Partial characterization of a 36-kDa antigen of Entamoeba histolytica and its recognition by sera from patients with amoebiasis

A 36-kDa antigen of axenically grown pathogenic Entamoeba histolytica (HMI- IMSS) was eluted from the sodium dodecyl sulfate-polyacrylamide gel electro phoresis (SDS-PAGE)-resolved crude amoebic extract antigens. The immunoreac tivity of this partially purified 36-kDa antigen with monoclonal antibody ( MoAb) D-3(10) altered significantly (P < 0.01) after heat and trypsin treat ment but remained unaltered after treatment with sodium metaperiodate (P > 0.5), thereby indicating the protein nature of the epitope recognized by Mo Ab D-3(10). The epitope was found to be localized on the surface as well as in the cytoplasm of the E. histolytica trophozoites with the majority of i t in the cytoplasm. In addition, this epitope was also found to be present on the cyst form of the parasite. The 36-kDa molecule was recognized by the sera from 29 (85%) of the 34 patients with amoebic liver abscess and five (83%) of the six patients with amoebic colitis. No serum samples From asymp tomatic cyst passers, from patients with non-amoebic hepatic or intestinal disorders and apparently healthy subjects had antibodies that reacted with this 36-kDa molecule. The immune responses in man to this 36-kDa amoebic mo lecule indicate a potential specific role for this molecule in invasive amo ebiasis. (C) 2000 Federation of European Microbiological Societies. publish ed by Elsevier Science B.V. All rights reserved.