SARS-CoV-2 Receptor Binding Domain (RBD) Protein-Protein Conjugate Induces Similar or Better Antibody Responses as...

Area of Science:

• Vaccinology
• Immunology
• Virology

Background:

• The COVID-19 pandemic necessitated rapid vaccine development, highlighting novel platforms like mRNA.
• The SARS-CoV-2 Spike protein and its Receptor Binding Domain (RBD) are key targets for vaccine development.
• Previous research demonstrated that chemically conjugating RBD to EcoCRM® carrier protein enhanced immune responses in mice.

Purpose of the Study:

• To compare the immunogenicity of an AS01-adjuvanted RBD-EcoCRM® conjugate vaccine with an approved mRNA vaccine.
• To evaluate antibody responses, receptor binding inhibition, and virus neutralization activity over nine months.
• To assess the durability and quality of immune responses induced by both vaccine types.

Main Methods:

• Rhesus macaques were immunized with either the RBD-EcoCRM® conjugate vaccine or a Pfizer/BioNTech mRNA vaccine.
• Immunogenicity was assessed over a nine-month period.
• Key immune parameters measured included antibody levels, receptor binding inhibition, virus neutralization, IgG subclass profiles, and antibody avidity.

Main Results:

• The AS01-adjuvanted RBD conjugate induced similar or superior antibody responses compared to the mRNA vaccine.
• Both vaccines elicited comparable receptor binding inhibition and virus neutralization activity against various SARS-CoV-2 variants.
• IgG subclass profiles shifted over time, and antibody avidity remained similar between vaccine groups.

Conclusions:

• The RBD-EcoCRM® conjugate vaccine demonstrated comparable immunogenicity to the Spike mRNA vaccine in rhesus macaques.
• These findings support the potential of the RBD-EcoCRM® conjugate as a viable vaccine candidate against SARS-CoV-2.
• The study highlights the efficacy of targeting the RBD for vaccine development.