|Human red blood cells are surrounded and invaded by malaria parasites (purple).--Courtesy of Sheetij Dutta, CC-BY|
An experimental malaria vaccine that showed early promise but ultimately proved unsuccessful in recent clinical trials is being reformulated as scientists hope to one day deliver the jab to patients in endemic countries.
Researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, are working on improving their decade-old original vaccine, which was designed to spur production of antibodies against a key malaria parasite protein, AMA1. The vaccine was effective in lab and animal experiments, and showed potential in early-stage clinical trials but turned out to be ineffective in late-stage trials.
The challenge with developing a malaria vaccine is that the malaria parasite in general as well as its AMA1 surface protein both exist as multiple strains.
The new version of the vaccine candidate delivers AMA1 protein together with part of a second parasite protein called RON2. When a host is infected, the malaria parasite uses this AMA1-RON2 protein complex to attach to and invade red blood cells.
The NIAID team injected the new AMA1-RON2 vaccine candidate in mice, finding that it spurred the production of antibodies and protected the animals from a lethal form of mouse malaria.
Investigators then administered antibodies produced in response to the vaccine to a group of nonvaccinated mice. The antibodies had the same effect as the vaccine, acting as a safeguard against malaria infection.
Malaria remains a major public health concern in many parts of the world, and no vaccine exists to prevent the disease despite intensive research in the field.
The investigators hope to further fine-tune their investigational vaccine and eventually test it in humans.