Virus-specific T cells are retained and remain functional after administration of AP1903. Quantification of pathogen-specific T cells detected by IFN-γ ELISPOT in each patient who received AP1903 to control acute GVHD. Patients had viral infection and/or reactivation for: VZV (A, Pt. 6), EBV (B, Pt. 8 and C, Pt. 9), CMV (D, Pt. 8 and E, Pt. 9), BKV (F, Pt. 9). Black histograms represent response from total T cells and striped histograms represent response from endogenous T cells. The value of their difference represents the response from infused iC9-T cells. The gray dashed line indicates the viral load at multiple time points.