In vitro Entamoeba histolytica adhesion to human endothelium: a comparison using two strains of different virulence.

Extraintestinal dissemination of Entamoeba histolytica is frequently manifested by the life-threatening amebic liver abscess (ALA). The hepatic establishment of amebas implies invasion of blood vessels and contact with the endothelium. By means of a fluorescence-based quantitative adhesion assay, we assessed the binding to human endothelial cells of two E. histolytica strains of different virulence. The highly virulent strain (L-A) adhered substantially more strongly to unstimulated endothelium than the non-virulent one (BG3). Attachment of L-A was increased by treatment of endothelial cells with interleukin-1 beta (IL1 beta). Other proinflammatory cytokines such as interferon-gamma (IFN gamma) and tumor necrosis factor-alpha (TNF alpha) did not modify the spontaneous adhesion capacity of amebas. For purposes of comparison we also performed adhesion of the parasites to skin fibroblasts. Adhesion to this cell type was quite low (< 10%). Parasite virulence, differential adhesive capacity to endothelial cells, and modulation of the latter phenomenon by proinflammatory factors (IL1 beta) may influence the evolution and outcome of extraintestinal amebiasis, especially hepatic abscesses.