Expansion of antiviral T cells correlated with viral load under the influence of complement blockade. (A-E) Peripheral blood mononuclear cells (PBMCs) were isolated from patients at the time of VST infusion and weekly for the first 4 weeks afterward. Interferon-γ ELISpot was performed on samples after stimulation with pools of overlapping viral peptides (pepmix) from the treated virus. Interferon-γ (IFN-γ)–secreting T cells at each time point were plotted with the corresponding viral polymerase chain reaction quantification at that time. The timing of complement blockade is indicated by the start of eculizumab (ecu), discontinuation of ecu, and the time of CH50 normalization. CH50 normalization is a marker that complement blockade is no longer occurring in blood. Each panel represents ELISpot assay performed on samples isolated from distinct individual patients. ADV, adenovirus; BKV, BK virus; SFC, spot-forming cell.