T cells specific for different latent and lytic viral proteins efficiently control Epstein-Barr virus-transformed B cells

Background aims. Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disorders (PTLD) belong to the most dreaded complications of immunosuppression. The efficacy of EBV-specific T-cell transfer for PTLD has been previously shown, yet the optimal choice of EBV-derived antigens inducing polyclonal CD4þ and CD8þ T cells that cover a wide range of human leukocyte antigen types and efficiently control PTLD remains unclear. Methods. A pool of 125 T-cell epitopes from seven latent and nine lytic EBV-derived proteins (EBVmix) and peptide pools of EBNA1, EBNA3c, LMP2a and BZLF1 were used to determine T-cell frequencies and to isolate T cells through the use of the interferon (IFN)-g cytokine capture system. We further evaluated the phenotype and functionality of the generated T-cell lines in vitro. Results. EBVmix induced significantly higher T-cell frequencies and allowed selecting more CD4þIFN-gþ and CD8þIFN-gþ cells than single peptide pools. T cells of all specificities expanded similarly in vitro, recognized cognate antigen, and, to a lower extent, EBV-infected cells, exerted moderate cytotoxicity and showed reduced alloreactivity. However, EBVmix-specific cells most efficiently controlled EBV-infected lymphoblastoid cell lines (LCLs). This control was mainly mediated by EBVspecific CD8þ cells with an oligoclonal epitope signature covering both latent and lytic viral proteins. Notably, EBVspecific CD4þ cells unable to control LCLs produced significantly less perforin and granzyme B, probably because of limited LCL epitope presentation. Conclusions. EBVmix induces a broader T-cell response, probably because of its coverage of latent and lytic EBV-derived proteins that may be important to control EBV-transformed B cells and might offer an improvement of T-cell therapies.