Researchers are developing a candidate vaccine that is showing positive results against various strains of malaria, reports a study led by Sheetij Dutta of the Walter Reed Army Institute of Research in Silver Springs, Maryland.
Malaria is the condition caused by the parasite genus Plasmodium, with the most potent species, falciparum and vivax, attributed to the stronger form of the condition. The parasite uses mosquitoes as a vector, typically via female Anopheles mosquitoes that tend to be strongly anthropophilic; they prefer human blood over that of other animals.
The parasite has two life cycle stages: one in the liver and the other in the blood stream. Mosquitoes carrying the Plasmodium inject the parasite into the blood stream, which travels to the liver within red blood cells, where they multiply within the organ’s cells. These cells then rupture, causing the parasite to return to the bloodstream, which can then be ingested once again by another feeding mosquito.
Effective treatment exists against the condition, however, mortality is still high in many parts of the world, with several strains now developing resistance to the medication, according to the paper published on the online journal Public Library of Science: Pathogens.
However, the researchers are making great strides in developing a universal vaccine that could cover several strains of the condition, using a “cocktail” approach.
Apical Membrane Antigen-1 (AMA1) was a candidate vaccine that targeted P.falciparum during the blood stage of it’s life cycle. The vaccine triggered an immune response to produce AMA1 antibodies that prevented the parasite from entering red blood cells, and this prevention was correlated with protection in primate models.
However, the use of this vaccine was highly strain-specific. Phase II(b) clinical trials, that test the efficacy of the drugs, showed that the vaccine was indeed potent, although only against vaccine-like strains, reports the paper. The authors attributed the parasite diversity as a cause.
In order to make a successful vaccine that could overcome the parasite diversity, it must contain several components for it to counter the antigenic variation shown by the different parasites, says the paper.
This concept has been used in medical history, however. Polio, influenza and HPV vaccines, explained the article, all use several strains or serotypes in the medication which the body will respond to, increasing the broad spectrum efficacy of the drug.
They tested the effects of creating a “cocktail” of antibodies from different parasites. The study came to several conclusions, noting that using three parasite strains was more effective than just two, whilst one “cocktail” based on a combination of four antibodies combined to create a medication that had an extremely wide range.
Accordingly, the researchers developed a medication called “Quadvax”, made from four malarial strains. Once the body had produced the antibodies from the Quadvax vaccine, the scientists noted that a total of twenty six parasite strains were inhibited.
This is extremely encouraging, with the researchers hoping their results will contribute to a novel blood stage vaccine that would be able to counteract the various strains of malaria around the globe.
Which aspects of modern medicine would you like to see this research used in?