FIG 1.

Schematic of two virus infections. Ferrets (n = 32) were infected with the H1N1 A/Singapore/6/1986 (Sing/86) virus (10⁶ PFU), and 84 days later they were divided into two groups (n = 16) and infected with either A/New Caledonia/20/1999 (NC/99) (10⁶ PFU) or A/Brisbane/59/2007 (Bris/07) (10⁶ PFU). At day 168, ferrets were further subdivided and ferrets (n = 4) were vaccinated with one of three VLPs expressing P1, X6, or CA/09 HA protein. Each VLP also expressed the NA protein from A/mallard/Alberta/24/2001, H7N3. The final group of ferrets was mock vaccinated with a VLP expressing no HA or NA proteins. Blood was collected prior to initial infection and at days 14, 84, 98, 168, 182, and 252 postinfection.