Identification of surface antigens of schistosomula of Schistosoma mansoni recognized by antibodies from mice immunized by chronic infection and by exposure to highly irradiated cercariae

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Abstract
Surface components of mechanically transformed schistosomula of S. mansoni were labeled by lactoperoxidase-catalyzed iodination. After solubilization with Triton X-100, antigens were identified by immunoprecipitation. Serum from chronically infected Swiss mice reproducibly precipitated 7 major polypeptides with .apprx. MW (.times. 103) of 94, 68, 45, 40-32, 22, and 16. The antigens of MW (.times. 103) of 94, 40-32, 22, and 16 were shown to be exposed on the parasite surface by interaction of the antibodies with intact labeled schistosomula. Sera from several strains of infected inbred mice precipitated the same polypeptides. The antibodies produced during chronic infection were stimulated by adult worms since sera from 6 wk infected animals precipitated none of the surface antigens, and the pattern produced by precipitation with antibodies from a mouse infected with male worms only was indistinguishable from the pattern obtained with sera from mice with bisexual infections. Antibodies from mice immunized with highly irradiated cercariae reproducibly precipitated major polypeptides of .apprx. (.times. 103) 94, 68, 45, 32, 22, 19, and 15 daltons. The antigens of (.times. 103) 94, 43, 32, 22, and 15 daltons were shown to be exposed on the parasite surface by interaction of the antibodies with intact labeled schistosomula. The 15 .times. 103-dalton surface protein was recognized by sera from vaccinated, but not chronically infected, mice, suggesting that it represents a stage-specific immunogen present on schistosomula but not on adult worms. Sera from 2 inbred strains of mice which develop different degrees of immunity recognized the same antigens.