A Robust Neutralization Test for Plasmodium falciparum Malaria

Malarial merozoites are released from infected erythrocytes, passing rapidly through the plasma to invade normal erythrocytes. It has long been thought that antibodies directed against merozoite surface proteins (MSPs) play an important role in natural immunity against Plasmodium falciparum and that these antibodies may at least in part act through blocking erythrocyte invasion by merozoites. Indeed, such a view underpins much of the search for antigens suitable for use as vaccines, targeting blood stage parasites, and has a major influence on ideas on the acquisition of active immunity and on the passive protection of infants through uptake of maternal antibodies. Although convincing evidence that antibodies from immune sera can clear an infection has been obtained by passive transfer experiments 1,2,3,4, IgG did not block invasion 3,4. This paradox may...