Plasmodium falciparum 25 kDa surface protein (Pfs25) (Pfs25)

The Plasmodium falciparum 25 kDa surface protein, commonly known as Pfs25, is a major surface antigen expressed during the sexual stages of the malaria parasite's life cycle. It is specifically located on the surface of zygotes and ookinetes after the parasite has been ingested by an Anopheles mosquito. Structurally, Pfs25 is a cysteine-rich, glycosylphosphatidylinositol (GPI)-anchored protein characterized by four tandem epidermal growth factor (EGF)-like domains. Its biological role is critical for ookinete maturation and the subsequent traversal of the mosquito midgut epithelium to form oocysts, which are essential steps for completing the parasite's life cycle. Because Pfs25 is not expressed in the human host, it is not subject to human immune pressure and remains highly conserved across various parasite isolates. This makes it a leading candidate for transmission-blocking vaccines (TBVs), which aim to induce high-titer antibodies in humans that neutralize the parasite within the mosquito midgut. Clinical development has explored various platforms, including protein-protein conjugates like Pfs25-EPA and viral-vectored vaccines, though achieving long-lasting immunity remains a significant hurdle. Safety profiles are generally favorable, although early trials using potent oil-in-water adjuvants identified specific risks such as erythema nodosum.

Other names

Surface protein Pfs25Pfs25 antigen25 kDa ookinete surface antigen25 kDa zygote surface proteinOokine surface protein 25

Transmission-blocking; immunization induces host antibodies that, when ingested by a mosquito, bind to Pfs25 on the parasite surface to inhibit its development from zygote to oocyst within the mosquito midgut.