Expression, purification, and efficient in vitro refolding of SARS-CoV-۲ omicron variant receptor-binding domain (RBD) in Escherichia coli

The receptor binding domain (RBD) of SARS-CoV-۲ mediates the viral entry into the host cells by binding with the host receptor angiotensin-converting enzyme-۲ (ACE۲). Compared to the SARS-CoV-۲ wild type, omicron contains ۱۵ receptor-binding domain (RBD) mutations. Therefore, serology test applications developed for detecting antibody responses against the RBD protein of wild-type-like strains do not give reliable results when testing plasma samples from omicron infection convalescent individuals. In the current study, recombinant omicron RBD was overexpressed in Escherichia coli BL-۲۱(DE۳) and purified by a Ni-NTA column. The recombinant RBD was analyzed by SDS-PAGE, and refolding was performed using the dialysis method.