Axenic in vitro cultivation of Echinococcus multilocularis metacestode vesicles and the generation of primary cell cultures.

Parasitic helminths are a major cause of disease worldwide, yet the molecular mechanisms of host-helminth interaction and parasite development are only rudimentarily studied. A main reasons for this lack of knowledge are the tremendous experimental difficulties in cultivating parasitic helminths under defined laboratory conditions and obtaining sufficient amounts of parasite material for molecular analyses. For one member of this neglected group of pathogens, the fox-tapeworm Echinococcus multilocularis, we have established and optimized in vitro cultivation systems by which the major part of the parasite's life cycle, leading from early metacestode vesicles to the production of protoscoleces, can be mimicked under laboratory conditions. The methodology comprises co-cultivation systems for host cells and parasite larvae by which large amounts of parasite vesicles can be generated. Furthermore, we have established an axenic (host cell-free) cultivation system that allows studies on the influence of defined host factors on parasite growth and development. On the basis of this system, the isolation and maintenance of primary Echinococcus cells that are devoid of overgrowing host cells is now possible. The availability of the primary cell culture system constitutes a first step toward the establishment of genetic manipulation methods for the parasite that will be of great interest for further research on infection strategies and development of Echinococcus and other cestodes.