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 CD4' and CD8' 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 (EBVmjx) 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)-y 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 CD4+ IFN-y+ and CD4+ IFN-γ+ 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 CD8+ cells with an oligoclonal epitope signature covering both latent and lytic viral proteins. Notably, EBVspecific CD4+ cells unable to control LCLs produced significantly less perforin and granzymc B, probably because of limited LCL epitope presentation. Conclusions: EBVmjx 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. [ABSTRACT FROM AUTHOR]