Consistently, flow cytometry of intracellular cytokine staining showed that M2e and N2-specific CD4+ T (Figs 5E and 2F) and CD8+ T cells (Fig 5G), which secrete IFN-γ, were substantially increased in the lung of m-cNA-M2e VLP group compared to the naïve infection group. Here, CD4 is linked to infection.