FIG 3.

rILL346 mediates increased viral pathogenicity in ferrets—an effect associated with swine virus HA, NA, and PA genes. (A) Ferrets were intranasally infected with 10⁶ PFU of virus, and weight loss was evaluated on a daily basis for n = 3 ferrets per group and is represented as the average percentage of the preinfection weight of the ferret. (B) Viral titers were determined from nasal washes at days 2, 4, and 6 p.i. Endpoint titers are expressed as mean log₁₀ TCID₅₀/ml ± standard deviation. The limit of virus detection was 10 TCID₅₀/ml. (C) Influenza virus-specific antibody responses were measured based on microneutralization assays of serum collected from infected ferrets at day 14 p.i. Neutralization titers are presented as the log₁₀ serum dilution at which virus could no longer be detected. (D) Histopathology was performed on lungs and nasal turbinates of infected ferrets. Nasal turbinates and lung tissues were collected at days 2 and 4 postinfection from n = 2 ferrets per time point per virus, and lesion severity was scored on a 4-point scale relative to the overall pathology induced during infection. (E) Representative H&E-stained sections of ferret nasal turbinates and lung tissues 2 days p.i. All data are representative of two independent experiments.