Distribution of repetitive and non-repetitive circumsporozoite protein epitopes on Plasmodium falciparum sporozoites and immunochemical characterization of human malaria antisera

Abstract

The presence and distribution of circumsporozoite protein (CSP) epitopes located in the repetitive and non-repetitive regions were studied in three Plasmodium falciparum strains, NF54, IFA5 and IFA6. It was found by immunofluorescence, Western blotting and immunoelectron microscopy that mAbs to epitopes of the repetitive domaine bound similarly to the CSP of all three strains. MAbs to epitopes of the flanking regions yielded either some strain differences (mAbs to the C-terminal end), or reacted only in immunofluorescence tests on whole sporozoites (mAbs to the N-terminal end). Human sera from an area endemic for malaria, two of them positive in ELISA on (NANP)40 and two negative, were tested for their reactivity with epitopes of the flanking regions of the CSP. The presence of antibodies to such epitopes could be demonstrated by Western blots and immunocytochemistry independent of the reactivity of the sera to recognize (NANP)40. All tested bound to salivary gland tissues but not to their secretory product in immunocytochemical experiments.