Revolutionizing the War against Malaria

Malaria kills more than a million people worldwide each year, most of them children in sub-Saharan Africa, according to the World Health Organization. The disease is caused by Plasmodium parasites, protozoa that are transmitted from person to person by female Anopheles mosquitoes. Researchers have proposed a method of controlling the spread of malaria by introducing into the wild mosquitoes that can't transmit the parasite, but computer models suggest that malaria-resistant mosquitoes must almost completely replace the native population in order to stop the cycle of transmission.

University of Arizona scientists have claimed to have developed the first strain of mosquitoes that are not susceptible to Plasmodium. 

According to the federal Centers for Disease Control and Prevention, an estimated 700,000 to 2.7 million people die of malaria each year, 75 percent of them African children

This development may signal the start of a worldwide program to replace natural populations of mosquitoes with the newly genetically designed variety in an attempt to kill off malaria once and for all.

For their experiments, the scientists used Anopheles stephensi.

When they fed on malaria-infected mice, the resistant mosquitoes had a higher survival rate than nonresistant ones, meaning they could eventually replace the ones that can carry the disease, according to a report in Tuesday’s issue of Proceedings of the National Academy of Sciences.

The researchers targeted one of the many biochemical pathways inside the mosquito's 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 signaling enzyme called Akt. Akt functions as a messenger molecule in several metabolic functions, including larval development, immune response and lifespan.

"It was known that the Akt enzyme is involved in the mosquito's growth rate and immune response, among other things," Riehle said. "So we went ahead with this genetic construct to see if we can ramp up Akt function and help the insects' immune system fight off the malaria parasite."

The second rationale behind this approach was to use Akt signaling to stunt the mosquitoes' growth and cut down on its lifespan.

"In the wild, a mosquito lives for an average of two weeks," Riehle explained. "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."

His research team discovered that mosquitoes carrying two copies of the altered gene had lost their ability to act as malaria vectors altogether.

"In that group of mosquitoes, not a single Plasmodium oocyst managed to form."

At this point, the modified mosquitoes exist in a highly secured lab environment with no chance of escape. Once researchers find a way to replace wild mosquito populations with lab-bred ones, breakthroughs like the one achieved by Riehle's group could pave the way toward a world in which malaria is all but history.


By Bioquest Group.