Human T-lymphocyte proliferation, lymphokine production, and amebicidal activity elicited by the galactose-inhibitable adherence protein of Entamoeba histolytica.

We studied human T-lymphocyte responses to the purified Entamoeba histolytica galactose-inhibitable adherence protein. Individuals having serum anti-adherence protein antibodies possess peripheral blood lymphocytes which demonstrate antigen-specific responses to the purified adherence protein (10 micrograms/ml) and whole soluble amebic antigen (100 micrograms/ml). This was determined by incorporation of [3H]thymidine (53,080 and 73,114 dpm, respectively) and by increased production of interleukin-2 and gamma interferon (42.0 and 67.5 U/ml, respectively) (P less than 0.05 for each in comparison with values for control lymphocyte responses). Lymphocytes from antiamebic antibody-positive subjects develop in vitro amebicidal activity only when incubated for 5 days with the purified adherence protein (P = 0.02). In conclusion, the E. histolytica galactose-inhibitable adherence protein elicits an in vitro amebicidal cell-mediated immune response, further supporting the potential for the use of this protein in a subunit amebiasis vaccine.