Author summary The pig is considered to be a “mixing vessel” for influenza viruses because it can be infected by both human and avian influenza viruses. This mixing of viruses could potentially produce novel recombinant strains that are more adaptable to humans or other mammals. The permissive mechanism that allows pig cells to be infected with avian influenza virus is largely unknown. Here we reveal that the pig cellular protein ANP32A has a unique 106V/156S signature, different from tha...