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The viral spike of coronaviruses is a trimeric assembly of the S glycoprotein. In the viral cycle, the spike recognizes a specific receptor on the cell surface, angiotensin convertase II for SARS-CoV-2, SARS-CoV-1 and human coronavirus NL63, the latter antigenically distant from the phylogenetic lineage of SARS-CoVs.

We have previously identified aminopeptidase-n as a receptor for porcine transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus. After selecting neutralizing monoclonal antibodies recognizing cellular proteins, we identified the protein recognized by all of these antibodies as porcine aminopeptidase-n. Transfection of a plasmid encoding this enzyme into non-permissive cells confers sensitivity to the virus. The interaction between the virus and its receptor could be validated by various biochemical tests. This work enabled the group of K. Holmes to demonstrate that another alphacoronavirus, the human coronavirus 229E recognized human aminopeptidase-n as a receptor. Unexpectedly, the porcine deltacoronavirus (PDCoV), which is phylogenetically very distant from the alphacoronaviruses, also uses aminopeptidase-n as a receptor, but it seems less exclusively. Indeed, while pigs knocked out for expression of porcine aminopeptidase-n are completely resistant to TGEV, they retain residual susceptibility to PDCoV.

We are currently developing different strategies to identify receptors for avian and porcine coronaviruses having a strong economic impact. It will help the understanding of these virus biology as well as the evolutionary mechanisms associated with the recognition of a specific receptor.