cDNA microarray analysis was utilized to detect the mRNA expression of ER stress-related genes in four mouse brains (day 0, 7, 14 and 21 post-infection), including GRP78, IRE1, TRAF2, PERK, eIF2, ATF4 and CHOP. The data indicated a trend of elevated mRNA expression levels (Fig. 2). Here, ATF4 is linked to infection.