Single-domain antibody delivery using an mRNA platform protects against lethal doses of botulinum neurotoxin A

Front Immunol. 2023 Feb 14:14:1098302. doi: 10.3389/fimmu.2023.1098302. eCollection 2023.


Single-domain antibodies (sdAbs, VHHs, or nanobodies) are a promising tool for the treatment of both infectious and somatic diseases. Their small size greatly simplifies any genetic engineering manipulations. Such antibodies have the ability to bind hard-to-reach antigenic epitopes through long parts of the variable chains, the third complementarity-determining regions (CDR3s). VHH fusion with the canonical immunoglobulin Fc fragment allows the Fc-fusion single-domain antibodies (VHH-Fc) to significantly increase their neutralizing activity and serum half-life. Previously we have developed and characterized VHH-Fc specific to botulinum neurotoxin A (BoNT/A), that showed a 1000-fold higher protective activity than monomeric form when challenged with five times the lethal dose (5 LD50) of BoNT/A. During the COVID-19 pandemic, mRNA vaccines based on lipid nanoparticles (LNP) as a delivery system have become an important translational technology that has significantly accelerated the clinical introduction of mRNA platforms. We have developed an mRNA platform that provides long-term expression after both intramuscular and intravenous application. The platform has been extensively characterized using firefly luciferase (Fluc) as a reporter. An intramuscular administration of LNP-mRNA encoding VHH-Fc antibody made it possible to achieve its rapid expression in mice and resulted in 100% protection when challenged with up to 100 LD50 of BoNT/A. The presented approach for the delivery of sdAbs using mRNA technology greatly simplifies drug development for antibody therapy and can be used for emergency prophylaxis.

Keywords: BoNT/A inhibitor; Clostridium botulinum; VHH-Fc antibody; mRNA platform; single-domain antibody.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Botulinum Toxins, Type A*
  • COVID-19*
  • Dose-Response Relationship, Drug
  • Humans
  • Mice
  • Pandemics
  • Single-Domain Antibodies* / genetics


  • Botulinum Toxins, Type A
  • Single-Domain Antibodies

Grants and funding

This research was funded by National Research Centre for Epidemiology and Microbiology named after Honorary Academician N F Gamaleya (from the income-generating activities) and the grant #121102500071-6 provided by the Ministry of Health of the Russian Federation, Russia.