Scientists have for the first time found that carbohydrates on the surface of malaria parasites play a critical role in malaria’s ability to infect mosquito and human hosts. The discovery may help improve the only vaccine approved to protect people against Plasmodium falciparum malaria — the most deadly form of the disease, researchers said.
The study found that the malaria parasite ‘tags’ its proteins with carbohydrates in order to stabilise and transport them, and this process was crucial to completing the parasite’s life cycle. “We found that the parasite’s ability to tag key proteins with carbohydrates is important for two stages of the malaria life cycle,” said Justin Boddey, from Walter and Eliza Hall Institute in Australia.
“It is critical for the the earliest stages of human infection, when the parasite migrates through the body and invades in the liver, and later when it is transmitted back to the mosquito from an infected human, enabling the parasite to be spread between people,” said Boddey, who led the study published in the journal Nature Communications.
Interfering with the parasite’s ability to attach these carbohydrates to its proteins hinders liver infection and transmission to the mosquito, and weakens the parasite to the point that it cannot survive in the host, researchers said. Malaria infects over 200 million people worldwide each year and kills around 650,000 people, predominantly pregnant women and children. Efforts to eradicate malaria require the development of new therapeutics, particularly an effective malaria vaccine.
The first malaria vaccine approved for human use -RTS,S/AS01 – was approved by European regulators in July 2015 but has not been as successful as hoped, with marginal efficacy that wanes over time, researchers said. “The protein used in the RTS,S vaccine mimics one of the proteins we have been studying on the surface of the malaria parasite that is readily recognised by the immune system,”said Ethan Goddard-Borger from Walter and Eliza Hall Institute.
“With this study, we have shown that the parasite protein is tagged with carbohydrates, making it slightly different to the vaccine, so the antibodies produced may not be optimal for recognising target parasites,” Goddard-Borger said. He said there were many documented cases where attaching carbohydrates to a protein improved its efficacy as a vaccine. “It may be that a version of RTS, S with added carbohydrates will perform better than the current vaccine,”Goddard-Borger said.