Purification and biological characterization of shiga toxin from Shigella dysenteriae 1

Shiga toxin has been purified in milligram quantities to near homogeneity from cell lysates of Shigella dysenteriae 1 strain 3818-0. Purification involved an initial ultracentrifugation, ammonium sulfate fractionation, chromatography on DEAE-cellulose and carboxymethyl cellulose, gel filtration, and preparative isoelectric focusing in sucrose gradients. The purified toxin was resolved by discontinuous polyacrylamide gel electrophoresis into a major cytotoxic protein band and a closely migrating, cytotoxic protease-nicked minor band. Antiserum generated by immunization with glutaraldehyde-inactivated toxin was shown to be monospecific against S. dysenteriae cell lysates. This highly purified toxin was cytotoxic to HeLa cells, enterotoxic in rabbit ileal loops, and lethal to mice. Monospecific antiserum to the toxin neutralized completely these toxin activities in both purified toxin preparations and crude shigella cell lysates.