Used in vaccine development and antibody testing due to its role in viral entry. The Q493K mutation affects receptor binding, making it valuable for studying immune evasion and neutralizing antibody responses. The Fc tag allows for easy detection and purification in immunoassays and facilitates binding to Fc receptors in cell-based assays. Commonly used in research to evaluate monoclonal antibody efficacy and serum neutralization in response to Omicron variants.