Abstract
The emergence of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected global public health and economy. Despite the substantial efforts, only few vaccines are currently approved and some are in the different stages of clinical trials. As the disease rapidly spreads, an affordable and effective vaccine is urgently needed. In this study, we investigated the immunogenicity of plant-produced receptor-binding domain (RBD) of SARS-CoV-2 in order to use as a subunit vaccine. In this regard, RBD of SARS-CoV-2 was fused with Fc fragment of human IgG1 and transiently expressed in Nicotiana benthamiana by agroinfiltration. The plant-produced RBD-Fc fusion protein was purified from the crude extract by using protein A affinity column chromatography. Two intramuscular administration of plant-produced RBD-Fc protein formulated with alum as an adjuvant have elicited high neutralization titers in immunized mice and cynomolgus monkeys. Further it has induced a mixed Th1/Th2 immune responses and vaccine-specific T-lymphocyte responses which was confirmed by interferon-gamma (IFN-γ) enzyme-linked immunospot assay. Altogether, our results demonstrated that the plant-produced SARS-CoV-2 RBD has the potential to be used as an effective vaccine candidate against SARS-CoV-2. To our knowledge, this is the first report demonstrating the immunogenicity of plant-produced SARS-CoV-2 RBD protein in mice and non-human primates.
Highlights
In December 2019, the unknown pneumonia cases have been first reported in Wuhan, Hubei Province, China, which were initially reported to be caused by novel coronavirus and later named as SARS-CoV-2
For expression of receptor-binding domain (RBD)-Fc fusion protein in plants, N. benthamiana plants were infiltrated with Agrobacterium containing pBYR2e-SARS-CoV-2 RBD-Fc (Figure 1)
The leaves infiltrated with Agrobacterium containing pBYR2e-SARS-CoV-2 RBD-Fc showed significant phenotypic necrosis compared to the leaves infiltrated by Agrobacterium without the plant expression vector (Figure 2A)
Summary
In December 2019, the unknown pneumonia cases have been first reported in Wuhan, Hubei Province, China, which were initially reported to be caused by novel coronavirus (nCoV-2019) and later named as SARS-CoV-2. The virus was closely related to the severe acute respiratory syndrome coronavirus (SARS-CoV) that cause massive outbreak in 2002– 2003 (Amanat and Krammer, 2020; Li Q. et al, 2020; Malik et al, 2020; Quinlan et al, 2020; She et al, 2020; Singhal, 2020). The development of affordable effective vaccine or therapeutics is highly essential to control and prevent the infection
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