Failure to respond to the surface of Plasmodium falciparum infected erythrocytes predicts susceptibility to clinical malaria amongst African children.

Following infection with Plasmodium falciparum malaria, children in endemic areas develop antibodies specific to antigens on the parasite-infected red cell surface of the infecting isolate, antibodies associated with protection against subsequent infection with that isolate. In some circumstances induction of antibodies to heterologous parasite isolates also occurs and this has been suggested as evidence for cross-reactivity of responses against the erythrocyte surface. The role of these relatively cross-reactive antibodies in protection from clinical malaria is currently unknown. We studied the incidence of clinical malaria amongst children living on the coast of Kenya through one high transmission season. By categorising individuals according to their pre-season parasite status and antibody response to the surface of erythrocytes infected with four parasite isolates we were able to identify a group of children, those who failed to make a concomitant antibody response in the presence of an asymptomatic parasitaemia, at increased susceptibility to clinical malaria in the subsequent 6 months. The fact that this susceptible group was identified regardless of the parasite isolate tested infers a cross-reactive or conserved target is present on the surface of infected erythrocytes. Identification of this target will significantly aid understanding of naturally acquired immunity to clinical malaria amongst children in endemic areas.