Plant-based expression of SARS-CoV-2 antigen for use in an oral vaccine

Oral and intra-nasal vaccines represent a key means of inducing mucosal-based immunity against infection with SARS-CoV-2, yet such vaccines represent only a minority of candidates currently in development. In this brief communication, we assessed the expression of the SARS-CoV-2 Receptor Binding Domain (RBD) subunit of the surface-exposed Spike glycoprotein in the leaves of nine edible plant species (lettuce, spinach, collard greens, tomato, cucumber, radish, arugula, pepper, and Coho greens), with a goal of identifying a suitable candidate for the development of an oral vaccine against COVID-19. We report lettuce (Lactuca sativa L. cv. Hilde II Improved) to be a preferred host to support in planta expression of SARS-CoV-2 RBD, representing an important first step towards development of a plant-based oral vaccine.