We have previously shown that M2e-specific lung Trm cells were effectively generated through i.n immunizations with the CTA1-3M2e-DD fusion protein and strong protection against a lethal challenge infection with a heterosubtypic influenza virus strain was observed.5,11,56,57 Here we asked if the route of immunization influenced the level of protection and to what extent M2e-specific CD4 T cells were directly involved. The gene discussed is CD4; the disease is infection.