Fig. 4.

T cell sub-population IFN-γ response to in vitro re-stimulation with influenza proteins. Pigs were vaccinated twice (day 0 and 21pv1) i.d. with needle-free delivery with 200 μg (n = 6), 800 μg (n = 6) or 1972 μg (n = 5) DNA, or not DNA vaccinated at all (n = 5). PBMC from the vaccinated pigs on day 35pv1 were cultured in vitro in the presence of recombinant influenza NP 2009, NP 1918, M1 1918 and HA 2009. After 24 h, the cells were stained with anti-CD3, -CD4, -CD8 and -IFN-γ monoclonal antibodies and analyzed by flow cytometry. Three T cell subsets were identified based on their CD4 and CD8 expression: (a) CD4-CD8+, (b) CD4+CD8+ and (c) CD4+CD8- cells. Error bars indicate the mean ± SEM, and significant differences from the no-vaccine control group are indicated by: ***: p < 0.001; **: p < 0.01; *: p < 0.05.