August 03, 2021
Malaria is a leading cause of death around the world, a disease spread by mosquitoes, which kills hundreds of thousands of people each year. At present there are many methods to prevent getting malaria (including mosquito netting around beds, insect repellent and medication) although none have successfully managed to eradicate the mosquitos that spread the infection, Anopheles gambiae.
An international team of researchers, led by Imperial College London, believe they may have found a solution, make the female mosquitoes infertile using a technology called “gene drive”. Essentially gene drive alters the way that genes are inherited by offspring. You will recall from high school biology that offspring typically inherit one copy of a gene from one parent, and another copy from the other parent. In this way genes ordinarily have a 50% chance of being passed along to the next generation. Gene drive however increases the chance of the gene being passed on to almost 100% of offspring.
Imagine a made up mosquito gene XXXYYY. Using gene editing the gene drive is inserted into the gene, changing it into XXXinfertileYYY. If a mosquito inherits one copy of XXXYYY, and one copy of the XXXinfertilityYYY gene drive, the gene drive instructs the cell to chop the XXXYYY version of the gene in a specific place (in this made up case, between the X and Y). The cell then attempts to patch up the cut gene, and uses the gene drive as a template, and adds in the new information. When the XXXYYY gene is patched back up again it now looks identical to the gene drive; XXXinfertilityYYY. This mosquito will now pass on XXXinfertilityYYY to all of its own offspring. Over generations XXXinfertilityYYY will pass to all individuals in a population, and the mosquitoes will no longer be able to reproduce.
Initial laboratory trials have been incredibly successful, a single release of mosquitoes with the gene drive into a population of wild mosquitos living within a large cage resulted in a complete crash of the population of mosquitoes within a year. Importantly this crash happened without any further involvement from humans. The hope is that this approach will be proven to be both safe and effective in further laboratory experiments, and only if this is the case will a field trial be held in a testing site. However, no field trial will be held until a comprehensive environmental risk assessment has been completed, and the ethical and regulatory questions raised by a project like this have been answered sufficiently in the next 10 years or so. Should the study progress to a field trial it will likely be held in Burkina Faso, an area that accounts for four percent of malaria-related deaths each year.
While field trials of other genetically modified mosquitoes are either incomplete (such as the current trial in Florida to try and prevent of the spread of Zika virus) or were deemed unsuccessful (such as the trial in the Cayman Island to prevent the spread of dengue fever, Zika virus and more), this current gene drive trial uses a different approach. If successful, this approach has the potential to revolutionize the way malaria is prevented from spreading and causing illness and death around the globe. Although it is worth noting that at this stage the laws that regulate the use of genetically modified mosquitoes are inconsistent between countries, experts are urging this to change before this new technology is more widely used.
Source: The Guardian
Learn more: https://www.theguardian.com/world/2021/jul/28/genetic-engineering-test-with-mosquitoes-may-be-game-changer-in-eliminating-malaria