FIG. 2.

Growth curves of wild-type vA187-1 and vA187-Ubi. SK-6 cells seeded in 25-cm² flasks (2 × 10⁶ cells/flask) were infected at a multiplicity of infection of 2, either with wild-type vA187-1 or with vA187-Ubi. After 1 h at 37°C, cells were washed and incubated in fresh medium for up to 48 h. At different time points postinfection, the cultures were frozen and thawed twice and the virus contained in the cleared supernatants was titrated on SK-6 cells. TCID₅₀, 50% tissue culture infective dose.