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Scientists have developed a new vaccination strategy for malaria — boosting immunity through bites from mosquitoes carrying a genetically engineered version of the parasite that causes malaria. In a trial, the approach reduced participants’ susceptibility to malaria, potentially paving the way for more effective ways to stop the disease, which infects some 250 million people a year.
“These findings represent a significant step forward in malaria vaccine development,” says Julius Hafalla, an immunologist at the London School of Hygiene & Tropical Medicine. “The ongoing global malaria burden makes the development of more effective vaccines a critical priority.”
The study, which was published1 in The New England Journal of Medicine on 20 November, exposed participants to bites from mosquitoes that had a modified version of the Plasmodium falciparum parasite, which causes malaria. In humans, the parasites travel to the liver and then infect red blood cells. The parasites were engineered to stop developing shortly after delivery into a human. Nearly 90% of participants exposed to the modified parasites avoided contracting the disease after being bitten by malaria mosquitoes.
There are two approvedmalaria vaccines. Both aim to provide long-term immunity by producing antibodies that block malaria parasites from infecting liver cells, as well as targeting breakthrough infections.
But the vaccines are only about 75% effective, and require booster shots. So immunologists are continuing to explore alternative strategies.
One approach is using genetically modified parasites. The research team had previously trialled the effectiveness of a modified malaria parasite, called GA1, that is designed to stop developing about 24 hours after infection in humans2. But the GA1 parasite protected only a few participants against malaria, leading the team to engineer a second parasite, GA2. GA2 is designed to stop developing about six days post-infection, during the crucial period where the parasites replicate in human liver cells.
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