Immunization with a pool of HA peptides restores CD4 T cell reactivity to the selected HA epitopes following a secondary infection.

<p>Mice were infected and immunized as depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0176407#pone.0176407.g003" target="_blank">Fig 3</a>. At day 8 following the secondary infection, individual spleens and mediastinal lymph nodes were harvested. CD4 T cells were isolated by MACS cell purification and reactivity to a panel of peptide-epitopes was measured by IL-2 Elispot assay. <b>A:</b> CD4 T cell reactivity in the spleen. Data represent results from 9–13 individual mice averaged in each experimental group. <b>B:</b> CD4 T cell reactivity within the mediastinal lymph node. Data presented represent the average results from 6–13 individual mice in each experimental group. All data are presented as the spot count normalized to 10⁶ CD4 T cells after subtracting background, with error bars depicting the standard error of the mean. * = p<0.05; ** = p<0.01; *** = p<0.001 by Kruskal-Wallis one-way ANOVA test.