FIG. 4.
Viable BVDV mutants expressing Npro and HCV NS3 protease. (A) Genome organizations of N-H/B and N-Npro-H/B viruses. Npro protein (black-filled box) was cloned upstream of the HCV-NS3 protease of the N-H/B virus. The HCV NS5A-NS5B boundary amino acids are underlined. (B) Plaque phenotypes of wt NADL, N-H/B, and N-Npro-H/B. Bovine testicle cells were infected with the different viruses for 4 days at 37°C. Plaque formation was revealed by crystal violet staining. Mean plaque diameters ± standard error values are shown. (C) Interferon induction by the Npro restored virus (N-Npro-H/B). Harvested culture media were assayed for interferon using the ISRE reporter cell line as described in Materials and Methods. The induction was calculated relative to values from mock-infected cells. The error bars indicate standard deviations.