Humoral Immune Response to SARS-CoV-2 Spike Protein Receptor-Binding Motif Linear Epitopes

Area of Science:

• Immunology
• Virology
• Vaccinology

Background:

• SARS-CoV-2 variants pose ongoing threats due to immune evasion.
• The receptor-binding motif (RBM) is critical for viral entry via ACE2 interaction.
• Understanding antibody responses to RBM is vital for vaccine development.

Purpose of the Study:

• To assess serum immunogenicity against wild-type and mutated SARS-CoV-2 RBM peptides.
• To investigate the impact of Omicron variant mutations on antibody binding and neutralization.
• To evaluate the role of the linear RBM in the overall humoral immune response.

Main Methods:

• Microscale thermophoresis was used to measure binding affinity of neutralizing antibodies (nAbs) to RBM peptides.
• Serum samples from vaccinated individuals were analyzed for IgA and IgG responses.
• Analysis focused on the receptor-binding motif (RBM) and its interaction with ACE2.

Main Results:

• Vaccine-induced antibodies showed modest responses to wild-type RBM, with significantly lower titers against Omicron variants due to specific mutations.
• The primary antibody isotypes detected were Immunoglobulin A (IgA) and Immunoglobulin G (IgG).
• Reduced seroreactivity was observed in the RBM, a critical subregion of the receptor-binding domain (RBD), potentially impacting protective nAb generation.

Conclusions:

• The linear RBM of SARS-CoV-2 is not immunodominant in vaccinated individuals.
• Omicron variant mutations in the RBM diminish antibody effectiveness.
• Further research into humoral response dynamics is crucial for next-generation coronavirus vaccines.