Fig 1. Experimental protocol.

Male Fitch ferrets (Mustela putorius furo), approximately 6 months of age were used in this study. Groups of 8 ferrets were infected intranasally with 1 x 10⁶ pfu of A/Perth/16/09, or groups of 4 to 6 ferrets were mock infected. Baseline weights and temperatures were obtained for the three consecutive days prior to challenge and on day 0 (the day of challenge). Following challenge, ferrets were monitored for change in body weight and temperature as well as clinical signs of illness on a daily basis for 5 days. Blood samples were collected for Flow Cytometry (days 0–5) and serum collected (days 0, 2 and 5) to asses antibody responses (HI assays). All ferrets were euthanized on day 2 (4 Perth/16-infected ferrets) or day 5 post-challenge (4 Perth/16-infected and all mock-infected ferrets). Viral titers were determined from nasal washes (days 0–5) nasal turbinates (days 2 and 5), BALF (days 2 and 5) and trachea (upper and lower regions; days 2 and 5). Leukocyte purification was performed from peripheral blood (days 0–5), from lymph nodes (days 2 and 5) and from BALF (days 2 and 5).