During malaria infection, sporozoites injected from the salivary gland of the biting mosquito must migrate to the hepatocytes of the victim's liver to multiply and develop. To access the hepatocytes, the sporozoites must pass from the circulation across a layer of liver sinusoidal cells. This stage of malaria transmission is a promising target for vaccines and drugs, but is not as well characterized as other stages of the parasite life cycle.
Ishino et al. have explored the route by which sporozoites exit the bloodstream and cross the sinusoidal cell layer of the liver. They discovered a novel protein important for parasite motility and invasion called SPECT, which was specifically produced by the parasite at this stage, and was localized to and secreted from a specialized compartment of the parasite termed the microneme. Parasites were observed to attach to and migrate over the surface of the epithelial cells lining the sinusoidal veins until they reached a Kupffer cell (a liver macrophage-like cell that forms up to 30% of the sinusoidal layer), through which they migrated to reach the hepatocytes. SPECT-deleted parasites could not cross the sinusoidal layer even though they could still invade hepatocytes in vitro. -- CA
PloS Biol. 2, 77 (2004).
