Potential of an epitope rich peptide from S2 domain of spike protein in serodiagnosis of SARS-CoV-2

Abstract

A rapid and highly reliable diagnostic method is paramount to control spread of the life threatening pandemic COVID-19 caused by SARS-CoV-2. A highly immunogenic fragment rich in epitopes could provide high sensitivity and specificity for detecting antibodies in serodiagnosis of SARS-CoV-2. Based on epitope positions on spike protein a fragment F5 having fourteen known epitopes, was generated from S2 domain of spike protein. F5 was cloned in pET28a (+) using restriction sites NheI and XhoI. The recombinant plasmid was expressed in E. coli BL21-CodonPlus (DE3)-RIPL inducing the cells with the optimized concentration of 0.1 mM IPTG. Protein was expressed in the form of inclusion bodies, which were solubilized in 8 M Tris-urea buffer (pH 8.0). Solubilized protein was purified by Ni⁺² affinity chromatography and urea content was removed by dialysis. The antigenic fragment F5 thus produced, could be used to raise antisera for applications in diagnostic procedures based on ELISA. Being rich in epitopes, serodiagnosis based on this immunogenic fragment can provide high sensitivity and specificity of neutralization effect against anti- SARS-CoV-2 antibodies in COVID-19 patients.