Simple method for purifying choleragenoid, the natural toxoid of Vibrio cholerae

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Abstract
Choleragenoid, a nontoxic aggregate of the B subunit of cholera toxin, was purified from concentrated culture filtrates in a single step by ion-exchange chromatography on phosphocellulose or other cation-exchange resins. This procedure is far simpler than others currently used to isolate choleragenoid and yields a preparation essentially free from nucleic acid, lipopolysaccharide, toxin and other proteins present in the crude culture filtrates. The purified choleragenoid retained the specific receptor-binding capacity of the toxin but exhibited no enterotoxic activity by either the ileal loop assay or the skin permeability assay. This purification method may therefore be superior to others currently used for obtaining choleragenoid for immunization or other purposes.