In vivo T-cell response and virologic response after adoptive transfer of pp65-specific T cells for the treatment of refractory CMV infection post allogeneic stem cell transplantation. Adoptive T-cell transfer of pp65-specific T cells was performed in 18 patients after allogeneic SCT. All recipients had no detectable T-cell response before adoptive T-cell transfer. (A) Shown is the in vivo expansion of the transferred T cells within 4 weeks after adoptive T-cell transfer. Twelve of 16 patients had a successful T-cell response after adoptive T-cell transfer. Detection of Ag-specific T cells was done by stimulation of blood samples with recombinant pp65, followed by intracellular cytokine staining in flow cytometry after 16 hours. Although control Ag's did not usually stimulate any IFN-γ production, the percentage of specific T cells was calculated by subtraction of the frequency obtained by the respective negative control. The threshold of a positive Ag-specific T-cell response was 0.01% of viable T cells. (B) Shown is the virologic response to adoptive T-cell transfer in terms of viral copies in peripheral blood. Before the T-cell transfer, all patients had increasing viral load unresponsive to treatment with ganciclovir or foscarnet or both. In patients 4, 7, 15, and 16 quantitative polymerase chain reaction of the virologic response was not available, but qualitative polymerase chain reaction results changed from positive to negative. In patient 13 only pp65 antigenemia was available, which turned to zero 26 days after adoptive T-cell transfer. Patients 2 and 15 are missing in panel A, because blood samples were not available for analysis.