zahra Rahbar - Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
Shahram Nazarian - Department of Biology, Imam Hossein University, Tehran, Iran
Ruhollah Dorostkar - Applied Virology Research Center, Baqiyatallah University of Medical Sciences, Iran
Fattah Sotoodehnejadnematalahi - Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
Jafar Amani - Applied Microbiology Research Center, System Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran

Objective(s): The severe acute respiratory syndrome coronavirus-۲ (SARS-CoV-۲), giving rise to the coronavirus disease ۲۰۱۹ (COVID-۱۹), has become a danger to wellbeing worldwide. Thus, finding efficient and safe vaccines for COVID-۱۹ is of great importance. As a basic step amid contamination, SARS-CoV-۲ employs the receptor-binding domain (RBD) of the spike protein to lock in with the receptor angiotensin-converting enzyme ۲ (ACE۲) on host cells. SARS-CoV-۲ receptor-binding domain (RBD) is the main human antibody target for developing vaccines and virus inhibitors, as well as neutralizing antibodies. A bacterial procedure was developed for the expression and purification of the SARS-CoV-۲ spike protein receptor-binding domain.Materials and Methods: In this research study, RBD was expressed by Escherichia coli and purified with Ni-NTA chromatography. Then it was affirmed by the western blot test. The immunogenicity and protective efficacy of RBD recombinant protein were assessed on BALB/c mice. Additionally, RBD recombinant protein was tested by ELISA utilizing sera of COVID-۱۹ healing patients contaminated with SARS-CoV-۲ wild type and Delta variation. Results: Indirect ELISA was able to detect the protein RBD in serum of the immunized mouse expressed in E. coli. The inactive SARS-CoV۲ was detected by antibodies within the serum of immunized mice. Serum antibodies from individuals recovered from Covid۱۹ reacted to the expressed protein.Conclusion: Our findings showed that RBD is of great importance in vaccine design and it can be used to develop recombinant vaccines through induction of antibodies against RBD.

Neutralizing antibodies, RBD, Recombinant proteins, SARS-CoV-۲, Vaccines