Monoclonal antibodies against ?-bungarotoxin

Hybridomas secreting monoclonal antibodies against ?-bungarotoxin were produced from the fusions of mice lymphocytes from hyperimmune animals with two mice myeloma cell lines ((NSI/1 or Sp2/0). Several anti-?-bungarotoxin monoclonal antibodies were derived and characterized. One of these (spB57) belonged to the IgG(1) subclass and bound potently to ?-bungarotoxin in a radioimmunoassay. This effect was specific to the anti-?-bungarotoxin antibody; a control series of antibodies (against tyrosine hydroxylase, enkephalin, neurofilament and the nerve growth factor receptor) did not bind radiolabelled toxin. Furthermore, the anti-?-bungarotoxin antibody did not interact with other radiolabelled receptor ligands. Using autoradiographic techniques, spB57 was shown to block the binding of [(125)I]?-bungarotoxin to brain sections. Similarly, spB57 blocked radiolabelled toxin binding to brain membranes; again this was an effect specific to the anti-?-bungarotoxin antibody. The decrease in [(125)I]?-bungarotoxin binding suggested that spB57 specifically bound the toxin molecule such that it could no longer interact with its receptor. Since the ?-BGT site has the characteristics of a nicotinic receptor, the effect of the antibody was also tested on the inhibition of [(125)I]?-bungarotoxin binding by cholinergic ligands. SpB57 partially reversed the inhibition of ?-toxin binding observed with nicotinic agonists and d-tubocurarine, but not with other nicotinic antagonists nor with muscarinic receptor ligands. These effects appeared to be specific for spB57, as they occurred to a much lesser extent with two other anti-?-BGT mAbs, nsB8 and spB28. These results suggest that an antibody against the ?-toxin can affect the interaction of nicotinic receptor ligands at the ?-BGT site.