TMEV-infected T-bet-tg mice had a significant reduction of CD4, CD8a, Ifng, and Gzmb, but not Nkp46, expression in the brain with decreased anti-TMEV cellular responses; following TMEV infection, T-bet-tg mice had impaired acquired immunity but not innate immunity, which was associated with splenic T cell depletion. Here, CD4 is linked to infection.