Although a low level of XBP1 splicing due to ER stress is observed in both IAV-WT and IAV-NS-T infection (Figure 3E left), silencing of the UPR activation—marked by the transcriptions of XBP1-regulated genes EDEM1 and HSPA5 (and other chaperone proteins highlighted in Figure 2B) (Oslowski and Urano, 2011)—is only observed during IAV-WT infection (Figure 3E right). Here, XBP1 is linked to infection.