Porcine Circovirus Type 2 Explores the Autophagic Machinery for Replication in Pk-15 Cells

Porcine circovirus type 2 (PCV2), an important pathogen of pigs, causes lymphoid depletion in infected tissues most probably by inducing apoptosis although the precise pathogenesis of PCV2-associated diseases remains unknown. We speculate whether autophagy, another cellular response to stress or infections by bacterial or viral pathogens, is involved in PCV2 infection. Here, we provide the first evidence that PCV2 could trigger autophagosome formation and enhance autophagic flux in PK-15 cells, most likely by its capsid protein. Using activators or inhibitors including siRNA targeting atg5, autophagy was found to enhance viral replication and capsid protein expression. These results suggest that PCV2 might employ the autophagy machinery to enhance its replication in host cells, thus raising the possibility of targeting autophagic pathway as a potential antiviral strategy against PCV2 infection.