XBP1 and infection: In the case of SFTSV infection, intracellular expression levels of NP, NSs, RdRP, and GP were lower in PERK or ATF6 knockdown cells but not in XBP1 knockdown cells (Fig. 6A), which was in accordance with the above results that knockdown of ATF6 or PERK led to reduced virus replication and production (Fig. 4C and D).