Development of amebicidal cell-mediated immunity in gerbils (Meriones unguiculatus) immunized with the galactose-inhibitable adherence lectin of Entamoeba histolytica.

The galactose-inhibitable adherence lectin of Entamoeba histolytica is a protective antigen in the gerbil model of amebic liver abscess. To further understand the mechanisms of vaccine efficacy, we studied the cell-mediated immune response to the lectin in gerbils. Splenocytes harvested from immunized gerbils demonstrated in vitro proliferation and production of interleukin-2 and gamma-interferon in response to purified adherence lectin (P < 0.05 for each compared to control splenocytes). Splenocytes from immunized gerbils developed direct amebicidal activity (P = 0.014) following in vitro stimulation with the adherence lectin. Splenocytes harvested from immunized gerbils following intrahepatic challenge with viable E. histolytica adherence lectin. Splenocytes harvested from immunized gerbils following intrahepatic challenge with viable E. histolytica trophozoites demonstrated proliferative and amebicidal responses (P < 0.05). In conclusion, immunization with the E. histolytica galactose-inhibitable adherence lectin elicits an amebicidal cell-mediated response that is enhanced by parasite challenge.