Swine alveolar macrophage cell model allows optimal replication of influenza A viruses regardless of their origin

- Porcine alveolar macrophage cell line as a model for influenza A virus replication.
- The IPAMs support replication of IAVs from multiple host backgrounds to high titres.
- All IAVs isolates replicated well in IPAMs at 37 °C.
- Replication preference of IAVs for 33 °C or 41 °C was influenced by their origin.
- Replication preference of IAVs was reflected in amino acid profiles of their PB2.

The importance of pigs in interspecies transmission of influenza A viruses has been repeatedly demonstrated over the last century. Eleven influenza A viruses from avian, human and swine hosts were evaluated for replication phenotypes at three physiologically relevant temperatures (41 °C, 37 °C, 33 °C) in an immortalized swine pulmonary alveolar macrophage cell line (IPAM 3D4/31) to determine whether this system would allow for their efficient replication. All isolates replicated well in IPAMs at 37 °C while clear distinctions were observed at 41 °C and 33 °C, correlating to species of origin of the PB2, reflected in distinct amino acid residue profiles rather than in one particular PB2 residue. A strong TNF-α response was induced by some mammalian but not avian IAVs, while other selected cytokines remained below detection levels. Porcine IPAMs represent a natural host cell model for influenza virus replication where the only condition requiring modification for optimal IAV replication, regardless of virus origin.