XBP1 and infection: By examining the three branches of UPR marker molecules PERK/eIF2α, ATF6, IRE1α/XBP1 splicing, we find that UPR did not occur until 24 h post-infection (hpi) as shown by elevation of phosphorylated form of PERK and eIF2α (p-PERK and p-eIF2α) (Figure 1A), a similar time point when autophagy was induced.