Low-Iron Bovine Lactoferrin Affects Adhesion, Erythrophagocytosis, Cytotoxicity, and Proteolytic Activity in Entamoeba histolytica Trophozoites

For Entamoeba histolytica to establish an infection, it must employ several mechanisms of pathogenicity to produce and secrete virulence factors that allow the parasite to adhere to and finally colonize and invade the host. However, in the intestinal epithelium, trophozoites (amoebae) encounter lactoferrin (Lf), a glycoprotein of the first line of defense, together with immunoglobulins and other molecules. We previously reported that iron-free bovine Lf (bLf) could kill amoebae both in vitro and in animal models of intestinal and hepatic amoebiasis. In this work, selected pathogenic mechanisms were evaluated in trophozoites by exposing cultures to sublethal concentrations of bLf to determine which amoebic functions could be altered. At a sublethal bLf concentration, this glycoprotein was removed from the trophozoite. In the presence of erythrocytes, bLf colocalized with erythrocytes at the capping site; this was observed by confocal microscopy of living cells. In addition, the erythrophagocytosis rate, proteolytic activity, adhesion, and cytotoxic properties towards Caco2 colonic cancer cells were reduced in the presence of bLf. Lactoferrin could be a particularly important protein that naturally protects colonic epithelial cells from E. histolytica infection.