Genetically modified approaches to fighting malaria succeed in new tests

Malaria is caused by a parasite that lives in the mosquito's gut and infects humans when the mosquito bites. Photo / 123RF

A laboratory tweak which attracts mosquitoes to genetically modified mates is showing promise in the battle against malaria.

The mosquito-borne disease is proving increasingly resistant to drugs so researchers are turning to GM ideas.

In 2015, there were roughly 212 million cases of malaria and 429,000 deaths. Two studies published in the journal Science illustrate the potential of genetic engineering for fighting the disease. Both studies were conducted at Johns Hopkins University's Malaria Research Institute.

Malaria is caused by a parasite that lives in the mosquito's gut and infects humans when the mosquito bites.

The first study focused on whether mosquitoes genetically modified to be more resistant to the malaria-causing parasite became weaker and less able to mate and breed.

The study, led by mosquito vector biologist George Dimopoulos, found one type of genetically modified mosquito not only bred well, but became more attractive to normal mosquitoes.

Dimopoulos took a group of genetically modified mosquitoes and a group of wild normal mosquitoes and locked them up together.

To his surprise, the normal male mosquitoes preferred the genetically modified females, while the genetically modified males went wild over normal females. Those mating preferences meant that within one generation, the mosquito population was becoming 90 per cent genetically modified.

The results suggest the genetically modified mosquitoes would not just thrive but could possibly drive their genetic immunity to the malaria parasite into mosquito populations to which they are introduced.

The biggest concern about such an approach, as it is with all applications of genetic modification, is the spectre of unintended consequences. The second study uses genetic modification of bacteria found inside mosquitoes to fight malaria. Researchers genetically modified a type of bacteria, causing it to secrete a substance inside the mosquitoes' gut that killed off the malaria-causing parasite before it could develop properly.

The researchers, led by biologist Marcelo Jacobs-Lorena, worked for five years on a way to use genetically modified bacteria against malaria.

Early on in their work, researchers struggled to find a way by which the genetically modified bacteria could be handed down to the offspring of the treated mosquitoes.

Through happenstance, while dissecting the bodies of mosquitoes during earlier attempts, they found a type of bacteria that consistently wormed its way into the ovaries of female mosquitoes and the reproductive glands of male mosquitoes in addition to the mosquito's gut. Because of that placement in the reproductive organs, the genetically modified versions of the bacteria automatically spread to offspring in generation after generation.

The next step for both approaches - the genetically modified mosquitoes and bacteria - is to test if they work outside the lab in conditions simulating nature. Johns Hopkins has built a "mosquito house" research facility in Zambia designed specifically for such experiments.

"It's like a greenhouse but instead of glass, it's covered with nets to keep the mosquitoes inside," Jacobs-Lorena said.

But the researchers must first convince the Zambian government to allow their genetically modified subjects into its borders.