New Burnet Institute malaria research reveals:

• The RTS,S vaccine induces antibodies that recruit proteins in the blood to assist in blocking and killing malaria
• Prior exposure to malaria may have a bearing on the immune response
• The immune response declines rapidly within months of vaccination

Burnet Institute scientists have made important discoveries about the workings of the malaria vaccine, RTS,S (Mosquirix, GSK), that could inform the future development of more effective and longer-lasting vaccines.

The leading vaccine candidate, and the only vaccine tested in phase III clinical trials, RTS,S provides only partial protection against malaria; 36 percent in children and 26 percent in infants.

That’s well short of the 75 percent effectiveness threshold that the World Health Organization and funding partners have set for WHO’s goal of a licensed malaria vaccine by 2030.

Image: RTS,S study lead author, Burnet PhD candidate Liriye Kurtovic

A new study published in BMC Medicine demonstrates for the first time that RTS,S can induce antibodies in young malaria-exposed children that recruit proteins in the blood called complement.

Prior studies by Burnet researchers and collaborators demonstrated that recruitment of complement could lead to the blocking and killing of malaria forms that are injected by mosquitoes and can infect the liver.

The research also reveals important differences in the responses of younger children aged one-to-two, and older children aged from two-to-five from a high malaria transmission site in Mozambique.

“So it could be that the older kids had a higher amount of natural malaria exposure before they’ve been vaccinated, and that’s why they didn’t have as strong an immune response compared to the younger kids who are probably more naïve to natural malaria. This effect may be due to malaria exposure inferring with immune function.

“This is interesting, because if you want to implement a vaccine in a location where malaria naturally occurs, you have to factor in whether the kids have already been exposed, what immune response they have, and how that might affect how well your vaccine is going to work.”

Ms Kurtovic said another notable finding of the study was a rapid decline of the immune response within a few months after vaccination.

“We already know that the protective effect of the vaccine also wanes with time, which suggests that maybe it’s related to this loss of functional antibody responses” she said.

Ms Kurtovic said expanded testing is already underway to determine the relationship between children with antibodies that recruit complement and their protection against clinical malaria.

This work was conducted in collaboration with ISGlobal (Spain), and Centro de Investigação em Saúde de Manhiça (Mozambique).

Find out more about Burnet’s malaria research.