Scientists Pursue Vaccine Against Severe Malaria
The NIAID Malaria Vaccine Development Branch (MVDB) works in close collaboration with the NIAID Division of Microbiology and Infectious Diseases (DMID) to respond to the global need for vaccines against malaria. MVDB was commissioned in 2001 to research, develop, and produce prototype malaria vaccines and to conduct early phase clinical trials of promising vaccine candidates. Its goal is to develop malaria vaccines that reduce severe disease and death among children in regions where the disease is rampant.
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| A boy receives the MVDB malaria vaccine candidate at a clinical site in Mali, Africa. Credit: NIAID |
Effective vaccines enhance the natural ability of the body to recognize and attack disease-causing agents. In the case of malaria, the immune system is slow to recognize parasites that cause the disease and any acquired immunity is short-lived, leaving children at a higher risk of severe malaria. This weak reaction makes the search for a malaria vaccine particularly difficult, as scientists have greater obstacles to overcome to make the immune response strong and long-lasting.
Targeting Parasites in the Blood
MVDB is developing a vaccine that targets the “blood stage” of the deadliest malaria-causing parasite, Plasmodium falciparum. A blood-stage vaccine elicits immune responses capable of either destroying malaria parasites in the bloodstream or inhibiting parasites from infecting red blood cells. In either case, it reduces or prevents the burden of parasites, which decreases the incidence, severity, or complications of the disease. Such a vaccine either primes infant immune systems in anticipation of future exposure or boosts natural immunity in young children who have already been infected by the parasite.
Blood-stage vaccines have been the most promising vaccine candidates but have faced obstacles in development. MVDB is taking several approaches to overcome these obstacles. A vaccine composed of many immunity-inducing agents, called antigens, will increase the number of individuals who respond to at least one component of the vaccine. The inclusion of multiple and varying proteins will decrease the likelihood of different forms of the malaria parasite breaking through immunity.
Promising Advances
Such maneuvers have found recent success: In collaboration with scientists at Merck and NIH, MVDB recently made the observation that, in rhesus monkeys immunized with certain pairs of blood-stage antigens, protection from malaria persisted for years and was remarkably boosted by antigen alone. This finding shows that paired blood-stage antigens, called antigen conjugates, can induce immunity that would actually be boosted by repeated infections by the malaria parasite.
MVDB researchers are currently evaluating blood-stage vaccines at sites in Mali, Africa, in collaboration with scientists at the Malaria Training and Research Center in Bamako, Mali.
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