FIG. 2.

Killing of BHK-21 cells by FMDV C-S8p260, C-S8p260p3d, MARLS, and C-S8c1. Time needed to kill 10⁴ BHK-21 cells as a function of the initial number of viral particles added. One representative experiment of four is shown. For standard viruses (open symbols) the time T required to produce complete cell killing is a logarithmic function of the initial number of viral particles n_o. Least square fits to the experimental data (continuous lines) yielded the following functions: for C-S8p260p3d, T = −2.35 ln (n_o) + 51.8, with a regression coefficient r² = 0.96; for MARLS, T = −2.34 ln (n_o) + 52.4, r² = 0.96; for C-S8c1, T = −3.41 ln (n_o) + 93.3, r² = 0.98. For the defective RNAs containing viral population C-S8p260 (solid symbols), the time T follows instead a power-law function, such that ln (T) = ln (44844) − 0.46 ln (n_o), with r² = 0.91.