Mammalian Cells Utilize the Autophagy Process to Restrict Avian Influenza Virus Replication

Host adaptive mutations in the influenza A virus (IAV) PB2 protein are critical for human infection, but their molecular action is not well understood. We observed that when IAV containing avian PB2 infects mammalian cells, vRNP aggregates that localize to the microtubule-organizing center (MTOC) are formed. These vRNP aggregates resemble LC3-associated autophagosome structures, with aggresome-like properties, in that they cause re-distribution of vimentin. However, electron microscopy revealed that these LC3-associated aggregates are not canonical double-membrane autophagosomes. Compared to mammalian-PB2 virus, avian-PB2 virus induces higher autophagic flux in infected cells, indicating an increased rate of autophagosomes containing avian vRNPs fusing with lysosomes. We found that p62 is essential for the formation of vRNP aggregates and that the Raptor-interacting region of p62 is required for interaction with vRNPs through the PB2 polymerase subunit. Selective autophagic sequestration during late stage virus replication is thus an additional strategy for host restriction of avian-PB2 IAV.