FIG. 3.
Virus isolation from swine after inoculation with the rearranged viruses. Swine were inoculated with 2.5 × 107 PFU of virus as described in Materials and Methods. Nasal and probang swabs were taken as indicated. Samples were titrated, and virus was recovered by cultivation on BHK-21 cells at 37°C for 3 days for N1G4(WT) and G1N2 or 31°C for 4 days for G3N4 and G1N4. Each box represents an individual animal, and samples that were positive (■) or negative (□) for viral CPE are shown. The presence of virus and the gene order were confirmed by RT-PCR.