To broaden the specificity of single T cells lines to include the three most common viral pathogens of stem cell recipients, the investigators reactivated CMV and adenovirus-specific T cells by using mononuclear cells transduced with a recombinant adenoviral vector encoding the CMV antigen pp65 (Ad5f35CMVpp65). Subsequent stimulations with EBV-LCL transduced with the same vector both reactivated EBV-specific T cells and maintained the expansion of the activated adenovirus and CMV-specific T cells. This method reliably produced T cells with cytotoxic function specific for all three viruses, which the investigators infused into 14 stem cell recipients in a Phase I prophylaxis study. The investigators observed recovery of immunity to CMV and EBV in all patients but an increase in adenovirus-specific T cells was only seen in patients who had evidence of adenovirus infection pre-infusion. A follow-up study in which the frequency of adenovirus-specific T cells was increased in the infused T cells produced similar results, thus highlighting the importance of endogenous antigen to promote the expansion of infused T cells in vivo. Nevertheless, all patients in both clinical trials with pre-infusion CMV, adenovirus or EBV infection or reactivation were able to clear the infection, including one patient with severe adenoviral pneumonia requiring ventilatory support. T cells recognizing multiple antigens can therefore produce clinically relevant effects against all three viruses.