Fig. 2: Spike D614G substitution increases SARS-CoV-2 replication in the upper airway, but not the lungs, of hamsters.
a–i,Three- to four-week-old male Syrian golden hamsters were infected intranasally with 2 × 104 PFU of D614 or G614 SARS-CoV-2 or PBS (mock). All data are from a single experiment. a, Weight loss was monitored for seven days after infection. Data are mean ± s.d.; n = 18 (D614 and G614) and n = 14 (mock) at days 0–2; n = 12 (D614 and G614) and n = 10 (mock) at days 3 and 4; n = 6 (all cohorts) at days 5–7. Weight loss was analysed by two-factor analysis of variance (ANOVA) with Tukey’s post hoc test. P > 0.05 for D614 vs G614 at all time points. b–d, Infectious titres (b, c) and amount of viral genomes (d) were measured in the nasal wash, trachea and lung on days 2 (b, d), 4 (c, d) and 7 (d) after infection. e, f, Genome/PFU ratios on days 2 (e) and 4 (f) after infection were calculated as a measure of infectivity. In b–f, symbols represent individual hamsters (n = 6). Centre lines (b, c, e, f) and bar heights (d) represent means, and error bars represent s.d. Two-factor ANOVA with Sidak’s post hoc test. g–i, Hamsters were inoculated with 1:1 mixtures of D614 and G614 viruses (104 PFU each). Nasal wash, trachea and lungs were collected on days 2 (g), 4 (h) and 7 (i) after infection. Relative amounts of D614 and G614 RNAs were assessed by RT–PCR and Sanger sequencing. In g–i, dots represent individual hamsters (n = 6), the centre line represents the mean, shaded regions represent s.e.m., the width represents the distribution of the model-adjusted means, and heights extend to 99.8% of the distribution; y-axes use a log10 scale. P values are calculated for the group (strain) coefficient for each linear regression model.
