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Two VHH Antibodies Neutralize Botulinum Neurotoxin E1 by Blocking Its Membrane Translocation in Host Cells

Journal Article · · Toxins
 [1];  [2];  [3];  [1]
  1. Univ. of California, Irvine, CA (United States)
  2. Cornell Univ., Ithaca, NY (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Tufts Univ., North Grafton, MA (United States)

Botulinum neurotoxin serotype E (BoNT/E) is one of the major causes of human botulism, which is a life-threatening disease caused by flaccid paralysis of muscles. After receptor-mediated toxin internalization into motor neurons, the translocation domain (HN) of BoNT/E transforms into a protein channel upon vesicle acidification in endosomes and delivers its protease domain (LC) across membrane to enter the neuronal cytosol. It is believed that the rapid onset of BoNT/E intoxication compared to other BoNT serotypes is related to its swift internalization and translocation. We recently identified two neutralizing single-domain camelid antibodies (VHHs) against BoNT/E1 termed JLE-E5 and JLE-E9. Here, we report the crystal structures of these two VHHs bound to the LCHN domain of BoNT/E1. The structures reveal that these VHHs recognize two distinct epitopes that are partially overlapping with the putative transmembrane regions on HN, and therefore could physically block membrane association of BoNT/E1. This is confirmed by our in vitro studies, which show that these VHHs inhibit the structural change of BoNT/E1 at acidic pH and interfere with BoNT/E1 association with lipid vesicles. Therefore, these two VHHs neutralize BoNT/E1 by preventing the transmembrane delivery of LC. Furthermore, structure-based sequence analyses show that the 3-dimensional epitopes of these two VHHs are largely conserved across many BoNT/E subtypes, suggesting a broad-spectrum protection against the BoNT/E family. In summary, this work improves our understanding of the membrane translocation mechanism of BoNT/E and paves the way for developing VHHs as diagnostics or therapeutics for the treatment of BoNT/E intoxication.

Research Organization:
Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
Sponsoring Organization:
USDOE; National Institutes of Health (NIH); National Institute of Allergy and Infections Diseases (NIAID)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1673777
Journal Information:
Toxins, Journal Name: Toxins Journal Issue: 10 Vol. 12; ISSN 2072-6651
Publisher:
MDPICopyright Statement
Country of Publication:
United States
Language:
ENGLISH

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