Stability of rSARS-CoV-EIC⁻ after serial infections.

<p>(<b>A</b>) Groups of eleven 16 week-old BALB/c mice were infected with 100000 PFU of either the parental virus (wt) or three clones of the mutant viruses missing IC activity: N15A C1, N15A C2, N15A C3, V25F C1, V25F C2 and V25F C3. At 2 dpi and 4 dpi 3 mice of each group were sacrificed, lung RNA was extracted, and E gene was sequenced. The rest of the mice (5 per group) participated in the weight-loss and survival experiment. When any mouse died, from 4 to 10 dpi, lung RNA was extracted and E gene was sequenced. Bars represent different E protein sequences, either that of parental or the mutant viruses. The central colored part represents the transmembrane domain of the protein. Letters and numbers in red represent the amino acid changes detected after viral evolution and their relative position within transmembrane domain, respectively. Numbers accompanying bars indicate from how many mice (first number) out of the total of the animals analyzed (second number) arose the indicated sequence change. Dead mice are indicated by a †. (<b>B</b>) Vero E6 cells were infected with the wt virus or the mutant clones N15A C1 and N15A C2, V25F C1 and V25F C2 at an initial MOI of 0.5, and supernatants were serially passaged for 24 times every 24 hours. E gene in the viral population was sequenced at passages 0, 8, 16 and 24. Colored bars represent the transmembrane domain of different E protein sequences and letters and numbers in red represent the amino acid mutations identified and their relative position, respectively.