Thrombospondin related anonymous protein (TRAP) of Plasmodium falciparum in parasite-host cell interactions

Thrombospondin related anonymous protein (TRAP) of Plasmodium falciparum is characterized by the presence of an amino acid motif based on the sequence Trp-Ser-Pro-Cys-Ser-Val-Thr-Cys-Gly (WSPCSVTCG) that is found in a growing family of proteins. The sequence WSPCSVTCG is considered to confer sulpho-galactosyl-cerebroside (sulphatide) binding properties to antistasin, TSP, CS protein and properdin. The observation that TRAP is localized both on the micronemes and on the surface of P. falciparum sporozoites would suggest a role played by TRAP, and its putative sulphated glycoconjugates binding motif, in the recognition and/or entry of hepatocytes by the sporozoite. Our results indicated that TRAP constructs, expressed in E. coli, bind to sulpho-galactosyl-cerebrosides (sulphatides) and to the surface of HepG2 cells using the conserved amino acid motif WSPCSVTCG. Antisera raised against TRAP constructs inhibited sporozoite invasion of HepG2 cells thus suggesting, thus, that TRAP may be one of the parasite-encoded molecules implicated in the sporozoite invasion of hepatocytes. Moreover, the possibility that TRAP antibodies may be relevant in malaria immunity is supported by the results obtained in a prospective study conducted in a malaria endemic area. In adolescents, the presence of TRAP antibodies, before malaria transmission, correlated positively with the control of parasite density.