# Molecular mechanisms of botulinum neurotoxin neutralization

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA-IRVINE · 2020 · $567,527

## Abstract

Project summary
Botulism is caused by exposure to protein toxins called botulinum neurotoxins (BoNTs) that are produced by Clostridium
botulinum. BoNTs are CDC Tier 1 select agent for which no antidote currently exists. Seven different BoNT serotypes
have been discovered to date (BoNT/A-G), many having numerous additional BoNT subtypes. However the only
currently available treatments are serum based antitoxin products derived from large animals that are only effective if
administered soon after BoNT intoxication. The challenge of developing BoNT therapeutics is exacerbated by the fact that
the seven known BoNT serotypes are each distinct toxins with distinct receptor specificities and proteases that cleave at
distinct sites on SNARE proteins to disrupt nerve transmission. Due to the severity of the risk, the paucity of treatment
options, and the complexity of the challenge, novel approaches to the prevention and treatment of BoNT intoxication are
clearly needed. We now have extensive evidence in multiple toxin models demonstrating that bispecific VHH-based
neutralizing agents (VNAs), consisting of two covalently linked, toxin-neutralizing VHHs, are antitoxins with potencies
that often exceed that of current monoclonal and polyclonal antitoxin agents. Furthermore, VNAs offer substantial
advantages over serum and mAb antitoxin products as they are economical to produce and highly versatile; offering
innovative new prevention and treatment strategies for toxin exposures and infections with toxin-producing pathogens
such as gene therapies and direct delivery to enteric and pulmonary sites of challenge. In this proposal, we test the
hypothesis that integrating structural and mechanistic information into VNA design will lead to even greater antitoxin
efficacy and versatility. The Specific Aims are to (1) determine the crystal structures of selected BoNT-binding VHHs in
complex with their target BoNTs; (2) define the mechanisms by which VHHs selected in Aim 1 block BoNT toxicity,
and; (3) design and test bispecific VNAs with enhanced antitoxin properties by exploiting structure/function data from
Aims 1 and 2. This will be the first comprehensive structural mapping of BoNT neutralizing epitopes, which will be
complemented with mechanistic studies of BoNT function and BoNT-host interactions. Furthermore, this study will
improve general understanding of how structural and mechanistic information can inform the design of even more
effective VNA antitoxin agents and should permit rapid development of commercial antitoxin therapeutics to treat
exposures to all BoNT serotypes and other toxin biothreat agents.

## Key facts

- **NIH application ID:** 9918242
- **Project number:** 5R01AI125704-05
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **Principal Investigator:** Rongsheng Jin
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $567,527
- **Award type:** 5
- **Project period:** 2016-05-10 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9918242

## Citation

> US National Institutes of Health, RePORTER application 9918242, Molecular mechanisms of botulinum neurotoxin neutralization (5R01AI125704-05). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9918242. Licensed CC0.

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