Camelid VHH Antibodies that Neutralize Botulinum Neurotoxin Serotype E Intoxication or Protease Function

Area of Science:

• Immunology
• Neuroscience
• Biochemistry

Background:

• Botulinum neurotoxin (BoNT) serotype E is a significant cause of human botulism and a Tier 1 Select Agent.
• BoNT/E is characterized by rapid onset and short duration of intoxication, posing a public health concern.

Purpose of the Study:

• To develop and characterize novel camelid single-domain antibodies (VHHs) targeting BoNT/E holotoxin and its light chain protease domain (LC/E).
• To evaluate the neutralizing and inhibitory potential of these VHHs against BoNT/E activity and intoxication.

Main Methods:

• Selection of two large panels of unique camelid VHHs against BoNT/E holotoxin and LC/E.
• Characterization of VHH binding specificity and neutralization of BoNT/E intoxication in neuronal cell cultures.
• Assessment of VHH inhibition of LC/E protease activity.
• In vivo efficacy studies using heterodimer antitoxins in mouse models challenged with BoNT/E.

Main Results:

• Nineteen VHHs binding to BoNT/E were identified, with 8 demonstrating neutralization of neuronal intoxication.
• Heterodimer antitoxins composed of neutralizing VHHs protected mice against high doses of BoNT/E.
• Twenty-two VHHs binding to LC/E were identified, with 9 inhibiting protease activity.
• Differential binding of VHHs depending on the form of LC/E (plastic-coated vs. soluble/captured) was observed.

Conclusions:

• Camelid VHHs represent a promising therapeutic strategy for neutralizing BoNT/E.
• The developed VHH panels provide insights into BoNT/E function and potential for antidotes.
• Further development of these VHHs could lead to effective treatments for BoNT/E-induced paralysis.