FIG 6.

The I109V substitution in the MNV protease results in reduced susceptibility to rupintrivir during viral replication in cell culture. (A) The growth kinetics of the WT and I109V recombinant MNV were assessed following infection of BV-2 cells at MOIs of 0.1, 1, and 10 TCID₅₀/cell. Viral infectivity levels were determined by measuring the release of infectious virus into the culture supernatant at various times postinfection by determination of the TCID₅₀. (B) The inhibitory effects of rupintrivir and 2CMC against either the WT or the recombinant MNV I109V mutant were assessed following infection of BV-2 cells at MOIs of 0.1 and 1 TCID₅₀/cell. A significant difference in viral titers following treatment with 10 and 20 μM and 10, 20, and 40 μM rupintrivir was observed between the WT and I109V recombinant viruses at MOIs of 0.1 and 1, respectively (*, P < 0.05; **, P < 0.01; ***, P < 0.001). In contrast, there were no significant differences in virus titers following treatment with 2CMC.