Many pathogens express proteins similar to perforin, a pore-forming protein used by immune cells to lyse target cells. However, the role of these perforin-like proteins (PLPs) in bacteria and protozoa had not yet been characterized. A new study demonstrates that a PLP from the intracellular protozoan pathogen Toxoplasma gondii, which can cause flu-like symptoms in humans, enables the parasite to exit host cells by rapidly permeabilizing the host cell membrane and parasite-encasing membrane. Mutating the PLP had little effect on parasite growth in culture, but dramatically reduced the acute virulence of the pathogen in mice. Targeting PLPs may be a new strategy for not only reducing the virulence of this protozoa, but also other PLP-expressing pathogens, such as malaria.
Kafsack BF, Pena JD, Coppens I, Ravindran S, Boothroyd JC, Carruthers VB (2009). Rapid membrane disruption by a perforin-like protein facilitates parasite exit from host cells. Science 323, 530– 533.
