Purified antigen radioimmunoassay in serological diagnosis of schistosomiasis mansoni.

A radioimmunoassay has been developed for detecting human schistosomiasis with a highly purified Schistosoma mansoni egg antigen labelled with iodine-125. The antigen, major serologic antigen 1 (M.S.A.1), has striking immunochemical and species specificity and appears to be the principal antigen responsible for the granulomatous response to S. mansoni eggs. This 125I-antigen was tested with 5 microliter of patient serum as a potential serodiagnostic test for schistosomiasis. 92 control sera from uninfected St. Vincentian patients were seronegative. In studies on 135 lightly infected St. Lucians the 5 microliter serum 125I-M.S.A.1 serodiagnostic test was more sensitive than any tests available at the Center for Disease Control, with 64% of infected children, 83% of adolescents, and 98% of adults being positive. 49 heavily infected Kenyans of all age-groups were uniformly (100%) seropositive. Finally, a semiquantitative version of the 125I-M.S.A.1 radioimmunoassay that uses 0-5 microliter of patient sera demonstrated quantitatively significant differences among age-watched and intensity-watched groups of patients with S. mansoni, S. haematobium, and S. japonicum infections.