This study suggests that genetically engineered malaria
parasites that are stunted through precise gene deletions (genetically
attenuated parasites, or "GAP") could be used as a vaccine that
protects against malaria infection.
This means that the
harmless (attenuated) version of the parasite would interact with the body in
the same way as the infective version, but without possibility of causing disease.
GAP-vaccination would induce robust immune responses that protect against
future infection with malaria.
According to the World Health Organization, there were 219
million documented cases of malaria in 2010, causing the deaths of up to 1.2
million people worldwide. Antimalarial treatments are available to reduce the
risk of infection, but as yet there is no effective vaccine against the
Last month, a team of scientists announced the results of a
trial with a new kind of malaria vaccine, a whole-parasite preparation weakened
by radiation. The trial showed promising results, but the method of vaccination
was not optimal, requiring intravenous administration and multiple high doses.
This current paper outlines a method of attenuation through genetic engineering
rather than radiation, which offers hope for a more consistent vaccine that gives
"Malaria is one of the world's biggest killers, and
threatens 40% of the world's population, yet still no effective vaccine
exists," said Stefan Kappe, PhD, lead author of the paper and professor at
Seattle BioMed. "In this paper we show that genetically engineered
parasites are a promising, viable option for developing a malaria vaccine, and
we are currently engineering the next generation of attenuated parasite strains
with the aim to enter clinical studies soon."
For the first time, researchers created a weakened version
of the human malaria parasite by altering its DNA. They tested the safety of
the new modified parasite by injecting six human volunteers through mosquito
bites. Five of the six volunteers showed no infection with the parasite,
suggesting that the new genetic technique has potential as the basis for a
"Our approach offers a new path to make a protective
malaria vaccine that might overcome the limitations of previous development
attempts. Genetically engineered parasites potentially provide us with a
potent, scalable approach to malaria vaccination," said Kappe. "Our
results are very encouraging, providing a strong rationale for the further
development of live-attenuated strains, using genetic engineering."