Gene Editing Mosquitoes May Stop Spread Of Malaria

Thanks to research performed at the University of California (UC), we may be one step closer to stopping the transmission of malaria via mosquito vectors. Using a gene editing technique called CRISPR, the researchers generated a new strain of mosquito which is capable of transmitting malaria-resistance genes to their offspring.

Using the CRISPR technique, the researchers inserted the gene encoding anti-malaria antibodies into a specific site in the mosquito embryo’s germ cell DNA. The hope is that the genes will be rapidly disseminated throughout the mosquito population in any given area, effectively eliminating the spread of the disease.

Nearly half of the world’s population is at risk of contracting malaria – a blood-borne parasite that is transmitted through bites from female mosquitoes. By the end of 2015, approximately 214 million people will have become infected with the parasite, and 438,000 of those infected will have died from the disease, according to estimates from the World Health Organization (WHO).

The research team at UC performed their research using a species of mosquito called Anopheles stephensi – the primary carrier of malaria in Asia. After inserting a DNA element into the reproductive cells of the mosquito using CRISPR, 99.5 percent of the resulting offspring were confirmed to be unable to transmit malaria.

“This opens up the real promise that this technique can be adapted for eliminating malaria,” said Anthony James, a professor at UC-Irvine with 20 years of experience genetically manipulating mosquitos to prevent the spread of disease. The results of the study were published in the journal, Proceedings of the National Academy of Sciences.

Previous research conducted by James and his colleagues showed that by introducing antibodies collected from mice into mosquitoes, it was possible to disrupt the life cycle of the malaria parasite. Unfortunately, once incorporated into the mosquito’s germ cells, the trait was not homozygous resulting in only 50 percent of the offspring being resistant to malaria.

Inspired by research conducted at UC-San Diego, the researchers found that both copies of a gene could be transformed with the inserted DNA sequence using CRISPR. Both labs collaborated on the current study by creating a genetic cassette consisting of the genes for malarial resistance, along with the genes necessary to allow for insertion of the antimalarial DNA into the mosquito embryo’s germ cells.

In order to confirm successful incorporation of the gene insertion, the researchers used a reporter gene, which caused the mosquitos eyes to glow a fluorescent red. James commented that it was an “amazing result” when they found that 99.5 percent of mosquito offspring had red fluorescent eyes.

The researchers admit they face a long road ahead before being able to test the method in the field. The antibodies need to be confirmed to be effective against malaria, and the researchers must overcome regulatory hurdles in order to release the mosquitos into the wild.

“This is a significant first step,” said James. “We know the gene works. The mosquitoes we created are not the final brand, but we know this technology allows us to efficiently create large populations.”

Sources:

• Gene-edited mosquitoes cannot transmit malaria – http://www.medicalnewstoday.com/articles/303047.php
• Gantz, V., Jasinskiene, N., Tatarenkova, O., Fazekas, A., Macias, V., Bier, E., and James, A. (2015). Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Anopheles stephensi. PNAS.