Please pass the salad - Edible vaccines produced in lettuce to protect against COVID-19

Faculty of Science
Aerial view of the campus and rideau canal
Two words: edible vaccines. They may seem like a pipe dream, but Department of Biology Professor Allyson MacLean and undergraduate researcher Monique Power have accomplished the first steps in bringing an edible vaccine to life … using the humble lettuce!

With the help of an advanced technique known as agrobacterium-mediated transient transformation, the MacLean research team used a specific type of bacteria to transfer genes from bacteria to plants. Specifically, the team focused on the transfer of a gene sequence that corresponded to SARS-CoV-2 spike protein, an antigen target upon which most vaccines are based.

The technique had already been optimised with inedible plants such as Nicotiana benthamiana (a close relative of the tobacco plant). Thanks to the pioneering efforts of Prof. MacLean and Ms. Power, this is now possible with edible plants. Before striking success with lettuce, Monique tested a variety of edible plants including arugula, Choho hybrid greens, collard greens, cucumber, pepper, radish, spinach and tomato. The desired viral protein expression was finally observed in lettuce, which was chosen as the most successful candidate for an edible vaccine.

Professor Allyson MacLean and undergraduate student Monique Power
Professor Allyson MacLean and undergraduate student Monique Power

The importance of this discovery could potentially revolutionize how the world looks at vaccines and how they can be delivered. Not only is this delivery method much easier than injectable vaccines, but it also stimulates the development of mucosal immunity, which offers protection at mucosal surfaces including the lungs. Furthermore, it would allow us to combine injectable and edible vaccines for a more comprehensive immune response and protection against COVID-19 and other viral pandemics in the future. Advantages of this method include the low production cost, since there is no need for a cold chain for distribution, as well as avoiding the use of needles. Eliminating the need for a cold chain would greatly facilitate the administration of vaccines in rural areas and expedite vaccination efforts in developing countries around the world.

The next step will be animal studies to determine the effective dosage of antigen necessary to elicit an effective immune response. The results of this research have strong potential to take us one step closer to making edible vaccines available to the public.

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