The measurement of Ascaris suum protein by radioimmunoassay in sera from patients with helminthiasis and with gastrointestinal diseases.

In this study, we have developed a reliable radioimmunoassay (RIA) for Ascaris suum protein (Asp) and have measured the serum concentration of Asp in control subjects and in patients with helminthiasis and a variety of gastrointestinal diseases. The cross-reactivities of Asp antibody with other helminth worm antigens were also measured by RIA. Ascaris lumbricoides contained approximately the same amount of Asp antigenic substance as did Ascaris suum. Toxocara canis had a high concentration of a substance partially cross-reactive with Asp. Small amounts of substance cross-reacting with Asp were also exhibited by Anisakis larvae, Schistosoma japonicum and Taenia saginata. However, no cross-reactivities of Fasciola hepatica and Paragonimus westermani with Asp were observed in this study. Almost all the serum levels of Asp from normal control subjects were below the sensitivity of this RIA (10 ng/ml). High concentrations of Asp were observed in sera from patients with ascariasis (64.5 +/- 18.8 ng/ml: mean +/- S.E.), anisakiasis (75.2 +/- 28.0 ng/ml), toxocariasis (78.4 +/- 31.3 ng/ml) and schistosomiasis japonica (14.3 +/- 3.4 ng/ml). Asp levels in sera from patients with other helminthiasis were not significantly high. From these findings, it was suggested that RIA for Asp may not be specific for diagnosis of ascariasis, but might be a suitable screening method for patients with some kinds of helminthiasis. Interestingly, high concentrations of Asp were also observed in sera from patients with ulcerative colitis (24.8 +/- 2.5 ng/ml) and Crohn's disease (19.8 +/- 5.2 ng/ml), but Asp levels from 7 other gastrointestinal diseases seemed not to be significantly high. These findings remain unexplained but may derive from cross-reactivities between helminthic and gut mucosal antigens.