Used in vaccine development and antiviral research to study immune response against the Omicron BA.4 variant of SARS-CoV-2. Serves as a key antigen for neutralizing antibody detection in diagnostic assays. Supports structural studies to understand spike protein behavior and host cell receptor interaction. Employed in therapeutic antibody screening to identify effective monoclonal antibodies targeting the BA.4 variant. Enables evaluation of vaccine efficacy by measuring antibody binding and neutralization capacity.