Thus, we determined the functionality of the epitope-specific CD8 T cells in the three groups of mice by intracellular cytokine staining (ICS) for the presence of IFNγ- and/or TNFα-producing cells and calculating the ratio of IFNγ+TNFα+/IFNγ+ cells at days 7 and 13 post infection. This evidence concerns the gene IFNG and infection.