Protection of gerbils from amebic liver abscess by vaccination with a 25-mer peptide derived from the cysteine-rich region of Entamoeba histolytica galactose-specific adherence lectin

The protozoan parasite Entamoeba histolytica causes extensive morbidity and mortality through intestinal infection and amebic liver abscess. Here we show that immunization of gerbils with a single keyhole limpet hemocyanin-coupled 25-mer peptide derived from the 170-kDa subunit of the E. histolytica galactose-binding adhesin is sufficient to confer substantial protection against experimentally induced amebic liver abscesses. Vaccination provided total protection in 5 of 15 immunized gerbils, and abscesses were significantly smaller (P < 0.01) in the remaining vaccinated animals. The degree of protection correlated with the titer of antibodies to the peptide, and results of passive transfer experiments performed with SCID mice were consistent with a role for antibodies in protection. In addition, parenteral or oral vaccination of gerbils with 13-amino-acid subfragments of the peptide N-terminally fused to the B subunit of cholera toxin also significantly inhibited liver abscess formation (P < 0.05). These data indicate that small peptides derived from the galactose-binding adhesin administered by the parenteral or oral route can provide protection against amebic liver abscess and should be considered as components of a subunit vaccine against invasive amoebiasis.