Monoclonal and polyclonal antibodies against dendrotoxin: Their effects on its convulsive activity and interaction with neuronal acceptors.
Three stable hybrid cell lines have been established that secrete monoclonal antibodies of G(1) sub-class to dendrotoxin, a convulsant polypeptide (M(r) = 7000). Using [(125)I]labelled dendrotoxin the resultant ascitic fluids were found to show no cross-reactivity with homologous toxins (toxins 1, B and E from Dendroaspis polylepis, toxin Dv-14 from Dendroaspis viridis and ?-bungarotoxin from Bungarus multicinctus). In contrast, polyclonal antibodies raised against dendrotoxin cross-reacted to varying degrees with its congeners; most importantly, the rank order of cross-reactivities was in accordance with their potencies in eliciting convulsions when injected intracerebroventricularly into rat brain. All the antibodies prevented significantly the binding of dendrotoxin to its protein acceptor in brain synaptic membranes. Moreover, when they were injected into rat brain together with lethal doses of dendrotoxin they delayed, or in some cases prevented, the onset of convulsive symptoms. Ultracentrifugation of the complexes formed by [(125)I]labelled dendrotoxin and one or more of the monoclonal antibodies showed only a single peak of radioactivity with an S(20.w) of 7S, indicating that all these mono-specific antibodies are directed to the same or overlapping epitope(s). Conversely, polyclonal antisera produced larger complexes with the antigen, revealing the presence of at least two determinants on this molecule. Such antibodies are proving helpful in identifying regions of the toxin responsible for the neurotoxicity and associated interaction with its acceptor, a putative constituent of A-current K(+)-channels.
Mehraban
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F
Department of Biochemistry, Imperial College, London SW7 2AZ, U.K.
Haines
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A
Dolly
J O
JO