ACE2 and infection: Thus, as we documented the functional ability of the RDB-Fc protein to bind ACE2 in a native state and as histo-blood group antigens, by contrast, are well preserved on paraffin embedded tissue sections despite the processing, collectively, these data indicate that even if the RBD of the SARS-CoV-2 spike protein does attach to an A histo-blood group antigen, this binding is very weak and difficult to detect, raising questions about its relevance to the infection process.