Immunization of hamsters by intramuscular injections of an amebic extract and of two of its fractions, emulsified with complete Freund's adjuvant, resulted in protection against the development of amebic liver abscess, following intrahepatic inoculation of axenic trophozoites of Entamoeba histolytica such that Fraction I, Fraction II, and the whole antigen conferred protection to 18 out of 18, 4 out of 18, and 11 out of 18 hamsters, respectively. Splenomegaly was found to accompany the development of hepatic liver absceses in this experimental system. There was a very high degree of correlation (r = 0.95) between the weights of the abscesses and the spleens. On the other hand, there was no correlation between the anti-amebic antibody titers (determined by the indirect hemagglutination test) and the development of the liver abscesses within the time-span of the experimental protocol used in this study.
Present address: Department of Pathology, School of Medicine, Georgetown University, Washington, D. C. 20007.