"But nobody had put the three together," Christophides said. "Now we can show that there's a pathway in effect."
How It Might Work
A mosquito-up approach to malaria control is feasible in the long term, researchers say. There are a couple of ways it could work.
In one scenario, scientists could create genetically modified mosquitoes, granting their immune systems pumped-up malaria-killing abilities.
The key would be to find a genetic drive mechanism—some factor that would give the new, malaria-fighting genes a selective advantage and help them spread quickly through wild mosquito populations via breeding, said Gregory Lanzaro, director of the Vector Genetics Lab at the University of California, Davis.
No one has figured this out for mosquitoes yet. But the U.S. Centers for Disease Control and Prevention is already testing a similar concept in blood-sucking assassin bugs as a way to stop the spread of deadly, difficult-to-cure Chagas disease, Lanzaro said.
The other option would be to develop antibodies that can fight the parasites' early, mosquito-dwelling forms—and "feed" the antibodies to the insects via human blood.
Mosquito immune systems don't produce antibodies on their own. And by the time the parasites reach humans, they have matured and found ways to hide out from human antibodies, said Marcelo Jacobs-Lorena, professor of molecular microbiology and immunology at the Johns Hopkins Malaria Research Institute in Baltimore.
But if we vaccinate humans with antibodies that target mosquito-stage malaria, those antibodies could be passed on to the mosquitoes when they feed on treated human blood, Jacobs-Lorena said.
Combined with a second, protective vaccine, this could be a real possibility, he said.
"There's a partially effective vaccine that protects humans that's being tested," Jacobs-Lorena said. "Neither it, nor the transmission-blocking vaccine would be 100 percent effective, but the combination may work."
(See malaria pictures.)
No Quick Fix
Getting to these paradigm-shifting malaria prevention techniques isn't likely to be quick or easy.
The three-protein mechanism isn't the only factor involved in mosquitoes' malaria-fighting powers. And the new study might not provide the full picture.
The work was done using a model parasite—a version of malaria adapted to rodents, rather than humans—and laboratory mosquitoes, which are often genetically different from their wild cousins.
Studies done this way haven't always reflected what happens in nature, the University of California's Lanzaro said. Johns Hopkins's Jacobs-Lorena agreed.
"Research in recent years has shown that mosquitoes react differently to a parasite they aren't used to seeing, as opposed to the ones they've co-adapted with in the field," Jacobs-Lorena said.
The new discovery, he added, "is an important finding, but it must be validated with human parasites."
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