ERN1 and infection: Additionally, immunoblotting was performed to analyze the possibility that the activation of IRE1 may contribute to cell apoptosis; however, maybe the transient activation of IRE1 in PK-15 is not adequate enough to stimulate JNK signal, we found no up-regulation in phosphorylated JNK during the course of infection (data not shown), suggesting that the IRE1-JNK-mediated apoptosis pathway was not activated by CSFV, which suppose to favor viral persistent infection.