A team of researchers, including grantees of the National Institute of
Allergy and Infectious Diseases (NIAID), today reported positive results of
research on a new, broad-based malaria vaccine. A paper describing their
findings appears in the February 16 issue of the Proceedings of the National
Academy of Sciences USA.
Health officials have long sought a vaccine to prevent malaria, a disease
that affects 300 to 500 million people and kills up to 3 million people
worldwide each year. "Improving international health is a high priority of
the NIAID, and malaria research is a major area of interest," comments
Anthony S. Fauci, M.D., director of the institute. "Although these results
are preliminary and the candidate vaccine has yet to be tested in people,
its effectiveness in laboratory tests makes it an interesting candidate for
The most severe form of malaria is caused by a microscopic parasite,
Plasmodium falciparum, that is transmitted to humans by mosquitoes. The
parasite has a complex life cycle. Following injection into the
bloodstream, it rapidly travels to the liver where it multiplies. New forms
of the parasite are then released into the bloodstream where they invade red
blood cells, ultimately destroying them. In their recent paper, a research
team directed by Altaf A. Lal, Ph.D., of the U.S. Centers for Disease
Control and Prevention (CDC), describes a new candidate vaccine that targets
the malaria parasite at several stages of its life cycle.
The scientists combined segments of 21 different P. falciparum proteins to
form a single recombinant protein, which they used to immunize rabbits.
Each of the 21 segments, or peptides, was selected because it was recognized
by the immune systems of people with malaria, as shown in earlier studies.
Furthermore, the peptides targeted different branches of the immune system:
B cells, helper T cells and cytotoxic T lymphocytes (CTLs).
Laboratory tests showed that the vaccine induced a high level of antibodies
that recognized the parasite at different stages of development. The
antibodies also blocked P. falciparum invasion into the rabbits' liver cells
and inhibited growth of the organism in their blood. Although the
researchers have not yet looked at the T-cell responses in vaccinated
animals, these studies are under way.
"Multicomponent vaccines may offer an advantage over single-component
vaccines because they may provide multiple levels of protection against
different parasite stages," says Lee Hall, M.D., Ph.D., program officer for
parasite vaccine development at NIAID. "Such vaccines may also reduce the
spread of vaccine-resistant strains, which can arise when a pathogen changes
a surface protein to avoid detection by the immune system."
NIAID is a component of the National Institutes of Health (NIH). NIAID
conducts and supports research to prevent, diagnose and treat illnesses such
as HIV disease and other sexually transmitted diseases, tuberculosis,
malaria, asthma and allergies. NIH is an agency of the U.S. Department of
Health and Human Services.
Press releases, fact sheets and other NIAID-related materials are available
on the NIAID Web site at