ATM and infection: In the present study, we demonstrated that infection of PCV2 stimulates DDR activation including all ATM, ATR, and DNA-PK signalings in the cultured cells, as evidenced by increased accumulations of ATM, ATR, and DNA-PK phosphorylations as well as their downstream effectors H2AX and RPA32 phosphorylations (Figs 1D and 2A), and colocalization of these kinase phosplorylations with PCV2 ORF1 protein in the viral replication centers (Figs 1B,C and 2B) after infection.