Human AdV-specific T cells: persisting in vitro functionality despite lethal irradiation

Viral infections caused by human adenovirus (HAdV) or CMV remain life-threatening complications in immunocompromised patients undergoing allogeneic hematopoietic stem cell transplantation. Adoptive immunotherapy with virus-specific T cells showed impressive clinical results without or with only mild GvHD. However, because of high costs and high regulatory barriers, these protocols are accessible to only a few centers. The infusion of unmanipulated donor lymphocytes (DLIs) that contain virus-specific T cells is not feasible because of the risk of GvHD. Reports about three patients treated with irradiated granulocytes or DLIs that potentially comprised virus-specific T cells discussed an active role of virus-specific lymphocytes despite irradiation, but real evidence could not be provided. Therefore, we tested the effect of irradiation on HAdV-specific T cells, which had been expanded in vitro, by stimulating PBMCs with HAdV-peptide pools and IL-15 for 12 days. Cells were then irradiated with 30 Gy, as performed for normal granulocyte concentrates. Cell viability and polyfunctional activity were determined by flow cytometry. Even 48 h after irradiation, 15.6% of expanded HAdV-specific T cells were apparently viable and cytolytically active. Although the in vivo antiviral activity was not tested, these data support earlier assumptions about the potential role of irradiated cells in patients.