Malaria blocking genes
An Anopheles stephensi mosquito obtains a blood meal from a human host through its pointed proboscis. A known malarial vector, the species can found from Egypt all the way to China.Jim Gathany / Centre for Disease Control and Prevention

American scientists have created a form of mosquitoes that can rapidly generate malaria-blocking genes into a mosquito population via its progeny, and eventually ruin the insects' capability to spread the disease to human beings.

A research team from the University of California's, Irvine and San Diego campuses incorporated a DNA element into the germ line of Anopheles stephensi mosquitoes, which in turn made the gene prevent malaria transmission to 99.5% of offspring.

The research is based on the increasing utility of the Crispr method – a powerful gene editing tool, which lets access to the nucleus of a cell to cut DNA to either substitute mutated genes or incorporate new ones.

Earlier this year, Ethan Bier and Valentino Gantz from UC San Diego, while working on their research with fruit flies, declared the development of a new method for producing generations in both copies of a gene. This mutagenic chain reaction needed the utilisation of the Crispr-related Cas9 nuclease enzyme and permitted for mutation spread via the germ line with an inheritance rate of 95%.

In the latest development, the research team  followed Gantz's theory, where he had enclosed antimalaria genes with a Cas9 enzyme that can cut DNA and a guide RNA to develop a genetic "cassette". Once injected into the mosquito embryo, the cassette aimed a significant spot on the germ line DNA in order to incorporate the antimalaria antibody genes.

Furthermore, to ensure the malaria-blocking antibodies reach the desired spot in the germ line DNA, the research team placed a protein in the cassette that is responsible for the progeny "red fluorescence" in the eyes.

As a result, 99.5% of the offspring showed this trait where the progeny generated anti-malaria genes in them.

"This opens up the real promise that this technique can be adapted for eliminating malaria," said Anthony James, Distinguished Professor of molecular biology & biochemistry and microbiology & molecular genetics at UC Irvine, and lead author of the study.

However, he cautioned that further tests need to be conducted in order to confirm the efficiency of the antibodies. "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," he said.

According to the World Health Organisation (WHO), nearly half of the world's population at 3.2 billion suffers from a risk of malaria.

According to the Centre for Disease Control & Prevention, 300 million to 500 million cases of malaria get registered every year with almost 1 million people dying from the disease annually.

The paper is published in the online edition of Proceedings of the National Academy of Sciences.

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