Plant-based production of SARS-CoV-2 antigens for use in a subunit vaccine

Abstract

The COVID-19 pandemic has brought to the forefront an urgent need for the rapid development of highly efficacious vaccines, particularly in light of the ongoing emergence of multiple variants of concern. Plant-based recombinant protein platforms are emerging as cost-effective and highly scalable alternatives to conventional protein production. Viral glycoproteins, however, are historically challenging to produce in plants. Herein, we report the production of plant-expressed wild-type glycosylated SARS-CoV-2 Spike RBD (receptor-binding domain) protein that is recognized by anti-RBD antibodies and exhibits high-affinity binding to the SARS-CoV-2 receptor ACE2 (angiotensin-converting enzyme 2). Moreover, our plant-expressed RBD was readily detected by IgM, IgA, and IgG antibodies from naturally infected convalescent, vaccinated, or convalescent and vaccinated individuals. We further demonstrate that RBD binding to the ACE2 receptor was efficiently neutralized by antibodies from sera of SARS-CoV-2 convalescent and partially and fully vaccinated individuals. Collectively, these findings demonstrate that recombinant RBD produced in planta exhibits suitable biochemical and antigenic features for use in a subunit vaccine platform.

Plant production of high affinity nanobodies that block SARS-CoV-2 spike protein binding with its receptor, human angiotensin converting enzyme

“…The His tag facilitated enrichment from the plant proteome but would need to be removed prior to the development of plant-based nanobody therapies for the treatment of human or other animal diseases. A recent example of production of RBD in planta exhibits suitable biochemical and antigenic features for use in a subunit vaccine platform (Demone, Nourimand et al 2021). We posit that molecular farming of nanobodies, and other biologicals is an under-developed area for cost savings and increased global access for the production of protein and small molecule therapies.…”

Plant production of high affinity nanobodies that block SARS-CoV-2 spike protein binding with its receptor, human angiotensin converting enzyme

“…Moreover, a modified nanobody with a scrambled RBD binding domain did not demonstrate the inhibition ability observed with the spike protein-targeted antibody, demonstrating the binding specificity of the interaction between the plant-produced RBDbinding nanobodies and the RBD. A recent example of production of RBD in planta exhibits suitable biochemical and antigenic features for use in a subunit vaccine platform (Dhama et al, 2020;Demone et al, 2021;Maharjan et al, 2021;Mamedov et al, 2021;Mardanova et al, 2021;Ceballo et al, 2022). Thus, scientists have shown that both the RBD antigen and RBDspecific antibodies can be generated in plants [Also see: (Diego-Martin et al, 2020)].…”