It is increasingly clear that vaccines are among the primary solutions to the COVID-19 pandemic. However, cost-effective and large-scale production is key for ensuring vaccination all over the world, specifically in lower-middle income countries. In this pre-print, not yet peer-reviewed, study that was partly funded by the CITF and led by Dr. Marc-André Langlois and his colleague, Dr. Allyson MacLean at the University of Ottawa, researchers have generated SARS-CoV-2’s receptor-binding domain (RBD) portions of the spike protein in plants which could aid in the development of vaccines. This plant-based RBD has proved to be effective at eliciting an immune response capable of neutralizing COVID-19.

The research team successfully modified and incorporated the original Wuhan strain of the SARS-CoV-2 RBD protein sequence into N. benthamiana leaves which generate copies of the RBD protein throughout the leaves that were injected. The leaves were removed and RBD protein was isolated and thoroughly evaluated for its ability to illicit an immune response in humans. In-vitro assays with samples from people who had recovered from COVID-19, or who were partially or fully vaccinated showed:

  • Plant-produced RBD could strongly bind to SARS-CoV-2’s conventional receptor known as ACE2;
  • It can be recognized and bound by monoclonal IgA, IgG and IgM;
  • It can also be recognized by polyclonal antibodies from sera of SARS-CoV-2- infected individuals;
  • While IgG antibodies were equally capable of binding to plant-produced RBD and mammalian-expressed RBD, IgM and IgA antibodies were less capable of doing so.

This technology could possibly be applied to the development of an alternative to injectable vaccines, such as nasal spray-based vaccines, a potentially attractive immunization option to vaccine-hesitant and needle-phobic individuals.

Demone JJ, Maltseva M, Nourimand M, Nasr-Sharif M, Galipeau Y, Langlois MA, MacLean AM. Plant-based production of SARS-CoV-2 antigens for use in a subunit vaccine. bioRxiv. 2021 Jan 1. doi: 10.1101/2021.10.17.464700