Killer immune cells that halt malaria could hold key to new vaccines

Scientists have revealed that immune cells called natural killer (NK) cells may play a key role in ridding the body of malaria-infected blood cells, a study in eLife reports. 

The discovery adds to knowledge of how natural immunity to malaria develops in people living in areas where the parasite is common, and provides a new mechanism that could be exploited in the mission to create a malaria vaccine.

"One of the main objectives in malaria research is to define the mechanisms by which naturally acquired antibodies provide protection," says lead author Gunjan Arora, Postdoctoral Fellow at the National Institute of Allergy and Infectious Diseases (NIAID), US.

"We know that NK cells kill virus-infected cells and cancer cells, but a clear role for them in contributing to protection from malaria is yet to be established.

The team wanted to find the mechanism behind antibody-driven attack by NK cells. Blood cells infected with malaria have molecules on their surface that antibodies recognize and use to attract immune cells. The team identified a molecule that was essential for activation of NK cells in response to malaria-infected blood cells. Although PfEMP1 was already known to be important in antibody recognition of malaria-infected cells, this study showed for the first time that it is crucial for activating NK cells in a manner dependent on antibodies.

"Considering the essential role of antibodies in granting clinical immunity to people living in areas of high malaria transmission, and the limited effectiveness of malaria vaccines tested so far, any immune responses that depend on antibodies warrant further investigation," says senior author Eric Long, Senior Investigator at NIAID. "Our discovery of antibody-mediated killing of malaria-infected blood cells by NK cells adds an additional immune mechanism to those already known."