Researchers have created a genetically engineered fungus with the goal of blocking transmission of malaria parasites by mosquitoes.
In a study appearing today in Science, researchers from the University of Maryland, Johns Hopkins School of Public Health, and the University of Westminster in London describe how they inserted the genes of specific biological agents into Metarhizium anisopliae, a naturally occurring fungus found throughout the world that causes disease in various insects. The transgenic fungi reduced the number of infectious sporozoites by up to 98% in a rodent malarial model. Sporozoites are the form of the malaria parasite that the mosquito transmits to humans.
The researchers generated various genetically modified strains of M anisopliae that produced a peptide that blocks attachment of sporozoites to the mosquito salivary glands, an antibody that causes sporozoites to clump together, an antimicrobial toxin, or a combination of all three, tailored to target sporozoites. Their greatest success came with an M Anisopliae–expressing scorpine (an antimicrobial peptide isolated from scorpion venom) and a fusion protein that combined attributes of scorpine and the attachment-blocking peptide. They added that their best success rate was also related to exposing a mosquito to the fungal biopesticide soon after the insect ingested the malaria parasite, which takes from 12 to 14 days to develop into infectious sporozoites.
In addition, as the malarial parasites develop resistance, scientists can introduce genetic modifications to the fungi to counter this problem.
One potential advantage of using a fungus to fight malaria is that it infects through direct contact with the mosquito’s outer shell, lending itself to treatment strategies currently used for insecticides, such as being sprayed on indoor surfaces, including cotton ceiling hangings, curtains, and bed nets, or in outdoor odor-baited traps. In addition, the fungal spores can remain on some treated surfaces for months.
It is estimated that nearly half of the world’s population is at risk of contracting malaria. More than 1 million children, mostly in Africa, die of the disease every year.