Fig. 4. Enhanced pathogenicity by the P681R mutation in hamsters.
Syrian hamsters were intranasally inoculated with the D614G and D614G/P681R viruses. a, Body weight changes in hamsters after viral infection. Body weights of virus-infected (n = 4 each) and uninfected (n = 3) hamsters were monitored daily for 7 days. b, Pulmonary function analysis in infected hamsters. Enhanced pause (PenH), which is a surrogate marker for bronchoconstriction or airway obstruction, was measured using whole-body plethysmography. c, Virus replication in infected hamsters. Four hamsters per group were euthanized at 3 d.p.i. and 7 d.p.i. for virus titration. Virus titres in the lungs (top) and nasal turbinates (bottom) were determined by plaque assay using VeroE6/TMPRSS2 cells. The points indicate data from individual Syrian hamsters. p.f.u., plaque-forming units. d, Histopathological examination of the lungs of infected Syrian hamsters. Representative pathological images of D614G- and D614G/P681R-infected lungs at 3 d.p.i. and 7 d.p.i. Scale bars, 200 μm. Data are mean ± s.e.m. In a, b, statistically significant differences were determined by multiple regression and P values are indicated in the figure. Statistically significant difference at each timepoint was also determined using two-sided unpaired Student’s t-tests without adjustment for multiple comparisons, and those versus uninfected hamsters (*P < 0.05) are indicated by asterisks. The P value of the comparison between D614G and D614G/P681R at each d.p.i. is indicated in the figure.