PfEMP1: an antigen that plays a key role in the pathogenicity and immune evasion of the malaria parasite Plasmodium falciparum.

The deadliest form of human malaria is caused by the protozoan parasite Plasmodium falciparum affecting millions worldwide every year. P. falciparum virulence is attributed to its ability to evade the human immune system by modifying infected host red blood cells to adhere to the vascular endothelium and to undergo antigenic variation. The main antigenic ligands responsible for both cytoadherence and antigenic variation are members of the P. falciparum Erythrocyte Membrane Protein-1 (PfEMP1) family. These polymorphic proteins are encoded by a multi-copy gene family called var. Each individual parasite expresses a single var gene at a time, maintaining the remaining approximately 60 var genes found in its genome in a transcriptionally silent state. As the antibody response against the single expressed PfEMP1 develops, small sub-populations of parasites switch expression to alternative forms of PfEMP1 and re-establish the infection. Therefore, PfEMP1 is considered a key player in the pathogenicity of P. falciparum.