Ionic interfaces and diphtheria toxoid interactions

We present here a systematic study on the purification of the diphtheria toxoid (Dtxd) produced at the Instituto Butantan, byadding only one step on the entire process of its production. Aliquots of 1.0 ml of Dtxd were added to an equal amount of QSepharosepreviously equilibrated with 500mM Tris, pH 5.0–9.0 (increments of 0.5 pH units). The best condition for the Dtxdmonomer adsorption was achieved at pH 9.0. The best condition for desorption was obtained with 300mM NaCl. After studyingthe gel binding capacity for Dtxd, a column (C20/20) equilibrated with 500mM Tris, pH 9.0, was prepared. The purification factorfor Dtxd was 1.5. The final recovery of Dtxd was 68.75%, with 90.31% purity. The process methodology presented here is a veryrealistic sequence of separation steps, which is perfectly compatible with the production requirements. Vaccination with ‘‘toxoidhighly purified toxin’’ is known to confer a strong immunity on people in the absence of undesirable reactions, which led experts ofEuropean Pharmacopoeia to recommend its use both for children and adult vaccination.