Characterization of the laminated layer of in vitro cultivated Echinococcus vogeli metacestodes

The metacestode (larval) stages of the cestode parasites Echinococcus vogel i and E. multilocularis were isolated from the peritoneal cavity of experim entally infected C57BL/6 mice and were cultured in vitro for a period of up to 4 mo under conditions normally applied for the in vitro cultivation of E. multilocularis metacestodes. In contrast to E. multilocularis, E. vogeli did not exhibit extensive exogenous budding and proliferation but increase d in size with a final diameter of up to 10 mm. Most metacestodes contained protoscoleces, singly or in groups, either associated with brook capsules or growing directly out of the germinal layer. Each individual metacestode was covered by an acellular translucent laminated layer that was considerab ly thicker than the laminated layer of E. multilocularis metacestodes. The ultrastructural characteristics, protein content, and carbohydrate composit ion of the laminated layer of in vitro cultivated E. vogeli and E. multiloc ularis were assessed using transmission electron microscopy, lectin fluores cence labeling, and lectin blotting assays. The laminated layer of E. vogel i is, as previously described for E. multilocularis metacestodes, largely c omposed of N-acetyl-beta -D-galactosaminyl residues and alpha- and beta -D- galactosyl residues, as well as of the core structure of O-linked carbohydr ate chains, N-acetylgalactosamine-beta -1,3-galactose. However, in contrast to E. multilocularis, N-linked glycopeptides and alpha -D-mannosyl and/or glucosyl residues were also associated with the laminated layer of E. vogel i. The laminated layer from both species was isolated from in vitro cultiva ted metacestodes, and the purified fractions were comparatively analyzed. T he protein : carbohydrate ratio (1:1) was similar in both parasites; howeve r, the protein banding pattern obtained by silver staining following sodium dodecyl sulfate polyacrylamide gel electrophoresis suggested intrinsic dif ferences in protein composition. A polyclonal antiserum raised against the E. multilocularis laminated layer and a monoclonal antibody, G11, directed against the major E. multilocularis laminated layer antigen Em2 did not cro ss-react with E. vogeli, indicating distinct compositional and antigenic di fferences between these 2 parasites.