Figure 2
Growth properties of new UL14 mutant viruses. (A) Plaque morphology of the viruses used in the study. Vero cells were infected with (a) UL14R-VP16GFP, (b) UL14K51M-VP16GFP, (c) UL14(3P)-VP16GFP, (d) UL14D-VP16GFP at a low MOI and maintained in medium containing Îł-globulin for 72 hours. The bar in panel B represents 0.5 mm. (B) Quantification of plaque size. Cells were infected at a low MOI with the indicated viruses in the presence of Îł-globulin and examined at 36 h.p.i. Thirty plaques or more were randomly selected and their diameters were measured under a Nikon microscope equipped with a CCD camera. The bar and whisker for each show the average diameter of the plaques and the standard deviation, respectively. There was a significant difference between the sizes of the plaques formed by 14R- and UL14(3P)-VP16GFP viruses (p < 0.001; t-test). (C) After the cells were infected with viruses at an MOI of 0.001, multi-step growth curves were examined. At 12, 24, 48, 80, 100 h.p.i. cells and media were harvested together, frozen, and subsequently thawed for titration on Vero cell monolayers. (D) The one-step growth curves of the strains examined after the viruses were infected at an MOI of 3.0. At 0, 6, 12, 24, 36, 48 h.p.i. cells and media were harvested together, frozen, and thawed for titration on Vero cell monolayers.