IGF1 and infection: To detect the regulation of IGF1 by IAV, A549 cells were infected with PR8 (104.58 TCID50/ml) at different multiplicity of infection (MOI) of 0.1, 0.5, or 1.0, and the level of IGF1 mRNA and protein expression was detected at 12, 24, 48, and 72 h post-infection.