For example, the Japanese encephalitis virus induces apoptosis and encephalitis by activating the PERK pathway, whereas porcine circovirus type 2 induces ORF3-independent apoptosis by activating ER stress and the PERK-activating transcription factor 4 (ATF4)-CHOP axis (20, 21, 49). This evidence concerns the gene ATF4 and encephalitis.