Surface proteins of Schistosoma mansoni and their expression during morphogenesis.

Surface components of Schistosoma mansoni have been identified by lactoperoxidasecatalyzed iodination. Cercariae have a simple labeling pattern in comparison to schistosomula. Transformation of cercariae to schistosomula results in the loss of a low molecular weight material which may be the glycocalyx, and the appearance of many more labeled proteins. Mechanical conversion of cercariae to schistosomula requires subsequent incubation at 37 degrees C for more than 1 h to give the full surface-labeling pattern of schistosomula. The majority of proteins found on schistosomula appear to be present throughout the remaining part of the developmental cycle, although adult male worms had only low levels of these antigens, and female worms had virtually no detectable surface antigens. The low level of expression of schistosome antigen could be caused by adsorbed host antigen, although no evidence for adsorbed host protein was found, or by a reduced level of antigens present on the worm surface. The low level of schistosome antigen could have a role in the resistance of adult worms to the host's immune response.