Plasmodium falciparum circumsporozoite (CS) protein peptides specifically bind to HepG2 cells

Hepatocyte invasion by malaria parasites is mediated by specific molecular interactions. Several lines of evidence suggest the importance of the surfa ce plasmodial circumsporozoite (CS) protein in the sporozoite invasion of h epatocytes. Identification of the sequences involved in binding to hepatocy tes is an important step towards understanding the structural basis for the sporozoite-hepatocyte interaction. In this study, binding assays between P lasmodium falciparum CS peptides and HepG2 cells were performed. Fifteen ov erlapping residue 20 mer long peptides, spanning the entire CS sequence. we re tested in HepG2 cell binding assays. Five High Binding Activity Peptides (HBAPs) to HepG2 cells were identified: 4593, (NANPNANPNANP); 4383. (NSRLS LGENDDGNNEDNEKLR); 4388, (GNGQGHNMPNDPNRNVDENA), 4389, (HNMPNDPNRNVDENANANS A) and 4390, (DPNRNVDENANANSAVKNNN). The HBAP HepG2 interaction is independ ent of charge and amino-acid composition, but sequence dependent, Four HBAP s (4383. 4388, 4389 and 4390) are bound with similar affinity to a 50 kDa m olecule. These HBAPs define three Hepatocyte Binding Sequences (HBSs): HBS- 1, located between residues 68 and 87 (HBAP 4383) HBS-11. the repeat NANP r egion (HBAP 4593), for which anti repeat antibodies are able to specificall y inhibit sporozoite invasion of hepatocytes have been reported, and HBS-11 1, between residues 286 and 315 (HBAPs 4388. 4388 and 4390). respectively. Interestingly, HBS I I I carries two earlier- reported B-epitopes (underlin ed) in peptides 4388, 4389 and 4390 (GNGQGHNMPNDPNRNVD ENANANSAVKNN) in its sequence. The HBSs reported here show lesser interspecie-variability than the entire protein in species invading the same kind of hepatic cells. This data supports these HBSs' important role in CS-protein function, they coul d be used as ligand by the sporozoite to invade hepatic cells. (C) 2001 Pub lished by Elsevier Science Ltd.