A versatile method for purification of diphtheria toxoid for immunization purposes.

Diphtheriae growth supernatant. The toxoid was quantitatively recovered from the immunosorbent in two fractions: the first in 0.005 M hydochloric acid and the second in 6' M urea containing 0.1 M HCL. Both fractions were soluble in aqueous solvents, and both had a similar specific activity: between 200 and 250 Lf/mg protein, and about 1.5 protective unit (ED50) per l Lf unit, as assayed in guinea pigs. Using the same procedure, the specific activity of a commerical toxoid preparation, purified and concentrated, was increrased two fold, from 130 Lf/mg to 260 Lf/mg protein.