Design, Preparation and Immune Characterization of SARS-CoV-2 Multi-Epitope Chimeric Protein

ABSTRACT

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can cause respiratory symptoms such as fever, cough and dyspnea after infection, and Coronavirus Disease 2019 (COVID-19), severe acute respiratory syndrome, and even death can occur in severe cases.SARS-CoV-2 infection has no specific treatment drugs, mainly rely on vaccination to block its transmission.In various structural proteins of SARS-CoV-2, Spike protein (S) and Nucleocapsid protein (N) are the main antigenic proteins, which are also important candidate proteins for developing SARS-CoV-2 vaccine and antibody detection reagents.To express chimeric protein containing multiple epitopes of SARS-CoV-2 by prokaryotic expression system, and to verify the immunogenicity of the chimeric protein, antigenic epitopes of SARS-CoV-2 structural proteins were analyzed and screened by molecular biology software, the selected antigenic epitopes were connected in tandem, and expressed high efficiently in E.coli as a chimeric protein by genetic engineering technology.The soluble chimeric protein of high purity was obtained after purification and renaturation.Mice were immunized with the purified chimeric protein together with MF59 adjuvant, aluminum adjuvant or no adjuvant at different doses respectively.Humoral immunity and cellular immunity induced by the chimeric protein were evaluated by detecting the antibody titer of antiserum and the level of related cytokine.The expressed chimeric protein was in the form of inclusion body and exists in the sediment, soluble chimeric protein was obtained after renaturation.The specific antibodies with high titer were produced in the immunized mice, and strong cellular immunity was induced also.Higher concentration of chimeric protein had better elicited immune effect than the lower concentration of chimeric protein.The immune effect induced by the chimeric protein with MF59 adjuvant was no different from that induced with aluminum adjuvant.This study provides novel ideas for the design and renaturation of SARS-CoV-2 chimeric protein, and the chimeric protein is expected to be used for the development of SARS-CoV-2 recombinant protein vaccine and diagnosis reagent.