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Enhancement of immunogenicity and neutralizing responses against SARS-CoV-2 spike protein using the Fc fusion
Yahya Ehteshaminia1, Seyedeh Farzaneh Jalali2, Farhad Jadidi-Niaragh3
1Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Aims:
Vaccination has played an important role in protecting against death and the severity of COVID-19. The recombinant protein vaccine platform has a long track record of safety and efficacy. Here, we fused the SARS-CoV-2 spike S1 subunit to the Fc region of IgG and investigated immunogenicity, reactivity to human vaccinated sera, and neutralizing activity as a candidate protein vaccine.
Materials And Method:
We evaluated the immunogenicity of CHO-expressed S1-Fc fusion protein and tag-free S1 protein in rabbits via the production of S1-specific polyclonal antibodies. We subsequently compared the neutralizing activities of sera from immunized rabbits and human-vaccinated individuals using a surrogate Virus Neutralization Test (sVNT).
Key Findings:
The results indicate that S1-specific polyclonal antibodies were induced in all groups; however, antibody levels were higher in rabbits immunized with S1-Fc fusion protein than tag-free S1 protein. Moreover, the reactivity of human vaccinated sera against S1-Fc fusion protein was significantly higher than tag-free S1 protein. Lastly, the results of the virus-neutralizing activity revealed that vaccination with S1-Fc fusion protein induced the highest level of neutralizing antibody response against SARS-CoV-2.
Significance:
Our results demonstrate that the S1 protein accompanied by the Fc fragment significantly enhances the immunogenicity and neutralizing responses against SARS-CoV-2. It is hoped that this platform can be used for human vaccination.
