Antigenicity and immunogenicity of SARS-CoV-2 surface glycoprotein fragment in CHO cells.

Background and Objectives: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) glycoprotein that projects from the virus surface is highly immunogenic. It is considered to be the target of many neutralizing antibodies as well as a target in vaccine design efforts. Evaluation the immunogenicity of a recombinant fragment of the spike protein (rfsp) that is comprised of Receptor Binding Domain (RBD), S1/S2 cleavage site, and fusion peptide (FP) as immunogenic proteins of SARS-COV-2, in BALB/c mice and evaluation of the efficacy of epitopes rfsp as a multi-subunit chimeric vaccine. Materials and Methods: The present study made use of CHO-K1 (Chinese hamster ovary K1) cells to create a cell line for constant expression rfsp. The rfsp was purified with Ni-NTA chromatography and confirmed by Western blotting. The immunogenicity and neutralizing antibody efficacy of rfsp were evaluated in BALB/c mice. ELISA was employed to test rfsp via sera of COVID-19 convalescent patients infected with SARS-CoV-2 alpha and delta variants. Results: Our results showed significant differences in antibody titers in immunized mice compared to the control groups and neutralizing antibodies were positive, sera from mice immunized are capable of bound SARS-CoV-2 virus, chimer peptide is capable bound antibodies patients infected with SARS-CoV-2 and patients infected with delta variant SARS-CoV-2. Conclusion: Overall, these results indicate that rfsp protein would be a novel potential antigen candidate for the development of a subunit SARS CoV-2 vaccine and rfsp has the potential to be a useful option for the development of the assays for serodiagnosis of SARS-CoV-2 infection.