Plasmodium falciparum surface protein 25 (Pfs25) (Pfs25)

Plasmodium falciparum surface protein 25 (Pfs25) is a 25 kDa cysteine-rich protein expressed on the surface of the malaria parasite during its sexual stages within the Anopheles mosquito midgut, specifically on zygotes and ookinetes (UniProt: P08550). It is characterized by four epidermal growth factor (EGF)-like domains and is anchored to the parasite membrane via a glycosylphosphatidylinositol (GPI) anchor. Pfs25 is a leading candidate for transmission-blocking vaccines (TBVs), which aim to interrupt the malaria life cycle by inducing antibodies in the human host. When a mosquito ingests these antibodies during a blood meal, they bind to Pfs25 and prevent the ookinete from invading the mosquito midgut wall, thereby halting the development of oocysts and sporozoites (PubMed: 26839135). This mechanism does not protect the vaccinated individual from infection but serves as a public health tool to reduce the parasite reservoir in a population. Clinical trials have evaluated various formulations, such as Pfs25 conjugated to Pseudomonas aeruginosa Exoprotein A (EPA), to overcome the protein's low intrinsic immunogenicity (PubMed: 24106295). Despite its potential, maintaining the high antibody titers necessary for effective transmission blockade remains a primary therapeutic challenge.

Other names

25 kDa ookinete surface antigenP25Pfs25 antigen

Induction of host antibodies that are ingested by the Anopheles mosquito during a blood meal; these antibodies bind to Pfs25 on the surface of zygotes and ookinetes, sterically hindering their ability to invade the mosquito midgut epithelium and halting the parasite life cycle (PubMed: 18443225).