Protection of hamsters from amebic liver abscess formation by immunizationwith the 150-and 170-kDa surface antigens of Entamoeba histolytica

A monoclonal antibody, EH3015, prevents in vitro adherence of Entamoeba his tolytica trophozoites to mammalian cells and inhibits amebic liver abscess formation in hamsters. By immunoaffinity chromatography with the monoclonal antibody, purified E. histolytica antigens with molecular masses of 150 an d 170 kDa under Iron-reduced conditions were obtained. Hamsters were immuni zed with these antigens (group I) or with fractions further purified by pol yacrylamide gel electrophoresis (group II). Pooled immune sera from the two groups inhibited in vitro amebic adherence to Chinese hamster ovary cells by 98% at 1:10 dilutions. The immunized hamsters were challenged by the int rahepatic injection of E. histolytica trophozoites. Complete protection fro m abscess formation was observed in 38% of hamsters in group I and 67% in g roup II, whereas all control hamsters inoculated only with adjuvant develop ed amebic liver abscesses. In the immunized hamsters, the abscesses in the two groups were significantly smaller than in the controls. These results d emonstrate that the E. histolytica antigens are possible vaccine candidates for amebiasis.