Figure 9.

Long term memory and role of CD4 and CD8 T cells in vaccine-induced immunity to influenza virus. Three hundred sixty-two days after booster vaccination, mice were challenged with H1N1/PR8 strain of influenza A virus (A–C). Viral titers were quantified in the lungs on D6 after challenge (A). Numbers and frequencies of NP366-specific CD8 T cells and NP311-specific CD4 T cells in lungs (B). The linear regression curve was plotted for data from individual mice frequencies of NP366-specific CD8 T cells or NP311-specific CD4 T cells plotted against its Log₁₀ viral titer value, (D, E): Mice were vaccinated with NP formulated in ADJ+PLP-GLA, and 3 weeks later, either CD4 or CD8 T cells were depleted immediately prior to and during a lethal H1N1 PR8 influenza challenge. An additional cohort of ADJ+PLP-GLA vaccinated mice was treated with FTY720 immediately before and during viral challenge. Viral titers were quantified in the lungs on D6 after challenge (D). Numbers and frequencies of NP366-specific CD8 T cells and NP311-specific CD4 T cells in lungs (E). *, **, ***, and **** indicate significance at P < 0.1, 0.01, 0.001, and 0.0001, respectively.