Practical Use of Tobravirus-Based Vector to Produce SARS-CoV-2 Antigens in Plants

A plant-based heterologous expression system is an attractive option for recombinant protein production because of its based on a eukaryotic system of high feasibility, and low biological risks. Frequently, binary vector systems are used for transient gene-expression in plants. However, plant virus vector-based systems offer advantages for higher protein yields due to their self-replicating machinery. In the present study, we show an efficient protocol using a plant virus vector based on a tobravirus, pepper ringspot virus, that was employed for transient expression of severe acute respiratory syndrome coronavirus 2 partial genes of the spike (named S1-N) and the nucleocapsid (named NC) proteins in Nicotiana benthamiana plants. Purified proteins yield of 40~60 µg/g of fresh leaves were obtained. Both proteins, S1-N and NC, showed high and specific reactivities against convalescent patients’ sera by the enzyme-linked immunosorbent assay format. The advantages and critical points in using this plant virus vector are discussed.