Plasmodium falciparum antigen (Pf Ag)

Plasmodium falciparum antigens are a diverse group of proteins expressed by the P. falciparum parasite, the primary cause of severe malaria in humans. These proteins are essential for the parasite's complex life cycle, facilitating processes such as sporozoite invasion of the liver, merozoite invasion of red blood cells, and the sequestration of infected cells in the host vasculature to avoid splenic clearance. From a clinical perspective, these antigens are the primary targets for malaria vaccines, such as the WHO-recommended RTS,S/AS01 (Mosquirix) and R21/Matrix-M, which target the circumsporozoite protein (CSP). Additionally, they are the basis for rapid diagnostic tests (RDTs), which most commonly detect the Histidine-Rich Protein 2 (HRP2) secreted by the parasite. The extreme genetic diversity and the ability of the parasite to vary the expression of these antigens (antigenic variation) pose significant hurdles for the development of universal vaccines and can lead to diagnostic failures, particularly in regions where pfhrp2 gene deletions are prevalent.

Other names

Pf AgMalarial antigenPlasmodium falciparum surface proteinPfHRP2PfCSPMerozoite surface proteinCircumsporozoite protein

Vaccines and monoclonal antibodies target specific antigens (e.g., CSP) to neutralize the parasite, preventing host cell invasion and infection. Diagnostic antibodies bind to secreted antigens (e.g., HRP2) to allow for the visual or electronic detection of the parasite in blood samples.