Affinity purification of tetanus toxin using polyclonal and monoclonal antibody immunoadsorbents

Tetanus toxin has been immunopurified on immunoadsorbent columns derived from equine polyclonal antitoxin coupled to cyanogen bromide-activated Sepharose CL4B. Desorption of bound toxin in active form was achieved only when the immunoadsorbent was mixed with Sephadex G15 and this mixture overlaid on a further volume of Sephadex G15. With equine antibody, 64% of adsorbed toxin was recovered with a specific activity of 2400 limiting flocculation units (Lf)/mg protein N (1.2 × 10⁸ minimum lethal doses (MLD)/mg protein N). Similarly prepared immunoadsorbent derived from murine monoclonal antitoxin of low affinity had improved desorption with less acidic desorbents, without the requirement for Sephadex G15; greater than 80% of adsorbed toxin was recovered with a specific activity of 3000 Lf/mg protein N (1.6 × 10⁸ MLD/mg protein N).