Plant-Produced S1 Subunit Protein of SARS-CoV-2 Elicits Immunogenic Responses in Mice

Abstract

SARS-CoV-2 is responsible for the ongoing COVID-19 pandemic. The virus spreads rapidly with a high transmission rate among humans, and hence virus management has been challenging owing to finding specific therapies or vaccinations. Hence, an effective, low-cost vaccine is urgently required. In this study, the immunogenicity of the plant-produced S1 subunit protein of SARS-CoV-2 was examined in order to assess it as a potential candidate for SARS-CoV-2. The SARS-CoV-2 S1-Fc fusion protein was transiently produced in Nicotiana benthamiana. Within four days of infiltration, the SARS-CoV-2 S1-Fc protein was expressed in high quantities, and using protein A affinity column chromatography, plant-produced S1-Fc protein was purified from the crude extracts. The characterization of plant-produced S1-Fc protein was analyzed by SDS-PAGE and Western blotting. Immunogenicity of the purified S1-Fc protein formulated with alum induced both RBD specific antibodies and T cell immune responses in mice. These preliminary results indicated that the plant-produced S1 protein is immunogenic in mice.

Tomato-made edible COVID-19 vaccine TOMAVAC induces neutralizing IgGs in the blood sera of mice and humans

“…In this study, we report the first edible COVID-19 tomato vaccine, TOMAVAC, derived by constitutively overexpressing the consensus sequence of the S1 protein of SARS-CoV-2, covering the sequence variation of SARS-CoV-2 spread in Uzbekistan ( 26 ). In contrast, recently, the SARS-CoV-2-S1-Fc fusion protein ( 16 – 18 ) or a SARS-CoV-2 perfusion spice trimer protein ( 19 ) was transiently expressed in tobacco and harvested for parenteral vaccination studies in animals.…”

“…The receptor-binding domain (RBD) of the S1 protein was immunogenic and non-allergenic, with very subtle side effects when used as a parenteral protein subunit recombinant vaccine in a previous study ( 28 ). Recent studies ( 16 – 18 ) reported that the plant-produced S1 subunit protein vaccines against SARS-CoV-2 were immunogenic without any safety concerns in animal experiments. Previous studies also showed that three injections of 10 μg/dose of RBD-specific antigen of S1 protein adequately induced systemic immunity in mice ( 29 ).…”

“…Previous studies also showed that three injections of 10 μg/dose of RBD-specific antigen of S1 protein adequately induced systemic immunity in mice ( 29 ). It was reported that two-dose parenteral vaccination with purified 10 μg and 25–50 μg of tobacco-produced SARS-CoV-2 RBD-Fc fusion protein caused high levels of NAbs in mice and monkeys, respectively ( 16 – 18 ). However, with edible plant-based vaccines, a higher dose of expressed antigen may be needed than that used for parenteral immunizations ( 13 , 14 ).…”

SARS-CoV-2 spike protein S1 subunit induces potent neutralizing responses in mice and is effective against Delta and Omicron variants

“…A S1 subunit of SARS-CoV-2 fused with the Fc domain was expressed in the N. benthamiana plant using the pBYR2e geminiviral plant expression vector. It was shown that mice immunized with purified S1-Fc protein induced antigen-specific antibodies and T-cell responses in mice ( Panapitakkul et al., 2022 ). The expression level, determined by ELISA to be reported as 30 mg/kg of fresh leaf, seems to be low for commercialization.…”

Plant Viruses as Adjuvants for Next-Generation Vaccines and Immunotherapy

“…Currently, the most widely used vectors in this approach are RNA viruses, including Tobamoviruses, Potexviruses, Comoviruses and DNA-viruses, e.g., Geminiviruses [ 8 , 9 , 10 , 11 , 12 ]. For example, plant viruses, as an expression system, are used for the generation of individual proteins (antigens) for further use in subunit vaccines (e.g., PA protein of B. anthracis , S1 subunit protein of SARS-CoV-2 [ 13 , 14 , 15 ]).…”