A solid-phase enzyme immunoassay (EIA) was used to detect circulating antibodies to histolysain, the major cysteine proteinase of Entamoeba histolytica. Serum samples from 40 healthy controls, 33 asymptomatic E. histolytica cyst passers and 22 patients with amoebic liver abscess were tested. Antibodies to histolysain were found in 72·7% of cases of amoebic liver abscess, 18·1% of the cyst passers and 2·5% of healthy controls, which suggests that a humoral immune response is induced by histolysain during amoebic liver abscess.
