The P. falciparum circumsporozoite protein (PfCSP) is the most abundant antigen expressed on the surface of P. falciparum sporozoites. This pre-erythrocytic antigen contains a stretch of 6 highly conserved, immunodominant tetrapeptide repeats (NANP) in the middle, while its N- and C-terminal regions contain two crucial protective regions termed RI and RII-plus, respectively. Both play key roles during parasite invasion. PfCSP has been the main target antigen in the development of preerythrocytic malaria vaccines, including subunit proteins with adjuvants or attenuated viral platforms. Studies show that high titers of antibodies directed to PfCSP are believed to interrupt the invasion of hepatocytes by blood-borne sporozoites, thereby abrogating the development of blood-stage malaria.

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