Abstract:
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PfEMP1 is an antigenically variable molecule which mediates the adhesion of parasitized erythrocytes to a
variety of cell types and which is believed to constitute an important target for naturally acquired protective
immune responses in malaria. For 9 years we have monitored individuals living in an area of low-intensity,
seasonal, and unstable malaria transmission in eastern Sudan, and we have used this database to study the
acquisition, specificity, and duration of the antibody response to variant parasitized erythrocyte surface
antigens. Both the levels and the spectrum of reactivity of these antibodies varied considerably among
individuals, ranging from low levels of antibodies recognizing only few parasitized erythrocyte surface antigens
to high levels of broad-specificity antibodies. In general, episodes of clinical malaria were associated with
increases in the levels of parasitized erythrocyte surface-specific antibodies that subsided within months of the
attack. This response was often, but not always, specific for the antigenic variants expressed by the parasite
isolate causing disease. Our study provides evidence that Palciparum falciparum malaria is associated with a
short-lived, variant-specific antibody response to PfEMP1-like antigens exposed on the surface of parasitized
erythrocytes. Furthermore, our data suggest that the antigenic repertoires of variant antigens expressed by
different parasite isolates show considerable overlapping, at least under Sahelian conditions of low-intensity,
seasonal, and unstable malaria transmission. Finally, we demonstrate the existence of persistent differences
among individuals in the capacity to mount antibody responses to variant surface antigens. |