PROTECTION OF GERBILS FROM AMEBIC LIVER-ABSCESS BY IMMUNIZATION WITH RECOMBINANT ENTAMOEBA-HISTOLYTICA 29-KILODALTON ANTIGEN

The goal of our study was to obtain a highly conserved Entamoeba histo lytica recombinant antigen for study as a subunit amebiasis vaccine. W e screened a Uni-Zap cDNA library off. histolytica (strain HM1:IMSS),v ith human immune sera and isolated a dominant 804-bp cDNA clone. A 33- kDa fusion protein expressed from the cDNA clone was determined by mon oclonal antibody binding, DNA hybridization, and nucleotide sequence t o be the complete E. histolytica 29-kDa antigen. Serum antibodies to t he recombinant protein were detected by enzyme linked immunosorbent as say in 80% of subjects from Egypt and South Africa with amebic liver a bscess. Similar results were found with the native 29-kDa protein. Nat ive and recombinant 29-kDa antigens induced proliferation of lymphocyt es harvested from patients,vith amebic liver abscess (P < 0.01 compare d with controls). Intraperitoneal immunization of gerbils with the rec ombinant fusion protein (10 mu g) with Titermax adjuvant elicited an a ntigen-specific serum immunoglobulin G antibody response and was parti ally protective (54%) against intrahepatic challenge with 5 x 10(5) vi rulent axenic trophozoites (strain HM1:IMSS). In summary, the recombin ant form of the E. histolytica 29-kDa antigen demonstrated serologic s pecificity for amebic liver abscess, exhibited conserved T-cell epitop es, and was effective as a subunit vaccine in an experimental animal m odel of amebic liver abscess.