Isolation of a human monoclonal antibody with strong neutralizing activity against diphtheria toxin.

We isolated a human monoclonal antibody against diphtheria toxin (DT). It bound to fragment B with a binding activity (Kd) of 3.01 nM. The neutralizing activity assayed by the rabbit skin test was estimated to be 73,600 IU/g. This could be used as a therapeutic drug against DT in place of the traditional equine sera.