Although initially surprising given that both CyCMV/SIV- and RhCMV/SIV-mediated protection against SIV replication depends on the presence of SIV-specific, MHC-E-restricted CD8 + T cells and an IL-15-based signaling pathway17,29,36, this observation is in line with previous reports of the importance of CD4 + T cells in influenza infection. The gene discussed is CD4; the disease is influenza.