PIGR and viral infectious disease: Since dimerization is a unique feature that SARS-CoV-2 ORF8 has acquired but that is absent in the ORF8 of SARS-CoV and other coronaviruses, it is speculated that SARS-CoV-2 ORF8 may be more effective in dampening pIgR-mediated mucosal immunity and thus better assist viral infection and spread.