Arming human regulatory T cells from healthy donors or multiple sclerosis patients with switchable chimeric antigen receptors for the treatment of inflammatory diseases

Regulatory T cells (Tregs) possess a central role in impeding harmful immune reactions and represent important immunomodulatory players in the pathogenesis of inflammatory diseases. For that reason, Tregs are intensively studied as an innovative cell product for the treatment of autoimmunity e.g. multiple sclerosis (MS) or Graft-versus-Host disease. In recent years, several preclinical mouse model clearly demonstrate a superior suppressive capacity of antigen-specific Tregs compared to polyclonal cells. On the downside, isolation of Tregs with a distinct antigen-specificity is a highly time-consuming and laborious process.
To overcome these challenges, we armed polyclonal Tregs isolated from healthy donors or MS patients with a universal chimeric antigen receptor (UniCAR) construct. As T cells and target cells are indirectly cross-linked by a separate, antigen-binding targeting module (TM), this innovative technology enables side-specific redirection of Tregs to any desired surface structure. Moreover, UniCAR armed Tregs are silenced in the absence of the TM allowing for a finely tuned regulation of Treg activity between an “on” and “off” status.
Here, we demonstrate that highly pure CD4+CD25highCD127dimCD45RA+ Tregs isolated from both healthy donors or MS patients stably express a UniCAR construct with an intracellular 4-1BB/ζ signaling domain. UniCAR-engrafted Tregs vigorously expand and maintain their phenotype even under pro-inflammatory conditions. Most importantly, upon TM-activation UniCAR-endowed Tregs significantly hamper autologous T effector cells both in vitro and in vivo.
Taken together, our results underline the enormous therapeutic potential of the UniCAR system for treatment of inflammatory diseases including MS, as it facilitates an antigen-specific and precisely controlled Treg activation at the side of inflammation. Moreover, this innovative technology allows redirection of Tregs against a wide range of surface structures simply by exchanging the TM and might thereby broaden current treatment modalities.