Vacina de nova geração contra o paludismo
April 27, 2022 - O Jenner Institute da Universidade de Oxford está a realizar ensaios de Fase III a uma vacina do paludismo – R21/Matrix-M – no norte da Tanzânia. A vacina revelou uma eficácia de 77 por cento.
Scientists behind the Oxford-AstraZeneca coronavirus shot produced the vaccine.
“This was by far a much more difficult vaccine to make work,” Adrian Hill, the institute’s director, said in northern Tanzania on a visit to field trials of the R21/Matrix-M malaria vaccine.
While the coronavirus responsible for Covid-19 has 12 genes, Plasmodium -- the parasite that causes malaria, has more than 5,000 genes. It’s an organism that infects the liver and bloodstream, infecting red blood cells.
Hill explains that R21/Matrix-M combines the R21 vaccine with a vaccine booster or adjuvant Matrix-M, which stimulates the human immune system to attack the parasite.
When an infectious mosquito feeds on a human being, it injects parasites in a form called sporozoites into the bloodstream, where they travel directly to the liver.
The sporozoites divide rapidly, producing around 20,000 merozoites that rupture the liver cells and invade red blood cells.
R21 targets a circumsporozoite protein (CSP) present on the parasite’s surface during the sporozoite stage. CSP rarely mutates among the four strains of malaria parasites that infect humans.
The human body does not readily react with a complete immune response to foreign proteins. The R21 focus on CSP -- boosted by the proprietary Novavax adjuvant -- produces a more robust, better-targeted antibody response.
Clinical trials are now moving to the third phase in four countries across Africa -- Mali, Tanzania, Kenya and Burkina Faso.