(CN) – A recent clinical trial with human volunteers showed a next-generation malaria vaccine stimulates an appropriate immune response and had a favorable safety profile, offering a potential tool against the devastating mosquito-borne virus.
The vaccine candidate was also well tolerated by trial participants, scientists from the Infectious Disease Research and Fred Hutchinson Cancer Research Center say in a recent study published in the journal Science Translational Medicine.
Malaria parasites are transmitted to humans by mosquitos, which infect the liver before spreading to the blood. There were more than 200 million malaria infections and half a million deaths worldwide in 2015.
While many at-risk individuals currently protect themselves from the virus by using insecticide-treated bed nets and antimalarial drugs, the new vaccine candidate could be the tool to completely eliminate malaria.
The team used a genetically engineered malaria parasite that they weakened by removing three specific genes necessary for the parasite to successfully infect and cause the disease in humans.
Known as genetically attenuated parasites (GAPs), these modified parasites are incapable of multiplying in the human liver, but are alive and effectively stimulate the immune system to build up defenses against a real malaria infection.
“We had already good indicators in preclinical studies that this new ‘triple knock-out’ GAP (GAP3K0), which has three genes removed, is completely attenuated,” said project leader Sebastian Mikolajczak. “The clinical study also shows that even after only a single administration, it elicits a robust immune response against the malaria parasite.”
Attenuation is a common strategy for making vaccines and has been used for bacterial and viral vaccines dating back to Edward Jenner’s first vaccine against smallpox.
“This report is a major advance in malaria vaccine development by providing the first evidence that genetically attenuated Plasmodium falciparum parasites are safe and immunogenic in humans,” said Robert Seder, a scientist from the National Institutes of Health who was not involved in the study.
“Future studies demonstrating protective efficacy will be the next critical milestone for continued development of this promising vaccine approach.”