Researchers in Europe have identified a handful of mosquito genes which the Science and Development Network says could be crucial in the control of the strain of malaria common in Africa. Focusing on the go-between — the mosquito — rather than the human victim could be the key, the team says.
Fotis Kafatos, Mike Osta and George Christophides of the European Molecular Biology Laboratory in Heidelberg, Germany, have pinpointed three mosquito genes that control the insect’s immune response to the malaria parasite. The genes thus directly affect whether the parasite, which causes the disease when it is injected into the human blood stream through a mosquito bite, can survive in the mosquito gut. Their results have been published in the journal Science.
”Many researchers focus on the direct effects of plasmodium (the parasite) on the human body, but the mosquito is an equally important battleground in fighting the disease,” notes Kafatos. ”We now see a way to potentially stop the parasite in its tracks.”
The researchers worked with anopheles gambiae, the principal middleman behind human malaria in Africa, and the rodent malaria parasite plasmodium berghei.
They showed that two mosquito genes make proteins that protect the parasite from the mosquito’s own immune system while it grows in the gut. In contrast, a third mosquito protein is lethal to the parasite.
When the first two protective genes were switched off, the mosquitoes’ immune systems killed off most of the invading parasites. But inactivating the lethal protein gene triggered a substantial increase in parasites. The results indicate the parasite has successfully co-evolved with its host, effectively subverting insect proteins in order to facilitate its own development.
”If we strip away protective proteins, the parasite becomes vulnerable to the mosquito’s immune system,” says Christophides. ”Developing novel chemicals to inhibit the ability of such proteins to protect the parasite is a promising avenue for reducing the prevalence of malaria.”
Kafatos agrees. ”These studies are the first to show the power of the mosquito’s immune system, and give us some very real options for fighting the disease in the insect before it even has a chance to be passed to a human,” he explains.
”There is no single magic bullet for controlling this ancient scourge of humanity, but we want to exploit this new lead to contribute to the defeat of malaria.”
In an article accompanying the paper in Science, Janet Hemingway and Alister Craig of the Liverpool School of Tropical Medicine are optimistic. But they warn that ”this achievement is only the first small step along the difficult road to practical implementation of such strategies.”
This team’s study is not the only European Molecular Biology Laboratory breakthrough in the war on malaria. A second team, led by Elena Levashina, has demonstrated that another mosquito gene makes a protein that kills off the parasite directly in the gut.
This study, whose results were published earlier in the journal Cell, also provides important insight into the reasons that individual mosquitoes of the same species display genetic variation in their susceptibility to parasites. The studies ”represent an important step,” says Levashina.
Stephanie Blandin, a co-author of the Cell article, says that both studies demonstrate that the mosquito’s immune system has the ability to defend itself against malaria. ”By enhancing these natural defenders, we may be able to block the parasite-mosquito cycle.” — SciDev.Net