Used in vaccine development and antiviral research to study immune response against the Omicron BA.2.75 variant of SARS-CoV-2. The Fc tag enables easy detection and purification, making it valuable in binding assays, neutralization tests, and structural analysis. It supports the evaluation of monoclonal antibodies and therapeutic efficacy by mimicking the viral spike protein's interaction with host cells. Commonly applied in ELISA, flow cytometry, and surface plasmon resonance studies.