A study protocol to prepare an RBD protein for vaccine against COVID-19

Abstract

Background: SARS-CoV-2 pandemic is a global threat to humans and the world’s economy. Effective and safe vaccines against this virus are essential to control and eradicate the pandemic. The currently applied vaccines carry SARS-CoV-2 spike-protein mRNA/cDNA. These vaccines go through several cellular processes in the recipients for producing antigens. On the contrary, the SARS-CoV-2 RBD (receptor binding domain)-protein is an antigen. It will directly stimulate antibody production against SARS-CoV-2. Hence, we propose to produce SARS-CoV-2 RBD-protein as a fast acting, effective and safe vaccine.  Methods: We propose to reconstruct a plasmid carrying three types of  DNA sequences: RBD cDNA, FP (fusion peptide) DNA and sfGFP(superfolder-green-fluorescent-protein), cDNA creating the RBD-FP-sfGFP DNA within an orf (open-reading-frame). Escherichia coli, C2566H, transformed with the reconstructed plasmid will express RBD-FP-sfGFP fusion protein producing green fluorescent cfu (colony forming unit). The RBD-protein will be separated from the sfGFP using an FP specific enterokinase, and eluted by HIC (hydrophobic-interaction-chromatography), detected with a BioVision-Elisa-Kit, and quantified by spectrophotometry at UV280nm and immune simulation will be carried out using C57BL mice.  Results: The plasmid reconstruct will carry ampr (ampicillin-resistant) gene as a selective marker and a T7 promoter controlling the expression of RBD-FP-sfGFP fusion protein. The transformed Escherichia coli will efficiently express the RBD-FP-sfGFP fusion protein. The highly efficient sfGFP fused within the RBD-FP-sfGFP will produce green fluorescent cfu. The RBD-FP-sfGFP protein extract from the green cfu, digested by enterokinase and separated by the HIC will produce pure immunoreactive RBD protein.  Conclusion: A positive BioVision-ELISA test detects <10 pg RBD protein/ml of the sample. A larger sample of the purified RBD protein can be used as a vaccine following a standard formulation and safety protocols. Once administered, the RBD protein will stimulate antibody production against the SARS-CoV-2 virus. The RBD protein has no potential to recombine with human genome.