The requirement for long-term immunosuppression to prevent rejections predisposes solid organ transplant recipients to severe or fatal viral complications, e.g. caused by cytomegalovirus (CMV). Classical antiviral medication is often problematic or ineffective. Hence, virus-specific adoptive T cell therapy emerged as attractive therapeutic option for viral diseases occurring after transplantation. Despite clinical safety of antiviral T cell products (TCPs) and impressive initial effectiveness,

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... ong-term efficacy is frequently limited in SOT recipients. This might originate in the short-term persistence of transferred T cells, which may be associated with a late differentiation state. Inhibition of the mechanistic-Target-of-Rapamycin-(mTOR)-pathway by Rapamycin regulates memory T cell differentiation and was integrated into our clinical protocol for the manufacture of virus-specific TCPs. Thereby, we optimized the T cell subset composition, yielding enriched proportions of early differentiated central-memory (TCM) and CD4+ T cells. Pre-clinical and clinical data imply this to enhance long-term efficacy of adoptive T cell therapy. The aim of the present study was to find evidence for this hypothesis in in vitro experiments by detailed molecular characterization of CMV-specific Rapamycin-treated (Rapa-)TCPs to thoroughly describe the underlying mechanism and to investigate transferability of the manufacturing process to patient samples. Rapamycin-treatment induced preferential expansion and reduced differentiation of virus-specific TCM as well as increasing virus-specific cytokine production of further differentiated CD8+ T cells. Moreover, Rapamycin-treatment resulted in enhanced T cell vitality inter alia in apoptosis-inducing conditions and even after freezing/thawing processes, which are required for clinical application. This may be mediated by increased levels of Bcl-2 protein. RNA sequencing revealed a beneficial transcriptome of Rapa-TCPs. Furthermore, metabolic analysis disclosed Rapa-TCPs to display a more [...]