Under UV light, this mosquito larva reveals a red fluorescent marker in its nervous system, causing eyes and nerves to glow. The marker's presence tells the researchers in Riehle’s team that this individual carries the genetic construct rendering it immune to the malaria parasite.
Credit: M. Riehle/University of Arizona
SYDNEY: Instead of inoculating humans to the malaria parasite, scientists have a new method: genetically engineering mosquitoes that are resistant to malaria.
"This is the first time an anti-malaria molecule completely blocked malaria parasite development," said entomologist Michael Riehle, from the University of Arizona, an author of the study in the journal PLoS Pathogens.
Strategies for dealing with malaria worldwide have been focus is on killing mosquitoes, eliminating their breeding grounds and protecting individuals from infection. Long-term vaccines have so far proved ineffective, as the Plasmodium have become resistant to a number antimalarial drugs and insecticides.
Genetic code turns on immune response
Plasmodium is the genus of the parasites that causes malaria, which causes fever, headache and vomiting in the person and sometimes death. According to the World Health Organisation, malaria was responsible for up to one million deaths in 2008, predominantly in Africa.
Riehle and his colleagues inserted a manufactured genetic code into malaria-carrying mosquito Anopheles stephensi.
The genetic code affected a signalling enzyme called Akt, which is involved immune response and lifespan. It effectively caused the enzyme to be in permanent activity, increasing their immune response to Plasmodium.
Genes to boost mosquitoes' immune system
The gene controlling Akt signalling can be found in other Anopheles mosquitoes meaning that the engineered genetic code can be applied to other Anopheles species.
They found that none of these malaria parasites infected the mosquitoes. The fact that no malaria parasites were able to infect the mosquitoes is important to malaria eradication because "if some parasites can evade the killing mechanism the parasites would quickly develop resistance making this approach less effective," Riehle said.
Riehle also hopes that the Ark function will shorten the mosquitos' lifespans and stunt their growth.
Releasing genetically engineered mosquitoes
The researchers said they hope the anti-malaria mosquitoes could replace the wild populations, although it is not as simple as releasing a swarm of laboratory manufactured mosquitoes into the wild.
The genetically engineered mosquitoes have to have a competitive advantage over the wild population in order for them to become a dominant species. "At this point the mosquito does not have a competitive advantage" but Riehle's teams and several other labs are working on making it so.
Don Gardiner researches malaria biology at the Queensland Institute of Medical Research concedes that "proving that it is possible to 'malaria proof' mosquitoes is the first step" but when it comes to the anti-malaria mosquitoes displacing the wild populations, he is more sceptical.
"I think in the end this is one method that may eventually enhance our ability to eradicate malaria, but it is unlikely to be successful in of itself," he said.
Using Mosquitos for drug delivery
Using Mosquitos as a host to deliver mass vaccinations to 3rd world countries may also be another potential use.