Malaria Vaccine Candidate Generates Robust Immune Response
- By BSTQ Staff
Findings from a first in-human study for a new malaria vaccine candidate have shown a robust immune response while significantly delaying parasitemia (a measurement of parasite load in the organism and an indication of the degree of an active parasitic infection) in 59 percent of vaccinated subjects. In the study, researchers at Walter Reed Army Institute of Research immunized 30 volunteers (who took part in a controlled human malaria infection [CHMI] model in which they were bitten by malaria-infected mosquitoes) with three doses of the vaccine. Efficacy of the vaccine was determined based on whether the volunteers developed malaria by looking at blood smears or if it took longer for malaria parasites to appear in the blood. Plasmodium vivax malaria can be dormant, causing no symptoms, and then become active causing symptomatic malaria weeks to months after initial infection.
“This study represents the first vaccine study to test the effectiveness of a P vivax vaccine candidate in humans using controlled human malaria infection,” said Jason W. Bennett, the study’s lead investigator. The CHMI model relies on blood donations from infected humans to initiate infections in mosquitoes.
Researchers were also able to demonstrate that individuals with low or absent levels of a specific liver enzyme were unable to convert primaquine, the only FDA-approved drug to treat the dormant stages of vivax malaria, to an active drug form to kill the dormant stage of the parasites.
