CARBOHYDRATE EPITOPES OF ENTAMOEBA-HISTOLYTICA CELL-SURFACE GLYCOPROTEINS ARE MAJOR TARGETS OF THE HUMAN HUMORAL RESPONSE

The antigens of Entamoeba histolytica recognized by antibodies in 11 i ndividual sera from patients treated for amebic liver abscess were det ermined both by immunoprecipitation of metabolically-radiolabeled whol e trophozoite proteins and by immunoblotting. Collectively, twenty-sev en antigens ranging from 167 to 21 kDa were detected in immunoblots of whole trophozoite extracts; eight of these were recognized by all tes ted patient sera. Immunoprecipitation studies also revealed a complex amebic antigenic profile. Of a total of twenty immunoprecipitated poly peptides (from 200 to 24 kDa), seventeen were uniquely recognized by t he patient sera. Eight of these seventeen antigens were immunoprecipit ated by most immune sera. The cellular localization of trophozoite ant igens was determined by analyzing plasma membrane and soluble cytosol fractions. Plasma membranes contained virtually as many antigenic moie ties as the total trophozoite extract; in contrast, the soluble fracti on was antigenically less complex. Mild periodate oxidation of plasma membrane antigens indicated that surface glycoproteins are highly immu nogenic for the human host and that antibodies to their carbohydrate e pitopes are a major component of the total response of most patients.