Malaria is a life-threatening disease transmitted to humans by infected mosquitoes. In 2018 alone there were 228 million cases and 405,000 deaths worldwide, affecting mostly children under five years of age. Scientists have long been looking for an effective vaccine, but haven't yet been able to produce one.
Human malaria is caused by five species of Plasmodium parasites, with Plasmodium falciparum the most deadly of them. But there are other Plasmodium parasites that can infect and cause malaria in other mammals. About ten years years ago, a group of researchers in Portugal, led by Miguel Prudêncio, decided to explore the possibility of using a rodent parasite called Plasmodium berghei in a vaccine against malaria.
They developed a P. berghei parasite genetically modified to look like P. falciparum, meaning that it carried P. falciparium proteins on its surface. Being a rodent parasite makes it non-pathogenic to humans, and as it was covered by proteins from the human parasite they reasoned that it could potentially induce an immune response to the human parasite. They deliberately chose a protein active during the stage where the malaria parasite infects our livers. Acting at this stage blocks the life cycle of the parasite and prevent it from reaching the bloodstream.
A clinical trial for this rodent-inspired vaccine started in 2017. Last month the results of the first stages of this trial were published in Science Translational Medicine. The trial involved 24 healthy adult volunteers in the Netherlands. After the trial showed that the new vaccine was safe at the tested doses, it entered phase two, aimed at testing the efficacy of the immunization. The vaccinated volunteers were actually infected with the human malaria parasite P. falciparum. When compared with the unvaccinated control group, the volunteers had 95% less parasites in their liver and also produced antibodies that recognized P. falciparum.
While the vaccine did not confer full protection to the infection, it looks to be a promising approach and may lead the way to create an effective malaria vaccine.