MAPK3 and infection: As shown in Fig. 5a, although there were basal levels of phospho-AKT and phospho-ERK1/2 after the serum was removed from culture medium during infection, the levels of both phospho-AKT and phospho-ERK1/2 were increased at late infection time; meanwhile, a gradual increase of phospho-JNK and phospho-p38 were clearly detected.