Development of a Recombinant RBD Subunit Vaccine for SARS-CoV-2

Area of Science:

• Immunology
• Vaccinology
• Virology

Background:

• The COVID-19 pandemic remains a global threat, necessitating diverse vaccine strategies.
• Current approved COVID-19 vaccines include only one recombinant subunit vaccine, highlighting the need for additional options.
• The receptor binding domain (RBD) of the SARS-CoV-2 spike protein contains key neutralizing epitopes, but its monomeric form has limited immunogenicity.

Purpose of the Study:

• To develop a novel recombinant subunit vaccine candidate for COVID-19.
• To enhance the immunogenicity of the SARS-CoV-2 RBD.
• To evaluate the humoral and cellular immune responses induced by the novel vaccine candidate.

Main Methods:

• Construction of a fusion protein by linking the RBD monomer with a modified human IgG1 Fc fragment (RBD-Fc).
• Immunization of mice with the RBD-Fc fusion protein vaccine candidate.
• Assessment of IgG and neutralizing antibody levels, as well as cytokine secretion (IFN-γ, IL-2, IL-10) from splenocytes.

Main Results:

• The RBD-Fc vaccine candidate successfully induced high levels of IgG and neutralizing antibodies in immunized mice.
• The induced antibody responses were sustained for at least three months post-immunization.
• Significant increases in IFN-γ, IL-2, and IL-10 secretion were observed in splenocytes stimulated with RBD from immunized mice, indicating cellular immune activation.

Conclusions:

• The RBD-Fc fusion protein vaccine candidate effectively elicits robust humoral immunity against SARS-CoV-2.
• This vaccine strategy also stimulates significant cellular immune responses, as evidenced by increased cytokine production.
• The RBD-Fc vaccine represents a promising alternative strategy for controlling the COVID-19 pandemic.