Biochemical properties of larval excretory-secretory glycoproteins of the parasitic nematode Toxocara canis

Abstract

Toxocara canis larvae, infective to Man, secrete a number of antigenic macromolecules into culture medium over prolonged periods of time. These antigens have been collected and characterised with respect to molecular weight by sodium dodecyl sulphate-polyacrylamide gel electrophoresis following extrinsic and intrinsic radiolabelling, or electrophoresis followed by gel staining or immunoblotting. Panels of enzymes and lectins have been applied to examine protease sensitivity and carbohydrate composition, respectively, and a number of other biochemical data have been noted. Taken together, the excretory-secretory molecules contain more than 40% carbohydrate of which the majority is N-acetylgalactosamine and galactose. The individual antigens may readily be separated by gel filtration on a Sepharose 6B column, and it is shown that the major excretory-secretory macromolecules are all glycoproteins which differ in essential characteristics. For example, the 32 kDa antigen (TES-32) binds concanavalin A, is sensitive to a range of proteases and is the band most readily stained by silver and Coomassie blue. Both TES-120 and TES-400 components are resistant to tryptic or peptic cleavage, bind to Helix pomatia lectin and stain with periodic acid-Schiff, yet unlike TES-120, TES-400 does not incorporate radioactive methionine nor can it be stained by silver stain techniques. Finally, one protease, staphylococcal V8, reveals cleavage sites only in the TES-70 and TES-400 molecules.