Isolation and characterization of human monoclonal antibodies to digoxin

Fab preparations of sheep polyclonal anti-digoxin Abs have proven useful fo r reversal of the toxic effects of digoxin overdoses in patients. Unfortuna tely, the use of foreign species proteins in humans is limited because of t he potential for immunological responses that include hypersensitivity reac tions and acute anaphylaxis, Immunization of recently developed transgenic mice, whose endogenous mu heavy and kappa light chain Ig genes are inactiva ted and which carry human Ig gene segments, with a digoxin-protein conjugat e has enabled us to generate and isolate eight hybridoma cell lines secreti ng human sequence anti-digoxin mAbs, Six of the mAbs have been partially ch aracterized and shown to have high specificity and low nanomolar affinities for digoxin, In addition, detailed competition binding studies performed w ith three of these mAbs have shown them to have distinct differences in the ir digoxin binding, and that all three structural moieties of the drug, the primary digitoxose sugar, steroid, and five-member unsaturated lactone rin g, contribute to Ab recognition.