IL2 enhances ex-vivo expanded regulatory T cell persistence after adoptive transfer

As regulatory T cell (Treg) adoptive therapy continues to develop clinically, there is a need to determine which immunomodulatory agents pair most compatibly with Tregs to enable persistence and stabilize suppressor function. Prior work has shown that mechanistic target of rapamycin (mTOR) inhibition can increase stability of thymic Tregs. In this study we investigated the transcriptomic signatures of ex-vivo expanded Tregs after adoptive transfer in the setting of clinically relevant immunosuppression using a non-human primate (NHP) model as a prelude to future transplant studies. Here, we found that adding interleukin-2 (IL2) to rapamycin in vivo supported a logarithmic increase in the half-life of adoptively transferred CFSE-labeled, autologous NHP Tregs, effectively doubling the number of cells in the peripheral blood Treg compartment compared to Treg infusion with rapamycin alone. Using single cell transcriptomics, we found that transferred ex-vivo expanded Tregs initially exhibit a gene expression signature consistent with an activated state. Moreover, those cells with the highest levels of activation also expressed genes associated with p53-mediated apoptosis. In contrast, transferred Tregs interrogated at Day +20 post-transfer demonstrated a gene signature more similar to published profiles of resting Tregs. Together, these preclinical data further support combining IL2 and rapamycin in vivo as adjunctive therapy for ex-vivo expanded adoptively transferred Tregs and suggest that the activation status of ex-vivo expanded Tregs is critical to their persistence.