Scientists engineer mosquitoes that cannot transmit malaria

Half of the world’s population is at risk of malaria, which remains one of the world’s most devastating diseases. In 2021 alone, it infected 241 million and killed 627,000 people, mostly children aged below five years old in sub-Saharan Africa, the Imperial College of London informs.

Scientists have engineered mosquitoes that cannot spread malaria to humans, stating that their work could potentially eliminate the disease.

Researchers from the Transmission: Zero team at Imperial College London have reportedly engineered mosquitoes that slow the growth in their gut of the parasites that cause malaria.

This delay would mean the mosquito would reach its natural lifespan before the parasite would reach the mosquitoes' salivary glands. So, a bite from the mosquito would not spread the disease.

Malaria is spread when a female mosquito bites a person infected with the malaria parasite.

The parasite then develops in the mosquito's gut - it travels to its salivary glands, and can spread to the next person the mosquito bites.

However, only about 10% of mosquitoes live long enough for the parasite to become infectious and the genetic engineering would reportedly delay that development.

This was made possible by causing mosquitoes to produce two molecules called antimicrobial peptides in their guts after they've eaten a blood meal.

These peptides impair the malaria parasite's development by a few days. Imperial states that these peptides were originally isolated from honeybees and African-clawed frogs.

The peptides also cause a shorter lifespan for the mosquitoes.

This technique has been shown to dramatically reduce the possibility of malaria spreading in the lab but if it is proven to be safe and effective in the real world it could offer a powerful new tool to help eradicate malaria.

Study co-author and researcher from the college's Department of Life Sciences Tibebu Habtewold is reported to have said, "Since 2015, the progress in tackling malaria has stalled. Mosquitoes and the parasites they carry are becoming resistant to available interventions such as insecticides and treatments, and funding has plateaued. We need to develop innovative new tools."

The peptides work by interfering with the energy metabolism of the parasite, which also has some effect on the mosquito - causing the mosquitoes to have a shorter lifespan and further decreasing their ability to pass on the parasite.

Co-first author of the study Astrid Hoermann, from the Department of Life Sciences at Imperial, said: “For many years, we have been trying to no avail to make mosquitoes that cannot be infected by the parasite or ones that can clear all the parasites with their immune system. Delaying parasite’s development inside the mosquito is a conceptual shift that has opened many more opportunities to block malaria transmission from mosquitoes to humans.”

Researchers needed to use a genetic trick called gene drive (a system of biased inheritance) to ensure that the lab-bred modification could spread to wild mosquitoes. Though normal breeding would spread it to a certain degree, the shorter lifespan of the genetically modified mosquitoes would mean their type would be eliminated.

So, by adding gene drive to the mosquitoes allows the modification to be preferentially inherited, so it can spread more quickly amongst wild mosquitoes, the researchers note.

In addition, it’s critical that the team minimizes any risks through careful planning and lab trials before moving forward, as the strategy is so new. The Transmission: Zero team is therefore using two separate but compatible strains of modified mosquitoes - one will have the anti-parasite modification and the other will have the gene drive.

They can then test the anti-parasite modification on its own first and only add in the gene drive once it has been shown to be effective.

Co-lead author Dr Nikolai Windbichler, from the Department of Life Sciences at Imperial is quoted as saying, “We are now aiming to test whether this modification can block malaria transmission not just using parasites we have reared in the lab but also from parasites that have infected humans. If this proves to be true, then we will be ready to take this to field trials within the next two to three years.”

This work was funded by the Bill and Melinda Gates Foundation and the findings were published in the journal Science Advances.