Age-dependent occurrence of protective anti-Plasmodium falciparum sporozoite antibodies in a holoendemic area of Liberia

Abstract
Antibodies to Plasmodium falciparum sporozoites were detected in children aged 6 months to 9 years, and in adults, in a holoendemic village near Yekepa, Liberia, by enzyme linked immunosorbent assay (ELISA) using the recombinant circumspprozoite protein R32tet32 or by inhibition of sporozoite invasion (ISI) of hepatoma cells. Both assays were significantly correlated with each other and showed that anti-sporozoite antibodies increase with age. ISI was more sensitive than ELISA and demonstrated significantly increased anti-sporozoite antibodies at age 5–6 years, when young children show partial clinical resistance to malaria. These results suggest that anti-sporozoite antibodies, as measured by ISI, may contribute to protection against malaria.