Animal toxicity of Shigella dysenteriae cytotoxin: evidence that the neurotoxic, enterotoxic, and cytotoxic activities are due to one toxin.

The lethal effect to rabbits and mice of Shigella dysenteriae toxin and the ability of the toxin to induce fluid accumulation in rabbit ileal loops were studied in relation to the cytotoxic activity. The relative concentrations of the three activities were approximately the same in a crude toxin preparation and in purified, electrophoretically homogenous toxin. The cytotoxic and lethal activities eluted identically from a high pressure liquid chromatography column and migrated at the same rate in polyacrylamide gel electrophoresis under nondenaturing conditions. The cytotoxic, lethal, and enterotoxic activities were inactivated to essentially the same extent upon incubation for few minutes at 80 degrees C and upon treatment with urea. Graded precipitation of Shigella toxin with different amounts of an antiserum to Shigella toxin in each case removed essentially the same fraction of the cytotoxic, the lethal, and the enterotoxic activity. The data indicate that one molecular entity is responsible for the three biologic effects of Shigella toxin studied. After i.v. injection, the LD50 dose was estimated to be 2.2 ng/kg in rabbits and 450 ng/kg in mice.