HSPA5 and infection: To study the mechanism of cellular UPR induced by BVDV, we initially examined the expression abundance of the key marker (GRP78) of ER stress following BVDV 1-NADL standard strain (cp BVDV) and BVDV-BJ175170 isolate strain (ncp BVDV) infection in Madin-Darby bovine kidney (MDBK) cells.