TCF7 and infection: In humans, expression of TCF-1 in subpopulations of virus-specific CD8+ T cells has been reported in individuals chronically infected with hepatitis B virus (HBV) (39), hepatitis D virus (HDV) (40), or Epstein-Barr virus (EBV) (40), and TCF-1 expression has been correlated with virus-specific T cell expansion capacity in the context of infection with hepatitis C virus (HCV) (37, 41).