Developmental changes in proteins and glycoproteins revealed by direct radio-iodination of viable Taenia saginata larvae.

Direct surface 125I radio-isotope labelling techniques and SDS-PAGE analysis were used to compare the proteins and lentil-lectin adherent glycoproteins of the bovine stage of viable Taenia saginata larvae at three points in their development, the invasive oncospheres, immature (4-week-old) and mature (12 to 16-week-old) cysticerci. Some proteins and glycoproteins were present on all three of the ages of the parasite examined but there were also distinct age-specific proteins and glycoproteins detected on oncospheres and 4-week-old cysticerci and a marked difference between the protein/glycoprotein profiles of the parasite was apparent at these earlier stages of development and the mature cysticeri. The latter were characterized by the presence of high, 160-200 kDa molecular weight, lysine rich, glycoproteins, whereas small 16 and 18 kDa glycoproteins and a reduction-sensitive 23 kDa glycoprotein were first detected on 4-week-old immature cysticerci. Antigenic characterization of the isotope-labelled proteins and glycoproteins by immunoprecipitation against a panel of clinically defined bovine sera combined with SDS-PAGE analysis indicated that relatively few proteins were precipitated by sera from T. saginata-infected cattle as compared to the glycoproteins. However, both protein and glycoprotein antigens of possible protective and/or diagnostic significance were identified from oncospheres and cysticerci. Of particular note were low molecular weight oncospheral proteins and low and high molecular weight cysticercal glycoproteins. The immunogenicity of these protein and glycoprotein antigens of T. saginata larvae and their age-related changes are of relevance to the design of diagnostic assays, vaccines and possibly to the survival of this parasite in its bovine host.