Maruoka and coworkers demonstrated that the expression levels of immunoglobulin heavy-chain binding protein (BiP) mRNA, one of major molecular chaperons in the lumen of endoplasmic reticulum (ER), increased in human bronchial epithelial cells by the virus infection, indicating that ER stresses occur in the virus-infected cells [193]. Here, HSPA5 is linked to viral infectious disease.