Compared to H9N2 (wt) infection, there were less dead cells (annexin V+PI+) detected in the H9N2-infected group (ΔPB1-F2) at 6 and 12 hrs p.i. However, there was no difference in apoptotic cells between the two groups at the later stage (24 hrs p.i.)(Figure 1(d)). This evidence concerns the gene ANXA5 and infection.