IFNA1 and infection: As shown in Fig 6D, the P protein was detected before 18 hpi, however, the V protein was under detectable level before 30 hpi in A549 cells and 24 hpi in DF1 cells, suggesting that the levels of expression of V protein in the infected cells is not sufficient to block IFN signaling at early times post infection and consequent induction of ISGs.