Compared to a control virus expressing M36 and FADDDN (M36.FADDDN), the CD8 T-cell response was consistently enhanced by infection with mCMV-ΔM36 for the panel of viral epitopes tested, and this was reversed by expression of FADDDN after infection with virus mCMV-ΔM36.FADDDN. This evidence concerns the gene CD8A and infection.