CD8A and cytomegalovirus infection: Despite these limitations we conclude that MDD patients show several signs of a CMV independent MDD state associated premature T cell aging, such as a CMV independent increase in CD4+ T memory cells and a latent naïve CD4 T-cell reduction and a latent CD8+ T-cell increase, these two latent T cell senescence abnormalities only becoming evident after CMV infection (double hit).