The results demonstrated that both the mRNA and protein levels of IFIT1 and IFIT2 were increased in rIBV-ΔPL1pro-N infected cells at 16 and 20 h post-infection to different degrees (Fig. 6a, b), indicating that the N-terminal region of PL1pro affects the expressions of ISGs during later stages of infection. The gene discussed is IFIT1; the disease is infection.