Establishment and Operation of a Third-Party Virus-Specific T Cell Bank within an Allogeneic Stem Cell Transplant Program.

Hematopoietic stem cell transplantation (HSCT) donor-generated virus-specific T cells (VSTs) can provide effective treatment for viral infection post-HSCT but are not readily accessible to all patients. Off-the-shelf cryopreserved VSTs suitable for treatment of multiple patients are an attractive alternative. We generated a bank of 17 cytomegalovirus (CMV)-, 14 Epstein-Barr virus (EBV)-, and 15 adenovirus (AdV)-specific T cell products from 30 third-party donors. Donors were selected for expression of 6 core HLA antigens expressed at high frequency in the local transplant population. T cells were generated by co-culturing venous blood or mobilized hematopoietic stem cell (HSC)-derived mononuclear cells with monocyte-derived dendritic cells pulsed with overlapping peptides covering CMV pp65, AdV5 hexon, or EBV BZLF1/LMP2A/EBNA1 proteins. Addition of a CD14 selection step instead of plate adherence to isolate monocytes before culture initiation significantly improved expansion in cultures from HSC material. Phenotyping showed the CD8 subset to have significantly higher numbers of terminal effector T cells (CD45RA62L) and lower numbers of effector memory T cells (CD45RA62L) when compared with the CD4 subset. Increased expression of the immunoinhibitory markers PD-1 and TIM-3 was noted on CD4 but not CD8 cells when compared with the control group. VST showed antiviral activity restricted through a variety of common HLAs, and modelling suggested a suitably HLA-matched product would be available for >90% of HSCT patients. Only a small number of carefully selected third-party donors are required to generate a VST bank of broad coverage, indicating the feasibility of local banking integrated into existing allogeneic HSCT programs.