Comparison of adherence, cytotoxicity, and Gal/GalNAc lectin gene structure in Entamoeba histolytica and Entamoeba dispar

The recent development of axenic culture for E. dispar allowed us to examine this ameba's ability to bind and lyse target cells and compare it to E. histolytica which has been axenically cultured for years. We found that under axenic conditions, E. dispar's adherence to target cells, ligand binding, and cytotoxicity were less than that of E. histolytica. These events were Gal/GalNAc-inhibitable supporting the idea that E. dispar expresses a lectin similar to E. histolytica. Genetic analysis showed that E. dispar had at least two members of the lectin heavy subunit family and four members of the lectin light subunit family that hybridized to ehhgl and ehlgl gene probes. A library screen produced clones which were isolated and sequenced. Derived amino acid sequences showed that the E. dispar heavy and light subunit clones were 86% and 79% identical, respectively, to their E. histolytica counterparts. In particular, the region which contains the epitopes for two adherence-enhancing monoclonal antibodies and a complement-sensitizing monoclonal antibody (amino acids 882–959 of the lectin heavy subunit) were conserved between the species.