Identification of a parasite-specific cytoplasmic 67 kDa Entamoeba histolytica antigen recognized by patient sera and monoclonal antibodies.

To avoid false positive reactions in tests for anti-ameba antibodies, we wanted to identify parasite-specific component(s). Amebiasis patient sera recognized an antigen of 67 kDa by immunoblotting in an active E. histolytica fraction obtained by ion exchange chromatography. Monoclonal antibodies against the fraction were made. Antibody 3G2 reacted with three antigenic components of 67, 40 and 25 kDa and in the immunocytology with an epitope located in the cytoplasm of E. histolytica trophozoites. ELISAs using the isolated parasite fraction and monoclonal antibody 3G2 (to assay inhibition of binding) were capable of distinguishing specific reactivity in sera from amebiasis patients.