Metabolic products of adult Clonorchis sinensis: their composition and antigenic potential

AdultClonorchis sinensiswere taken from the bile ducts of infected rabbits and incubated in Ringer's fluid. The soluble metabolic products secreted by the living flukes during incubation were found to include carbohydrate and protein. Enzyme activities of protease, carbohydrases and esterase, but not of lipase, were detected in the samples.

Samples with a nitrogen content of 3 μg/ml or more reacted as antigen in immunodiffusion tests in gel against sera of rabbits infected withC. sinensisor immunised against whole fluke extract.

The demonstration of enzymes in the metabolic products, the reactions of the samples as antigen and the correlation of antigenic activity with the nitrogen content of the samples suggests that the enzymes detected are effective antigens in clonorchiasis, although complete identity was not demonstrated in this study.

The enzymes investigated were those associated with digestion; intracellular enzymes which have less opportunity to elicit antibody production were not investigated.