Washington,July 16: For years, researchers have attempted to create genetically altered mosquitoes that cannot infect humans with malaria which claims over one million lives worldwide every year. Now, for the first time, scientists claim to have successfully succeeded in genetically altering mosquitoes in a way which renders them completely immune to the parasite, a single-celled organism called Plasmodium.

If you want to effectively stop the spreading of the malaria parasite, you need mosquitoes that are no less than 100 per cent resistant to it. If a single parasite slips through and infects a human, the whole approach will fail, said Michael Riehle, who led a team at University of Arizona. For the research, Riehles team used molecular biology techniques to design a piece of genetic information capable of inserting itself into a mosquitos genome. This construct was then injected into the eggs of the mosquitoes.

The emerging generation carries the altered genetic information and passes it on to future generations. In their experiments, the scientists used Anopheles stephensi, a mosquito species that is an important malaria vector throughout the Indian subcontinent. They targeted one of the many biochemical pathways inside the mosquitos cells. Specifically, they engineered a piece of genetic code acting as a molecular switch in the complex control of metabolic functions inside the cell.

The genetic construct acts like a switch that is always set to on, leading to the permanent activity of a signalling enzyme called Akt which functions as a messenger molecule in several metabolic functions, including larval development, immune response and lifespan. When the scientists studied the genetically modified mosquitoes after feeding them malaria-infested blood, they noticed that the Plasmodium parasites did not infect a single study animal.

We were surprised how well this works. We were just hoping to see some effect on the mosquitoes growth rate, lifespan or their susceptibility to the parasite, but it was great to see that our construct blocked the infection process completely, Riehle said. The scientists hope that someday they will be able to replace wild mosquitoes with lab-bred populations unable to act as vectors, ie, transmit the malaria-causing parasite. In the wild, a mosquito lives for an average of two weeks. Only the oldest mosquitoes are able to transmit the parasite. If we can reduce the lifespan of the mosquitoes, we can reduce the number of infections, Riehle said. The findings have been published in the latest edition of the Public Library of Science Pathogens journal.

-PTI