Activity of cytokines and regulation of signaling pathways
As the invasions, viruses should have the capability to adjust the activities of cytokines and regulate intracellular signaling pathways of the host cells following invasion, thereby facilitating the replication and proliferation of viral particles. Indeed, pronounced changes of the expression of numerous proteins occur, as revealed by proteomic analysis in PEDV infected Vero cells. Moreover, these altered proteins are identified to participated in various biologic processes such as apoptosis, signal transduction and stress response (Z. S et al., 2015). For instance, PEDV induced apoptosis is mainly mediated by the activation of caspase-dependent mitochondrial apoptotic inducible factor (AIF) signaling pathway in target cells (K. Y & C, 2014). Likewise, PEDV infection can also activate the components of intracellular MAPK signaling pathway including ERK (extracellular signaling-regulated kinase), p38 MAPK and JNK (c-Jun N-terminal kinase) (K. Y & C, 2015). In addition, PEDV infection induced endoplasmic reticulum (ER) stress response and the activation of NF-κB signaling, have been found and described as well (W. K et al., 2012; Xu et al., 2013). Therefore, it is reasonable and logical to believe that the PEDV induced alterations of protein expression, cellular response and signaling collectively create a conducive microenvironment for its proliferation in the host cells.