Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 15 1 2023 02 15 128 137 Sahar Karimi Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran Shahram Nazarian Department of Biology, Imam Hossein University, Tehran, Iran Fattah Sotoodehnejadnematalahi Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran Roohollah Dorostkar Applied Virology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Jafar Amani Applied Microbiology Research Center, System Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran 2022 08 13 2023 02 11 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. https://ijm.tums.ac.ir/index.php/ijm/article/view/3862 https://ijm.tums.ac.ir/index.php/ijm/article/download/3862/1550