme (iron), it will increase the oxidative stress in the mosquito midgut, thus hampering Plasmodium at a crucial point in the parasite's life cycle. Working with two common malaria-transmitting mosquitoes (Anopheles gambiae and Anopheles stephensi), the researchers proceeded to isolate the gene encoding mosquito FLVCR proteins.

Using gene-silencing techniques, they were then able to reduce significant levels of FLVCR in the mosquito gut, in effect creating a tool that breaks the cycle of transmission occurring when a person is bitten by a mosquito bearing the parasite. The next step in the research will be to analyze the effects on parasite transmission, and to develop a vaccine to block transmission. If this is successful, as the researchers claim, the mosquito "would no longer be a womb but a tomb for Plasmodium”. The study was presented at the American Society of Hematology's 2010 annual meeting, held during December 2010 in Orlando (FL, USA).

"If disruption of the function of the protein inhibits parasite transmission, then we can potentially use parts of the protein as an antigen to try to stimulate a vaccine in people,” said senior author and study presenter John Quigley, MD, an assistant professor of medicine at the UIC College of Medicine. "So the antibody blocks FLVCR and increases oxidative stress, and now the Plasmodium is not able to complete its life cycle, thus preventing the spread of malaria.”

Female mosquitoes ingest large amounts of hemoglobin from blood, which serves as a food source required for mosquito egg development. When a mosquito ingests infected blood, Plasmodium reproduces in the mosquito gut, and the fertilized egg cells cross the lining of the mosquito gut, developing into oocysts; after maturing, the oocysts rupture and release thousands of new parasites that allow the mosquito to transmit malaria when it bites another human.

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