Isolation of a Cytotoxin-Enterotoxin from Entamoeba histolytica

Abstract

A heat-labile material with cytotoxic and enterotoxic activities was isolated from axenically cultivated Entamoeba histolytica. The cytotoxin-enterotoxin was partially purified from the particulate-free supernatant of sonicated trophozoites by ammonium sulfate precipitation and gel filtration. Cytotoxic activity, assayed on monolayers of HeLa or BHK-21 cells, was restricted to proteins that eluted in the molecular weight range of 25,000--35,000 daltons. Cytotoxicity was demonstrated at protein concentrations as low as 2--4 microgram/ml, was heat-labile (75 C, 30 min), and was inhibited by specific immune IgG and by an undetermined factor in nonimmune serum. Enterotoxic activity of the partially purified toxin was demonstrated by induction of fluid secretion in ligated rabbit ileal loops. The cytotoxin-enterotoxin of E. histolytica may play an important role in the production of diarrhea and mucosal injury in amoebic colitis.

Virulence of Entamoeba histolytica trophozoites. Effects of bacteria, microaerobic conditions, and metronidazole.

“…One of the better known pathogenic strains, HM-I:IMSS, very readily produces hepatic lesions in hamsters (5, 6), lyses cultured mammalian cells (8), and phagocytizes erythrocytes (10). It also has an active collagenase system (34,35), as well as other soluble toxic substances that have not yet been fully characterized (11)(12)(13). Strains with attenuated pathogenicity, such as HK-9, have been repeatedly shown to have considerably less virulent properties in all these tests.…”

Hemolytic activity of Trichomonas vaginalis and Tritrichomonas foetus

“…The strongest hemolytic potency in E. histolytica was observed in the most virulent strains (López-Revilla & Said-Fernández 1980). However, there is no correlation between this activity and an enterotoxin isolated from this amoeba (Lushbaugh et al 1979).…”

Hemolytic uremic syndrome associated withEntamoeba histolytica intestinal infection

“…Among the known factors, the expression of adhesions molecules with lytic properties (lectins), pore-forming proteins (amebapores) and cystein proteinases seems crucial in the cellular damage [7]. Lushbaugh et al have studied differences regarding the virulence of E. histolytica strains, showing some strains with higher amounts of immunogenic cytotoxins than the less virulent ones [8], suggesting that the risk of tissue damage, even extraintestinal damage, may be dependent on the ameba strain. This higher virulence might be related to the presence of specific amebic cystein proteinases [9].…”