Immuno-biological properties of chagastoxin (lipopolysaccharide)

Chagastoxin is a toxic fraction extracted with 88% phenol from virulent Trypanosoma cruzi. It is a white amorphous precipitate, insoluble in water, saline, alcohol, ether, acetone, acids and alkalis, unstable at room and refrigeration temperatures and in a 0·2% phenol suspension, but maintaining its potency when lyophilized. In doses of 25 to 200 μg. it induces partial protection of mice against T. cruzi; 500 μg. doses repeated on 16 occasions produce solid immunity. Massive doses activate latent chronic Chagas's disease to an actue, fatal infection; doses of less than 10 μg. fail to activate such an infection. Intradermal injection in infected and immunized rabbits gives rise to a reaction; in normal animals no such reaction is observed. The lethal dose in mice is 500 to 1000 μg. repeated on 4 successive days. In rabbits it gives rise to hyperpyrexia and leucocytosis. Microscopic examination of the tissues of mice which die of chagastoxin indicates that there is focal necrosis and round cell infiltration in the liver, the kidneys and the heart.