FIG 5.

Impact of rupintrivir resistance-conferring mutations on the recovery of recombinant MNV. (A and B) Virus titers obtained at 24 h after transfection of BSR-T7 cells with MNV cDNA (A) or in vitro-transcribed and capped MNV RNA (B). The virus titers in BV-2 cells were determined by the TCID₅₀ method. Error bars represent means ± standard deviations from three independent experiments. Dotted lines, detection limit of the assay. (C) The increase in the RNA level (the RNA level at 12 h postinoculation minus the RNA level at 1 h postinoculation) was determined by qRT-PCR after three passages with BV-2 cells. The supernatant of BSR-T7 cells transfected with MNV cDNA was inoculated onto BV-2 cells. At 48 h postinoculation, the supernatant of BV-2 cells was next inoculated onto BV-2 cells. This passage was repeated two times. After three passages, the supernatant was inoculated onto BV-2 cells and the increase in the RNA level was measured. No increase in the amount of viral RNA of the A105V and A105V/I109V recombinant viruses was observed.