Extracellular matrix: A tool for defining the extracorporeal function of parasite proteases.

The significance of cysteine protease activity present in excretory/secretory products of the feeding stages of Haemonchus contortus is discussed here by Marcia Rhoads and Raymond Fetterer. Based, in part, on the in vitro degradation and uptake of extracellular matrix components by live parasites, they argue that the cysteine proteases have an essential extracorporeal function in the digestion of host tissues. They also outline the merits of the extracellular matrix model, which mimics the in vivo structure of connective tissue and basement membranes, in analyzing host-parasite interactions and (possibly) parasite developmental processes.