Abstract
The neurotoxins from Clostridium botulinum (BoNT serotypes A-G) exert their lethal effect by preventing the release of acetylcholine at the neuromuscular junction. As with tetanus toxin, immunization with a non-toxic fragment, the 50 kDa C-terminal portion of BoNT A (H C; residues 861–1296), protects mice against lethal challenges with the intact toxin. To locate the neutralizing epitopes, several protective monoclonal antibodies (mAbs) against BoNT A-H C were isolated and cloned. Specific binding of the mAbs to BoNT A-H C was demonstrated by surface plasmon resonance, with K ds in the range of 10 −10 to 10 −11 M. These antibodies recognized a genetically engineered polypeptide (1150–1289) that was previously shown to induce protective immunity. Prior to the determination of the X-ray crystal structure of the tetanus neurotoxin H C fragment, molecular modelling studies indicated that it contained two highly solvent-exposed loops. Based on these predictions, two 25-mer H C-peptides corresponding to these two regions were synthesized and were demonstrated to bind the neutralizing mAbs. Mice immunized with the H C-peptides had high levels of antibodies that recognized BoNT A-H C . However, immunizations with only one of the H C peptides protected when mice were challenged with BoNT A . On the basis of these analyses, it should be possible to develop small peptides that could be useful in the design of future vaccines against these neurotoxins.
Published Version
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