Used in vaccine development and diagnostic assays to detect neutralizing antibodies against the Omicron BA.4 variant of SARS-CoV-2. Serves as a key antigen in serological testing to evaluate immune response in infected or vaccinated individuals. Employed in research studies focused on viral entry mechanisms and antibody binding affinity. Supports the development of monoclonal antibodies and therapeutic agents targeting the spike protein’s receptor-binding domain. Facilitates structural studies to understand mutations and their impact on infectivity and immune evasion.