Research on preventing malaria often focuses on mosquitoes, seeking to kill them or to make them immune to infection by the Plasmodium protists that cause the disease. A new idea was published February 25 in Science. There, scientists sought to prevent the transmission of malaria by infecting mosquitoes with a genetically souped-up version of a fungus that naturally attacks the insects in the wild. To show where the Metarhizium anisopliae fungus circulates in the mosquito body, the researchers tagged the fungus with green fluorescent protein, creating this glowing mosquito.

Metarhizium anisopliae infects mosquitoes through their cuticle, and then enters their immune system. Researchers took Metarhizium anisopliae's DNA and added several genes to it. One gene was [SM1]₈, which makes a protein that prevents protists from entering mosquito salivary glands. Malaria-causing cells are transferred through the salivary glands when mosquitoes bite. Another gene expressed the protein scorpine, which makes an antimicrobial molecule that scorpions naturally produce in their venom. The researchers created genetically altered fungi carrying just [SM1]₈, just the scorpine gene and both the [SM1]₈ and scorpine genes.

The researchers then fed mosquitoes blood infected with Plasmodium falciparum, the deadliest of the four Plasmodium organisms that cause malaria. Eleven days later, they sprayed the mosquitoes with different combinations of the transgenic fungi they had made.

The most effective treatment combined two types of the transgenic fungi. Only 25 percent of the mosquitoes treated with both the scorpine-enhanced fungus and the [SM1]₈/scorpine-enhanced fungus carried malarial cells after treatment, compared to 94 percent of untreated mosquitoes. The treated mosquitoes that did still carry infectious cells showed a 98 percent reduction in Plasmodium falciparum in their bodies.

The researchers are in the midst of U.S. federal evaluation of their transgenic fungi, said Raymond St. Leger, a University of Maryland entomologist and one of the co-authors of the study, in a prepared statement. After that, he said, "our principal aim is to get this technology into field-testing in Africa as soon as possible."

—Francie Diep