Further studies on a cytotoxin/enterotoxin from Entamoeba histolytica

More virulent strains of Entamoeba histolytica contain more cytotoxic activity per trophozoite than do less virulent strains. Clarified sonicates of the more virulent strains are more cytotoxic than those of less virulent strains. The cytotoxins of all these strains are inhibited by specific immune IgG raised in rabbits or produced by natural human infection. Non-immune IgG's had no antitoxic activity. Serum fractions of non-immune serum containing alpha globulins (alpha 2 macroglobulin and alpha 1 antitrypsin) had a non-specific inhibitory effect on the cytotoxicity of the E. histolytica toxin. The positive correlation of strain cytotoxicity and the amount of toxin per trophozoite, with virulence suggests that the cytotoxin could play a role in production of human disease. The presence of immunoglobulins against the toxin in serum from a patient with clinical amebiasis indicates that the toxin is immunogenic in human infections and provides additional support for the relevance of E. histolytica cytotoxin to pathogenesis.