Monoclonal antibody-based ELISA for the detection of circulating Entamoeba histolytica antigen in hepatic amebiasis in hamsters (Mesocricetus auratus).

Circulating amebic antigens were determined by using a sandwich ELISA with specific monoclonal antibody in the sera of 35 group I hamsters, 7 of which were sacrificed at intervals after hepatic inoculation with 500,000 axenically grown HM:1:IMSS strain of E. histolytica trophozoites, 7 group II infected hamsters in which metronidazole treatment was given and 18 group III uninfected controls. Amebic antigenemia was demonstrated in 5 of 7 (71.4%), 6 of 7 (85.7%), 7 of 7 (100%), 7 of 7 (100%) and 7 of 7 (100%) of group I hamsters on days 5, 10, 15, 20 and 30 of infections respectively, whereas 6 of 7 (85.7%) of group II hamsters were weakly positive, one was negative and all 18 group III hamsters were negative. The sensitivity of the assay was 100% after the animals were infected 15 days onwards. The level of antigenemia in hamsters of group I with abscess was significantly higher than those of the same group without abscess (p < 0.05). Absence or reduction of antigenemia after treatment could be interpreted to mean a positive test of cure and favorable therapeutic response. The MAb-PAb-based ELISA for the detection of circulating E. histolytica represents a simple and sensitive diagnostic test for invasive amebiasis in hamsters. Application of this test in amebic liver abscess patients should be of diagnostic value for indication of present infection or test of cure after successful treatment.

Pyruvate: ferredoxin oxidoreductase from Entamoeba histolytica recognized by a monoclonal antibody.

A mouse monoclonal antibody, Eh208C2-2 MAb, raised against whole cell antigens of Entamoeba histolytica trophozoites of the pathogenic strain HM-1: IMSS and polyclonal antisera (PAb) against membrane antigens of E. histolytica trophozoites of strain HTH-56: MUTM were screened against a cDNA library of the pathogenic strain, SFL3. The monoconal antibody detected many phage plaques expressing an E. histolytica protein. The DNA sequence encoding the protein was approximately 55% identical, over 1,100bp, to Trichomonas vaginalis pyruvate: ferredoxin oxidoreductase (PFOR) and pyruvate: flavodoxin oxidoreductase from Klebsiella pneumoniae, Anabaena variabilis and Enterobacter agglomerans. Two of seven clones detected by mouse polyclonal antisera also encoded this protein. Two others encoded Entamoeba Hsp70, another encoded Entamoeba alkyl-hydroperoxide reductase and the remaining two were unidentified sequences. Entamoeba PFOR is an abundant, antigenic protein which may be a useful target for the development of protective host immune responses against invasive amebiasis.