Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the ongoing global outbreak of coronavirus disease (COVID-19) which is a significant threat to global public health. The rapid spread of COVID-19 necessitates the development of cost-effective technology platforms for the production of vaccines, drugs, and protein reagents for appropriate disease diagnosis and treatment. In this study, we explored the possibility of producing the receptor binding domain (RBD) of SARS-CoV-2 and an anti-SARS-CoV monoclonal antibody (mAb) CR3022 in Nicotiana benthamiana. Both RBD and mAb CR3022 were transiently produced with the highest expression level of 8 μg/g and 130 μg/g leaf fresh weight respectively at 3 days post-infiltration. The plant-produced RBD exhibited specific binding to the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2). Furthermore, the plant-produced mAb CR3022 binds to SARS-CoV-2, but fails to neutralize the virus in vitro. This is the first report showing the production of anti-SARS-CoV-2 RBD and mAb CR3022 in plants. Overall these findings provide a proof-of-concept for using plants as an expression system for the production of SARS-CoV-2 antigens and antibodies or similar other diagnostic reagents against SARS-CoV-2 rapidly, especially during epidemic or pandemic situation.
Denosumab, an anti-receptor activator of nuclear factor-kappa B ligand antibody (anti-RANKL), is a fully human monoclonal antibody (mAb) available for the treatment of osteoporosis. In the present study, an anti-RANKL mAb was transiently expressed using the geminiviral expression system in Nicotiana benthamiana, and the functional activity of the plant-produced mAb was determined. The highest expression level of the plant-produced mAb was found at 8 days post-infiltration, and it was estimated to be 0.5 mg/g leaf fresh weight. The recombinant mAb from the plant crude extracts was purified by using Protein A affinity column chromatography. The plant-produced mAb demonstrated good in vitro affinity binding with human RANKL, as determined by RANKL-ELISA binding. The function of the plant-produced mAb was evaluated in vitro. CD14-positive cells isolated from human peripheral blood mononuclear cells (PBMCs) were cultured in vitro in the presence of human RANKL and macrophage-colony-stimulating factor (M-CSF) to stimulate osteoclastogenesis. The results demonstrated that plant-produced mAb could significantly decrease the number of osteoclasts compared to commercial denosumab. These results demonstrated that the plant-produced mAb has the potential to inhibit osteoclast differentiation and that it could be considered for osteoporosis treatment.
Severe acute respiratory syndrome coronavirus-2 is responsible for an ongoing global outbreak of coronavirus disease (COVID-19) and represents a significant public health threat. The rapid spread of COVID-19 necessitates the development of cost-effective technology platforms for the production of diagnostic reagents/biopharmaceuticals for COVID-19. We explored the possibility of producing an anti-SARS-CoV monoclonal antibody (mAb) CR3022 and the receptor binding domain (RBD) of SARS-CoV-2 in Nicotiana benthamiana. Both RBD and the mAb were transiently expressed with the expression of 8μg/g and 130μg/g leaf fresh weight respectively. The plant-purified mAb binds to SARS-CoV-2, but fails to neutralize it in vitro. This is the first report showing the functional characterization of an anti- SARS-CoV mAb CR3022 in plants. Overall these findings showed that plants are a promising platform to produce anti-SARS-CoV mAb to use as a research reagent or a biotherapeutic in a cost-effective manner, which is especially important to developing economies during epidemics.
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