ACE2 and infection: Finally, we compared post-vaccine antibody responses to spike proteins representing D614G and the SARS-CoV-2 alpha, beta, and gamma variants of concern in a subset of ten infection-naive and ten SARS-CoV-2-infected individuals with a surrogate neutralisation assay based on competition for ACE2 binding to spike (figure 4B) and a live virus neutralisation assay (figure 4C, D).