IFNG and viral infectious disease: In general, the IFN-γ response in CD4+ T cells upon stimulation with all the selected peptides decreased after virus infection (average frequency from 1.5 to 0.7%, with a 2.1-fold decrease), while the frequencies of IFN-γ+ CD8+ T cells increased (average frequency of 4.7–6.0%, with a 1.3-fold increase; Figures 4A,B).