Regulatory Interpretation: Constructs of Botulinum Neurotoxin Genes

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Date: April 18, 2022

Subject: Request for Interpretation on Constructs of Botulinum Neurotoxin Genes Subject to the Select Agent Regulations as outlined in 42 CFR. §73.3(c)(2)

This is in response to your letter dated April 7, 2022, requesting clarification of which constructs containing genes encoding botulinum neurotoxin would be subject to the select agent regulations as outlined below and in 42 CFR § 73.3(c)(2). The regulatory provision provides:

  • 73.3 (c) Genetic Elements, Recombinant and/or Synthetic Nucleic Acids, and Recombinant and/or Synthetic Organisms:
    • (2)  Recombinant and/or Synthetic nucleic acids that encode for the toxic form(s) of any of the toxins listed in paragraph (b) of this section if the nucleic acids:
      • (i) Can be expressed in vivo or in vitro, or
      • (ii)  Are in a vector or recombinant host genome and can be expressed in vivo or in vitro.

The Division of Select Agents and Toxins (DSAT) has determined the following based on the submitted questions:

  1. Are plasmids containing full-length botulinum neurotoxin genes without a promoter for expression of the neurotoxin gene (DNA only, cannot be expressed even in a bacterial strain) subject to the select agent regulations?
  • No. Plasmids containing genes encoding the full-length botulinum neurotoxin without a promoter for expression of the neurotoxin genes are not regulated nucleic acids because the plasmids cannot be expressed in vitro or in vivo as outlined in § 73.3(c)(2).
  1. Are plasmids containing full-length botulinum neurotoxin genes with a promoter for expression of the neurotoxin gene (DNA only, can be expressed only in a bacterial expression strain) subject to the select agent regulations?
  • Yes. Plasmids containing genes encoding the full-length botulinum neurotoxin with a promotor for expression of the neurotoxin genes are regulated nucleic acids because the plasmids can be expressed in the bacterial strain as outlined in § 73.3(c)(2).
  1. Are plasmids containing full-length botulinum neurotoxin genes with no promoter for expression of the neurotoxin gene in a bacterial strain subject to the select agent regulations?
  • No. Plasmids containing genes encoding the full-length botulinum neurotoxin without a promoter for expression of the neurotoxin genes in a bacterial strain are not regulated nucleic acids because the plasmids cannot be expressed in vitro or in vivo as outlined in § 73.3(c)(2).
  1. Are plasmids containing full-length botulinum neurotoxin genes with a promoter for expression of the neurotoxin gene in a bacterial strain subject to the select agent regulations?
  • Yes. Plasmids containing full-length botulinum neurotoxin genes with a promotor for expression of the neurotoxin gene in a bacterial strain are regulated nucleic acids because the plasmids can be expressed in the bacterial strain as outlined in § 73.3(c)(2).