KRT18 and susceptibility to pneumonia measurement: Furthermore, interstitial pneumonia and lymphocyte infiltration were detected in the lungs of the K18-hDPP4 mice infected with wild-type MERS-CoV (Figure 5H), while no pneumonia was observed in the lungs of the K18-hDPP4 mice infected with the cold-adapted MERS-CoV vaccine strain (Figure 5I), or in the lungs of the PBS-mock uninfected K18-hDPP4 mice (Figure 5G).