Identification of a surface antigen of Schistosoma mansoni

The aim was to identify the biochemical nature of the schistosomula surface and the changes which take place at this level as a result of host-parasite interaction. Ultrastructural observations showed that S. mansoni tegument consists of a syncytial epithelium covered by a multilaminate outer membrane. Proteins of the outermost layer of the tegument have not yet been identified. To accomplish this proteins from the schistosomula tegument previously treated with 125I by either the lactoperoxidase or Bolton-Hunter methods had their tegument extracted with 0.3M CaCl2 and processed for SDS-polyacrylamide gel electrophoresis and autoradiography. In addition, autoradiographic comparison was made between electrophoretic patterns of teguments labelled with 14C-amino acid and 125I. The results suggest that a tyrosine-rich material of low turnover rate occurs in the schistosomula surface. Trypsin treatment of schistosomula modifies the autoradiography pattern of the tegument and renders the parasite more susceptible to the killing effect of antibody plus complement. Electrophoretic patterns from worm teguments of each sex, extracted by 0.3M CaCl2 and stained by Coomassie Blue, showed qualitative differences. These differences were less remarkable in the autoradiography pattern obtained from the gel electrophoresis of tegument proteins labelled with 125I by the lactoperoxidase technique. Poorly labelled protein bands were observed in the autoradiography of adult worm teguments extracted by freezing and thawing. By comparison of schistosomula and adult worm autoradiographic patterns it was possible to identify clearly at least one stage-specific antigen