Antibody research brings malaria vaccine one step closer

An international team of researchers has narrowed down the malaria proteins and disease-fighting antibodies that could be used to develop a vaccine against the most severe forms of malaria.

There were 219 million cases of malaria worldwide in 2017, leading to an estimated 435,000 deaths. As explained by research leader Associate Professor Alyssa Barry, malaria parasites grow within red blood cells, where they insert proteins (known as PfEMP1) into the surface.

“As part of their survival strategy within the human host, malaria parasites use PfEMP1 to stick to the walls of blood vessels, and this can cause blockages to blood flow and inflammation, leading to severe disease,” said Assoc Prof Barry, who heads the Translational Genomics Group at the Burnet Institute.

“Malaria parasites change these proteins to escape from developing immune responses, and every strain has a different set of proteins, making the identification of vaccine targets like finding a needle in a haystack.”

Assoc Prof Barry collaborated with researchers from the Walter and Eliza Hall Institute of Medical Research, James Cook University and malaria experts from Papua New Guinea (PNG), France and the US to collect hundreds of PfEMP1 proteins from malaria strains from children in PNG who had been naturally infected by the disease. The research team managed to pinpoint which antibodies were most effective in fighting the most severe forms of malaria by using antibody measurements to the different proteins, disease monitoring and machine learning.

“It’s the first time anyone has shown this — for years, researchers have thought that developing a malaria vaccine based on PfEMP1 would be virtually impossible, because the proteins are just so diverse,” Assoc Prof Barry said.

“It’s similar to the flu vaccine, where you have to keep adjusting and updating it as the virus strains evolve from year to year. Malaria is even more diverse than influenza — one village in a country such as PNG could contain thousands of possible malaria strains.

“But in malaria-endemic areas, children who are repeatedly infected develop immunity to severe malaria by the time they’re about two years old, so we know antimalarial immunity is possible, and it can develop after exposure to only a few strains.”

Assoc Prof Barry said while immunity to milder forms of malaria presents a “formidable obstacle”, immunity to severe malaria targets only a small subset of proteins that have many similarities between strains — making the essential components for a vaccine much easier to identify.

“Using genomic sequencing, we collected PfEMP1 proteins from different strains of malaria, measured antibodies to those proteins and then used machine learning to identify the protective antibody — the biomarker of immunity — that protects kids against disease,” she said.

“We were able to identify these antibodies by monitoring for patterns of disease, following the children in PNG for 16 months to determine which of them were susceptible to the more severe forms of the disease, and those who were protected and only experienced milder forms of the disease.”

Assoc Prof Barry said the findings, published in the journal Cell Host & Microbe, mark a major step towards developing a viable vaccine for the disease.

“It’s been a long road and has involved a large team, but it’s a major step forward, and this provides hope that creating a vaccine might be possible,” she said.

Image credit: ©stock.adobe.com/au/mycteria

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