Neutralization of botulinum neurotoxin by a human monoclonal antibody specific for the catalytic light chain

Area of Science:

• Immunology
• Neuroscience
• Toxicology

Background:

• Botulinum neurotoxins (BoNT) are potent category A bioterror agents.
• Antibody therapeutics show promise for BoNT treatment.
• The therapeutic potential of antibodies targeting the BoNT light chain domain (LC) is underexplored.

Purpose of the Study:

• To clone and characterize a fully human antibody specific for the BoNT/A light chain domain (LC).
• To evaluate the therapeutic utility of this LC-specific antibody against BoNT/A.
• To elucidate the mechanisms of action for LC-specific BoNT neutralization.

Main Methods:

• Utilized an optimized hybridoma method to generate a fully human antibody (4LCA) against BoNT/A LC.
• Assessed in vivo neutralization efficacy of 4LCA alone and in combination with a heavy chain (HC) antibody.
• Investigated the effect of 4LCA on SNAP-25 cleavage in Neuro-2a cells.
• Examined BoNT/A cellular entry and intracellular localization in the presence of 4LCA.
• Determined the in vitro catalytic activity inhibition of BoNT/A by 4LCA.

Main Results:

• The 4LCA antibody demonstrated potent in vivo neutralization of BoNT/A.
• 4LCA collaborated with an HC antibody for enhanced neutralization.
• In neuronal cells, 4LCA prevented SNAP-25 cleavage, indicating inhibition of catalytic activity.
• Unlike HC antibodies, 4LCA did not block BoNT/A entry but was internalized into synaptic vesicles.
• 4LCA directly inhibited BoNT/A catalytic activity in vitro.

Conclusions:

• Antibodies targeting the BoNT/A LC can effectively inhibit the toxin in vivo and in vitro.
• The mechanisms of inhibition involve direct catalytic activity neutralization and intracellular targeting.
• LC-specific antibodies represent a promising strategy for developing novel BoNT antidotes.