Camelid VHH Antibodies that Neutralize Botulinum Neurotoxin Serotype E Intoxication or Protease Function
Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA
The United States Army Medical Research Institute of Chemical Defense, Fort Detrick, MD 21010, USA
Department of Physiology & Biophysics, University of California, Irvine, CA 92697-4560, USA
Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA
Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD 21702-5011, USA
Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
Author to whom correspondence should be addressed.
Toxins 2020, 12(10), 611; https://doi.org/10.3390/toxins12100611
Received: 18 August 2020 / Revised: 2 September 2020 / Accepted: 11 September 2020 / Published: 24 September 2020
(This article belongs to the Special Issue Inhibitors and Countermeasures against Bacterial and Plant Toxins)
Botulinum neurotoxin (BoNT) serotype E is one of three serotypes that cause the preponderance of human botulism cases and is a Tier 1 Select Agent. BoNT/E is unusual among BoNT serotypes for its rapid onset and short duration of intoxication. Here we report two large panels of unique, unrelated camelid single-domain antibodies (VHHs) that were selected for their ability to bind to BoNT/E holotoxin and/or to the BoNT/E light chain protease domain (LC/E). The 19 VHHs which bind to BoNT/E were characterized for their subunit specificity and 8 VHHs displayed the ability to neutralize BoNT/E intoxication of neurons. Heterodimer antitoxins consisting of two BoNT/E-neutralizing VHHs, including one heterodimer designed using structural information for simultaneous binding, were shown to protect mice against co-administered toxin challenges of up to 500 MIPLD50. The 22 unique VHHs which bind to LC/E were characterized for their binding properties and 9 displayed the ability to inhibit LC/E protease activity. Surprisingly, VHHs selected on plastic-coated LC/E were virtually unable to recognize soluble or captured LC/E while VHHs selected on captured LC/E were poorly able to recognize LC/E coated to a plastic surface. This panel of anti-LC/E VHHs offer insight into BoNT/E function, and some may have value as components of therapeutic antidotes that reverse paralysis following BoNT/E exposures.