SFTPB and infection: In the 3 × 103 PFU-inoculated groups, all mice inoculated with rKUNV-LP died at 5 days post-infection, whereas all mice inoculated with SP-B, rKUNV-LP-EF156S, or rKUNV-LP-ET332K died at 6 days post-infection (Figure 5B).