Differentiation of Entamoeba histolytica from E. dispar facilitated by monoclonal antibodies against a 150-kDa surface antigen

Abstract

Murine monoclonal antibodies (mAbs) were produced against an n-octyl-beta-D-glucopyranoside-extracted fraction of trophozoites of Entamoeba histolytica HM-1:IMSS. Four of the mAbs were reactive with a 150-kDa surface antigen characterized by Western-immunoblot analysis under nonreducing conditions. When the reactivity of the four mAbs with nine reference strains of E. histolytica was examined by an indirect fluorescence antibody test, two of the mAbs (EH3015 and EH3023) were found to react with all nine strains and the other two mAbs (EH3056 and EH3126) reacted with seven strains. The four mAbs did not react with any E. dispar reference strain or with other enteric protozoan parasites. The reactivity of EH3015 and EH3023 with numerous isolates of E. histolytica and E. dispar collected in our laboratories was also examined. The 2 mAbs reacted with all of the 37 E. histolytica isolates tested but did not react with any of the 33 isolates of E. dispar. These results indicate that common antigenic epitopes of E. histolytica are on the 150-kDa surface molecule and that mAbs can distinguish between E. histolytica and E. dispar.

Evaluation of Recombinant Fragments of Entamoeba histolytica Gal/GalNAc Lectin Intermediate Subunit for Serodiagnosis of Amebiasis

“…Another possibility is that antigenic differences among E. histolytica isolates may exist in the N terminus of Igl. In the previous study, monoclonal antibodies EH3015 and EH3023 were reactive with all of the 47 E. histolytica isolates but with none of the E. dispar isolates, indicating the existence of a common epitope in E. histolytica isolates (23). On the other hand, a difference in the reactivity of monoclonal antibodies EH3056 and EH3126 was observed among E. histolytica isolates, suggesting that qualitative and/or quantitative differences of Igl may exist.…”

“…We recently identified a GPI-anchored 150-kDa intermediate subunit (Igl) of lectin, which is noncovalently associated with Hgl (4,8). A mouse monoclonal antibody specific for Igl significantly inhibits adherence and cytotoxicity of trophozoites to mammalian cells, erythrophagocytosis, and liver abscess formation in hamsters (5,7,23). Igl is a cysteine-rich protein that consists of 1,101 amino acids (aa) and contains multiple CXXC motifs in amino acid sequences (4).…”

Characterization ofEntamoeba histolyticaIntermediate Subunit Lectin-Specific Human Monoclonal Antibodies Generated in Transgenic Mice Expressing Human Immunoglobulin Loci

“…In our previous study, SDS-PAGE analysis of the native Igl gave two bands with molecular masses of 150 and 170 kDa (11,13). Western immunoblot analysis has also shown that MAb EH3015 recognizes 150-and 170-kDa molecules in the H-302: NIH strain of E. histolytica (48). The present study revealed that the 170-kDa band is Igl1 and the 150-kDa band is Igl2, although the molecular mass calculated from the DNA sequence is larger for Igl2 than for Igl1 (9).…”

“…We have demonstrated previously that a 150-kDa intermediate subunit (Igl), which is noncovalently associated with Hgl, also contributes to adherence (13). A mouse monoclonal antibody (MAb) specific for Igl significantly inhibits the adherence and cytotoxicity of trophozoites to mammalian cells and inhibits erythrophagocytosis (10,48,51). The immunization of hamsters with native Igl can inhibit amebic liver formation (11).…”

Intermediate Subunit of the Gal/GalNAc Lectin of Entamoeba histolytica Is a Member of a Gene Family Containing Multiple CXXC Sequence Motifs

“…The cytoplasmic tail of Hgl has homology to the cytoplasmic domain of ␤2 and ␤7 integrins, including regions implicated in binding of the intracellular signaling molecules Shc and Grb2. Overexpression of the cytoplasmic tail results in a dominant negative effect on endogenous lectin activity, with decreased adherence, cytotoxicity, and in vivo virulence (44).The 150-kDa lectin intermediate subunit (Igl) was originally identified as a trophozoite surface antigen recognized by MAbs which block trophozoite adherence to mammalian cells in vitro (9)(10)(11)42). The EH3015 MAb specific for Igl significantly inhibits adherence of amebae to erythrocytes and CHO cells, erythrophagocytosis by amebae, and amebic cytotoxicity to CHO cells (9).…”