Genetic engineering researchers hope to fight off diseases by altering the genes of sick people and by editing the genes of the creatures that transmit them to us.
Consider the mosquito, a transmitting agent that kills more than half a million people every year. It is the first transmission vector of yellow fever, dengue, zika virus, malaria, among other deadly diseases. Some of these diseases have no vaccine or cure. For years, scientists have altered the genome of mosquitoes hoping to interfere with their ability to spread disease among people.
The main attempts involved basically the possibility of making the insects sterile. The British company Oxitec, for example, has worked on making male Aedes aegypti mosquitoes with the zika virus carrying a lethal gene that kills all pups it may have with a female, preventing the mosquito population from proliferating with the disease.
Now, a new study shows a way to use genetic engineering to deal with the greatest threat of all transmitted by mosquitoes: malaria.
Using the CRISPR / Cas9 gene-editing technique, scientists at Johns Hopkins University have deactivated a gene called FREP1, which makes Anopheles mosquitoes less susceptible to the parasite that causes malaria in humans. Several mosquito proteins are involved in the cycle that allows the Plasmodium parasite to reach the insect’s salivary glands, which is the transmission medium in humans that are stung. In the study published last week in Plos Pathogens, researchers showed that using CRISPR to delete a single FREP1 gene satisfactorily interfered with this process.
Malaria is one of the deadliest diseases in the world . And this discovery can be a great weapon to fight the spread of the disease in millions of people and prevent the deaths of thousands of infected people.
However, there are some obstacles to this materializing. To begin with, disabling FREP1 in laboratory mosquitoes made them less fit. Which means that if they are released to mate and spread malaria-resistant DNA, they may not be able to compete with other mosquitoes bred in the wild.
Fitness has been a major concern in other projects aimed at altering mosquitoes. They are more fragile than other insects, despite their threatening tendencies. Other insects, for example, are easily hit by radiation, which can make them sterile; however, when this type of experiment is done, they become too weak to mate – which is a problem, as the mutant mosquitoes mate with other species of nature.
Even if a mosquito looks like it is in the laboratory, there is nothing to say how it will be in nature. To correct this, the study authors are exploring to deactivate only the gene present in the adult female mosquito gland, hoping that the ability will be less severe, but resistance is still effective.
And although Anopheles gambiae is the main malaria transmitter in sub-Saharan Africa, there are at least 40 subspecies of this mosquito that can transmit the disease to people. It has not been mentioned whether this method of genetic editing will work in these other species.
Safety and public opinion will also be at stake in the decision to release these genetically modified mosquitoes. It was thanks to public opinion, not to regulations, that Oxitec shut down the testing of its modified mosquitoes in Key West, Florida.
The Bill and Melinda Gates Foundation has invested heavily in the use of genetic engineering to deal with malaria, however, the institution describes the attempt as “long term” due to public objections to projects and technological obstacles. These concerns include unintended consequences that could alter the insect’s behavior until it initiates a problematic chain reaction throughout an ecosystem with these altered mosquitoes.
Other ways to fight malaria include genetically modifying bacteria inside the mosquito to fight the parasite, or inserting new genes to help the mosquito not transmit malaria.
However, scientists are already preparing for a likely release of genetically modified mosquitoes in places like Burkina Faso . It may not be now, but when the day comes we should see thousands of life be saved by them.
Top image: mosquitoes that have been genetically modified using CRISPR. They shine because of a green protein used to monitor changes. Credit: Dong Y, et al (2018)
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