Similar levels of CD8 and CD4 T cell responses against HA were induced by different DNA immunization regimens.

<p>Mice were immunized as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041332#pone-0041332-g001" target="_blank">Figure 1</a>. At two weeks after the final immunization, mice were sacrificed and splenocytes were prepared for analysis of T cell responses by intracellular cytokine staining and flow cytometry. (<b>a</b>) Comparison of CD8+ T cell responses induced in mice after DNA immunizations. Splenocytes were stimulated with a peptide corresponding to known CD8+ T cell epitopes in HA for 6 h in the presence of Brefeldin A, and then stained for cell surface CD8 as well as intracellular IFN-γ, followed by flow cytometry analysis. The percentages of IFN-γ-producing CD8+ T cells in splenocytes from each individual mouse after stimulation are shown. (<b>b</b>) Comparison of CD4+ T cell responses induced in mice after DNA immunizations. Splenocytes from immunized mice were stimulated with dendritic cells that have been pulsed with different VLPs as indicated. After 6 h stimulation in the presence of Brefeldin A, the cells were stained for cell surface CD4 as well as intracellular IFN-γ, followed by flow cytometry analysis. The percentages of IFN-γ-producing CD4+ T cells in splenocytes from each individual mouse after stimulation are shown. Data are presented as the mean ± standard deviation.