A Three Monoclonal Antibody Combination Potently Neutralizes Multiple Botulinum Neurotoxin Serotype E Subtypes

Area of Science:

• Immunology
• Microbiology
• Neuroscience

Background:

• Human botulism is primarily caused by botulinum neurotoxin (BoNT) serotypes A, B, and E.
• Developing effective antitoxins against diverse BoNT/E subtypes is crucial for public health.

Purpose of the Study:

• To create human monoclonal antibodies (mAbs) capable of binding and neutralizing multiple BoNT/E subtypes.
• To identify cross-reactive antibodies for broad-spectrum BoNT/E neutralization.

Main Methods:

• Generated yeast-displayed single chain variable fragment (scFv) antibody libraries from immunized humans.
• Isolated BoNT/E-binding scFv using Fluorescence-Activated Cell Sorting (FACS).
• Converted lead scFv to IgG format and tested neutralization in a mouse model.

Main Results:

• Identified 10 scFv with nanomolar binding affinities to BoNT/E subtypes.
• Developed three cross-reactive scFv that bind all tested BoNT/E subtypes at distinct epitopes.
• Demonstrated potent neutralization of BoNT/E1, E3, and E4 by a combination of three mAbs in vivo.
• Achieved IgG dissociation constants (K_D) as low as 2.28 pM.

Conclusions:

• Human mAbs can be developed to neutralize multiple BoNT/E subtypes effectively.
• These mAbs show promise as broad-spectrum therapeutic antitoxins and diagnostic tools.
• A combination of three mAbs (NTM-1633) is advancing to pre-clinical development.