Figure 3. Evaluation of H1N1-HA DNA vaccine combined with exogenous 5mer4 adjuvant in ferrets.

Ferrets were immunized with 200 µg of the H1N1-HA DNA vaccine with or without the 5mer4 (200 µg) adjuvant. (a) Hemagglutination inhibition antibody responses. Ferrets received immunizations with the H1N1-HA DNA vaccine, administered 3 times at one month intervals. Serum was collected after each vaccination and prior to challenge. HI antibody responses were evaluated at days 55 and day 66 post-immunization and detected using turkey red blood cells. (b) HA-specific T-cell responses. PBMCs were collected by ficoll gradient from all ferrets following challenge with the H1N1-2009 virus. T-cell responses were evaluated following re-stimulation with 3 peptide pools representing the H1N1-2009 HA protein. (c) HA-specific T-cell responses following re-stimulation with 3 peptide pools representing the H1N1-1918 HA protein. (d) Clinical observations of ferrets following H1N1-2009 challenge. Ferrets were scored on a scale of 1–10, where 0 = no signs of disease, 10 = most severe. (E) Infectious and total virus particles. Ferret nasal washes were collected at days 1, 3, and 9 following infection. Left axis: Infectious virus titre from the nasal washes of H1N1-HA + 5mer4 (□), H1N1-HA (▪), and control (♦) ferrets was detected by TCID₅₀ assay. Right axis: Following RNA extraction, nasal wash samples were probed with H1HA specific primers using quantitative real-time RT-PCR. H1N1-HA + 5mer4 (○), H1N1-HA (•), and control (▴) ferrets. Error bars represent the SEM.