CHARACTERIZATION OF MONOCLONAL-ANTIBODIES AGAINST NAJA-NAJA-OXIANA NEUROTOXIN-I

Seven monoclonal antibodies (mAbs) were developed against neurotoxin I (NT-1), a protein from central Asian cobra (Naja naja oxiana) venom w hich binds specifically to nicotinic acetylcholine receptor (AchR). Al l of the mAbs cross-reacted with another long-chain post-synaptic neur otoxin, Bungarus multi-cinctus alpha-bungarotoxin (alpha-BT), but not Naja naja kaouthia alpha-cobratoxin, in an enzyme-linked immunosorbent assay (e.l.i.s.a.). Short-chain post-synaptic neurotoxins like Naja n aja atra cobrotoxin, Laticauda semifasciata erabutoxin b, or N. n. oxi ana neurotoxin II did not cross-react with the NT-1 mAbs, but an antig en(s) found in Dendroaspis polylepis, Acanthophis antarcticus and Pseu dechis australis venoms was immunoreactive. The e.l.i.s.a. readings fo r dithiothreitol-reduced NT-1 and NT-1 mAbs ranged from 13 to 27% of t hose for native toxin but reduced alpha-BT was not immunoreactive. Syn thetic NT-1 peptides were used in epitope-mapping studies and two, non -contiguous regions (Cys(15)-Tyr(23) and Lys(25)-Gly(33) or Pro(17)-Ly s(25) and Asp(29)-Lys(37)) were recognized by the NT-1 mAbs. The NT-1 mAbs individually inhibited 31-71% of alpha-BT binding to AchR in vitr o and afforded a slight protective effect in vivo with a toxin:antibod y mole ratio of 1:1.5. This report is the first to describe mAbs which recognize and protect against a heterologous, long-chain, post-synapt ic neurotoxin from snake venom.