Figure 5.

Effect of the S S375F mutation on viral growth dynamics

(A) Scheme of the S-chimeric recombinant SARS-CoV-2 used in this study. The numbers in parentheses are identical to those in Figures 5B–5E.

(B–D) SARS-CoV-2 infection. VeroE6/TMPRSS2 cells were infected with a series of S-chimeric recombinant SARS-CoV-2 (summarized in A) at an m.o.i. 0.01. The viral RNA in the supernatant (B) and GFP intensity (C) were measured routinely. Note that the yaxes of the graphs shown in B are log scales. The results for the respective parental S are shown in other panels as broken green lines. Assays were performed in quadruplicate (B and C).

(D) Syncytium formation. Left, GFP-positive area at 48 h.p.i. Scale bar, 500 μm. Right, summarized results. I, n = 6,483 cells; VI, n = 2,780 cells; II, n = 5,393 cells; and VII, 12,857 cells. The results for B.1-GFP (virus I) and Omicron-GFP (virus II) in C and D (right) are identical to those shown in Figures 1I and 1J (right). Representative images are shown in Figure S1.

(E) Plaque assay. Left, representative figures.Right, summary of the plaque diameters (20 plaques per virus). Each dot indicates the result of an individual plaque. Data are expressed as the mean with SD (B, C, and E) or the median with 95% CI (D). In B and C, statistically significant differences (∗FWERs<0.05) versus Omicron-GFP (virus II) through timepoints were determined by multiple regression. FWERs were calculated using the Holm method. In D and E, statistically significant differences (∗p <0.05) versus Omicron-GFP (virus II) were determined by a two-sided Mann–Whitney U test. See also Figure S1.