As SARS-CoV-2 2P DS S only displays closed SB receptor-binding domains within the context of a folded trimer, we suggest it will be a useful tool for serology studies aiming at evaluating antibody responses in patients with COVID-19, and could complement tests using ACE2 inhibition as a proxy for evaluating the presence of neutralizing antibody titers in the human population. The gene discussed is ACE2; the disease is COVID-19.