To further clarify the role of IAV-induced GP96 in secondary pneumococcal pneumonia in vivo, mice were intranasally infected with a nonlethal dose of IAV (day 0), which was followed by intratracheal administration of the vehicle or GP96 inhibitor PU-WS13 on day 5; then, intranasal challenge with S. pneumoniae was performed on day 6 (Fig. 5a). Here, HSP90B1 is linked to pneumococcal pneumonia.